On Mon, 2018-11-26 at 00:17 +0500, Alexander E. Patrakov wrote: > On 11/16/18 11:13 AM, Tanu Kaskinen wrote: > > On Thu, 2018-11-15 at 23:50 +0500, Alexander E. Patrakov wrote: > > > Alexander E. Patrakov <patrakov@xxxxxxxxx>: > > > > Tanu Kaskinen <tanuk@xxxxxx>: > > > > > On Sat, 2018-10-13 at 22:29 +0500, Alexander E. Patrakov wrote: > > > > > > 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. > > > > > > Sorry, I have to do it later. I have too much non-PulseAudio work to do :( > > > > No problem, I'll postpone reviewing the patch until you've submitted > > the new version. From what I already saw, the general idea behind the > > patch seems good. > > > > Hello Tanu, > > thanks for your patience. I have tried to undo the half-baked LFE change > today, but found two more bugs in my patch that I would rather fix > before resubmitting it: > > 1. AUX input channels get sometimes routed to non-AUX output channels > rather than being dropped. Fixing this right how. > > 2. Some inconsistencies if either input or output channel map contains > duplicates. Cannot really fix, because I don't know what's expected. > > Could you please help with (2)? In particular, what would be the > expected channel matrix in the following two cases? > > Case A: > > front-left, front-right, front-center -> > front-left, front-right, front-center, front-center > > I would guess that we should generate two identical front-center output > channels, both duplicating the front-center input channel with the > coefficient being 1.0. > > Case B: > > front-left, front-right, front-left, front-right -> front-left, front-right > > Would it be OK if I drop the redundant input channels, i.e. use only the > first copy of each channel name? Or should I average the redundant > inputs, or take a sum? > > Is there any spec? I'm not aware of any valid use cases for duplicated channels (except mono, which can be interpreted as a channel without defined position), so there's no spec and at least I don't have expectations of any particular behaviour. Your suggestion for case A seems reasonable, and for case B I think we should do whatever is easiest to implement. -- Tanu https://www.patreon.com/tanuk https://liberapay.com/tanuk _______________________________________________ pulseaudio-discuss mailing list pulseaudio-discuss@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
