[ from developer's site ]
It is a free library for decoding ATSC A/52 streams, aka AC-3. The
A/52 standard is used in a variety of applications, e.g., digital
television and DVD. The main goals in liba52 development are:

Portability - most of the code is written in C, and when we use
platform-specific optimizations we always have a generic C routine
to fall back on.

Reusability - we do not want liba52 to include any project-specific
code, but it should still include enough features to be used by
very diverse projects.

Precision - We are trying to implement all of the A/52 standard,
and to have a very precise output by doing all the calculations in
floating point. We have a test suite that detects any deviation in
the output when compared to previous versions. We do not have access
to official A/52 test vectors though, so we have to use our judgement
to ensure that such deviations are only introduced when we fix bugs!

Speed - liba52 is really fast, on any modern PC it should take only
a few percent of CPU time.