Tanu Kaskinen <tanuk@xxxxxx>: > > On Sat, 2018-10-13 at 22:29 +0500, Alexander E. Patrakov wrote: > > On 10/7/18 6:27 PM, Alexander E. Patrakov wrote: > > > вс, 7 окт. 2018 г. в 16:42, Karl Ove Hufthammer <karl@xxxxxxxxxx > > > <mailto:karl@xxxxxxxxxx>>: > > > > > > 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. > > > > As promised, here is a patch. > > Thanks a lot! Very nice fix for a common problem, I applied it now. I > expect to look into the big remixing rework patch soon. > > > Note that I am unhappy with it, because it fixes only a particular > > common problem case, while other related issues stay unfixed. E.g. if > > one tries to play 5.1 audio on 7.1 system, with or without this patch: > > > > - Front, Center and LFE channels are mapped 1:1, which is correct > > - Rear (or what mpv calls "Side") source channels are mapped to Side, > > which is also correct, because it's the Side speakers in the ITU-T 7.1 > > layout, not Rear, which have the nearest position to what Dolby > > specifies for Surround AC3 speakers. > > - The true rear channels get a mix between Front and Side, which is > > clearly incorrect. ITU R-REC-BS.775-3-201208 says that both sets of > > surround channels should be fed the same signal. > > Regarding that last point, do I understand correctly that the > recommendation is to duplicate the 5.1 rear(/side) channels to both the > side and rear channels in 7.1? Doesn't that cause imbalance by > amplifying the rear channels? Or is it compensated by attenuating the > signal? You understood correctly. In my big patch, it is compensated by attenuating the signal. Anyway, I am going to resubmit it later today without the half-baked change about the LFE volume. -- Alexander E. Patrakov _______________________________________________ pulseaudio-discuss mailing list pulseaudio-discuss@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
