[FFmpeg-devel] [PATCH] attachments support in matroska demuxer

Baptiste Coudurier baptiste.coudurier
Sun Jan 20 16:43:05 CET 2008


Michael Niedermayer wrote:
> Hi
> On Sun, Jan 20, 2008 at 10:10:50AM +0100, Reimar D?ffinger wrote:
>> Hello,
>> On Sun, Jan 20, 2008 at 03:42:09AM +0100, Michael Niedermayer wrote:
>> [...]
>>>>> iam against some undocumented char *type
>>>>> please document precissely what it repressents and how it differs from
>>>>> codec_tag, stream_codec_tag and codec_id
>>>>> or even better get rid of it and use codec_tag or explain why the type
>>>>> here should be special cased relative to these funny codec id strings in
>>>>> matroska
>>>> Currently, *type stores the standard mime type of the attachment.
>>> so it idetifies what the attachment is ...
>>> thats what codec_tag does alraedy ...
>> Sorry to be so flameish, but no, maybe codec_id does that, but codec_tag
>> certainly does not. E.g. for mp4 files all kind of audio has mp4a as
>> codec_tag and some other things like that.
> the mp4 demuxer is buggy, it intentionally violates the API as baptiste doesnt
> agree with the API. And choose to set codec_tag to something else than what
> it is supposed to be

We already discussed this issue, it is unclear in mp4 if codec_tag is
'stsd' tag or 'esds' objecttype id. Now mp3on4 use same object type id
as aac, so in that case it won't work anyway.

I would agree to set codec_tag to 'esds' objecttype id if mp4 muxer is
modified to correctly handle it in case of stream copy, and still where
is codec_tag supposed to be put in mp4 ? 'stsd' tag or objecttype id in
'esds' ? We are creating 'isom' brand mp4.

Since this is becoming a recurrent issue, I'll just forbid setting
'stsd' tag nor 'esds' objectype id to something specs does not define
for 3gp/mp4. I'll apply the modifications soon.

> (not that mpeg-ps/ts and matroska would set codec_tag correctly ...)

Yes, mpeg-ps should set codec_tag to startcode.


Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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