VP8, a codec from google, has been recently added in the amsip SDK on all platforms. VP8 is mostly equivalent to H264 for quality/bitrate and the libvpx implementation (BSD like license) from google is highly optimised. The main interest is that google is also providing all of their patents to allow free usage of VP8 in application.
VP8 is highly optimised for arm and neon platform. It provides significant performance improvements for iOS and android as well as for desktop (windows, macosx, linux) version.
Check latest version of Voip By Antisip on the android market to see the impressive results!