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HiFiBerry OS: Volume logic

Diederik

May 04, 2023 21:25

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Hi,

For this thread, I would like to understand how the volume works because it is not clear to me. Most of volume controls rely on an external one (in the app you cast from: e.g. Spotify) 

So I wanted to check values and found

1. 1) In the HiFiBerry OS WebUI, the audio is set at around 50%
2. 2) when I check alsamixer my Digital is set to 14%
3. 3) and my alsamixer Softvol is set to 100%.

So I have 3 different values:

When I use my phone to change the Spotify volume, it updates the alsamixer Digital volume.

When I use the WebUI to change the volume, it also updates the alsamixer Digital volume. But the HiFiBerry OS WebUI 50% seems to actually map with 14% in my case? When I go to around 80% in the WebUI it is only 51% in alsa:

 

My goal

I really need my HiFiBerries to start at 12-14% so that my neigbours would not murder me when they get bombarded with volume if it would start at Digital volumes of 30/50/100%.

Lucky for me I used Spotify most of the time and I can set the Digital volume in the /etc/vollibrespot.conf to start at 12%.

TO BE

I want to fix everything now so...

1. 1) How does the volume work in the webinterface control? Why is the % not the same? How can I make it so?
   
   
2. 2) What alsa volume should the audio sources control in HiFiBerry OS?
   In a different thread it is mentioned that the Softvol audio is set at 100% on boot so
   
   
3. 3) Does that mean Softvol volume control should not be used and kept at 100%?
   Because in that case I found that on snapcastmpris, the alsa volume is looking at the Softvol on the snapcastwrapper so I guess I should replace 

   mixer = self.alsa.Mixer('Softvol')

   with

   mixer = self.alsa.Mixer('Digital')

   ?
   
   
4. 4) So, would it not make sense on HiFiBerry OS to then NOT use snapcastmpris with the Softvol?

Thanks in advance for clarifying the audio volume logic questions I have on HiFiBerry OS.

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4 comments

• 0
  
  HiFiBerry team May 05, 2023 11:16

  Different sound cards use different mixer controls. You can find the right mixer control for your sound card in /etc/hifiberry.state

  However, you can't fix the volume. Every player can change the volume and Spotify will do so. Even if you set the volume in the UI, this can be changed by every player.

  The slider in the UI is just a slider. It doesn't correspond to any "%" values. It is using a volume control range that's usuable for your sound card. Therefore the range will be different for different sound cards.

• 0
  
  Diederik May 05, 2023 15:54

  Found the relevant info in the hifiberry state. And it does indeed use Digital.

  CURRENT_PIMODEL=3B+
  CURRENT_MIXER_CONTROL="Digital"
  CURRENT_SECONDARY_MIXER_CONTROL=""
  CURRENT_CARD="DAC+/Amp2"
  CURRENT_HW="card 0"
  CURRENT_HW_SHORT=0

  So from that I'll conclude that for my amp, all audio sources should use Digital (and not have their settings pick another one: e.g. default snapcastmpris?) That answers that.

  I do not have any problem with the ability to change the volume. It is just that I cannot have the audio sources start at at a volume where Digital is 100%. Is there documentation where default starting volume levels can be set for each source (like you can with Spotify)?

  Regarding the WebUI slider, I guess it has some exponential function behind it because from the slider 0-80, the alsa Digital goes from 0-46. And from there setting the slider 80-100, makes the alsa Digital go from 46-100. Where can I see this available volume control range?

  Thanks!

• 0
  
  HiFiBerry team May 06, 2023 10:36

  For most sources, there is no such functionality to set he starting volume.The best way is to diretcly control the source volume from the music source (e.g. BT, Airplay, ...=

• 0
  
  Diederik May 06, 2023 11:18

  Thanks! I guess it makes sense to start from the last volume setting. On any other device when turning it on, it starts from the position where it was last left.

  To be fair, it is not really obvious to me how volume should be seen when dealing with a HiFiBerry setup. You have volume mixer settings on your audio device but I guess you might have a volume setting in the source application itself (on the HiFiBerry) as well as the application you are sending from remotely. So when you say to directly control the source volume from the music source, I am not entirely certain what volume you'd be influencing.

  But anyway, it is something I also see happening in Windows where you have System volume mixer, Windows application level volume mixer (100), the volume slider in the application (e.g. Spotify/game/...). And in my case, a fourth one: a physical audio knob on my headset. 

  I'll try out comparing the loudness with different sources and what the external volume control actually affects.

   

  EDIT: I found the answer to the discrepancy between alsamixer and the volume slider in the HiFiBerry WebUI . There is a different calculation of the "value".

  You can see this below in the difference of % values even though the dB and playback is the same.

  the parameter -M will give you the alsamixer result
  VS
  without the -M parameter, it shows the value you can see in the WebUI

  amixer -M get Digital
  Simple mixer control 'Digital',0
    Capabilities: pvolume pswitch
    Playback channels: Front Left - Front Right
    Limits: Playback 0 - 207
    Mono:
    Front Left: Playback 124 [20%] [-41.50dB] [on]
    Front Right: Playback 124 [20%] [-41.50dB] [on]
  amixer get Digital
  Simple mixer control 'Digital',0
    Capabilities: pvolume pswitch
    Playback channels: Front Left - Front Right
    Limits: Playback 0 - 207
    Mono:
    Front Left: Playback 124 [60%] [-41.50dB] [on]
    Front Right: Playback 124 [60%] [-41.50dB] [on]
  
  See also [solved] amixer output differs from alsamixer? / Newbie Corner / Arch Linux Forums

  Edited by Diederik June 28, 2023 21:01