Fdk-aac

Fraunhofer FDK AAC is an open-source library for encoding and decoding AAC.

Though open-source, it is not entirely free.
Different open-source communities have different interpretations:

• Fedora - free
• Debian - undecided after long discussion, assumed to be non-free
• GNU Project - technically free, but dangerous

The fdkaac module is based off fdk-aac and used in VLC media player since 2.1.0. It is dual-licenced under LGPL v2.1 and BSD 2-clause.

Source code

• modules/codec/fdkaac.c

Links

• Git at Google - platform/external/aac (Official repository)
• GitHub - fdk-aac source code