使用aplay并在卡上选择要使用的输出。

Question

我有一个xmos-200板，可以记录8个频道，并通过8个渠道推动输出。我要把重点放在输出上。

对于输出，有4个3.5mm千斤顶，每个通道2个。这个板是Linux认可的，播放-L显示

sysdefault:CARD=x20
    xCORE USB Audio 2.0, USB Audio
    Default Audio Device
front:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    Front speakers
surround40:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    4.0 Surround output to Front and Rear speakers
surround41:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    IEC958 (S/PDIF) Digital Audio Output
dmix:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    Direct sample mixing device
dsnoop:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    Direct sample snooping device
hw:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    Direct hardware device without any conversions
plughw:CARD=x20,DEV=0
    xCORE USB Audio 2.0, USB Audio
    Hardware device with all software conversions

我可以播放来自所有输出端口和所有通道的音频文件

aplay --device plughw:CARD=x20,DEV=0 camera.wav

我想选择哪一个的4立体声输出是使用。对我怎么做有帮助吗？

Answer 1

这四个插孔在物理上是分开的，但是软件只看到一个8通道的设备。

您可以使用ALSA插件拆分此设备：

pcm_slave.eightchannels {
    pcm "hw:x20,0"
    channels 8
    rate 48000     # or whatever
}

pcm.stereo1 {
    type plug
    slave.pcm {
        type dshare
        ipc_key 20160316     # any random but unique number
        slave eightchannels
        bindings [ 0 1 ]
    }
}
pcm.stereo2 {
    type plug
    slave.pcm {
        type dshare
        ipc_key 20160316
        slave eightchannels
        bindings [ 2 3 ]
    }
}
pcm.stereo3 {
    type plug
    slave.pcm {
        type dshare
        ipc_key 20160316
        slave eightchannels
        bindings [ 4 5 ]
    }
}
pcm.stereo4 {
    type plug
    slave.pcm {
        type dshare
        ipc_key 20160316
        slave eightchannels
        bindings [ 6 7 ]
    }
}

若要允许多个应用程序使用相同的立体声设备，请将dshare替换为dmix。