OPUS, a totally open, royalty-free, highly versatile audio codec, has been recently added in the amsip SDK on all platforms. OPUS has been standardized by IETF, published as RFC 6716 and an implementation is provided under a BSD like license.
As for VP8, several patent holders (namely Xiph.Org, Broadcom and Microsoft) on opus, allow free usage of their patents.
Here is some info from the opus website:
Opus can handle a wide range of audio applications, including Voice over IP, videoconferencing, in-game chat, and even remote live music performances. It can scale from low bit-rate narrowband speech to very high quality stereo music. Supported features are:
- Bit-rates from 6 kb/s to 510 kb/s
- Sampling rates from 8 kHz (narrowband) to 48 kHz (fullband)
- Frame sizes from 2.5 ms to 60 ms
- Support for both constant bit-rate (CBR) and variable bit-rate (VBR)
- Audio bandwidth from narrowband to full-band
- Support for speech and music
- Support for mono and stereo
- Support for up to 255 channels (multistream frames)
- Dynamically adjustable bitrate, audio bandwidth, and frame size
- Good loss robustness and packet loss concealment (PLC)
- Floating point and fixed-point implementation
You can get full information by visiting www.opus-codec.org