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

[Måns Rullgård]

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.

-- 
M?ns Rullg?rd
mans at mansr.com