ALSA

This document provides a basic overview of configuring ALSA on a Debian system so that it is useful with things like liquidsoap and darkice.

These instructions are based on setup with Debian Jessie with a minimal installation.

To begin, you'll probably need to install alsa-utils if you're running a minimal system. To install alsa-utils, run this command as root:

1. apt-get install alsa-utils

Once this package is installed, you'll have tools to make use of ALSA on your system. The first thing we need to do is determine which capture card you will be using for your audio input and output. Connect an input audio source (like a scanner) to the line-in on your sound card. Connect a set of headphones or speakers to the headphone jack on the same sound card. Make sure your scanner has enough traffic for good monitoring or temporarily switch it over to a weather station so that you have regular sound input. Once you're ready to monitor, run this command as root:

1. alsamixer

This will produce a text-mode sound mixing console where you can configure the attributes of the sound card. We will be using this tool to determine which sound card you're using and what input should be selected.

To begin, press F6 to select your sound card. If you only see three options, you most likely only have one sound card that is detected. If you only have one, just press escape. If not, select the card that contains your input devices and press Enter.

Once the correct device is selected, press F3 to ensure that we're in PLAYBACK mode. We'll locate the input device this way using monitoring. Next, we need to unmute the sound system generally speaking. Using your arrow keys, make sure that the Master is highlighted red. Press the M key to unmute the master channel (it is muted by default). Right above the level, it will now show 00 instead of MM to indicate that it is unmuted: