* Refactor FrameReader
* decodeThread
* delete frame
* remove joined
* continue
* less diff
* robust cv wait
* cache fist 15 frames
* notify_all
* rename variables
* need call avformat_find_stream_info before dump_format
* get width&height from codec
* use std::string
* delete in removeSegment
* use std::mutex in lockmgr_cb
* fix wrong min/max
* no get in process
* cleanup
* always notify decodeThread to do prefetch