[FFmpeg-devel] [PATCH 1/5] movenc: use correct tag list for AVOutputFormat.codec_tag

James Almer jamrial at gmail.com
Tue Jul 4 18:52:11 EEST 2017

On 7/4/2017 12:09 PM, Derek Buitenhuis wrote:
> On 7/3/2017 3:00 AM, James Almer wrote:
>> Doesn't DTS have a bunch of unique tags? The ones listed in
>> ff_codec_movaudio_tags and http://www.mp4ra.org/codecs.html
> It looks like those only cover DTS extensions, which we all
> mark s AV_CODEC_ID_DTS. Is the DTS base layer 'mp4a'? I don't
> have a source on what is correct to do here, or how to fit it
> in (since this seems to imply DTS should have a 1-to-N mapping).
> Does copying these work post-patch? FATE passes, but we probably
> don't have stuff like a DTS-HD-MA-in-MP4 sample.
> (I changed the EAC3 entry locally but have not sent a new patch
> since I'm not 100% sure about the DTS stuff.)

Your patchset doesn't seem to affect DTS muxing. It's the same before
and after.
Before it would default to mp4a apparently for being audio and having an
entry in obj_type. After your patchset, mp4a is explicitly set for DTS
in codec_mp4_tags.

According to mp4ra.org, DTS core should have a dtsc codec tag. The rest
are for the extensions. A quick test changing mp4a to dtsc on top of
your patchset resulted in a wildly different output file, among other
reasons because the esds box isn't written (it expects an mp4a tag).

The DTS in ISOMF spec doesn't seem to be publicly available after a
quick search, so IMO just push this as is, which will retain the current
behavior, at least until we're sure how it should be done.

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