Quoting Marton Balint (2020-02-18 23:54:56) > > > On Tue, 18 Feb 2020, Anton Khirnov wrote: > > > Quoting Marton Balint (2020-02-05 19:55:24) > >> > >> > >> On Tue, 7 Jan 2020, Anton Khirnov wrote: > >> > >> > Quoting Nicolas George (2019-12-31 16:17:49) > >> >> Anton Khirnov (12019-12-29): > >> > >> >> > I do not agree. Duplicated channels in a layout are expected to be a > >> >> > fringe thing and how you handle them highly depends on the specific > >> >> > use > >> >> > case. I expect a typical caller will want to disregard that > >> >> > possibility > >> >> > and just take the first channel of each semantics. > >> >> > So I do not believe a dedicated function for this makes sense. We > >> >> > could > >> >> > always add something later though, if it turns out to be necessary. > >> >> > >> >> I think you are making a mistake. I think that as soon as it will be > >> >> technically possible, we will see cases with duplicated channels. And I > >> >> know that some filters will do exactly that as soon as they are ported > >> >> to this new API. > >> > >> Quicktime also allows duplicated channels in a single audio track, this is > >> unfortunately a commonly used feature. So if a new API is introduced to > >> overcome the limitations of the existing one, supporting this should be > >> seriously considered. > > > > Can you provide a link to more information about this? I'd like to know > > the specifics about how it's handled by quicktime. And do note that this > > API does have some ammount of support for duplicated channels (though I > > still consider streams containing them to be broken). > > The 'chan' atom can hold this information: > > https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-SW53 > > It holds an AudioChannelLayout structure as defined in CoreAudioTypes.h: > > https://developer.apple.com/documentation/coreaudiotypes/audiochannellayout > https://github.com/phracker/MacOSX-SDKs/blob/master/MacOSX10.15.sdk/System/Library/Frameworks/CoreAudioTypes.framework/Versions/A/Headers/CoreAudioBaseTypes.h#L1353 > > Which can hold an AudioChannelDescription array of channel descriptions > for each channel: > > https://developer.apple.com/documentation/coreaudiotypes/audiochannellayout > https://github.com/phracker/MacOSX-SDKs/blob/master/MacOSX10.15.sdk/System/Library/Frameworks/CoreAudioTypes.framework/Versions/A/Headers/CoreAudioBaseTypes.h#L1335 > > Which can signal the same AudioChannelLabel for every channel in a track > if needed.
Thanks for the links. As far as I can tell this can be mapped to the proposed API just fine (except for signalling precise speaker coordinates, which I don't think anything uses). -- Anton Khirnov _______________________________________________ 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".
