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Examples of Alsa warnings got by many applications (etc Matlab 2016a), which naturally appear in many applications but which differentiation into important and non-important ones has been difficult for me; I keep all warnings important, once I get them so I really would like to silent non-important warnings

ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:947:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:947:(find_matching_chmap) Found no matching channel map

MathWorks' support service proposes to silent the warnings by Alsa config file /etc/asound.conf. However, I disagree with their policies of giving such warnings in the first place i.e. calling the function audiodevinfo each time when calling sound/soundsc/audioplayer/audiorecorder commands in Matlab 2016a. So I would like to understand how it is good to silent those warnings such that you do not miss any critical piece of information. Open

  • ignorance - application specific
  • ...

Characteristics of the system

  • root@masi:/home/masi# less /proc/asound/cards

    0 [PCH            ]: HDA-Intel - HDA Intel PCH
                         HDA Intel PCH at 0xdf128000 irq 127
    

Rejected proposals

  1. Edit /usr/share/alsa/alsa.conf and change

    # https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=129648
    pcm.front cards.pcm.default # original pcm.front cards.pcm.front but issue with Matlab
    
  2. Restart pulse

    pulseaudio -k
    
  3. Output: unsuccessful, the errors keep coming

Matlab 2016a's part

Answer from MathWork's tech support

These warnings are generated when you execute the "audiodevinfo" function for the first time which is called internally when you execute the "sound/soundsc/audioplayer/audiorecorder" commands. The "audiodevinfo" tries to enumerate all the devices on the system.

The warnings are generated by the ALSA system libraries and it does not affect the behavior of MATLAB. The cause of this issue is not related to MATLAB. I would like to suggest you to take a look at the ALSA config files such as "/etc/asound.conf" to resolve the warning messages. However, assisting you with editing the ALSA config files would be outside the scope of our Technical Support.

I think Matlab should design their product such that you do not get those warnings. It can a mark of bad design if you call such an info function from another function.

How to proceed with the design of /etc/asound.conf?

Hardware: Asus Zenbook UX303UA
OS: Debian 8.5
Linux kernel: 4.6 (backports)
Matlab: 2016a, 2016b prerelease
Related: How to Configure ALSA in Ubuntu 16.04 for Macbook and Matlab? but for Ubuntu 16.04

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The common solution is to just ignore them at the moment because they should not be complicating and/or harming anything.

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