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I try to make a screencast where I need to record both microphone and pc output sound (and video of course) . I tried to make a loopback in pulseaudio to "merge" them and using this sink with the recording tool (first i tried recordmydesktop then ffmpeg/avconv).

But the issue is when I use this loopback , the sound is glitching (I think this is the better word describing it) and have progressive delay (meaning a lot lot delay after 2/3 minutes). This is not happening when using direct output (mic or pc output).

I tried to reduce the delay of the loopback to 1ms , didn't change anything (it didn't want 0ms)

Is there any way I can resolve this. I hear about realtime pulseaudio but i think this is a kind a cpu eater? (and we need a RT kernel wich I think I don't have)

I also try to install jackd but without great success (and apparently it's a pain in the ass to make it working with avconv).

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2 Answers 2

Rather than creating a loopack sink with pulseaudio-module-loopback in most sound card harwares we have the possibility to merge a source with a sink by using a duplex audio profile.

To switch to a duplex profile we can run pavucontrol Install pavucontrol to select the "Analog Stereo Duplex" profile for our soundcard in the "Configuration" tab.

enter image description here


We can also change sink output profile from the command line with <index> and possible <profiles> of cards listed with

pacmd list-cards

To change the card profile we may then issue

pacmd set-card-profile <index> <profile>

To combine output sinks we may run paprefs Install paprefs which give us an option for a "Simultaneous output device":

enter image description here

This combined device can also be loaded from the command line by loading the module module-combine-sink.

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I did succeed to add the virtual output , but i can't get the mic input in it (i can only redirect application that plays sound to the simultaneous output). I missing something ? –  eephyne Jan 12 '13 at 11:04
    
@eephyne: did you manage to choose a duplex profile? –  Takkat Jan 12 '13 at 13:09
    
yes i selected it via pavucontrol and pacmd said: active profile: <output:analog-stereo+input:analog-stereo> –  eephyne Jan 12 '13 at 13:39
    
@eephyne: just a guess: are any microphone or capture devices muted? See with alsamixer, or with pacmd list-sinks. –  Takkat Jan 12 '13 at 16:46
    
I don't think since I can record microphone (computer not on right now can't check this out). –  eephyne Jan 12 '13 at 18:45
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Duplex means the card acts as both an input and an output device for audio. It does not mean that it simply combines the output and the input into a single stream. And all the virtual output does is combine the sinks like you said, so that you can output from two separate cards at once. Neither of these accomplish what the OP, and myself, are trying to do.

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