GNU Radio: Use sound output as input source

Question

In gnuradio-companion I\'m using the audio source block as my input signal for the next blocks. All works almost fine. The only little problem is that I\'m

Answer 1

You will need build a "monitor" ALSA device.

I found this ArchLinux wiki page which recommends the following procedure, which should apply to Ubuntu, too, as that also uses PulseAudio:

pactl list|grep monitor

pick the right monitor string, e.g. alsa_output.pci-0000_00_1b.0.analog-stereo.monitor. Then create (if it doesn't exist) and edit .asoundrc in your home directory:

gedit ~/.asoundrc

Add

pcm.pulse_monitor {
  type pulse
  device <device name from above>
}

ctl.pulse_monitor {
  type pulse
  device <device name from above>
}

to that file.

Now, use pulse_monitor as your device string in the Audio source. Works well for me (on Fedora 22):

EDIT:

Added a GNU Radio wiki page about this.