解决ffmpeg在android移植的问题，使之不依赖底层surface和audiotrack-Solve the problem of ffmpeg in android transplant, so that does not depend on the underlying surface and audiotrack

实现播放视频的一个android视频播放器，主要能进行快进、快退，任意拖动进度，调节音量大小等等。-Play video android video player, major fast-forward, rewind, arbitrary drag the progress, adjust the volume, and so on.