[FFmpeg-devel] [FFmpeg-cvslog] avcodec/dca: add new decoder based on libdcadec

[James Almer]

On 1/31/2016 3:51 PM, Michael Niedermayer wrote:
> On Sun, Jan 31, 2016 at 05:14:14PM +0100, foo86 wrote:
>> ffmpeg | branch: master | foo86 <foobaz86 at gmail.com> | Sat Jan 16 11:54:38 2016 +0300| [ae5b2c52501d5009fe712334428138a9b758849b] | committer: Hendrik Leppkes
>>
>> avcodec/dca: add new decoder based on libdcadec
>>
>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ae5b2c52501d5009fe712334428138a9b758849b
>> ---
>>
> 
> 
> this breaks request_channel_layout
> 
> example:
> ./ffmpeg -i dts/lotr_5.1_768.dts test.wav
> 
> Input #0, dts, from '/home/michael/videos/dts/lotr_5.1_768.dts':
>   Duration: 00:02:05.18, start: 0.000000, bitrate: 768 kb/s
>     Stream #0:0: Audio: dts (DTS-ES), 48000 Hz, 6.1, fltp, 768 kb/s
> 
> 
> vs.
> ./ffmpeg -request_channel_layout 3 -i dts/lotr_5.1_768.dts test-req3.wav
> 
> Input #0, dts, from '/home/michael/videos/dts/lotr_5.1_768.dts':
>   Duration: 00:02:05.18, start: 0.000000, bitrate: 768 kb/s
>     Stream #0:0: Audio: dts (DTS), 48000 Hz, 5.1(side), fltp, 768 kb/s
> 
> vs.
> ./ffmpeg-ref -request_channel_layout 3 -i dts/lotr_5.1_768.dts test-ref-req3.wav
> 
> Input #0, dts, from '/home/michael/videos/dts/lotr_5.1_768.dts':
>   Duration: 00:02:05.18, start: 0.000000, bitrate: 768 kb/s
>     Stream #0:0: Audio: dts (DTS-ES), 48000 Hz, stereo, fltp, 768 kb/s
> 
> 
> previously it resulted in 2 channels now it produces 5.1 when
> requesting stereo

libdcadec (and thus this new decoder) doesn't force stereo when downmix
coefficients are not embedded in the stream, leaving the work to the
resampler instead. Try the libdcadec wrapper and it will do the same.

It's an intended change in behavior compared to the old dca decoder, so
i guess it could documented.