修复多次关闭可能导致重复free的问题.

Signed-off-by: Jack <jack.wgm@gmail.com>
rename unkown to generic

Signed-off-by: Jack <jack.wgm@gmail.com>
fixed av_probe_input_buffer crash, use av_malloc for m_io_buffer

Signed-off-by: Jack <jack.wgm@gmail.com>
implementation open_decoder2 for demux

Signed-off-by: Jack <jack.wgm@gmail.com>
use demux for avcore

Signed-off-by: Jack <jack.wgm@gmail.com>
remove source_context on libav, use demux, hehe

Signed-off-by: Jack <jack.wgm@gmail.com>
修复重复释放的问题.

Signed-off-by: Jack <jack.wgm@gmail.com>
1. 为generic_demux添加mutex, 使得数据访问同步.
2. 添加audio_codec和video_codec到media_base_info.
3. 修改打开解码器方式.

Signed-off-by: Jack <jack.wgm@gmail.com>