What is Fraunhofer?

It is a German research organization focussing on applied science in different fields. They have played an important role in developing Digital Audio Broadcasting (DAB).

What is FDK-AAC?

It is an open-source library used to create software AAC encoders and decoders. ODR-mmbTools uses this library for the AAC encoder (AudioEnc).

Make sure it is loaded into memory when compiling the ODR-mmbTools AudioEnc.

The library resides on GitHub under the name “fdk-aac” but will be installed anyway when installing the “ODR-AudioEnc” module. It accepts PCM and WAV audio input streams and codes them into AAC LC (default), HE-AAC v1 (SBR), HE-AAC v2 (SBR+PS), AAC-LD, and AAC ELD.

For us interested in realizing a DAB+ radio transmitter with ODR-mmbTools AudioEnc, the following AAC types will be important.

  • AAC LC (for high bitrates)
  • HE-AAC v1 (+SBR for standard bitrates)
  • HE-AAC v2 (+SBR +PS for low bitrates)