A52 plugin

To enable 5.1 output through a digital output:

1. get a Dolby Digital encoder license; either
   • buy it from Dolby Labs, or
   • you already got one when you bought a sound card that ships with such an encoder, or
   • you don't need one because software patents are not valid in your jurisdiction;
2. install the ffmpeg package (which is not shipped with most distributions for legal reasons);
3. recompile the alsa-plugins package;
4. configure ALSA to use the a52 plugin (see doc/a52.txt).