вс, 7 окт. 2018 г. в 16:42, Karl Ove Hufthammer <[email protected]>:
> Alexander E. Patrakov skreiv 07.10.2018 09:44: > > > > I don’t understand why this is happening. Shouldn’t > > ‘remixing-use-all-sink-channels = no’ just affect *upmixing* of > > sound, > > and leave 5.1 material alone? > > > > > > This is a known bug that appears because there are two 5.1 standards: > > proper 5.1 and 5.1 Side. The video player (I guess you use mpv) says: > > the extra two channels have to come from the side. > > Looks like you’re right. If I run ‘ffprobe’ on my 5.1 test file, it > returns: > > Stream #0:1[0x1100]: Audio: dts (DTS-HD MA) ([134][0][0][0] / > 0x0086), 48000 Hz, 5.1(side), s32p (24 bit) > > So the video file (and mpv) seems to use the ‘5.1(side)’ standard. > (Which is a bit strange, since this is supposed to be a video file to > test a normal 5.1 setup, AFAICS.) > (speaking with my "DTS encoder author" hat on) The issue is that it is a DTS file. DTS uses completely different channel names than what's found in PulseAudio source. The proper normative reference is: https://www.etsi.org/deliver/etsi_ts/102100_102199/102114/01.03.01_60/ts_102114v010301p.pdf page 19, table 5.4 (note that the presence of the LFE channel is transmitted separately). Your file uses AMODE=0b001001=9, so the list of channels is: "Center", "Left", "Right", "Surround Left", "Surround Right". And there is also a 64x downsampled LFE channel. FFMmpeg-based decoders map "Surround" to "Side" because "Rear" also exists in other channel layouts and means something different. There is no way in DTS to express a layout with "Rear" but no "Surround" channels. > > > > But your system does not have speakers there, it has them on the rear. > > So PulseAudio attempts to remix. In fact, sound both with and without > > remixing-use-all-sink-channels is wrong. > > What’s wrong about the remixing when one uses > ‘remixing-use-all-sink-channels = yes’? > The rear channels will get not a copy of the side, but an average of front and side. -- Alexander E. Patrakov
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