AudioProvider.cpp initializing fails when using 4 channels.

[TheJollyDuck]

Hi,

I'm having problems with the AudioProvider.cpp code when allChannels = true in AudioProvider.cfg. I'd like to utilize all 4 channels. Here is the part I've had problems with in the code:

AudioProvider::AudioProvider()
{
  allChannels ? channels = 4 : channels = 2;
  int brokenFirst = (theDamageConfigurationHead.audioChannelsDefect[0] ? 1 : 0) + (theDamageConfigurationHead.audioChannelsDefect[1] ? 1 : 0);
  int brokenSecond = (theDamageConfigurationHead.audioChannelsDefect[2] ? 1 : 0) + (theDamageConfigurationHead.audioChannelsDefect[3] ? 1 : 0);
  unsigned i;
  for(i = 0; i < retries; ++i)
  {
    if(brokenFirst > brokenSecond)
      FAIL("Cannot handle broken microphones");
    if(snd_pcm_open(&handle, allChannels ? "PCH_input" : "default", SND_PCM_STREAM_CAPTURE, 0) >= 0)
      break;
    Thread::sleep(retryDelay);
  }
  ASSERT(i < retries);
// Rest of the code....

For some reason snd_pcm_open() returns a negative value, meaning that it fails to make the connection, which I found out as ASSERT(i < retries); fails. That leads me to ask these questions:

1. What is the significance "PCH_input" and "default", and why is "default" used for 2 channels, and the other used for 4 channels?
2. Are there some things I should do to avoid this issue, while being able to use all 4 channels?

[ahasselbring]

I'm not sure if we have ever tried using all channels after switching to the Ubuntu-based image.

"PCH_input" and "default" were the respective "PCM handle identifiers" (ALSA nomenclature is a bit complicated) on the standard NAO6 image.

[ahasselbring]

Maybe one needs to do additional things in the ALSA configuration to actually get a 4-channel audio stream (https://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html#pcm_plugins_multi). I remember something like that was done in the original Ubuntu image generator script by the Nao Devils, so they may know more.

[ahasselbring]

I am closing this since, although it's arguably a bug, it's not something that occurs in the default configuration of the system and is therefore out of the scope of things we fix after a release.