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mpd 无法打开 aplay 成功的 ALSA 设备

tag-icon • tag-icon audio raspberry-pi alsa raspbian mpd
mpd 无法打开 aplay 成功的 ALSA 设备

我正在尝试通过 ALSA LADSPA 插件使用板载声音硬件设置 Raspberry Pi / Raspbian 喘息音频播放器来立体声缩混和压缩音频。

aplay、sox、mpg123、moc ( cd ~/.moc && cp /usr/share/doc/moc/examples/config.example.gz ./ && gunzip config.example.gz && mv config.example config) 使用此自定义“设备”：

pi@raspberrypi ~ $ aplay -D mcl audiofile.wav
pi@raspberrypi ~ $ sox audiofile.wav -t alsa mcl
pi@raspberrypi ~ $ mpg123 -a mcl audiofile.mp3
pi@raspberrypi ~ $ speaker-test -t wav -c 2
pi@raspberrypi ~ $ speaker-test -t wav -c 2 -D mcl

我已经从源代码构建了当前的 mpd 版本（http://www.musicpd.org/download/mpd/0.19/mpd-0.19.8.tar.xz）遵循本教程： http://www.infofreako.info/2014/04/building-mpd-on-raspberry-pi-with-opus-support/（需要额外的依赖项libboost-dev和libicu-dev）

pi@raspberrypi ~ $ mpc version
mpd version: 0.19.0
pi@raspberrypi ~ $ mpd --version
Music Player Daemon 0.19.8

但仍然收到错误：

ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM mcl
Jan 25 10:23 : alsa_output: Failed to open "My ALSA Device" [alsa]: Failed to open ALSA device "mcl": No such file or directory
Jan 25 10:23 : output: Failed to open audio output
Jan 25 10:23 : client: [1] closed

default使用该设备时它确实工作正常（ladcomp也不起作用）。

所以我的 ALSA 配置中要么有其他玩家猜测的错误/缺失，要么 mpd 做错了。

没有 /etc/asound.conf，我使用多个源创建了以下 ~/.asoundrc

pcm.!default {
    type hw
    card 0
    device 0
    } 

ctl.!default {
    type hw
    card 0
    device 0
}


###############


# compressor

pcm.ladcomp_limiter {
    type ladspa
    slave.pcm "plughw:0,0";
#    slave.pcm "default";
#    slave.pcm "makemono";

    path "/usr/lib/ladspa";
    plugins [{
        label fastLookaheadLimiter
        input {
            #InputGain(Db) -20 -> +20 ; Limit (db) -20 -> 0 ; Release time (s) 0.01 -> 2
            controls [ 20 0 0.8  ]
        }
    }]
}

pcm.ladcomp_compressor {
    type ladspa
    slave.pcm "ladcomp_limiter";
    path "/usr/lib/ladspa";
    plugins [{
        label dysonCompress
        input {
            #peak limit, release time, fast ratio, ratio
            controls [0 1 0.5 0.99]
        }
    }]
}

pcm.ladcomp {
    type plug
    slave.pcm "ladcomp_compressor";
}




### test mono downmix

#pcm.card0 {
#  type hw
#  card 0
#  device 0
#}

#ctl.card0 {
#  type hw
#  card 0
#  device 0
#}


#pcm.monocard {
#  slave.pcm card0
#  slave.channels 2
#  type plug
#}

#ctl.monocard {
#  type hw
#  card 0
#  device 0
#}

#pcm.!default monocard

####### didnt work, try this


pcm.mcl {
#pcm.makemono {
    type route
   # slave.pcm "plughw:0,0"
    slave.pcm "ladcomp"

    ttable {

    # Copy both input channels to output channel 0 (Left).
    0.0 1.0
    1.0 1.0
    # copy both input channels to output channel 1 (Right).
    0.1 1.0
    1.1 1.0
    }
}

#pcm.!default monocomplimiter


# EOF

pi@raspberrypi ~ $ grep -v '^$\|^\s*#' /etc/mpd.conf

music_directory         "/var/lib/mpd/music"
playlist_directory              "/var/lib/mpd/"
db_file                 "/var/lib/mpd/tag_cache"
log_file                        "/var/lib/mpd/mpd.log"
pid_file                        "/var/run/mpd/pid"
state_file                      "/var/lib/mpd/state"
sticker_file                   "/var/lib/mpd/sticker.sql"
user                            "mpd"
bind_to_address         "any"
metadata_to_use "artist,album,title,track,name,comment"
input {
        plugin "curl"
}
audio_output {
        type            "alsa"
        name            "My ALSA Device"
        device          "mcl"
}
mixer_type                      "disabled"
filesystem_charset              "UTF-8"
id3v1_encoding                  "UTF-8"


pi@raspberrypi ~ $ uname -r
3.18.3+

如果您需要更多信息，请告诉我。

编辑：

pi@raspberrypi ~ $ cat /proc/asound/cards
 0 [ALSA           ]: bcm2835 - bcm2835 ALSA
                      bcm2835 ALSA
pi@raspberrypi ~ $ cat /proc/asound/devices
  0: [ 0]   : control
  1:        : sequencer
 16: [ 0- 0]: digital audio playback
 17: [ 0- 1]: digital audio playback
 33:        : timer
pi@raspberrypi ~ $

有没有办法让 ALSA 从此处的配置创建虚拟设备，mpd 可以在其中找到它（如果它确实在那里搜索）？

编辑：

pi@raspberrypi ~ $ cat /proc/asound/pcm
00-00: bcm2835 ALSA : bcm2835 ALSA : playback 8
00-01: bcm2835 ALSA : bcm2835 IEC958/HDMI : playback 1
pi@raspberrypi ~ $ ls /proc/asound/dev
ls: cannot access /proc/asound/dev: No such file or directory
pi@raspberrypi ~ $ ls /dev/snd
controlC0  pcmC0D0p  pcmC0D1p  seq  timer
pi@raspberrypi ~ $ ls /proc/sound/
ls: cannot access /proc/sound/: No such file or directory
pi@raspberrypi ~ $ ls /proc/sound
ls: cannot access /proc/sound: No such file or directory
pi@raspberrypi ~ $ amixer
amixer: Mixer attach default error: Invalid argument
pi@raspberrypi ~ $ alsamixer
cannot open mixer: Invalid argument
pi@raspberrypi ~ $

编辑：

pi@raspberrypi ~ $ alsamixer -c 0

作品。

答案1

mpd的alsa输出没有找到设备，因为它确实没有定义！ （守护程序）以不了解“常规”用户的mpd用户身份运行mpdpi/home/pi/.asoundrc

这可以通过以用户身份运行播放器来测试mpd：

pi@raspberrypi ~ $ sudo -u mpd speaker-test -t wav -c 2 -D mcl

我在其他地方发现实际上有一个 alsa 配置文件

pi@raspberrypi ~ $ sudo nano /usr/share/alsa/alsa.conf

#
#  ALSA library configuration file
#

# pre-load the configuration files

@hooks [
        {
                func load
                files [
                        {
                                @func concat
                                strings [
                                        { @func datadir }
                                        "/alsa.conf.d/"
                                ]
                        }
                        "/etc/asound.conf"
                        "~/.asoundrc"
                        "/home/pi/.asoundrc" # added !
                ]
                errors false
        }
]
...

我已经添加了pi本地配置。

然后它就起作用了：

pi@raspberrypi ~ $ sudo -u mpd speaker-test -t wav -c 2 -D mcl

speaker-test 1.0.25

Playback device is mcl
Stream parameters are 48000Hz, S16_LE, 2 channels
WAV file(s)
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 256 to 16384
Period size range from 256 to 16384
Using max buffer size 16384
Periods = 4
was set period_size = 4096
was set buffer_size = 16384
 0 - Front Left
 1 - Front Right
Time per period = 2.944647
 0 - Front Left
^C

还带有 mpd

pi@raspberrypi ~ mpc play

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