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-centerI 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-rightWould 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? -- Alexander E. Patrakov
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