高级 Linux 声卡架构/配置示例
以下内容应作为更高级 ALSA 设置的指南。如主文章所述，配置在 /etc/asound.conf 中进行。以下配置均不保证有效。
注意 使用主文章中解释的 ALSA 插件（如 upmix）可以更轻松地完成此处讨论的大部分工作。
使用 dmix 将立体声音源上混至 7.1，同时饱和音源不进行上混
# 2008-11-15
#
# This .asoundrc will allow the following:
#
# - upmix stereo files to 7.1 speakers.
# - playback real 7.1 sounds, on 7.1 speakers,
# - allow the playback of both stereo (upmixed) and surround(7.1) sources at the same time.
# - use the 6th and 7th channel (side speakers) as a separate soundcard, i.e. for headphones
# (This is called the "alternate" output throughout the file, device names prefixed with 'a')
# - play mono sources in stereo (like ekiga) on the alterate output
#
# Make sure you have "8 Channels" and NOT "6 Channels" selected in alsamixer!
#
# Please try the following commands, to make sure everything is working as it should.
#
# To test stereo upmix : speaker-test -c2 -Ddefault -twav
# To test surround(5.1): speaker-test -c6 -Dplug:dmix6 -twav
# To test surround(7.1): speaker-test -c6 -Dplug:dmix8 -twav
# To test alternative output: speaker-test -c2 -Daduplex -twav
# To test mono upmix: speaker-test -c1 -Dmonoduplex -twav
#
#
# It may not work out of the box for all cards. If it doesnt work for you, read the comments throughout the file.
# The basis of this file was written by wishie of #alsa, and then modified with info from various sources by
# squisher. Svenstaro modified it for 7.1 output support.
#Define the soundcard to use
pcm.snd_card {
type hw
card 0
device 0
}
# 8 channel dmix - output whatever audio, to all 8 speakers
pcm.dmix8 {
type dmix
ipc_key 1024
ipc_key_add_uid false
ipc_perm 0660
slave {
pcm "snd_card"
rate 48000
channels 8
period_time 0
period_size 1024
buffer_time 0
buffer_size 5120
}
# Some cards, like the "nforce" variants require the following to be uncommented.
# It routes the audio to the correct speakers.
# bindings {
# 0 0
# 1 1
# 2 4
# 3 5
# 4 2
# 5 3
# 6 6
# 7 7
# }
}
# upmixing - duplicate stereo data to all 8 channels
pcm.ch71dup {
type route
slave.pcm dmix8
slave.channels 8
ttable.0.0 1
ttable.1.1 1
ttable.0.2 1
ttable.1.3 1
ttable.0.4 0.5
ttable.1.4 0.5
ttable.0.5 0.5
ttable.1.5 0.5
ttable.0.6 1
ttable.1.7 1
}
# this creates a six channel soundcard
# and outputs to the eight channel one
# i.e. for usage in mplayer I had to define in ~/.mplayer/config:
# ao=alsa:device=dmix6
# channels=6
pcm.dmix6 {
type route
slave.pcm dmix8
slave.channels 8
ttable.0.0 1
ttable.1.1 1
ttable.2.2 1
ttable.3.3 1
ttable.4.4 1
ttable.5.5 1
ttable.6.6 1
ttable.7.7 1
}
# share the microphone, i.e. because virtualbox grabs it by default
pcm.microphone {
type dsnoop
ipc_key 1027
slave {
pcm "snd_card"
}
}
# rate conversion, needed i.e. for wine
pcm.2chplug {
type plug
slave.pcm "ch71dup"
}
pcm.a2chplug {
type plug
slave.pcm "dmix8"
}
# routes the channel for the alternative
# 2 channel output, which becomes the 7th and 8th channel
# on the real soundcard
#pcm.alt2ch {
# type route
# slave.pcm "a2chplug"
# slave.channels 8
# ttable.0.6 1
# ttable.1.7 1
#}
# ekiga is only mono, so route left channel to the right channel
# note: this gets routed to the alternative 2 channels
pcm.mono_playback {
type route
slave.pcm "a2chplug"
slave.channels 8
# Send audio channel 0 to the L and R speakers at full volume
#ttable.0.6 1
#ttable.0.7 1
}
# 'full-duplex' device for use with aoss
pcm.duplex {
type asym
playback.pcm "2chplug"
capture.pcm "microphone"
}
#pcm.aduplex {
# type asym
# playback.pcm "alt2ch"
# capture.pcm "microphone"
#}
pcm.monoduplex {
type asym
playback.pcm "mono_playback"
capture.pcm "microphone"
}
# for aoss
pcm.dsp0 "duplex"
ctl.mixer0 "duplex"
# softvol manages volume in ALSA
# i.e. wine likes this
pcm.mainvol {
type softvol
slave.pcm "duplex"
control {
name "2ch-Upmix Master"
card 0
}
}
#pcm.!default "mainvol"
# set the default device according to the environment
# variable ALSA_DEFAULT_PCM and default to mainvol
pcm.!default {
@func refer
name { @func concat
strings [ "pcm."
{ @func getenv
vars [ ALSA_DEFAULT_PCM ]
default "mainvol"
}
]
}
}
# uncomment the following if you want to be able to control
# the mixer device through environment variables as well
#ctl.!default {
# @func refer
# name { @func concat
# strings [ "ctl."
# { @func getenv
# vars [ ALSA_DEFAULT_CTL
# ALSA_DEFAULT_PCM
# ]
# default "duplex"
# }
# ]
# }
#}
Surround51 包括立体声上混 & dmix，左右声道互换，房间内音箱位置不佳
不推荐但对于几乎所有不需要额外按程序/文件自定义的情况都能正常工作
pcm.!default {
type route
## forwards to the mixer pcm defined below
slave.pcm dmix51
slave.channels 6
## "Native Channels" stereo, swap left/right
ttable.0.1 1
ttable.1.0 1
## original normal left/right commented out
# ttable.0.0 1
# ttable.1.1 1
## route "native surround" so it still works but weaken signal (+ RL/RF swap)
## because my rear speakers are more like random than really behind me
ttable.2.3 0.7
ttable.3.2 0.7
ttable.4.4 0.7
ttable.5.5 0.7
## stereo => quad speaker "upmix" for "rear" speakers + swap L/R
ttable.0.3 1
ttable.1.2 1
## stereo L+R => join to Center & Subwoofer 50%/50%
ttable.0.4 0.5
ttable.1.4 0.5
ttable.0.5 0.5
ttable.1.5 0.5
## to test: "$ speaker-test -c6 -twav" and: "$ speaker-test -c2 -twav"
}
pcm.dmix51 {
type dmix
ipc_key 1024
# let multiple users share
ipc_key_add_uid false
# IPC permissions (octal, default 0600)
# I think changing this fixed something - but I'm not sure what.
ipc_perm 0660 #
slave {
## this is specific to my hda_intel. Often hd:0 is just allready it; To find: $ aplay -L
pcm surround51
# this rate makes my soundcard crackle
# rate 44100
# this rate stops flash in firefox from playing audio, but I do not need that
rate 48000
channels 6
## Any other values in the 4 lines below seem to make my soundcard crackle, too
period_time 0
period_size 1024
buffer_time 0
buffer_size 4096
}
}
带 dmix 外部接口的环回接口
用于控制哪个输出到外部、环回或两者兼有。其他人报告称在不指定格式的情况下也能正常工作 [1]
# Use this to output to external
pcm.dmixerout {
type dmix
ipc_key 1024
ipc_key_add_uid false
slave {
pcm "hw:CARDNAME,0"
channels 2
period_time 0
period_size 1024
buffer_size 4096
rate 44100
}
bindings {
0 0
1 1
}
}
# Use this to output to loopback
pcm.dmixerloop {
type dmix
ipc_key 2048
ipc_key_add_uid false
slave {
pcm "hw:Loopback,0,0"
channels 2
period_time 0
period_size 1024
buffer_size 4096
# If format is absent ALSA gives me slave PCM not usable, but it works w/o it for others
format S32_LE
rate 44100
}
bindings {
0 0
1 1
}
}
# Sends to the two dmix interfaces
pcm.quad {
type multi
# Necessary to have both slaves be dmix; both as hw doesn't give errors, but wouldn't
slaves.a.pcm "dmixerout"
slaves.a.channels 2
slaves.b.pcm "dmixerloop"
slaves.b.channels 2
bindings {
0 { slave a; channel 0; }
1 { slave a; channel 1; }
2 { slave b; channel 0; }
3 { slave b; channel 1; }
}
}
# Duplicates to quad, use this to output to loopback & external
pcm.stereo2quad {
type route
slave.pcm "quad"
# ttable.A.B G
# where A - input channel
# B - output channel
# G - volume gain (1.0 = original)
ttable.0.0 1
ttable.1.1 1
ttable.0.2 1
ttable.1.3 1
}
# Listens to loopback
# trying to play to stereo2quad when something is already listening gives me slave PCM not usable
# but listening when something is already playing on stereo2quad works
# and so does starting to listen, then playing to dmixerloop
pcm.loopin {
type dsnoop
ipc_key 1111
ipc_key_add_uid false
slave.pcm "hw:Loopback,1"
}
pcm.!default {
type asym
playback.pcm "plug:stereo2quad"
capture.pcm "plug:loopin"
}