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Pulse Audio

PulseAudio is a sound server that is meant to handle all available sound streams, including the ones that applications attempt to write directly to hardware (/dev/dsp).

In a Linux installation, often ALSA is configured to use a virtual device provided by PulseAudio so applications use ALSA, but output sound via PulseAudio, which then uses ALSA to control the real sound card. PulseAudio can also be used by applications directly. The padsp utility, replaces device files such as /dev/dsp, so that applications that attempt to use /dev/dsp really go through PulseAudio.

  • How can I use a MIC input as an alternate Line In?
    • Run the following command:
      $ pactl load-module module-loopback [1]
      This command outputs a number that may be used to unload the module.
    • To stop the loop back of MIC IN to Line In:
      • Use the number output by the load-module command:
        $ pactl unload-module n
      • Use a one-liner that queries the module number:
        $ pactl unload-module `pactl list short modules | awk '$2 == "module-loopback" { print $1 }' - `
      • Use a script to unload it by name ( http://umonkey-tools.googlecode.com/hg/bin/pactl-unload-by-name ):
        $ pactl-unload-by-name module-loopback
    • To load module-loopback automatically on a per-user basis:
      • Append the load-module command to /etc/pulse/default.pa
        # # Make MIC IN equivalent to LINE IN. # load-module module-loopback