[pulseaudio-discuss] Play Audio from PC Line-In or Microphone

[Raymond Yau]

2014/1/20 James Board <jpboard2 at yahoo.com>

> I want to do something simple.  Play the audio that 's coming into my
> (CentOS)
> PC on Line-IN on my PC speakers.  How can I do this?  I tried the following
> command
>
>     load-module module-loopback latency_msec=1
>
> Which seems to work sometimes, but everytime I disconnect the input,
> I have to do the above command again.  And after a few times, when I
> run the above command, it crashes pulseaudio.  What's the correct
> way to play audio from the LineIN to the PC Speakers?  If this is
> possible outside pulseaudio, that is okay.
>

Assuming your PC have one blue line in jack

unmute "Line Playback Switch" and set "Line Playback Volume" using amixer
-c0 or alsamixer

some HDA codec may have a "Loopback mixing" switch which can enable/disable
the loopback mixer for power saving

you may also need to set "Line Boost" to 0dB for some HDA codec

for motherboard with three audio jacks at rear panel, you have to set
"channel mode" to "2ch" ,   since line in jack is retasked to output for
"4ch" and "6ch"

for motherboard with five audio jacks at rear panel, you need to set
"channel mode" to "6ch" since line in jack is retasked to output for "8ch"
to support 7.1

on some notebook with HDA codec and mic jack but no line in jack , you may
also retasked the mic jack to line in jack by switching "Mic jack Mode" to
"Line in" after you specify hint add_jack_modes = 1 by early patching

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/Documentation/sound/alsa/HD-Audio-Controls.txt

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/Documentation/sound/alsa/HD-Audio.txt
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