The file /etc/gnuradio/conf.d/gr-audio-alsa.conf contains the default options:

  • default_input_device = hw:0,0
  • default_output_device = hw:0,0

From the alsa entry in wikipedia:

the hw interface provides direct access to the kernel device, however, no software mixing or stream adaptation, while plughw or default enables sound output where the hw interface would produce an error.

So instead of everytime setting the options.audio_output parameter in our python code to “plughw:0,0”, it’s easier to just change these two values in the above mentioned file…