Ytdyklly

I am trying to set up an Raspberry Pi / Raspbian wheezy audio player using the onboard sound hardware via ALSA LADSPA plugins to stereo downmix and compress the audio.

aplay, sox, mpg123, moc (cd ~/.moc && cp /usr/share/doc/moc/examples/config.example.gz ./ && gunzip config.example.gz && mv config.example config) work with this custom "device":

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

I have built the current mpd version from source (http://www.musicpd.org/download/mpd/0.19/mpd-0.19.8.tar.xz) following this tutorial:
http://www.infofreako.info/2014/04/building-mpd-on-raspberry-pi-with-opus-support/ (needs additional dependencies libboost-dev and libicu-dev)

pi@raspberrypi ~ $ mpc version

mpd version: 0.19.0

pi@raspberrypi ~ $ mpd --version

Music Player Daemon 0.19.8

but still get the error:

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

It does work fine when using the default device (ladcomp does not work either).

So there is either something wrong/missing in my ALSA configuration that the other players are guessing or mpd is doing it wrong.

There is no /etc/asound.conf, I created the following ~/.asoundrc using several sources

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+

Let me know if you need more info.

Edit:

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 ~ $

Is there a way for ALSA to create virtual devices from the config in here, where mpd could find it (if it does search there)?

Edit:

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 ~ $

Edit:

pi@raspberrypi ~ $ alsamixer -c 0

works.

mpd's alsa output does not find the device, because it really is not defined!
mpd (the daemon program) is run as user mpd which does not know about the "regular" user pis /home/pi/.asoundrc

This can be tested by running a player as user mpd:

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

I have discovered elsewhere that there is in fact an alsa configuration file

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

        }

]

...

to which I have added pi's local config.

And then it works:

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

Also with mpd

pi@raspberrypi ~ mpc play