Linux音频问题

关键字： alsa, pulseaudio, gnome, gnome-volume, 右下角，喇叭，音量

alsactl, alsa-utils, pulseaudio-utils

一、音频调节工具

alsaunmute （alsa-utils） 是一个脚本，用于初始化ALSA声音设备。它调用了alsactl，并且以init为参数。它没有任何参数，直接就是：

$ alsaunmute

它的内容如下：

#!/bin/shexec /sbin/alsactl \  -E ALSA_CONFIG_PATH=/etc/alsa/alsactl.conf \  --initfile=/lib/alsa/init/00main \  init

alsactl 是alsa系统最重要的工具，它主要用于对alsa的声卡进行控制。它支持多块声卡，

如果你的声卡的功能不能在图形界面中进行控制，那么你就应该使用这个 alsactl 工具。

alsa最主要的三个用法如下：

1）alsactl store 命令将当前声卡的驱动程序状态保存到一个配置文件（默认是/etc/asound.state， 可以用 -f 来指定）中去；

2）alsactl restore 则从这个配置文件恢复原来的声卡驱动状态。

3）alsactl init 将声卡的状态初始化为默认状态。

二、配置文件语法

三、ALSA配置文件（/etc/asound.conf）的格式

# 从#开始的地方是注释# 把其他配置文件包含进来<filename># 简单赋值语句name [=] value [,|;]# 结构体赋值 (第一种风格)name [=] {name1 [=] value [,|;]...}# 结构体赋值 (第二种风格)name.name1 [=] value [,|;]# 数组赋值 (第一种风格)name [value0 [,|;]value1 [,|;]...]# 数组赋值 (第二种风格)name.0 [=] value0 [,|;]name.1 [=] value1 [,|;]# ******************************************************************************# 对服务器的定义server.NAME {  host STR# host where the server is located (if map to local address # server is local, and then it may be started automatically)  [socket STR]# PF_LOCAL socket name to listen/connect  [port INT]# PF_INET port number to listen/connect}# PCM类型定义pcm_type.NAME {  [lib STR]# 共享库文件 (默认 libasound.so)  [openSTR]# 打开函数 (默认 _snd_pcm_NAME_open)  [redirect {# 将这个PCM重定向到另一个PCM     [filename STR]# 配置文件说明     name STR# PCM名称说明  }]}# PCM范围类型定义pcm_scope_type.NAME {  [lib STR]# 共享库文件 (默认 libasound.so)  [open STR]# 打开函数 (default _snd_pcm_scope_NAME_open)}# PCM 范围定义pcm_scope.NAME {  type STR# Scope type  ...}# 从属 PCM 定义pcm_slave.NAME {  pcm STR# PCM name#or  pcm { }# PCM definition  format STR# Format  channels INT# Channels  rate INT# Rate  period_time INT# Period time  buffer_time INT# Buffer time  etc.}# Hook arguments definitionhook_args.NAME {  ...# Arbitrary arguments}# PCM hook typepcm_hook_type.NAME {  [lib STR]# Library file (default libasound.so)  [install STR]# Install function (default _snd_pcm_hook_NAME_install)}# PCM hook definitionpcm_hook.NAME {  type STR# PCM Hook type (see pcm_hook_type)  [args STR]# Arguments for install function (see hook_args)  # or  [args { }]# Arguments for install function}# PCM 定义pcm.NAME {  type STR# Type  [comment ANY]# Saved comments# PCM 类型:  type hw # Kernel PCM  card INT/STR# Card name or number  [device] INT# Device number (default 0)  [subdevice] INT# Subdevice number, -1 first available (default -1)  mmap_emulation BOOL# enable mmap emulation for ro/wo devices  type hooks # PCM with hooks  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition  }  hooks {    ID STR# Hook name (see pcm_hook)    # or    ID { }# Hook definition (see pcm_hook)  }  type plug# Format adjusted PCM  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition    [format STR]# Slave format (default nearest) or "unchanged"    [channels INT]# Slave channels (default nearest) or "unchanged"    [rate INT]# Slave rate (default nearest) or "unchanged"  }  route_policy STR# route policy for automatic ttable generation# STR can be 'default', 'average', 'copy', 'duplicate'# average: result is average of input channels# copy: only first channels are copied to destination# duplicate: duplicate first set of channels# default: copy policy, except for mono capture - sum  ttable { # Transfer table (bidimensional compound of         # cchannels * schannels numbers)    CCHANNEL {      SCHANNEL REAL# route value (0.0 ... 1.0)    }  }  type copy# Copy conversion PCM  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition  }  type linear# Linear format conversion PCM  type adpcm# IMA-ADPCM format conversion PCM  type alaw# A-Law format conversion PCM  type mulaw# Mu-Law format conversion PCM  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition    format STR# Slave format  }  type rate# Rate conversion PCM  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition    [format STR]# Slave format (default client format)    rate INT# Slave rate  }  type route# Attenuated static route PCM  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition    [format STR]# Slave format (default client format)    [channels INT]# Slave channels (default client channels)  }  ttable { # Transfer table (bidimensional compound of         # cchannels * schannels numbers)    CCHANNEL {      SCHANNEL REAL# route value (0.0 ... 1.0)    }  }  type multi# Linked PCMs (exclusive access to selected channels)  slaves {# Slaves definitions    ID STR# Slave name for slave N (see pcm_slave)    # or    ID {# Slave definition for slave N      pcm STR# Slave PCM name    # or      pcm { }# Slave PCM definition      channels INT# Slave channels    }  }  bindings {# Bindings table    N {# Binding for client channel N      slave STR# Slave key      channel INT# Slave channel    }  }  [master INT]# Define the master slave  type file# File plugin  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition  }  file STR# File name  # or  file INT# File descriptor  [format STR]# File format (NYI)  [perm INT]# File permission (default 0600)  type meter# Meter PCM  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition or name    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition  }  [frequency INT]# Updates per second  scopes {# Scopes    ID STR# Scope name (see pcm_scope)  # or    ID { }# Scope definition (see pcm_scope)  }  type droute# Attenuated dynamic route PCM (NYI)  slave STR# Slave name (see pcm_slave)  # or  slave {# Slave definition    pcm STR# Slave PCM name    # or    pcm { }# Slave PCM definition    [format STR]# Slave format (default client format)    [channels INT]# Slave channels (default client channels)  }  ctl STR# Ctl name  bindings {# Bindings table    ID {# Binding entry      cchannels {# Client channels        C INT# Client channel      }      schannel {# Slave channels        S INT# Slave channel      }      control STR# Control name of C * S (or C values: only if C == S)    }  }  type null# Null endpoint plugin  [time INT]# Time related or not (NYI)  type shm# Shared memory client PCM  server STR# Server name  pcm STR# PCM name on server  type share# Share PCM  slave STR# Slave name (see pcm_slave)  bindings {# Bindings table    N INT# Slave channel for client channel N  }  type mix# Mix PCM  slave STR# Slave name (see pcm_slave)  bindings {# Bindings table    N INT# Slave channel for client channel N  }  type ladspa# LADSPA plugin PCM  slave STR# Slave name (see pcm_slave)  path STR# Path or paths (delimited with ':')  plugins | playback_plugins | capture_plugins {    N {# Configuration for LADSPA plugin N      id ## LADSPA plugin ID (for example 1043)      label STR# LADSPA plugin label (for example 'delay_5s')      filename STR# Full filename of .so library with LADPA plugin code      policy STR# Policy can be 'none' or 'duplicate'      input | output {        bindings {          C INT or STR  # C - channel, INT - audio port index, STR - audio port name        }        controls {          I INT or REAL # I - control port index, INT or REAL - control value        }      }    }  }  type dmix# Direct mixing plugin  slave STR# Slave name (see pcm_slave)  ipc_key INT# Unique ipc key  ipc_perm INT# ipc permissions (default 0600)  ipc_gid INT# ipc gid (default -1 = disable)  ipc_key_add_uid BOOL  # Add current uid to ipc_key  bindings {# Bindings table    N INT# Slave channel for client channel N  }  type dsnoop# Direct snoop (split one capture stream to more)  slave STR# Slave name (see pcm_slave)  ipc_key INT# Unique ipc key  ipc_perm INT# ipc permissions (default 0600)  ipc_gid INT# ipc gid (default -1 = disable)  ipc_key_add_uid BOOL  # Add current uid to ipc_key  bindings {# Bindings table    N INT# Slave channel for client channel N  }  type dshare# Share channels from one stream  slave STR# Slave name (see pcm_slave)  ipc_key INT# Unique ipc key  ipc_perm INT# ipc permissions (default 0600)  ipc_gid INT# ipc gid (default -1 = disable)  ipc_key_add_uid BOOL  # Add current uid to ipc_key  bindings {# Bindings table    N INT# Slave channel for client channel N  }}# CTL type definitionctl_type.NAME {  [lib STR]# Library file (default libasound.so)  [open STR]# Open function (default _snd_ctl_NAME_open)}# CTL definitionctl.NAME {  type STR# Type  [comment ANY]# Saved comments# CTL types  type hw  card STR/INT# Card name or number  type shm# Shared memory client CTL  server STR# Server name  ctl STR# CTL name on server}# RAWMIDI type definitionrawmidi_type.NAME {  [lib STR]# Library file (default libasound.so)  [open STR]# Open function (default _snd_rawmidi_NAME_open)}# RAWMIDI definitionrawmidi.NAME {  type STR# Type  [comment ANY]# Saved comments# RAWMIDI types:  type hw # Kernel RAWMIDI  card INT/STR# Card name or number  [device] INT# Device number (default 0)  [subdevice] INT# Subdevice number, -1 first available (default -1)}# SEQ 类型定义seq_type.NAME {  [lib STR]# Library file (default libasound.so)  [open STR]# Open function (default _snd_seq_NAME_open)}# SEQ 定义seq.NAME {  type STR# Type  [comment ANY]# Saved comments# SEQ types:  type hw # Kernel SEQ}# 别名DEF.NAME1 NAME2# DEF.NAME1 是 DEF.NAME2 的别名举例如下:pcm.trident {type hwcard 0device 0}pcm.ice1712 {type hwcard 1device 0}pcm.ice1712_spdif {type plugttable.0.8 1ttable.1.9 1slave.pcm ice1712}pcm_slave.rs {pcm tridentrate 44100}pcm.r {type rateslave rs}pcm.m {type meterslave.pcm plug:tridentfrequency 50scopes [{type level}]}pcm_scope_type.level {lib /home/abramo/scopes/scope-level.so} # an example command is 'aplay -D plug:ladspa <filename>'# otherwise, the ladspa plugin expects FLOAT type which# is very rarepcm.ladspa {        type ladspa        slave.pcm "plughw:0,0";        path "/home/perex/src/ladspa_sdk/plugins";        plugins [                {                        label delay_5s                        input {                                controls [ 0.8 0.2 ]                        }                }        ]}# an example command for dmix plugin to force 44100Hz mixing rate:# aplay -D"plug:'dmix:RATE=44100'" <filename># an example command for dmix plugin to force 44100Hz and hw:1,0 output device# aplay -Dplug:\'dmix:SLAVE=\"hw:1,0\",RATE=44100\' <filename># an example command for dmix plugin to force 32-bit signed little endian format# aplay -D"plug:'dmix:FORMAT=S32_LE'" <filename>