[Libav-user] decode_video example pgm files distorted? (v4.0.2 Win build)

[Chris Bennett]

Hello All!

My apologies if this is a rookie question as I am just now learning the
innards of ffmpeg, but I am reaching out hoping someone may have had the
same issue as myself or has any advice.

I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing
decode_video. I ended up with this result:
https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing

At the top and bottom of the image there is is wavy distortion. I am not
sure what is causing it.
The source file is a quicktime of a Motion JPEG video.

I had also compiled the exe as well and ran this command

ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2
C:/frame-%03d.jpg

and those images turned out just fine (I am sure this probably runs some
completely different underlying code but I just wanted to make sure what I
compiled was capable of a successful result)

I figure I am doing something incorrectly but I do not know where else to
look. If anyone has any advice on what to tinker with, I would greatly
appreciate it.

Thanks,
Chris Bennett

[Strahinja Radman]

Hi Chris,

To me that looks like you wrote some wrong data inside the picture and it looks skewed. Some indexes could be wrong.

void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
FILE *f;
int i;

f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}

The above method should be called with pgm_save(frame->data[0], frame->linesize[0], frame->width, frame->height, “name.pgm”);

Kind regards,
Strahinja

From: Chris Bennett
Sent: 31 August 2018 19:41
To: libav-***@ffmpeg.org
Subject: [Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)

Hello All!

My apologies if this is a rookie question as I am just now learning the innards of ffmpeg, but I am reaching out hoping someone may have had the same issue as myself or has any advice.

I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing decode_video. I ended up with this result:  https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing

At the top and bottom of the image there is is wavy distortion. I am not sure what is causing it.
The source file is a quicktime of a Motion JPEG video.

I had also compiled the exe as well and ran this command

ffmpeg.exe -ss 0.5 -i my_quicktime.mov  -t 1 -s 480x300 -f image2 C:/frame-%03d.jpg

and those images turned out just fine (I am sure this probably runs some completely different underlying code but I just wanted to make sure what I compiled was capable of a successful result)

I figure I am doing something incorrectly but I do not know where else to look. If anyone has any advice on what to tinker with, I would greatly appreciate it.

Thanks,
Chris Bennett

[Chris Bennett]

Hey Strahinja!

Thank you very much for taking the time to help me out.

the pgm snippet you sent looks the same as the decode video example I am
seeing.

Here is the code that I am compiling and running if it helps, hopefully its
not too long. ( I had to add an extern "C" wrapper since my goal is to
build c++ tools with this, and also changed how the example finds the
decoder).

/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a
copy
* of this software and associated documentation files (the "Software"), to
deal
* in the Software without restriction, including without limitation the
rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

/**
* @file
* video decoding with libavcodec API example
*
* @example decode_video.c
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}

#define INBUF_SIZE 4096

static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;

f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}

static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;

ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}

while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}

printf("saving frame %3d\n", dec_ctx->frame_number);
fflush(stdout);

/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm", filename, dec_ctx->frame_number);
pgm_save(frame->data[0], frame->linesize[0],
frame->width, frame->height, buf);
}
}

int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t data_size;
int ret;
AVPacket *pkt;

if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];

pkt = av_packet_alloc();
if (!pkt)
exit(1);

/* set end of buffer to 0 (this ensures that no overreading happens for
damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);


//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->codecpar;
//-----

/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCodecParameters->codec_id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}

parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}

c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video codec context\n");
exit(1);
}

/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */

/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}

f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}

frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}

while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;

/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;

if (pkt->size)
decode(c, frame, pkt, outfilename);
}
}

/* flush the decoder */
decode(c, frame, NULL, outfilename);

fclose(f);

av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);

return 0;
}

Please let me know if you see anything incorrect with this.

Thanks!


Chris Bennett
Lead Animation Pipeline TD - Television

Post by Strahinja Radman
Hi Chris,
To me that looks like you wrote some wrong data inside the picture and it
looks skewed. Some indexes could be wrong.
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
The above method should be called with pgm_save(frame->data[0],
frame->linesize[0], frame->width, frame->height, “name.pgm”);
Kind regards,
Strahinja
*Sent: *31 August 2018 19:41
*Subject: *[Libav-user] decode_video example pgm files distorted? (v4.0.2
Winbuild)
Hello All!
My apologies if this is a rookie question as I am just now learning the
innards of ffmpeg, but I am reaching out hoping someone may have had the
same issue as myself or has any advice.
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing
decode_video. I ended up with this result: https://drive.google.com/file/
d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
At the top and bottom of the image there is is wavy distortion. I am not
sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
I had also compiled the exe as well and ran this command
ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2
C:/frame-%03d.jpg
and those images turned out just fine (I am sure this probably runs some
completely different underlying code but I just wanted to make sure what I
compiled was capable of a successful result)
I figure I am doing something incorrectly but I do not know where else to
look. If anyone has any advice on what to tinker with, I would greatly
appreciate it.
Thanks,
Chris Bennett
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user

[Chris Bennett]

*facepalm*

my bad. formatting makes that ugly.

perhaps this is better.

https://drive.google.com/file/d/1UQaGv4EwEj81hqk7GNeVz5hGFG0784RD/view?usp=sharing


Chris Bennett

[Strahinja Radman]

Hey Chris,

Can you try using
while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
while(!feof(f))

and then just send a packet to your decode method instead of a raw frame?

From: Chris Bennett
Sent: 31 August 2018 22:57
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted? (v4.0.2Winbuild)

Hey Strahinja!

Thank you very much for taking the time to help me out.

the pgm snippet you sent looks the same as the decode video example I am seeing.

Here is the code that I am compiling and running if it helps, hopefully its not too long. ( I had to add an extern "C" wrapper since my goal is to build c++ tools with this, and also changed how the example finds the decoder).

/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

/**
* @file
* video decoding with libavcodec API example
*
* @example decode_video.c
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}

#define INBUF_SIZE 4096

static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;

f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}

static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;

ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}

while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}

printf("saving frame %3d\n", dec_ctx->frame_number);
fflush(stdout);

/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm", filename, dec_ctx->frame_number);
pgm_save(frame->data[0], frame->linesize[0],
frame->width, frame->height, buf);
}
}

int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t   data_size;
int ret;
AVPacket *pkt;

if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];

pkt = av_packet_alloc();
if (!pkt)
exit(1);

/* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);


//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->codecpar;
//-----

/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCodecParameters->codec_id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}

parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}

c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video codec context\n");
exit(1);
}

/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */

/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}

f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}

frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}

while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;

/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;

if (pkt->size)
decode(c, frame, pkt, outfilename);
}
}

/* flush the decoder */
decode(c, frame, NULL, outfilename);

fclose(f);

av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);

return 0;
}

Please let me know if you see anything incorrect with this.

Thanks!



Chris Bennett
Lead Animation Pipeline TD - Television


On Fri, Aug 31, 2018 at 10:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hi Chris,
 
To me that looks like you wrote some wrong data inside the picture and it looks skewed. Some indexes could be wrong.
 
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
The above method should be called with pgm_save(frame->data[0], frame->linesize[0], frame->width, frame->height, “name.pgm”);
 
Kind regards,
Strahinja
 
From: Chris Bennett
Sent: 31 August 2018 19:41
To: libav-***@ffmpeg.org
Subject: [Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
 
Hello All!
 
My apologies if this is a rookie question as I am just now learning the innards of ffmpeg, but I am reaching out hoping someone may have had the same issue as myself or has any advice.
 
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing decode_video. I ended up with this result:  https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
 
At the top and bottom of the image there is is wavy distortion. I am not sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
 
I had also compiled the exe as well and ran this command
 
ffmpeg.exe -ss 0.5 -i my_quicktime.mov  -t 1 -s 480x300 -f image2 C:/frame-%03d.jpg
 
and those images turned out just fine (I am sure this probably runs some completely different underlying code but I just wanted to make sure what I compiled was capable of a successful result)
 
I figure I am doing something incorrectly but I do not know where else to look. If anyone has any advice on what to tinker with, I would greatly appreciate it.
 
Thanks,
Chris Bennett
 

[Chris Bennett]

Hm. Here is something strange.

When I try using while(av_read_frame(fmt_ctx, &packet) > 0), the method
immediately passes, making nothing happen.

I turned on debug in my stream, and this is the output (not much makes
sense/looks useful to me)

https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5lt4/view?usp=sharing

Let me know what you think. Thanks!

Chris Bennett

Post by Strahinja Radman
Hey Chris,
Can you try using
while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
while(!feof(f))
and then just send a packet to your decode method instead of a raw frame?
*Sent: *31 August 2018 22:57
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files distorted?
(v4.0.2Winbuild)
Hey Strahinja!
Thank you very much for taking the time to help me out.
the pgm snippet you sent looks the same as the decode video example I am seeing.
Here is the code that I am compiling and running if it helps, hopefully
its not too long. ( I had to add an extern "C" wrapper since my goal is to
build c++ tools with this, and also changed how the example finds the
decoder).
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* video decoding with libavcodec API example
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
#define INBUF_SIZE 4096
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;
ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}
printf("saving frame %3d\n",
dec_ctx->frame_number);
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm",
filename, dec_ctx->frame_number);
pgm_save(frame->data[0],
frame->linesize[0],
frame->width,
frame->height, buf);
}
}
int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t data_size;
int ret;
AVPacket *pkt;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file>
<output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];
pkt = av_packet_alloc();
if (!pkt)
exit(1);
/* set end of buffer to 0 (this ensures that no
overreading happens for damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0,
AV_INPUT_BUFFER_PADDING_SIZE);
//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate
memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->co
decpar;
//-----
/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCod
ecParameters->codec_id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video
codec context\n");
exit(1);
}
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}
f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret =
av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data,
data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;
if (pkt->size)
decode(c,
frame, pkt, outfilename);
}
}
/* flush the decoder */
decode(c, frame, NULL, outfilename);
fclose(f);
av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}
Please let me know if you see anything incorrect with this.
Thanks!
Chris Bennett
Lead Animation Pipeline TD - Television
Loading Image...]
Hi Chris,
To me that looks like you wrote some wrong data inside the picture and it
looks skewed. Some indexes could be wrong.
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
The above method should be called with pgm_save(frame->data[0],
frame->linesize[0], frame->width, frame->height, “name.pgm”);
Kind regards,
Strahinja
*Sent: *31 August 2018 19:41
*Subject: *[Libav-user] decode_video example pgm files distorted? (v4.0.2
Winbuild)
Hello All!
My apologies if this is a rookie question as I am just now learning the
innards of ffmpeg, but I am reaching out hoping someone may have had the
same issue as myself or has any advice.
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing
decode_video. I ended up with this result: https://drive.google.com/file/
d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
At the top and bottom of the image there is is wavy distortion. I am not
sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
I had also compiled the exe as well and ran this command
ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2
C:/frame-%03d.jpg
and those images turned out just fine (I am sure this probably runs some
completely different underlying code but I just wanted to make sure what I
compiled was capable of a successful result)
I figure I am doing something incorrectly but I do not know where else to
look. If anyone has any advice on what to tinker with, I would greatly
appreciate it.
Thanks,
Chris Bennett
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user

[Strahinja Radman]

Hey Chris,

I am not sure how exactly you modified your code but this should be the look of the loop

while(av_read_frame(fmt_ctx, &packet) > 0)
{
decode(c, frame, pkt, outfilename);
}

Kind regards,
Strahinja

From: Chris Bennett
Sent: 04 September 2018 20:54
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted?(v4.0.2Winbuild)

Hm. Here is something strange.

When I try using  while(av_read_frame(fmt_ctx, &packet) > 0), the method immediately passes, making nothing happen.

I turned on debug in my stream, and this is the output (not much makes sense/looks useful to me)

https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5lt4/view?usp=sharing

Let me know what you think. Thanks!


Chris Bennett

On Sat, Sep 1, 2018 at 12:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hey Chris,
 
Can you try using
                while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
                while(!feof(f))
 
and then just send a packet to your decode method instead of a raw frame?
 
From: Chris Bennett
Sent: 31 August 2018 22:57
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted? (v4.0.2Winbuild)
 
Hey Strahinja!
 
Thank you very much for taking the time to help me out.
 
the pgm snippet you sent looks the same as the decode video example I am seeing.
 
Here is the code that I am compiling and running if it helps, hopefully its not too long. ( I had to add an extern "C" wrapper since my goal is to build c++ tools with this, and also changed how the example finds the decoder).
 
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
 
/**
* @file
* video decoding with libavcodec API example
*
* @example decode_video.c
*/
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
 
#define INBUF_SIZE 4096
 
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
                char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
                const char *filename)
{
                char buf[1024];
                int ret;
 
                ret = avcodec_send_packet(dec_ctx, pkt);
                if (ret < 0) {
                                fprintf(stderr, "Error sending a packet for decoding\n");
                                exit(1);
                }
 
                while (ret >= 0) {
                                ret = avcodec_receive_frame(dec_ctx, frame);
                                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                                                return;
                                else if (ret < 0) {
                                                fprintf(stderr, "Error during decoding\n");
                                                exit(1);
                                }
 
                                printf("saving frame %3d\n", dec_ctx->frame_number);
                                fflush(stdout);
 
                                /* the picture is allocated by the decoder. no need to
                                free it */
                                _snprintf(buf, sizeof(buf), "%s-%d.pgm", filename, dec_ctx->frame_number);
                                pgm_save(frame->data[0], frame->linesize[0],
                                                frame->width, frame->height, buf);
                }
}
 
int main(int argc, char **argv)
{
                const char *filename, *outfilename;
                const AVCodec *codec;
                AVCodecParserContext *parser;
                AVCodecContext *c = NULL;
                FILE *f;
                AVFrame *frame;
                uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
                uint8_t *data;
                size_t   data_size;
                int ret;
                AVPacket *pkt;
 
                if (argc <= 2) {
                                fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
                                exit(0);
                }
                filename = argv[1];
                outfilename = argv[2];
 
                pkt = av_packet_alloc();
                if (!pkt)
                                exit(1);
 
                /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
                memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 
 
                //---from test1.cpp
                AVFormatContext *pFormatContext = avformat_alloc_context();
                if (!pFormatContext) {
                                fprintf(stderr, "ERROR could not allocate memory for Format Context");
                                return -1;
                }
                if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
                                fprintf(stderr, "ERROR could not open the file");
                                return -1;
                }
                AVCodecParameters *pLocalCodecParameters = NULL;
                pLocalCodecParameters = pFormatContext->streams[0]->codecpar;
                //-----
 
                /* find the video decoder */
                //codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
                codec = avcodec_find_decoder(pLocalCodecParameters->codec_id);
                if (!codec) {
                                fprintf(stderr, "Codec not found\n");
                                exit(1);
                }
 
                parser = av_parser_init(codec->id);
                if (!parser) {
                                fprintf(stderr, "parser not found\n");
                                exit(1);
                }
 
                c = avcodec_alloc_context3(codec);
                if (!c) {
                                fprintf(stderr, "Could not allocate video codec context\n");
                                exit(1);
                }
 
                /* For some codecs, such as msmpeg4 and mpeg4, width and height
                MUST be initialized there because this information is not
                available in the bitstream. */
 
                /* open it */
                if (avcodec_open2(c, codec, NULL) < 0) {
                                fprintf(stderr, "Could not open codec\n");
                                exit(1);
                }
 
                f = fopen(filename, "rb");
                if (!f) {
                                fprintf(stderr, "Could not open %s\n", filename);
                                exit(1);
                }
 
                frame = av_frame_alloc();
                if (!frame) {
                                fprintf(stderr, "Could not allocate video frame\n");
                                exit(1);
                }
 
                while (!feof(f)) {
                                /* read raw data from the input file */
                                data_size = fread(inbuf, 1, INBUF_SIZE, f);
                                if (!data_size)
                                                break;
 
                                /* use the parser to split the data into frames */
                                data = inbuf;
                                while (data_size > 0) {
                                                ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
                                                                data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
                                                if (ret < 0) {
                                                                fprintf(stderr, "Error while parsing\n");
                                                                exit(1);
                                                }
                                                data += ret;
                                                data_size -= ret;
 
                                                if (pkt->size)
                                                                decode(c, frame, pkt, outfilename);
                                }
                }
 
                /* flush the decoder */
                decode(c, frame, NULL, outfilename);
 
                fclose(f);
 
                av_parser_close(parser);
                avcodec_free_context(&c);
                av_frame_free(&frame);
                av_packet_free(&pkt);
 
                return 0;
}
 
Please let me know if you see anything incorrect with this.
 
Thanks!
 


Chris Bennett
Lead Animation Pipeline TD - Television

 
On Fri, Aug 31, 2018 at 10:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hi Chris,
 
To me that looks like you wrote some wrong data inside the picture and it looks skewed. Some indexes could be wrong.
 
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
The above method should be called with pgm_save(frame->data[0], frame->linesize[0], frame->width, frame->height, “name.pgm”);
 
Kind regards,
Strahinja
 
From: Chris Bennett
Sent: 31 August 2018 19:41
To: libav-***@ffmpeg.org
Subject: [Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
 
Hello All!
 
My apologies if this is a rookie question as I am just now learning the innards of ffmpeg, but I am reaching out hoping someone may have had the same issue as myself or has any advice.
 
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing decode_video. I ended up with this result:  https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
 
At the top and bottom of the image there is is wavy distortion. I am not sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
 
I had also compiled the exe as well and ran this command
 
ffmpeg.exe -ss 0.5 -i my_quicktime.mov  -t 1 -s 480x300 -f image2 C:/frame-%03d.jpg
 
and those images turned out just fine (I am sure this probably runs some completely different underlying code but I just wanted to make sure what I compiled was capable of a successful result)
 
I figure I am doing something incorrectly but I do not know where else to look. If anyone has any advice on what to tinker with, I would greatly appreciate it.
 
Thanks,
Chris Bennett
 

_______________________________________________
Libav-user mailing list
Libav-***@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/libav-user
 
 

_______________________________________________
Libav-user mailing list
Libav-***@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/libav-user

[Chris Bennett]

Hey Strahinja,

Yeah that is what I have. Here is the link to the latest version of the
modified code:

https://drive.google.com/file/d/1UQaGv4EwEj81hqk7GNeVz5hGFG0784RD/view?usp=sharing

Let me know what you think.

Thanks

Chris Bennett

Post by Strahinja Radman
Hey Chris,
I am not sure how exactly you modified your code but this should be the look of the loop
while(av_read_frame(fmt_ctx, &packet) > 0)
{
decode(c, frame, pkt, outfilename);
}
Kind regards,
Strahinja
*Sent: *04 September 2018 20:54
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files
distorted?(v4.0.2Winbuild)
Hm. Here is something strange.
When I try using while(av_read_frame(fmt_ctx, &packet) > 0), the method
immediately passes, making nothing happen.
I turned on debug in my stream, and this is the output (not much makes
sense/looks useful to me)
https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5
lt4/view?usp=sharing
Let me know what you think. Thanks!
Chris Bennett
Hey Chris,
Can you try using
while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
while(!feof(f))
and then just send a packet to your decode method instead of a raw frame?
*Sent: *31 August 2018 22:57
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files distorted?
(v4.0.2Winbuild)
Hey Strahinja!
Thank you very much for taking the time to help me out.
the pgm snippet you sent looks the same as the decode video example I am seeing.
Here is the code that I am compiling and running if it helps, hopefully
its not too long. ( I had to add an extern "C" wrapper since my goal is to
build c++ tools with this, and also changed how the example finds the
decoder).
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* video decoding with libavcodec API example
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
#define INBUF_SIZE 4096
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;
ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}
printf("saving frame %3d\n",
dec_ctx->frame_number);
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm",
filename, dec_ctx->frame_number);
pgm_save(frame->data[0],
frame->linesize[0],
frame->width,
frame->height, buf);
}
}
int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t data_size;
int ret;
AVPacket *pkt;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file>
<output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];
pkt = av_packet_alloc();
if (!pkt)
exit(1);
/* set end of buffer to 0 (this ensures that no
overreading happens for damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0,
AV_INPUT_BUFFER_PADDING_SIZE);
//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate
memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->
codecpar;
//-----
/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCodecParameters->codec_
id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video
codec context\n");
exit(1);
}
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}
f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret =
av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data,
data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;
if (pkt->size)
decode(c,
frame, pkt, outfilename);
}
}
/* flush the decoder */
decode(c, frame, NULL, outfilename);
fclose(f);
av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}
Please let me know if you see anything incorrect with this.
Thanks!
Chris Bennett
Lead Animation Pipeline TD - Television
http://www.dreamworksanimation.com/brand/signatures/Central/CentralEmailSigs06.jpg]
Hi Chris,
To me that looks like you wrote some wrong data inside the picture and it
looks skewed. Some indexes could be wrong.
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
The above method should be called with pgm_save(frame->data[0],
frame->linesize[0], frame->width, frame->height, “name.pgm”);
Kind regards,
Strahinja
*Sent: *31 August 2018 19:41
*Subject: *[Libav-user] decode_video example pgm files distorted? (v4.0.2
Winbuild)
Hello All!
My apologies if this is a rookie question as I am just now learning the
innards of ffmpeg, but I am reaching out hoping someone may have had the
same issue as myself or has any advice.
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing
decode_video. I ended up with this result: https://drive.google.com/file/
d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
At the top and bottom of the image there is is wavy distortion. I am not
sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
I had also compiled the exe as well and ran this command
ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2
C:/frame-%03d.jpg
and those images turned out just fine (I am sure this probably runs some
completely different underlying code but I just wanted to make sure what I
compiled was capable of a successful result)
I figure I am doing something incorrectly but I do not know where else to
look. If anyone has any advice on what to tinker with, I would greatly
appreciate it.
Thanks,
Chris Bennett
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user

[Strahinja Radman]

Chris,

I am using something similar to this and its working properly:


ret = avformat_open_input(&pFormatContext, input_filename, NULL, NULL);
if (ret < 0)
return ret;

ret = avformat_find_stream_info(pFormatContext, NULL);
if (ret < 0)
return ret;


//I assume you only have 1 stream
AVCodec *dec = avcodec_find_decoder(pFormatContext->streams[0]->codecpar->codec_id);

if (!dec)
printf("Failed to find decoder for stream ");

decoder = avcodec_alloc_context3(NULL);
if (!decoder)
printf("Failed to allocate the decoder context for stream ");

ret = avcodec_parameters_to_context(decoder, pFormatContext->streams[0]->codecpar);
if (ret < 0)
printf("Failed to copy decoder parameters to input decoder context for stream ");

ret = avcodec_open2(decoder, dec, NULL);
if (ret < 0)
printf("Failed to open decoder for stream ");


while (av_read_frame(pFormatContext, &pkt) > 0) {
decode(decoder, frame, &pkt, outfilename);
}

I cant test your code so I am not quite sure why doesn’t it work. I would suggest that you look into the transcoding.c example also.

From: Chris Bennett
Sent: 04 September 2018 22:42
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm filesdistorted?(v4.0.2Winbuild)

Hey Strahinja,

Yeah that is what I have. Here is the link to the latest version of the modified code:

https://drive.google.com/file/d/1UQaGv4EwEj81hqk7GNeVz5hGFG0784RD/view?usp=sharing

Let me know what you think.

Thanks


Chris Bennett

On Tue, Sep 4, 2018 at 12:06 PM, Strahinja Radman <***@gmail.com> wrote:
Hey Chris,
 
I am not sure how exactly you modified your code but this should be the look of the loop
 
while(av_read_frame(fmt_ctx, &packet) > 0)
{
                decode(c, frame, pkt, outfilename);
}
 
Kind regards,
Strahinja
 
From: Chris Bennett
Sent: 04 September 2018 20:54

To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted?(v4.0.2Winbuild)
 
Hm. Here is something strange.
 
When I try using  while(av_read_frame(fmt_ctx, &packet) > 0), the method immediately passes, making nothing happen.
 
I turned on debug in my stream, and this is the output (not much makes sense/looks useful to me)
 
https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5lt4/view?usp=sharing
 
Let me know what you think. Thanks!


Chris Bennett
 
On Sat, Sep 1, 2018 at 12:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hey Chris,
 
Can you try using
                while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
                while(!feof(f))
 
and then just send a packet to your decode method instead of a raw frame?
 
From: Chris Bennett
Sent: 31 August 2018 22:57
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted? (v4.0.2Winbuild)
 
Hey Strahinja!
 
Thank you very much for taking the time to help me out.
 
the pgm snippet you sent looks the same as the decode video example I am seeing.
 
Here is the code that I am compiling and running if it helps, hopefully its not too long. ( I had to add an extern "C" wrapper since my goal is to build c++ tools with this, and also changed how the example finds the decoder).
 
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
 
/**
* @file
* video decoding with libavcodec API example
*
* @example decode_video.c
*/
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
 
#define INBUF_SIZE 4096
 
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
                char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
                const char *filename)
{
                char buf[1024];
                int ret;
 
                ret = avcodec_send_packet(dec_ctx, pkt);
                if (ret < 0) {
                                fprintf(stderr, "Error sending a packet for decoding\n");
                                exit(1);
                }
 
                while (ret >= 0) {
                                ret = avcodec_receive_frame(dec_ctx, frame);
                                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                                                return;
                                else if (ret < 0) {
                                                fprintf(stderr, "Error during decoding\n");
                                                exit(1);
                                }
 
                                printf("saving frame %3d\n", dec_ctx->frame_number);
                                fflush(stdout);
 
                                /* the picture is allocated by the decoder. no need to
                                free it */
                                _snprintf(buf, sizeof(buf), "%s-%d.pgm", filename, dec_ctx->frame_number);
                                pgm_save(frame->data[0], frame->linesize[0],
                                                frame->width, frame->height, buf);
                }
}
 
int main(int argc, char **argv)
{
                const char *filename, *outfilename;
                const AVCodec *codec;
                AVCodecParserContext *parser;
                AVCodecContext *c = NULL;
                FILE *f;
                AVFrame *frame;
                uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
                uint8_t *data;
                size_t   data_size;
                int ret;
                AVPacket *pkt;
 
                if (argc <= 2) {
                                fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
                                exit(0);
                }
                filename = argv[1];
                outfilename = argv[2];
 
                pkt = av_packet_alloc();
                if (!pkt)
                                exit(1);
 
                /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
                memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 
 
                //---from test1.cpp
                AVFormatContext *pFormatContext = avformat_alloc_context();
                if (!pFormatContext) {
                                fprintf(stderr, "ERROR could not allocate memory for Format Context");
                                return -1;
                }
                if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
                                fprintf(stderr, "ERROR could not open the file");
                                return -1;
                }
                AVCodecParameters *pLocalCodecParameters = NULL;
                pLocalCodecParameters = pFormatContext->streams[0]->codecpar;
                //-----
 
                /* find the video decoder */
                //codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
                codec = avcodec_find_decoder(pLocalCodecParameters->codec_id);
                if (!codec) {
                                fprintf(stderr, "Codec not found\n");
                                exit(1);
                }
 
                parser = av_parser_init(codec->id);
                if (!parser) {
                                fprintf(stderr, "parser not found\n");
                                exit(1);
                }
 
                c = avcodec_alloc_context3(codec);
                if (!c) {
                                fprintf(stderr, "Could not allocate video codec context\n");
                                exit(1);
                }
 
                /* For some codecs, such as msmpeg4 and mpeg4, width and height
                MUST be initialized there because this information is not
                available in the bitstream. */
 
                /* open it */
                if (avcodec_open2(c, codec, NULL) < 0) {
                                fprintf(stderr, "Could not open codec\n");
                                exit(1);
                }
 
                f = fopen(filename, "rb");
                if (!f) {
                                fprintf(stderr, "Could not open %s\n", filename);
                                exit(1);
                }
 
                frame = av_frame_alloc();
                if (!frame) {
                                fprintf(stderr, "Could not allocate video frame\n");
                                exit(1);
                }
 
                while (!feof(f)) {
                                /* read raw data from the input file */
                                data_size = fread(inbuf, 1, INBUF_SIZE, f);
                                if (!data_size)
                                                break;
 
                                /* use the parser to split the data into frames */
                                data = inbuf;
                                while (data_size > 0) {
                                                ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
                                                                data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
                                                if (ret < 0) {
                                                                fprintf(stderr, "Error while parsing\n");
                                                                exit(1);
                                                }
                                                data += ret;
                                                data_size -= ret;
 
                                                if (pkt->size)
                                                                decode(c, frame, pkt, outfilename);
                                }
                }
 
                /* flush the decoder */
                decode(c, frame, NULL, outfilename);
 
                fclose(f);
 
                av_parser_close(parser);
                avcodec_free_context(&c);
                av_frame_free(&frame);
                av_packet_free(&pkt);
 
                return 0;
}
 
Please let me know if you see anything incorrect with this.
 
Thanks!
 


Chris Bennett
Lead Animation Pipeline TD - Television

 
On Fri, Aug 31, 2018 at 10:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hi Chris,
 
To me that looks like you wrote some wrong data inside the picture and it looks skewed. Some indexes could be wrong.
 
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
The above method should be called with pgm_save(frame->data[0], frame->linesize[0], frame->width, frame->height, “name.pgm”);
 
Kind regards,
Strahinja
 
From: Chris Bennett
Sent: 31 August 2018 19:41
To: libav-***@ffmpeg.org
Subject: [Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
 
Hello All!
 
My apologies if this is a rookie question as I am just now learning the innards of ffmpeg, but I am reaching out hoping someone may have had the same issue as myself or has any advice.
 
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing decode_video. I ended up with this result:  https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
 
At the top and bottom of the image there is is wavy distortion. I am not sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
 
I had also compiled the exe as well and ran this command
 
ffmpeg.exe -ss 0.5 -i my_quicktime.mov  -t 1 -s 480x300 -f image2 C:/frame-%03d.jpg
 
and those images turned out just fine (I am sure this probably runs some completely different underlying code but I just wanted to make sure what I compiled was capable of a successful result)
 
I figure I am doing something incorrectly but I do not know where else to look. If anyone has any advice on what to tinker with, I would greatly appreciate it.
 
Thanks,
Chris Bennett
 

_______________________________________________
Libav-user mailing list
Libav-***@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/libav-user
 
 

_______________________________________________
Libav-user mailing list
Libav-***@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/libav-user
 
 

[Chris Bennett]

Hey Strahinja,

I tried to recreate what you sent me, but I ended up with the same issue as
previous with the av_read_frame giving me 0.
I must have built my ffmpeg libs incorrectly or messed up my project
settings, because these examples seems straightforward yet not working for
me as intended.

I will also take a look at transcoding.c and see if I can find anything
there that can also assist my learning.

Thank you again for your time and help!

Chris Bennett

Post by Strahinja Radman
Chris,
ret = avformat_open_input(&pFormatContext,
input_filename, NULL, NULL);
if (ret < 0)
return ret;
ret = avformat_find_stream_info(pFormatContext, NULL);
if (ret < 0)
return ret;
//I assume you only have 1 stream
AVCodec *dec = avcodec_find_decoder(
pFormatContext->streams[0]->codecpar->codec_id);
if (!dec)
printf("Failed to find decoder for stream ");
decoder = avcodec_alloc_context3(NULL);
if (!decoder)
printf("Failed to allocate the decoder
context for stream ");
ret = avcodec_parameters_to_context(decoder,
pFormatContext->streams[0]->codecpar);
if (ret < 0)
printf("Failed to copy decoder parameters
to input decoder context for stream ");
ret = avcodec_open2(decoder, dec, NULL);
if (ret < 0)
printf("Failed to open decoder for stream ");
while (av_read_frame(pFormatContext, &pkt) > 0) {
decode(decoder, frame, &pkt, outfilename);
}
I cant test your code so I am not quite sure why doesn’t it work. I would
suggest that you look into the transcoding.c example also.
*Sent: *04 September 2018 22:42
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm filesdistorted?(v4.0.
2Winbuild)
Hey Strahinja,
https://drive.google.com/file/d/1UQaGv4EwEj81hqk7GNeVz5hGFG078
4RD/view?usp=sharing
Let me know what you think.
Thanks
Chris Bennett
Hey Chris,
I am not sure how exactly you modified your code but this should be the look of the loop
while(av_read_frame(fmt_ctx, &packet) > 0)
{
decode(c, frame, pkt, outfilename);
}
Kind regards,
Strahinja
*Sent: *04 September 2018 20:54
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files
distorted?(v4.0.2Winbuild)
Hm. Here is something strange.
When I try using while(av_read_frame(fmt_ctx, &packet) > 0), the method
immediately passes, making nothing happen.
I turned on debug in my stream, and this is the output (not much makes
sense/looks useful to me)
https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5
lt4/view?usp=sharing
Let me know what you think. Thanks!
Chris Bennett
Hey Chris,
Can you try using
while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
while(!feof(f))
and then just send a packet to your decode method instead of a raw frame?
*Sent: *31 August 2018 22:57
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files distorted?
(v4.0.2Winbuild)
Hey Strahinja!
Thank you very much for taking the time to help me out.
the pgm snippet you sent looks the same as the decode video example I am seeing.
Here is the code that I am compiling and running if it helps, hopefully
its not too long. ( I had to add an extern "C" wrapper since my goal is to
build c++ tools with this, and also changed how the example finds the
decoder).
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* video decoding with libavcodec API example
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
#define INBUF_SIZE 4096
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;
ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}
printf("saving frame %3d\n",
dec_ctx->frame_number);
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm",
filename, dec_ctx->frame_number);
pgm_save(frame->data[0],
frame->linesize[0],
frame->width,
frame->height, buf);
}
}
int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t data_size;
int ret;
AVPacket *pkt;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file>
<output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];
pkt = av_packet_alloc();
if (!pkt)
exit(1);
/* set end of buffer to 0 (this ensures that no
overreading happens for damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0,
AV_INPUT_BUFFER_PADDING_SIZE);
//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate
memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->
codecpar;
//-----
/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCodecParameters->codec_
id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video
codec context\n");
exit(1);
}
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}
f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret =
av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data,
data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;
if (pkt->size)
decode(c,
frame, pkt, outfilename);
}
}
/* flush the decoder */
decode(c, frame, NULL, outfilename);
fclose(f);
av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}
Please let me know if you see anything incorrect with this.
Thanks!
Chris Bennett
Lead Animation Pipeline TD - Television
http://www.dreamworksanimation.com/brand/signatures/Central/CentralEmailSigs06.jpg]
Hi Chris,
To me that looks like you wrote some wrong data inside the picture and it
looks skewed. Some indexes could be wrong.
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
The above method should be called with pgm_save(frame->data[0],
frame->linesize[0], frame->width, frame->height, “name.pgm”);
Kind regards,
Strahinja
*Sent: *31 August 2018 19:41
*Subject: *[Libav-user] decode_video example pgm files distorted? (v4.0.2
Winbuild)
Hello All!
My apologies if this is a rookie question as I am just now learning the
innards of ffmpeg, but I am reaching out hoping someone may have had the
same issue as myself or has any advice.
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing
decode_video. I ended up with this result: https://drive.google.com/file/
d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
At the top and bottom of the image there is is wavy distortion. I am not
sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
I had also compiled the exe as well and ran this command
ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2
C:/frame-%03d.jpg
and those images turned out just fine (I am sure this probably runs some
completely different underlying code but I just wanted to make sure what I
compiled was capable of a successful result)
I figure I am doing something incorrectly but I do not know where else to
look. If anyone has any advice on what to tinker with, I would greatly
appreciate it.
Thanks,
Chris Bennett
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user
_______________________________________________
Libav-user mailing list
http://ffmpeg.org/mailman/listinfo/libav-user
_______________________________________________
Libav-user mailing list
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[Strahinja Radman]

Chris,

There is an error on my side, replace
av_read_frame(pFormatContext, &pkt) > 0
with
av_read_frame(pFormatContext, &pkt) >= 0

av_read_frame returns less then zero if there is an error, but zero or above is fine. 😊. Sorry.

Kind regards,
Strahinja



From: Chris Bennett
Sent: 05 September 2018 18:48
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgmfilesdistorted?(v4.0.2Winbuild)

Hey Strahinja,

I tried to recreate what you sent me, but I ended up with the same issue as previous with the av_read_frame giving me 0.
I must have built my ffmpeg libs incorrectly or messed up my project settings, because these examples seems straightforward yet not working for me as intended.

I will also take a look at transcoding.c and see if I can find anything there that can also assist my learning.

Thank you again for your time and help!


Chris Bennett

On Wed, Sep 5, 2018 at 6:37 AM, Strahinja Radman <***@gmail.com> wrote:
Chris,
 
I am using something similar to this and its working properly:
 
 
                ret = avformat_open_input(&pFormatContext, input_filename, NULL, NULL);
                if (ret < 0)
                                return ret;
 
                ret = avformat_find_stream_info(pFormatContext, NULL);
                if (ret < 0)
                                return ret;
 
 
                //I assume you only have 1 stream
                AVCodec *dec = avcodec_find_decoder(pFormatContext->streams[0]->codecpar->codec_id);
 
                if (!dec)
                                printf("Failed to find decoder for stream ");
 
                decoder = avcodec_alloc_context3(NULL);
                if (!decoder)
                                printf("Failed to allocate the decoder context for stream ");
 
                ret = avcodec_parameters_to_context(decoder, pFormatContext->streams[0]->codecpar);
                if (ret < 0)
                                printf("Failed to copy decoder parameters to input decoder context for stream ");
 
                ret = avcodec_open2(decoder, dec, NULL);
                if (ret < 0)
                                printf("Failed to open decoder for stream ");
 
 
                while (av_read_frame(pFormatContext, &pkt) > 0) {
                                decode(decoder, frame, &pkt, outfilename);
                }
 
I cant test your code so I am not quite sure why doesn’t it work. I would suggest that you look into the transcoding.c example also.
 
From: Chris Bennett
Sent: 04 September 2018 22:42

To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm filesdistorted?(v4.0.2Winbuild)
 
Hey Strahinja,
 
Yeah that is what I have. Here is the link to the latest version of the modified code:
 
https://drive.google.com/file/d/1UQaGv4EwEj81hqk7GNeVz5hGFG0784RD/view?usp=sharing
 
Let me know what you think.
 
Thanks


Chris Bennett
 
On Tue, Sep 4, 2018 at 12:06 PM, Strahinja Radman <***@gmail.com> wrote:
Hey Chris,
 
I am not sure how exactly you modified your code but this should be the look of the loop
 
while(av_read_frame(fmt_ctx, &packet) > 0)
{
                decode(c, frame, pkt, outfilename);
}
 
Kind regards,
Strahinja
 
From: Chris Bennett
Sent: 04 September 2018 20:54

To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted?(v4.0.2Winbuild)
 
Hm. Here is something strange.
 
When I try using  while(av_read_frame(fmt_ctx, &packet) > 0), the method immediately passes, making nothing happen.
 
I turned on debug in my stream, and this is the output (not much makes sense/looks useful to me)
 
https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5lt4/view?usp=sharing
 
Let me know what you think. Thanks!


Chris Bennett
 
On Sat, Sep 1, 2018 at 12:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hey Chris,
 
Can you try using
                while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
                while(!feof(f))
 
and then just send a packet to your decode method instead of a raw frame?
 
From: Chris Bennett
Sent: 31 August 2018 22:57
To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
Subject: Re: [Libav-user] decode_video example pgm files distorted? (v4.0.2Winbuild)
 
Hey Strahinja!
 
Thank you very much for taking the time to help me out.
 
the pgm snippet you sent looks the same as the decode video example I am seeing.
 
Here is the code that I am compiling and running if it helps, hopefully its not too long. ( I had to add an extern "C" wrapper since my goal is to build c++ tools with this, and also changed how the example finds the decoder).
 
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
 
/**
* @file
* video decoding with libavcodec API example
*
* @example decode_video.c
*/
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
 
#define INBUF_SIZE 4096
 
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
                char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
                const char *filename)
{
                char buf[1024];
                int ret;
 
                ret = avcodec_send_packet(dec_ctx, pkt);
                if (ret < 0) {
                                fprintf(stderr, "Error sending a packet for decoding\n");
                                exit(1);
                }
 
                while (ret >= 0) {
                                ret = avcodec_receive_frame(dec_ctx, frame);
                                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                                                return;
                                else if (ret < 0) {
                                                fprintf(stderr, "Error during decoding\n");
                                                exit(1);
                                }
 
                                printf("saving frame %3d\n", dec_ctx->frame_number);
                                fflush(stdout);
 
                                /* the picture is allocated by the decoder. no need to
                                free it */
                                _snprintf(buf, sizeof(buf), "%s-%d.pgm", filename, dec_ctx->frame_number);
                                pgm_save(frame->data[0], frame->linesize[0],
                                                frame->width, frame->height, buf);
                }
}
 
int main(int argc, char **argv)
{
                const char *filename, *outfilename;
                const AVCodec *codec;
                AVCodecParserContext *parser;
                AVCodecContext *c = NULL;
                FILE *f;
                AVFrame *frame;
                uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
                uint8_t *data;
                size_t   data_size;
                int ret;
                AVPacket *pkt;
 
                if (argc <= 2) {
                                fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
                                exit(0);
                }
                filename = argv[1];
                outfilename = argv[2];
 
                pkt = av_packet_alloc();
                if (!pkt)
                                exit(1);
 
                /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
                memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 
 
                //---from test1.cpp
                AVFormatContext *pFormatContext = avformat_alloc_context();
                if (!pFormatContext) {
                                fprintf(stderr, "ERROR could not allocate memory for Format Context");
                                return -1;
                }
                if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
                                fprintf(stderr, "ERROR could not open the file");
                                return -1;
                }
                AVCodecParameters *pLocalCodecParameters = NULL;
                pLocalCodecParameters = pFormatContext->streams[0]->codecpar;
                //-----
 
                /* find the video decoder */
                //codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
                codec = avcodec_find_decoder(pLocalCodecParameters->codec_id);
                if (!codec) {
                                fprintf(stderr, "Codec not found\n");
                                exit(1);
                }
 
                parser = av_parser_init(codec->id);
                if (!parser) {
                                fprintf(stderr, "parser not found\n");
                                exit(1);
                }
 
                c = avcodec_alloc_context3(codec);
                if (!c) {
                                fprintf(stderr, "Could not allocate video codec context\n");
                                exit(1);
                }
 
                /* For some codecs, such as msmpeg4 and mpeg4, width and height
                MUST be initialized there because this information is not
                available in the bitstream. */
 
                /* open it */
                if (avcodec_open2(c, codec, NULL) < 0) {
                                fprintf(stderr, "Could not open codec\n");
                                exit(1);
                }
 
                f = fopen(filename, "rb");
                if (!f) {
                                fprintf(stderr, "Could not open %s\n", filename);
                                exit(1);
                }
 
                frame = av_frame_alloc();
                if (!frame) {
                                fprintf(stderr, "Could not allocate video frame\n");
                                exit(1);
                }
 
                while (!feof(f)) {
                                /* read raw data from the input file */
                                data_size = fread(inbuf, 1, INBUF_SIZE, f);
                                if (!data_size)
                                                break;
 
                                /* use the parser to split the data into frames */
                                data = inbuf;
                                while (data_size > 0) {
                                                ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
                                                                data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
                                                if (ret < 0) {
                                                                fprintf(stderr, "Error while parsing\n");
                                                                exit(1);
                                                }
                                                data += ret;
                                                data_size -= ret;
 
                                                if (pkt->size)
                                                                decode(c, frame, pkt, outfilename);
                                }
                }
 
                /* flush the decoder */
                decode(c, frame, NULL, outfilename);
 
                fclose(f);
 
                av_parser_close(parser);
                avcodec_free_context(&c);
                av_frame_free(&frame);
                av_packet_free(&pkt);
 
                return 0;
}
 
Please let me know if you see anything incorrect with this.
 
Thanks!
 


Chris Bennett
Lead Animation Pipeline TD - Television

 
On Fri, Aug 31, 2018 at 10:48 AM, Strahinja Radman <***@gmail.com> wrote:
Hi Chris,
 
To me that looks like you wrote some wrong data inside the picture and it looks skewed. Some indexes could be wrong.
 
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
                FILE *f;
                int i;
 
                f = fopen(filename, "w");
                fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
                for (i = 0; i < ysize; i++)
                                fwrite(buf + i * wrap, 1, xsize, f);
                fclose(f);
}
 
The above method should be called with pgm_save(frame->data[0], frame->linesize[0], frame->width, frame->height, “name.pgm”);
 
Kind regards,
Strahinja
 
From: Chris Bennett
Sent: 31 August 2018 19:41
To: libav-***@ffmpeg.org
Subject: [Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
 
Hello All!
 
My apologies if this is a rookie question as I am just now learning the innards of ffmpeg, but I am reaching out hoping someone may have had the same issue as myself or has any advice.
 
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing decode_video. I ended up with this result:  https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
 
At the top and bottom of the image there is is wavy distortion. I am not sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
 
I had also compiled the exe as well and ran this command
 
ffmpeg.exe -ss 0.5 -i my_quicktime.mov  -t 1 -s 480x300 -f image2 C:/frame-%03d.jpg
 
and those images turned out just fine (I am sure this probably runs some completely different underlying code but I just wanted to make sure what I compiled was capable of a successful result)
 
I figure I am doing something incorrectly but I do not know where else to look. If anyone has any advice on what to tinker with, I would greatly appreciate it.
 
Thanks,
Chris Bennett
 

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[Chris Bennett]

Hey Strahinja!

That did it, now I am getting the pgm files saved out again.

Unfortunately I am still getting the same wavy distortion results from the
beginning.
I am going to change some flags on my end to change up the compile, and see
if I stumble over the fix.

Thanks

Chris Bennett

Post by Strahinja Radman
Chris,
There is an error on my side, replace
av_read_frame(pFormatContext, &pkt) > 0
with
av_read_frame(pFormatContext, &pkt) >= 0
av_read_frame returns less then zero if there is an error, but zero or
above is fine. 😊. Sorry.
Kind regards,
Strahinja
*Sent: *05 September 2018 18:48
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgmfilesdistorted?(v4.0.
2Winbuild)
Hey Strahinja,
I tried to recreate what you sent me, but I ended up with the same issue
as previous with the av_read_frame giving me 0.
I must have built my ffmpeg libs incorrectly or messed up my project
settings, because these examples seems straightforward yet not working for
me as intended.
I will also take a look at transcoding.c and see if I can find anything
there that can also assist my learning.
Thank you again for your time and help!
Chris Bennett
Chris,
ret = avformat_open_input(&pFormatContext,
input_filename, NULL, NULL);
if (ret < 0)
return ret;
ret = avformat_find_stream_info(pFormatContext, NULL);
if (ret < 0)
return ret;
//I assume you only have 1 stream
AVCodec *dec = avcodec_find_decoder(
pFormatContext->streams[0]->codecpar->codec_id);
if (!dec)
printf("Failed to find decoder for stream ");
decoder = avcodec_alloc_context3(NULL);
if (!decoder)
printf("Failed to allocate the decoder
context for stream ");
ret = avcodec_parameters_to_context(decoder,
pFormatContext->streams[0]->codecpar);
if (ret < 0)
printf("Failed to copy decoder parameters
to input decoder context for stream ");
ret = avcodec_open2(decoder, dec, NULL);
if (ret < 0)
printf("Failed to open decoder for stream ");
while (av_read_frame(pFormatContext, &pkt) > 0) {
decode(decoder, frame, &pkt, outfilename);
}
I cant test your code so I am not quite sure why doesn’t it work. I would
suggest that you look into the transcoding.c example also.
*Sent: *04 September 2018 22:42
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm filesdistorted?(v4.0.
2Winbuild)
Hey Strahinja,
https://drive.google.com/file/d/1UQaGv4EwEj81hqk7GNeVz5hGFG078
4RD/view?usp=sharing
Let me know what you think.
Thanks
Chris Bennett
Hey Chris,
I am not sure how exactly you modified your code but this should be the look of the loop
while(av_read_frame(fmt_ctx, &packet) > 0)
{
decode(c, frame, pkt, outfilename);
}
Kind regards,
Strahinja
*Sent: *04 September 2018 20:54
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files
distorted?(v4.0.2Winbuild)
Hm. Here is something strange.
When I try using while(av_read_frame(fmt_ctx, &packet) > 0), the method
immediately passes, making nothing happen.
I turned on debug in my stream, and this is the output (not much makes
sense/looks useful to me)
https://drive.google.com/file/d/1Twft75sGLGGsHN5tuwkcI1KQVsPM5
lt4/view?usp=sharing
Let me know what you think. Thanks!
Chris Bennett
Hey Chris,
Can you try using
while(av_read_frame(fmt_ctx, &packet) > 0)
instead of using
while(!feof(f))
and then just send a packet to your decode method instead of a raw frame?
*Sent: *31 August 2018 22:57
*To: *This list is about using libavcodec, libavformat, libavutil,
*Subject: *Re: [Libav-user] decode_video example pgm files distorted?
(v4.0.2Winbuild)
Hey Strahinja!
Thank you very much for taking the time to help me out.
the pgm snippet you sent looks the same as the decode video example I am seeing.
Here is the code that I am compiling and running if it helps, hopefully
its not too long. ( I had to add an extern "C" wrapper since my goal is to
build c++ tools with this, and also changed how the example finds the
decoder).
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* video decoding with libavcodec API example
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
#define INBUF_SIZE 4096
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;
ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}
printf("saving frame %3d\n",
dec_ctx->frame_number);
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm",
filename, dec_ctx->frame_number);
pgm_save(frame->data[0],
frame->linesize[0],
frame->width,
frame->height, buf);
}
}
int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t data_size;
int ret;
AVPacket *pkt;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file>
<output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];
pkt = av_packet_alloc();
if (!pkt)
exit(1);
/* set end of buffer to 0 (this ensures that no
overreading happens for damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0,
AV_INPUT_BUFFER_PADDING_SIZE);
//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate
memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->
codecpar;
//-----
/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCodecParameters->codec_
id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video
codec context\n");
exit(1);
}
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}
f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret =
av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data,
data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;
if (pkt->size)
decode(c,
frame, pkt, outfilename);
}
}
/* flush the decoder */
decode(c, frame, NULL, outfilename);
fclose(f);
av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}
Please let me know if you see anything incorrect with this.
Thanks!
Chris Bennett
Lead Animation Pipeline TD - Television
http://www.dreamworksanimation.com/brand/signatures/Central/CentralEmailSigs06.jpg]
Hi Chris,
To me that looks like you wrote some wrong data inside the picture and it
looks skewed. Some indexes could be wrong.
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
{
FILE *f;
int i;
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
}
The above method should be called with pgm_save(frame->data[0],
frame->linesize[0], frame->width, frame->height, “name.pgm”);
Kind regards,
Strahinja
*Sent: *31 August 2018 19:41
*Subject: *[Libav-user] decode_video example pgm files distorted? (v4.0.2
Winbuild)
Hello All!
My apologies if this is a rookie question as I am just now learning the
innards of ffmpeg, but I am reaching out hoping someone may have had the
same issue as myself or has any advice.
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing
decode_video. I ended up with this result: https://drive.google.com/file/
d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
At the top and bottom of the image there is is wavy distortion. I am not
sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
I had also compiled the exe as well and ran this command
ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2
C:/frame-%03d.jpg
and those images turned out just fine (I am sure this probably runs some
completely different underlying code but I just wanted to make sure what I
compiled was capable of a successful result)
I figure I am doing something incorrectly but I do not know where else to
look. If anyone has any advice on what to tinker with, I would greatly
appreciate it.
Thanks,
Chris Bennett
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