I've been using pulseaudio with surround content for quite a bit and found some oddities around. When playing 5.1, 5.0 or 6.1 content, surround channels are labeled as REAR channels. This might be fine for people with up to 6.1 output since the surround channels are also labeled as REAR anyways, and most setups physically arrange it as a SIDE channel (not behind the listener, but exactly +/-90?) . However, once you try (for ex) 5.1 over 7.1 the 5.1 REAR channel ends up as the 7.1 REAR channel which is supposed to be behind the listener in a 7.1 setup. Ideally 5.1 REAR would end up as 7.1 SIDE which matches the same physical arrangement. One way to achieve this is changing 5.0/5.1/6.1 ch map to use SIDE instead of REAR. Another little nitpick is the lack of 6.1 mappings. Quite a bit of software rely on "pa_channel_map_init_auto" to find a usable mapping but fails because there is no case for 7 channel mapping, or it just returns a plainly wrong one. For example, running a 6.1 movie with smplayer/mplayer would fail because no 7ch mapping was available in "PA_CHANNEL_MAP_ALSA". Also, "PA_CHANNEL_MAP_WAVEEX" gives many wrong channel maps. As far as I know WAVEEX is supposed to work with a bitmask to select which channels you want to work with, not to religiously give the channels in the order the MS documentation provides. Let me put it better, you are supposed to hide the channels you don't need but still keep what you need at the same original order. Since "pa_channel_map_init_auto" does not provide any means to pass this bitmask, the WAVEEX condition should just return what is most common for X channels. For example, 7.1 (8ch) should have FL, FR, FC, LFE, RL, RR, SL, RR in this order, and not FL, FR, FC, LFE, RL, RR, FLC, FRC. Anything between RR and SL would be ignored. This, for example, fixes every single openal game/app with 7.1 sound. You can actually play minecraft and amnesia without a silly "Front Left of Center" channel making it's presence known. The good thing is.. I've come up with a patch that fixes these issues. But I cant guarantee it's a 100% fix. Fixing WAVEEX can't be done without guessing what some random app means about "4 channels!" and swapping REAR for SIDE in 5.0/5.1/6.1 mappings is probably not be the best way to solve this issue. If you want to test this, I highly recommend using this little command: watch "pacmd list-sink-inputs | grep -B 7 client:" You can easily keep track of what the hell is happening with channel mapping. -------------- next part -------------- A non-text attachment was scrubbed... Name: fix_chmap_v3.patch Type: application/octet-stream Size: 10037 bytes Desc: not available URL: <http://lists.freedesktop.org/archives/pulseaudio-discuss/attachments/20121005/db9270d3/attachment.obj>
