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Enrique Moreno Tent
Asked: 2012-11-03 12:56:32 +0800 CST

Get the audio from Line-in to output to the speaker

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I have connected a console to the line-in of my computer. How can I make it so that the sound comes out of the speakers?

I've tried alsamixer and it didnt help

Im using Ubuntu 12.04

sound

4 Answers

  1. Best Answer

    Try use the pulse audio: module-loopback, this module loops all incoming audio back through your outputs ,that isn’t enabled in Ubuntu by default.

    # Manually start the module-loopback.
pactl load-module module-loopback

# Configure your system to load module-loopback on startup.
# This places load-module module-loopback at the end of
# the /etc/pulse/default.pa pulseaudio configuration file.
sudo sh -c ' echo "load-module module-loopback" >>  /etc/pulse/default.pa '

    This solution is copied from PulseAudio: Monitoring your Line-In Interface .

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  2. modification to xranby's answer:

    I was having a problem with latency where there was quite a noticeable amount of lag between my button-press and the "immediate" sound.

    This fixes that: pactl load-module module-loopback latency_msec=1

    source of fix: http://thelinuxexperiment.com/fix-pulseaudio-loopback-delay/comment-page-1/#comment-2762

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  3. In the end I entered into "alsamixer" and rised the level of the Line-in, which was at 0 and it worked (in Ubuntu 10.13)

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  4. I tried to do this using xranby's answer, and I found it quite confusing and time-consuming to figure out, for several reasons.

    The loopback module is designed so that by default, it doesn't take input from the mic. This is meant so that you won't get feedback. However, my mics are USB mics, and therefore they're not automatically excluded. For this reason, it's necessary to use source=... when loading the loopback module.

    If you don't successfully shut off the mics as inputs to the loopback, then it's also possible to get confused because you think everything is working, but actually it's not the line-in that's working, it's input going through the air from your stereo speakers to your mics.

    To figure out which source you need, do "pacmd list-sources | grep name:" (note the colon at the end). On my system, the first two on the list were my USB mics, while the fourth was "alsa_input.pci-0000_00_1b.0.analog-stereo" and the third was like that but with ".monitor" on the end of the name. This told me that the source I wanted was number 4.

    So to start up the loopback:

    pactl load-module module-loopback source=4

    To turn it off:

    pactl unload-module module-loopback

    If you want to make these settings permanent, see xranby's answer.

    There turned out to be three different volume controls that I had to find and set appropriately. On my hardware, I had a volume knob on my computer's speakers/headphones. Also, there are two different volume controls in pavucontrol. There's one under the input devices tab, and once you start up the loopback module there will also be a separate control in the playback tab saying something like Built-in Audio Analog Stereo; Port: Line in. If any one of these three is all the way down, then you get nothing. If either of the software ones is too high, you can get distortion.

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