AudioTrack::start/stop，开始/停止播放，主要是：
- start、startOutput、start_output_stream
- stop、stopOutput、stop_output_stream
- pause、flush、release
AudioTrack::start
startOutput
AudioTrack::stop
stopOutput
AudioTrack::pause
remove活跃的track
AudioTrack::flush
清空buffer
AudioTrack::release
removeTrack_l