amixer和alsamixer使用说明

amixer和alsamixer说明

本文主要解答：
1. amixer与alsamixer的区别
2. amixer与alsamixer的使用

alsamixer与amixer的区别

alsamixer是Linux音频框架ALSA工具之一，用于配置音频各个参数;
alsamixer是基于文本图形界面的，可以在终端中显示.通过键盘的上下键，左右键等实现音量设置，开关操作等。

amixer，是alsamixer的文本模式,即命令行模式，以命令行的形式去配置声卡的各个选项，比如选择音频输入通道是Mic输入，还是Line输入。

alsamixer的使用

amixer的使用

root@linux:~$ amixer -h
Usage: amixer <options> [command]

Available options:
  -h,--help       this help
  -c,--card N     select the card
  -D,--device N   select the device, default 'default'
  -d,--debug      debug mode
  -n,--nocheck    do not perform range checking
  -v,--version    print version of this program
  -q,--quiet      be quiet
  -i,--inactive   show also inactive controls
  -a,--abstract L select abstraction level (none or basic)
  -s,--stdin      Read and execute commands from stdin sequentially
  -R,--raw-volume Use the raw value (default)
  -M,--mapped-volume Use the mapped volume

Available commands:
  scontrols       show all mixer simple controls
  scontents   show contents of all mixer simple controls (default command)
  sset sID P      set contents for one mixer simple control
  sget sID        get contents for one mixer simple control
  controls        show all controls for given card
  contents        show contents of all controls for given card
  cset cID P      set control contents for one control
  cget cID        get control contents for one control

常用的命令：
amixer controls 用于查看音频系统提供的操作接口
amixer contents 用于查看接口配置参数
amixer cget + 接口函数
amixer cset + 接口函数 + 设置值

通常是先用cget/sget命令去查看接口，然后再用cset/sset命令设置所要设置的值;sget/sset相当于简化版，实现简单的参数设置，一般情况下使用scontrols ,scontents即可满足需求;

 #./amixer  scontrols
 Simple mixer control 'Headphone',0
 ...
 Simple mixer control 'Line In',0
 Simple mixer control 'Left Capture Source',0 
 Simple mixer control 'Right Capture Source',0
 ...

#./amixer  sget  'Left Capture Source',0
/media/sda1/bin_mips_alsa/mips-alsa/bin/amixer controls
/media/sda1/bin_mips_alsa/mips-alsa/bin/amixer cset numid=4,iface=MIXER,name='Speaker Playback Volume' 100
Simple mixer control 'Left Capture Source',0
  Capabilities: enum
  Items: 'Mic 1' 'Mic 2' 'Line' 'Mono In' 'Headphone' 'Speaker' 'Mono Out' 'Zh'
  Item0: 'Mic 1'

如果想要修改对应设置，用amixer sset ，具体用法是：
amixer sset sID(控制字符串) P(支持的某个值)
其中sID，就是上面的Simple mixer control后面的那个字符串，比如 ‘Left Capture Source’ 而对其设置就是，

# ./amixer  sset 'Left Capture Source',0 Line
Simple mixer control 'Left Capture Source',0
  Capabilities: enum
  Items: 'Mic 1' 'Mic 2' 'Line' 'Mono In' 'Headphone' 'Speaker' 'Mono Out' 'Zh'
  Item0: 'Line'

# amixer controls
numid=3,iface=MIXER,name='Master Mode Switch'
numid=29,iface=MIXER,name='Master Mux'
numid=4,iface=MIXER,name='Master Quality Switch'
numid=2,iface=MIXER,name='Master Switch'
numid=1,iface=MIXER,name='Master Volume'
numid=7,iface=MIXER,name='PCM Mode Switch'
numid=6,iface=MIXER,name='PCM Switch'
numid=5,iface=MIXER,name='PCM Volume'
numid=21,iface=MIXER,name='Line Input Switch'
numid=16,iface=MIXER,name='Line Mode Switch'
numid=27,iface=MIXER,name='Line Mux'

# amixer contents
numid=3,iface=MIXER,name='Master Mode Switch'
; type=ENUMERATED,access=rw------,values=1,items=2
; Item #0 'Common Buffer Off'
; Item #1 'Common Buffer On'
: values=0

# amixer cget numid=5,iface=MIXER,name='PCM Volume'
numid=5,iface=MIXER,name='PCM Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=27,step=0
: values=27,27
| dBscale-min=-40.50dB,step=1.50dB,mute=0

如上PCM音量最大设定值为27，假设想要设置为25，那么就用cset去设置：

# amixer cset numid=5,iface=MIXER,name='PCM Volume' 25
numid=5,iface=MIXER,name='PCM Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=27,step=0
: values=25,25
| dBscale-min=-40.50dB,step=1.50dB,mute=0

alsa及aplay用法