This project implements a plugin for the Video Disk Recorder also called "VDR"
to support the bitstreamout of Dolby Digital audio streams also called "AC-3" or "A52"
out plug of a sound card supported by ALSA
(Advanced Linux Sound Architecture).
No decoding(!) of the bitstream will happen during forwarding the data, at least a sound card with S/P-DIF out and a hardware decoder or an amplifier/receiver with integrated decoder is required (most modern A/V Receiver have such thing) connected to the sound cards S/P-DIF out.
Video Disk Recorder http://www.cadsoft.de/people/kls/vdr
The ALSA project at http://www.alsa-project.org
The DVB driver at http://www.linuxtv.org/