When working with ALSA and SOC (system on a chip) drivers, the codec refers to the audio hardware. That is, the microchip that implements the audio system. These chips can be connected to the processor in various ways, and controlled through various protocols. Most of them are highly configurable with many different audio paths and gains to control. In general, the Linux driver for these chips will define a number of ALSA controls that applications can use for codec configuration.
Two of the applications that can configure codecs through ALSA are alsamixer and alsactl. The alsamixer program has a graphical interface that uses terminal line drawing to show a series of sliders and buttons that represent the various codec controls. The user can move between the controls and adjust their levels using the arrow keys. These adjustments have immediate effect, so alsamixer can be used with aplay and/or arecord to try out different configurations live. The alsactl program can store and load configurations to and from files. This is useful because a lot of embedded systems will use a static configuration that never changes. Once all the settings are decided on, alsactl can save them to a file, and that file can be loaded every time the system starts up.
VOCAL’s optimized vocoder software is available for the following platforms. Please contact us for specific vocoder supported platforms.