On Fri, Nov 20, 2020 at 10:53 PM Jan Ekström <jee...@gmail.com> wrote: > > On Fri, Nov 20, 2020 at 7:02 PM Leo Izen <leo.i...@gmail.com> wrote: > > > > MP4 already supports Apple Lossless, and it can be put inside by using > > muxer=ipod, but it's not tagged as supported in mp4. The mp4ra lists > > alac as a valid fourcc inside mp4, so it should be supported by spec. > > > > See: https://mp4ra.org/#/codecs > > I would just note in the paragraph that the identifier has been > registered to ISO and thus towards ISOBMFF (which we usually call > "mp4") at the MP4 registration authority. > > This can be changed when applying the patch, so no second revision > needed for this change. > > > --- > > libavformat/movenc.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/libavformat/movenc.c b/libavformat/movenc.c > > index fea8a86192..18fa3f9b5e 100644 > > --- a/libavformat/movenc.c > > +++ b/libavformat/movenc.c > > @@ -7128,6 +7128,7 @@ static const AVCodecTag codec_mp4_tags[] = { > > { AV_CODEC_ID_VP9, MKTAG('v', 'p', '0', '9') }, > > { AV_CODEC_ID_AV1, MKTAG('a', 'v', '0', '1') }, > > { AV_CODEC_ID_AAC, MKTAG('m', 'p', '4', 'a') }, > > + { AV_CODEC_ID_ALAC, MKTAG('a', 'l', 'a', 'c') }, > > { AV_CODEC_ID_MP4ALS, MKTAG('m', 'p', '4', 'a') }, > > { AV_CODEC_ID_MP3, MKTAG('m', 'p', '4', 'a') }, > > { AV_CODEC_ID_MP2, MKTAG('m', 'p', '4', 'a') }, > > -- > > 2.29.2 > > > > Not sure of the location in the list (this matches the ipod muxer's > ordering, while additional formats seem to have just been added into > their list/group as they popped up - that said since this is a static > symbol I would expect even if the addition was in the middle, it > should be a-OK), but after taking a quick look at the ALAC code paths > this seems to cause writing of boxes that seem to make sense (audio > description plus whatever is in the extradata). > > I will attempt to check tomorrow if there's a spec for this to > double-check against, but preliminarily this looks good to me.
Verified against the spec (https://github.com/macosforge/alac/blob/master/ALACMagicCookieDescription.txt#L177). As we already had the non-legacy (mode != MOV) support in place, the output - as expected - matches the specification (checked with L-SMASH's boxdumper). Thus, the change itself is LGTM. Jan _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
