FFmpeg Media Encoder — a set of free open source libraries that allow you to record, convert and transfer digital audio and video recordings in a variety of formats. It includes libavcodec, a library for encoding & decoding audio & video, and libavformat, a library for multiplexing & demultiplexing to a media container. The name comes from the name of the expert group MPEG and FF, meaning fast forward. (more)
FFmpeg is already built into the program and does not require downloading additional codecs.
Conversion takes place directly on the device (Internet is not required), and the speed of conversion depends on the speed of the device processor.
Supports: MPEG4, h264, mp3, 3gp, aac, ogg (vorbis и theora) and many other formats (you will find the list in the program itself). Optimization for ARMv6(vfp) и ARMv7 (cortex-a8)
Built-in: FFmpeg v0.10 + libx264 + libmp3lame + libvorbis + libtheora + libfaac