On Sun, 31 Jan 2016 20:51:23 +0100 Michael Niedermayer <mich...@niedermayer.cc> wrote:
> On Sun, Jan 31, 2016 at 04:04:41PM -0300, James Almer wrote: > > On 1/31/2016 3:57 PM, James Almer wrote: > > > 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 <fooba...@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. > > > > > > > To expand a bit based on what foo86 mentioned in a patch for the wrapper, > > with DTS-ES, DTS-HDMA and other extensions, if you request a stereo downmix > > and coefficients are not available it will not bother applying all the > > extensions to output 7 or 8 channels and instead output the core 5.1 stream > > as is, to simplify the work of the resampler. > > Trying to force a downmix using default coefficients may result in clipping. > > > > He can explain it much better than me, though. > > the output is float, that should not clip > also how is downmixing after the decoder better, it too would apply > some coefficients (either risking an increase in peak volume or > a average loss of volume or inconsistet attenuation > At least you have control over it and can get consistent results with other decoders. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
