[libav-user] ID3 Tags in ADTS AAC problem

[debanjana kayal]

Hi ,
I am using FFmpeg release verion 0.5 and i found that ffmpeg does not remove the ID3 tags from the packets.It can not detect the ID3 tags.
Thus I took the nightly build (26 Jun 05) and it seem to be able to detect the ID3 tags and strip the tag from the begining.
Hower if the tags are at the end of the file , it still have it and could not strip.
Could you provide some pointers.
Best Regards
Raja


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[Patrick Dehne]

debanjana kayal <debanjana.kayal at yahoo.com> writes:

Hi,

Post by debanjana kayal
I am using FFmpeg release verion 0.5 and i found that ffmpeg does not remove the ID3 tags from the packets.It can not detect the ID3 tags.
Thus I took the nightly build (26 Jun 05) and it seem to be able to detect the ID3 tags and strip the tag from the begining.
Hower if the tags are at the end of the file , it still have it and could not strip.

You are right. ID3 tag parsing for adts aac streams was a recent
addition. It is not part of version 0.5. The ID3V2 tag is parsed and
skipped. The ID3V1 tag is also parsed at the very beginning. I am not
sure if the ID3V1 tag was ever skipped.

Post by debanjana kayal
Could you provide some pointers.

The function adts_aac_read_header in libavformat/raw.c calls
ff_id3v1_read of libavformat/id3v1.h.

As said above, I am not aware of code that checks for ID3V1 tags in a
stream and makes sure it is skipped.

I think what should happen is that decoding should fail, automatically
skipping the ID3V1 tag while the parser tries to resync. If this is how
it should work, what you are seeing is a special case of the more
general issue 999 in roundup.

Patrick

[debanjana kayal]

--- On Thu, 2/7/09, Patrick Dehne <patrick at mysonicweb.com> wrote:


From: Patrick Dehne <patrick at mysonicweb.com>
Subject: Re: [libav-user] ID3 Tags in ADTS AAC problem
To: libav-user at mplayerhq.hu
Date: Thursday, 2 July, 2009, 7:43 AM


debanjana kayal <debanjana.kayal at yahoo.com> writes:

Hi,

Post by debanjana kayal
I am using FFmpeg release verion 0.5 and i found that ffmpeg does not remove the ID3 tags from the packets.It can not detect the ID3 tags.
Thus I took the nightly build (26 Jun 05) and it seem to be able to detect the ID3 tags and strip the tag from the begining.
Hower if the tags are at the end of the file , it still have it and could not strip.

You are right. ID3 tag parsing for adts aac streams was a recent
addition. It is not part of version 0.5. The ID3V2 tag is parsed and
skipped. The ID3V1 tag is also parsed at the very beginning. I am not
sure if the ID3V1 tag was ever skipped.

Post by debanjana kayal
Could you provide some pointers.

The function adts_aac_read_header in libavformat/raw.c calls
ff_id3v1_read of libavformat/id3v1.h.

As said above, I am not aware of code that checks for ID3V1 tags in a
stream and makes sure it is skipped.

I think what should happen is that decoding should fail, automatically
skipping the ID3V1 tag while the parser tries to resync. If this is how
it should work, what you are seeing is a special case of the more
general issue 999 in roundup.
?
That is my question why does the av_read_frame () returns me a packet with data from the ID3 tags .Should it not skip .I thought av_read_frame will always return me a valid packet or an error.
It is a bug in av_read_frame ()?

Patrick
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[Patrick Dehne]

Post by Patrick Dehne
Hi,

Post by debanjana kayal
I am using FFmpeg release verion 0.5 and i found that ffmpeg does not remove the ID3 tags from the packets.It can not detect the ID3 tags.
Thus I took the nightly build (26 Jun 05) and it seem to be able to detect the ID3 tags and strip the tag from the begining.
Hower if the tags are at the end of the file , it still have it and could not strip.

You are right. ID3 tag parsing for adts aac streams was a recent
addition. It is not part of version 0.5. The ID3V2 tag is parsed and
skipped. The ID3V1 tag is also parsed at the very beginning. I am not
sure if the ID3V1 tag was ever skipped.

Post by debanjana kayal
Could you provide some pointers.

The function adts_aac_read_header in libavformat/raw.c calls
ff_id3v1_read of libavformat/id3v1.h.
As said above, I am not aware of code that checks for ID3V1 tags in a
stream and makes sure it is skipped.
I think what should happen is that decoding should fail, automatically
skipping the ID3V1 tag while the parser tries to resync. If this is how
it should work, what you are seeing is a special case of the more
general issue 999 in roundup.
?
That is my question why does the av_read_frame () returns me a packet with data from the ID3 tags .Should it not skip .I thought av_read_frame will always return me a valid packet or an error.
It is a bug in av_read_frame ()?

If you think this is a bug, I suggest to file a bugreport on the ffmpeg
bugtracker.

Patrick