The best open source software from this category:
CDEX
CDex is a CD-Ripper, extracting digital audio data from an Audio CD. The application supports many Audio encoders, like MPEG (MP2,MP3), VQF, AAC encoders.
AC3Filter
AC3Filter is a high quality free audio decoder and processor filter. It allows media players to playback movies with AC3 and DTS audio tracks. Also it can process any audio track, much of processing options allows to adjust the sound in almost any way. It is possible to upmix any audio source to 6 channels. Filter can do multi-channel and digital (SPDIF) output. It can encode any audio source to AC3 on-the-fly and send it over SPDIF to the receiver.
Ghostscript
Ghostscript is an interpreter for the PostScript language and for PDF.
