[Ffmpeg-devel] [RFC] mp4 object types comments

[Baptiste Coudurier]

Hi

M?ns Rullg?rd wrote:
> Baptiste Coudurier <baptiste.coudurier at smartjog.com> writes:
> 
>> Hi
>>
>> Here are some modifications to mp4 object types Im not sure, can someone
>> confirm that 13818-3 can be decoded with MP2 id ?
> 
> 13818-3 extends 11172-3 (MPEG1 audio) with lower sampling rates and
> more channels.  An 11172-3 decoder will correctly decode basic stereo
> from a 13818-3 stream.  There are 3 defined layers corresponding to
> those in 11172-3.
> 
>> Index: libavformat/isom.c
>> ===================================================================
>> --- libavformat/isom.c	(revision 8491)
>> +++ libavformat/isom.c	(working copy)
>> @@ -25,7 +25,7 @@
>>  #include "riff.h"
>>  #include "isom.h"
>>  
>> -/* http://gpac.sourceforge.net/tutorial/mediatypes.htm */
>> +/* http://www.mp4ra.org */
>>  const AVCodecTag ff_mov_obj_type[] = {
>>      { CODEC_ID_MPEG4     ,  32 },
>>      { CODEC_ID_H264      ,  33 },
> 
> This hunk is OK, assuming the URL is relevant.
> 
>> @@ -39,10 +39,10 @@
>>      { CODEC_ID_AAC       , 102 }, /* MPEG2 AAC Main */
>>      { CODEC_ID_AAC       , 103 }, /* MPEG2 AAC Low */
>>      { CODEC_ID_AAC       , 104 }, /* MPEG2 AAC SSR */
>> -    { CODEC_ID_MP3       , 105 },
>> -    { CODEC_ID_MPEG1VIDEO, 106 },
>> -    { CODEC_ID_MP2       , 107 },
>> -    { CODEC_ID_MJPEG     , 108 },
>> +    { CODEC_ID_MP2       , 105 }, /* 13818-3 */
>> +    { CODEC_ID_MPEG1VIDEO, 106 }, /* 11172-2 */
>> +    { CODEC_ID_MP3       , 107 }, /* 11172-3 */
>> +    { CODEC_ID_MJPEG     , 108 }, /* 10918-1 */
>>      { CODEC_ID_PCM_S16LE , 224 },
>>      { CODEC_ID_VORBIS    , 221 },
>>      { CODEC_ID_QCELP     , 225 },
> 
> This mixes addition of comments with actual changes.  The added
> comments are fine.  The changed codec IDs are not.  All MPEG audio
> should use CODEC_ID_MP3.  Please make it so, but add the other two
> comments separately.

Yes. About codec_id, are you sure ? Different tags are needed if
codec_id is MP2 or MP3, and when stream copying codec_id is not
changed/altered.

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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