VisualOn AAC

Current AAC encoders (most to least recommended)
1	Apple AAC M/W
2	FhG AAC (Winamp) W
3	Fraunhofer FDK AAC S/L/M/W
4	Nero AAC L/W
5	FFmpeg 3.0+ AAC encoder S/L/M/W
6	FAAC S/L/M/W
7	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).

External links

• VisualOn at Wikipedia
• libvo-aac source at GitHub
• FFmpeg AAC encoders listening test (in Japanese) includes libvo-aac
• VisualOn AAC Encoder thread in the HydrogenAudio forum