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Use of ALSA

Richard Valler

April 14, 2015 02:00

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Hi,

How can enable plughw for the Amp as per the output from the beta testing thread:

i@pi:~$ aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
sysdefault:CARD=sndrpihifiberry
    snd_rpi_hifiberry_amp,
    Default Audio Device
dmix:CARD=sndrpihifiberry,DEV=0
    snd_rpi_hifiberry_amp,
    Direct sample mixing device
dsnoop:CARD=sndrpihifiberry,DEV=0
    snd_rpi_hifiberry_amp,
    Direct sample snooping device
hw:CARD=sndrpihifiberry,DEV=0
    snd_rpi_hifiberry_amp,
    Direct hardware device without any conversions
plughw:CARD=sndrpihifiberry,DEV=0
    snd_rpi_hifiberry_amp,
    Hardware device with all software conversions

I require the use of configuring /etc/asound.conf to convert the stereo output to mono and control the output of each channel

Regards

Richard

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15 comments

• 0
  
  HiFiBerry team April 14, 2015 09:37

  Dear Richard,
  
  we haven't tried to use plughw. Note that not all ALSA plugin might work. Some only works with mmap which is not supported on the Raspberry Pi I2S sound interface.
  
  Best regards
  Daniel
• 0
  
  Richard Valler April 14, 2015 19:36

  Hi Daniel,
  
  Thanks for the responce. It seams that using ALSA may not be possible for my application.
  
  Before using the Amp, I used the the following asound.conf file to downmix the stereo to mono and be able to output to each channel separately
  
  

  
  pcm.!default {
   	       type plug
          	slave.pcm "hw:0,0"
  	        slave.channels 2
  	        ttable.0.0 0.5          # L(0) to L(0) at 0.5 volume
  	        ttable.1.0 0.5          # R(1) to L(0) at 0.5 volume
  }
  
  ctl.!default {
  	        type hw
  	        card 0
  }
  
  pcm.right {
  	        type plug
  	        slave.pcm "hw:0,0"
  	        slave.channels 2
  	        ttable.0.1 0.5          #L to R at 0.5 Volume
  	        ttable.1.1 0.5          #R to R at 0.5 Volume
  }
  
  ctl.right {
  	        type hw
  	        card 0
  }
  

  
  
  
  
  Then ran 2 instances of squeezelite, one outputting to default the other to right.
  
  At the very least I need to downmix the stereo to mono (and then control each channel using amixer).
  
  Do you have any advice/pointers of how I can proceed?
  
  Regards
  
  Richard
• 0
  
  HiFiBerry team April 15, 2015 09:18

  Hi Richard,
  
  you might have a look at ALSAEqual. I'm not sure if if can only equalize or also mix.
  http://www.thedigitalmachine.net/alsaequal.html
  
  Best regards
  Daniel
• 0
  
  Richard Valler April 19, 2015 17:27

  Hi Daniel,
  
  Thank you for your pointer. In short, ALSA Equal does not also mix, but it does facilitate adding routing to the asound.conf file, enabling downmixing stereo to mono etc. (volume control per channel is through alsamixer or amixer)
  
  Now all that is required is a squeezebox plugin for balance controls!
  
  
  For anyone wanting mono output from the Hifiberry Amp:
  
  Install ALSAMixer - I followed the guide here
  
  But to reiterate:
  
  sudo apt-get install -y libasound2-plugin-equal
  
  Then edit or create /etc/asound.conf as follows
  

  ctl.equal {
       type equal;
       controls "/home/pi/.alsaequal.bin"
  }
   
  pcm.plugequal {
       type equal;
       slave.pcm "plughw:0,0";
       controls "/home/pi/.alsaequal.bin"
  }
   
  pcm.equal {
       type plug;
       slave.pcm plugequal;
       slave.channels 2
       ttable.0.0 0.5          # L(0) to L(0) at 0.5 volume
       ttable.1.0 0.5          # R(1) to L(0) at 0.5 volume
       ttable.0.1 0.5          # L(0) to R(1) at 0.5 Volume
       ttable.1.1 0.5          # R(1) to R(1) at 0.5 Volume
  }

  
  
  
  
  
  Finally edit the squeezelite settings file to use -o equal and reboot
  
  
  Regards
  
  Richard
• 0
  
  David Lichtenegger February 18, 2016 10:01

  Thanks for the mono-configuration. 

  Did you ever manage to run 2 instances of squeezelite and output the sound to the right and left channels of hifiberry amp+ individually ?
  In my opinion this would be the most flexible solution for this specific use-case.

  Maybe hifiberry-support can give some advice on how (or if) this is possible?

  If not possible, I'd also be interested in the squeezebox plugin for balance controls. Is there already a simple solution for controling the two channels individually?

  Thank you very much.

• 0
  
  HiFiBerry team February 18, 2016 10:03

  Dear David,

  we haven't tested this, so it's your turn to try out if this works. It might be also interesting for other users, let us know if you get it running.

  Best regards,
  Daniel

• 0
  
  David Lichtenegger February 19, 2016 08:05

  I managed to do it pretty easily because of finding this post:

  https://github.com/raspberrypi/linux/issues/1004#issuecomment-133852133 

  Here's the configuration:

  config.txt

  dtoverlay=i2s-mmap
  dtoverlay=hifiberry-amp

  asound.conf (I blacklisted the onboard audio driver hence hw:0)

  pcm.onboard {
  type hw
  card 0
  }

  pcm.!default {
  type plug
  slave.pcm "onboard_dmix"
  }

  pcm.onboard_dmix {
  type dmix
  ipc_key 1024
  ipc_key_add_uid 1
  ipc_perm 0666
  slave {
  pcm "onboard"
  channels 2
  }
  bindings {
  0 0
  1 1
  }
  }

  pcm.zone1 {
  type plug
  slave.pcm onboard_dmix
  slave.channels 2
  ttable {
  0.0 0.5
  1.0 0.5
  0.1 0
  1.1 0
  }
  }

  pcm.zone2 {
  type plug
  slave.pcm onboard_dmix
  slave.channels 2
  ttable {
  0.0 0
  1.0 0
  0.1 0.5
  1.1 0.5
  }
  }

   

• 0
  
  Dr Photon November 07, 2016 20:38

  Hi all,

  thanks for providing that setup!

  I have a Raspberry Pi 3 with a Hifiberry Amp+. In order to play sound to each of the speaker seperately I've used the suggested asound.conf . Streaming music to one of the channel (e.g. squeezelite -o zone1) works for a while; after a certain time the sound "hangs" (like a sratched CD). It is reproducable; second setup; same asound.conf .

  What is wrong on my setup?

  Can you please point me to the right direction?

  changes in config.txt done:
  dtoverlay=i2s-mmap
  dtoverlay=hifiberry-amp

  Regards.

  Edited by Dr Photon November 07, 2016 20:39
• 0
  
  Norbert Biedermann June 13, 2018 18:05

  For Amp2, the mono setup doesn't work anymore.

  Can anyone help to find out how mono works on Amp2?

   

  Thanks in advance,

  Norbert

   

  Edit: I found out that a simple hardware trick is solving the problem.

  Put the cable of your speaker to -pin  of the right channel and to +pin of the left channel. Result is mixed output, don't know if it is a supported way.

  Edited by Norbert Biedermann June 14, 2018 18:02
• 0
  
  Simon August 17, 2018 21:04

  Hi Norbet has this method worked out ok? I am looking to have the amp push to a mono spealer.

• 0
  
  Norbert Biedermann August 18, 2018 07:14

  Hi Simon,

  Yes for me it's working fine since 2 months :)

• 0
  
  mc-hollin October 06, 2021 13:43

  Hi,

  I have to reactivate the thread. I can't find an approach anywhere.

  My System is a Hifiberry miniamp with an Raspberry OS lite.

   

  I also want to split the speakers into two doorbells.

  After I re-set up the Raspi, it worked. But not anymore.

  The ~/.asoundrc also does not exist.

   

  Here is my asound.conf:

  pcm.hifiberry {
    type hw
    card 0
    device 0
  }
  
  pcm.hifiberry_dmix {
    type dmix
    ipc_key 1024
    ipc_key_add_uid 1
    ipc_perm 0666
    slave {
      pcm "hifiberry"
      channels 2
    }
    bindings {
      0 0
      1 1
    }
  }
  
  pcm.hifiberry_softvol {
    type softvol
    slave.pcm "hifiberry_dmix"
    control.name "Master"
    control.card 0
  }
  
  pcm.speaker_left {
    type plug
    slave.pcm "hifiberry_softvol"
    slave.channels 2
    ttable {
      0.0 1
      1.0 1
      0.1 0
      1.1 0
    }
    hint.description "Hifiberry miniamp speaker left"
  }
  
  pcm.speaker_right {
    type plug
    slave.pcm "hifiberry_softvol"
    slave.channels 2
    ttable {
      0.0 0
      1.0 0
      0.1 1
      1.1 1
    }
    hint.description "Hifiberry miniamp speaker right"
  }
  
  pcm.!default {
    type plug
    slave.pcm "hifiberry_softvol"
  }

  Only the right speaker is connected.

  mpg123 --audiodevice speaker_right --scale 8000 'Default.mp3'

  plays sound on the right speaker.

  mpg123 --audiodevice speaker_left --scale 8000 'Default.mp3'

  plays sound on the right speaker too.

  Why???

  My boot/config.txt:

  dtparam=i2c_arm=on
  dtparam=i2s=on
  dtparam=spi=on
  dtoverlay=hifiberry-dac
  dtoverlay=i2s-mmap

  I have the feeling Hifiberry is set to mono or something like that.

  Can anyone tell me what I'm doing wrong? I'm slowly despairing.

• 0
  
  mc-hollin October 07, 2021 19:03

  I think I found the error.

  The following entry was missing in the boot/config.txt, 

  force_eeprom_read=0

  After a reboot, the following setting worked.

  pcm.onboard {
  type hw
  card 0
  }
  
  pcm.!default {
  type plug
  slave.pcm "onboard_dmix"
  }
  
  pcm.onboard_dmix {
  type dmix
  ipc_key 1024
  ipc_key_add_uid 1
  ipc_perm 0666
  slave {
  pcm "onboard"
  channels 2
  }
  bindings {
  0 0
  1 1
  }
  }
  
  pcm.speaker_right {
  type plug
  slave.pcm onboard_dmix
  slave.channels 2
  ttable {
  0.0 1
  1.0 1
  0.1 0
  1.1 0
  }
  }
  
  pcm.speaker_left {
  type plug
  slave.pcm onboard_dmix
  slave.channels 2
  ttable {
  0.0 0
  1.0 0
  0.1 1
  1.1 1
  }

  I believe that not every change works directly.

  Most of the time, something has only changed after a reboot.

  Maybe that will help one or the other.

• 0
  
  HiFiBerry team October 07, 2021 19:06

  I'm pretty sure it has nothing to do with this as the MiniAmp doesn't have an EEPROM. Therefore this setting has just no effect. It doesn't hurt, but it doesn't explain that it works now. However, if you changed the asound.conf with the player software running, this will explain the problem as usually, this is only read when the program starts. Therefore, changes in the asound.conf require a restart of the player application.

• 0
  
  mc-hollin October 09, 2021 09:27

  Ok, then first thank you for the info.

  I have tested this and you are right.

  But now I don't understand why it works now.

  I change the asound.conf and then start mpg123 from the console with the respective parameter for the pcm device.

  mpg123 --audiodevice speaker_right test.mp3
  mpg123 --audiodevice speaker_left test.mp3

  And both plays on the right speaker.

  Only when I entered the parameter force_eeprom_read=0 in the boot/config.txt and restarted it, it worked.

  But I also have to say that I tried it more then once and don't even know what I've tried anymore.

  Is there still another area where settings for the Hifiberry may be saved?

  The file "~/.asoundrc" does not exist.

   

  P.S.:

  I have changed left and right in asound.conf.

  Speaker test has shown this.

  speaker-test -c2 -twav -l7

   

  Edited by mc-hollin October 09, 2021 09:31