Fldigi with QtRadio and Pulseaudio
A Skywave Linux user recently had a question about connecting the audio stream from QtRadio into Fldigi. It is not quite as simple as it seems, though it seems to work out-of-the-box on a lot of computers. On a lot of laptops, especially, speaker audio couples into the microphone and digimode reception is possible in Fldigi. A more effective way to operate is directing QtRadio's output into the Pulseaudio processing chain and also connecting Fldigi to that chain's "monitor". For example, look in QtRadio's audio settings and note that there's a choice for the equalizer-dynamics-limiter LADSPA modules. Feed audio into that and you can hear the receiver output. Next, start Fldigi and make sure its audio input is set to Pulse. Lastly, the critical connection is made in PaPrefs - where you route sound within Pulseaudio. Connect the "recording" audio for Fldigi to the same processing chain as the output from QtRadio. When that connection is made, signals from the radio should appear on the Fldigi waterfall, with no local noises picked up by the microphone. That's all there is to it. Simple as pi, right?
