ALSA配置如何在asound.conf中组合MMAP仿真和Ladspa插件

Question

我使用rpi dac在Raspberry Pi计算模块(Linux)上有一个工作的PCM输出和良好的声音.'aplay -l'命令输出显示以下内容:

>> aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpirpidac [snd_rpi_rpi_dac], device 0: RPi-DAC HiFi pcm1794a-hifi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
Subdevices: 8/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7
card 1: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
Subdevices: 1/1
Subdevice #0: subdevice #0

为了让音频完全正常工作,我不得不将我的/etc/asound.conf文件更改为如下所示:

pcm.mmap0 {
  type mmap_emul
  slave {
    pcm "hw:0,0"
  }
}

pcm.!default {
  type plug
  slave {
    pcm mmap0
  }
}

当我播放.wav文件时输出听起来很棒,但它有点安静,alsamixer不允许使用此驱动程序进行音量控制.

我想获得更多的音量,所以我研究了Ladspa项目软件放大器插件.以下示例代码在普通Pi上提升3.5 mm插孔的音量:

pcm.radio {
    type plug
    slave.pcm "ladspa"
    hint {
        show on
        description "in -> equal -> declip -> compressor -> limiter -> dmix -> out"
    }
}

#  LADSPA plugins:
#    "listplugins" to see the list of installed plugins
#    "analyseplugin <filename>" to see plugin controls
#    Use "ardour2" to experiment with plugin settings
pcm.ladspa {
    type ladspa
    slave.pcm "plughw:0,0"
    path "/usr/lib/ladspa"
    plugins {
        0 {
        # Limiter
            label amp
            input {
                controls [ 10 ]
            }
          }
    }
}

我一直在阅读这里的文档:http://alsa.opensrc.org/Asoundrc,但我正在努力理解如何结合2 - 我想要MMAP仿真以及放大.我怎么能做到这一点？谢谢.

Answer 1

请尝试下一个设置，它可以在我的 x86 linux 下工作：

pcm.mmap0 {
    type mmap_emul
    slave {
        pcm "hw:0,0"
        #    pcm ladspa
    }
}

pcm.ladspa {
type ladspa
#slave.pcm "plughw:0,0"
slave.pcm mmap0
path "/usr/lib/ladspa"
plugins {
    0 {
    # Limiter
        label amp
        input {
            controls [ 100 ]
        }
      }
}
}

pcm.!default{
type plug
slave {
    pcm mmap0
    #pcm ladspa
    }
}