| Current AAC encoders|
(most to least recommended)
|1||Apple AAC M/W|
|2||Fraunhofer FDK AAC S/L/M/W|
|3||Nero AAC L/W|
|4||FFmpeg 3.0+ AAC encoder S/L/M/W|
|6||Libav (pre-3.0 FFmpeg) AAC encoder S/L/M/W|
|S Source code available; L Linux; M macOS; W Windows|
|List of AAC encoders|
The VisualOn AAC encoder was included in early versions of Android as part of the Stagefright AV library. It is known to be very very poor, but its source code was available before Fraunhofer FDK AAC. The encoder supports only AAC-LC, 2 channels, CBR. The CBR mode, however, was found to be just a 64kbps encoder that adds extra padding to hit whatever target is requested.
It was developed by a company called VisualOn, although there was some question about where the code actually came from. It is probably just re-wrapped AAC reference implementation code.
Martin Storsjö (as the opencore-amr project) maintains a source code distribution of the VisualOn AAC library as libvo-aac. libvo-aac is supported in Libav, and was supported in FFmpeg until version 3.0 (February 2016).