[libav-user] [swscale] How to use sws_scale ?

[Stephane List]

Hi,

Since img_convert is deprecated, I'm trying to use sws_scale from the
latest svn.

The prototype of sws_scale is :
int sws_scale(SwsContext *c, uint8_t* src[], int srcStride[], int
srcSliceY, int srcSliceH, uint8_t* dst[], int dstStride[])

I want to convert from RGB8 to YUV420P from a buffer srcdata to a buffer
dstdata.

Here is my code in C++:

int src_pix_fmt = PIX_FMT_RGB8;
int dst_pix_fmt = PIX_FMT_YUV420P;
int w = 320;
int h = 240;
struct SwsContext *img_convert_ctx = sws_getContext(w, h, src_pix_fmt,
w, h, dst_pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);
if (img_convert_ctx == NULL) {
qDebug() << "Cannot initialize the conversion context!";
return;
}
int srcStride[3];
int dstStride[3];
uint8_t *src[3]= {srcdata, NULL, NULL};
uint8_t *dst[3]= {dstdata, NULL, NULL};
sws_scale(img_convert_ctx, src, srcStride, 0, h, dst, dstStride);



What should I put in srcStride and dstStride ?
Is the rest correct ?

Regards

Stephane

[Rafael Maia]

Hi,

here`s an example:




SwsContext* encoderSwsContext;
AVFrame* encoderRawFrame;
AVFrame* encoderRescaledFrame;

// init and fill the encoderRawFrame with your image data

// init encoderRescaledFrame

encoderSwsContext = sws_getCachedContext(encoderSwsContext, src_width, src_height, PIX_FMT_RGB24, dst_width, dst_height, YUV420P, SWS_BICUBIC, NULL, NULL, NULL);

sws_scale(encoderSwsContext, encoderRawFrame->data, encoderRawFrame->linesize, 0, src_height, encoderRescaledFrame->data, encoderRescaledFrame->linesize);



I hope this helps.

Rafael Maia

Date: Thu, 11 Sep 2008 17:17:24 +0200> From: slist at lilotux.net> To: libav-user at mplayerhq.hu> Subject: [libav-user] [swscale] How to use sws_scale ?> > Hi,> > Since img_convert is deprecated, I'm trying to use sws_scale from the> latest svn.> > The prototype of sws_scale is :> int sws_scale(SwsContext *c, uint8_t* src[], int srcStride[], int> srcSliceY, int srcSliceH, uint8_t* dst[], int dstStride[])> > I want to convert from RGB8 to YUV420P from a buffer srcdata to a buffer> dstdata.> > Here is my code in C++:> > int src_pix_fmt = PIX_FMT_RGB8;> int dst_pix_fmt = PIX_FMT_YUV420P;> int w = 320;> int h = 240;> struct SwsContext *img_convert_ctx = sws_getContext(w, h, src_pix_fmt,> w, h, dst_pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);> if (img_convert_ctx == NULL) {> qDebug() << "Cannot initialize the conversion context!";> return;> }> int srcStride[3];> int dstStride[3];> uint8_t *src[3]= {srcdata, NULL, NULL};> uint8_t *dst[3]= {dstdata, NULL, NULL};> sws_scale(img_convert_ctx, src, srcStride, 0, h, dst, dstStride);> > > > What should I put in srcStride and dstStride ?> Is the rest correct ?> > Regards> > Stephane> _______________________________________________> libav-user mailing list> libav-user at mplayerhq.hu> https://lists.mplayerhq.hu/mailman/listinfo/libav-user

_________________________________________________________________
Cansado de espa?o para s? 50 fotos? Conhe?a o Spaces, o site de relacionamentos com at? 6,000 fotos!
http://www.amigosdomessenger.com.br

[Luca Abeni]

Post by Stephane List
Hi,
Since img_convert is deprecated, I'm trying to use sws_scale from the
latest svn.
int sws_scale(SwsContext *c, uint8_t* src[], int srcStride[], int
srcSliceY, int srcSliceH, uint8_t* dst[], int dstStride[])
I want to convert from RGB8 to YUV420P from a buffer srcdata to a buffer
dstdata.

There is some example code that you can use as a reference in
libswscale/swscale-example.c (I do not know why all the examples and demos
are in different directories ;-); otherwise, you can look at ffmpeg.c for
some seeing how to use sws_scale()

Post by Stephane List
int src_pix_fmt = PIX_FMT_RGB8;
int dst_pix_fmt = PIX_FMT_YUV420P;
int w = 320;
int h = 240;
struct SwsContext *img_convert_ctx = sws_getContext(w, h, src_pix_fmt,
w, h, dst_pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);
if (img_convert_ctx == NULL) {
qDebug() << "Cannot initialize the conversion context!";
return;
}
int srcStride[3];
int dstStride[3];
uint8_t *src[3]= {srcdata, NULL, NULL};
uint8_t *dst[3]= {dstdata, NULL, NULL};

I do not know about RGB8, but for YUV420P this looks wrong (the Y, U, and
V planes are in different components of the array) - see the "data" field
in in AVFrame or AVPicture.

Post by Stephane List
What should I put in srcStride and dstStride ?

The number of bytes per line that you want to process. If you want to
process the whole video frame at one time, you can use the "linesize"
field of AVFrame or AVPicture.


Luca

[Stephane List]

Hi,

Thanks a lot Luca and Raphael,
It's working know,

I'm using AVPicture and avpicture_fill to avoid to have to fill all
complicated structures needed by sws_scale.

Regards

Stephane

Post by Luca Abeni

Post by Stephane List
Hi,
Since img_convert is deprecated, I'm trying to use sws_scale from the
latest svn.
int sws_scale(SwsContext *c, uint8_t* src[], int srcStride[], int
srcSliceY, int srcSliceH, uint8_t* dst[], int dstStride[])
I want to convert from RGB8 to YUV420P from a buffer srcdata to a buffer
dstdata.

There is some example code that you can use as a reference in
libswscale/swscale-example.c (I do not know why all the examples and demos
are in different directories ;-); otherwise, you can look at ffmpeg.c for
some seeing how to use sws_scale()

Post by Stephane List
int src_pix_fmt = PIX_FMT_RGB8;
int dst_pix_fmt = PIX_FMT_YUV420P;
int w = 320;
int h = 240;
struct SwsContext *img_convert_ctx = sws_getContext(w, h, src_pix_fmt,
w, h, dst_pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);
if (img_convert_ctx == NULL) {
qDebug() << "Cannot initialize the conversion context!";
return;
}
int srcStride[3];
int dstStride[3];
uint8_t *src[3]= {srcdata, NULL, NULL};
uint8_t *dst[3]= {dstdata, NULL, NULL};

I do not know about RGB8, but for YUV420P this looks wrong (the Y, U, and
V planes are in different components of the array) - see the "data" field
in in AVFrame or AVPicture.

Post by Stephane List
What should I put in srcStride and dstStride ?

The number of bytes per line that you want to process. If you want to
process the whole video frame at one time, you can use the "linesize"
field of AVFrame or AVPicture.
Luca
_______________________________________________
libav-user mailing list
libav-user at mplayerhq.hu
https://lists.mplayerhq.hu/mailman/listinfo/libav-user