Daniel Drake wrote:
> Now, I guess I want to set this system-wide, and preferably also using
> dmix. Is this a sensible thing to do, or will applications automatically
> use the correct surroundXY mixer on their own?
I *think* that ALSA applications are supposed to use the surroundXY
devices automatically for multichannel audio. But I'm not certain on
this, I've only ever used mplayer to play multichannel sound.
I doubt it's a good idea to try and set a 4 channel device as the system
default, as I imagine you'll run into issues with stuff that just wants
to play simple stereo. I think a better approach would probably be to
configure some form of upmixing 2.0 -> 4.0 for the default (stereo)
device and let true 4.0 programs output to the surroundXY devices.
The setup I have (for 5.1) is:
pcm.ch51dup {
type route
slave.pcm surround51
slave.channels 6
ttable.0.0 0.8
ttable.1.1 0.8
ttable.0.2 0.6
ttable.1.3 0.6
ttable.0.4 0.5
ttable.1.4 0.5
# ttable.0.5 0.5 # Sub -- speakers seem to have their own filters
to redirect other channels to sub.
# ttable.1.5 0.5
}
so I guess something like:
pcm.ch40dup {
type route
slave.pcm surround40
slave.channels 4
ttable.0.0 0.8
ttable.1.1 0.8
ttable.0.2 0.6
ttable.1.3 0.6
}
ought to work for you -- again, this is all completely untested.
> pcm.dmixer {
> type dmix
> ipc_key 1024
> slave {
> pcm "surround40"
> period_time 0
> period_size 1024
> buffer_size 4096
> rate 44100
> }
> bindings {
> 0 0
> 1 1
> }
> }
Looking at the .asoundrc on my other box, then for a multichannel dmix I
have:
pcm.dmix6 {
type dmix
ipc_key 1024
ipc_key_add_uid false # let multiple users share
ipc_perm 0660 # IPC permissions (octal, default 0600)
slave {
pcm "hw:0,0"
rate 48000
channels 6
period_time 0
period_size 1024 # try 2048 against skipping
buffer_time 0
buffer_size 5120 # in case of problems reduce this
# in case of skipping, try increasing
}
}
I don't actually use that setup at the moment (that box currently has no
need for dmix), but I think it works. So I guess changing:
pcm "surround40"
to:
pcm "hw:0,0"
rate 48000
channels 4
in your .asoundrc might be worth a try. Having said that, I'm on quite
uncertain ground here so YMMV!
Hope some of this is useful and not too much of it is wildly inaccurate!
Cheers,
-ol
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