ffmpeg是一个大项目，它包含各种音视频标准的codec，还支持各类file format（.avi, .mp4, .mkv and etc）的parsing。所以，很多开源项目都有直接或间接地采用了ffmpeg，-ffmpeg is a big project, which includes all the standard audio and video codec, also support a variety of file format (. avi,. then no time.

IOS中，H264视频编码的avi文件转mp4文件格式。-In IOS，change avi file to mp4 file with H64 video encode.