> On May 24, 2023, at 08:45, Joseph Chris <jos...@josephcz.xyz> wrote:
>
> Hello,
>
> I am writing this mail for request consider use codec id "sowt" instead of
> "ipcm" for AV_CODEC_ID_PCM_S16LE in mp4 muxer, and AV_CODEC_ID_PCM_S16BE
> accordingly. This only needs a minor change on code:
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index a9c8e104f0..2b984789f5 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -7816,6 +7816,9 @@ static const AVCodecTag codec_mp4_tags[] = {
> { AV_CODEC_ID_TTML, MOV_MP4_TTML_TAG },
> { AV_CODEC_ID_TTML, MOV_ISMV_TTML_TAG },
>
> + // To improve compatibility
> + { AV_CODEC_ID_PCM_S16BE, MKTAG('t', 'w', 'o', 's') },
> + { AV_CODEC_ID_PCM_S16LE, MKTAG('s', 'o', 'w', 't') },
> /* ISO/IEC 23003-5 integer formats */
> { AV_CODEC_ID_PCM_S16BE, MOV_MP4_IPCM_TAG },
> { AV_CODEC_ID_PCM_S16LE, MOV_MP4_IPCM_TAG },
>
Nope, they are tags of quicktime format, not ISO base media file format.
>
> Many players like VLC and potplayer, can recognize "sowt", but they can not
> recognize "ipcm" or "lpcm" (lpcm is defined on mp4ra). Even ffmpeg it self
> (current git master, d81558) can't recognize it. So this change can improve
> compatibility and interoperability of ffmpeg.
I can’t find d81558.
>
> This change is related to #9219 and #10185.
They have been fixed. I will update the status.
>
> This change fails fate-mov-mp4-pcm but passes all other tests.
> fate-mov-mp4-pcm checks the MD5 of output file, as the codec id changes also
> makes the MD5 change. So we have to rewrite the test while changing the code.
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