improve video quality

src/media/media_codec.h

src/media/media_encoder.cpp

src/media/socket_pair.cpp

src/media/socket_pair.h

src/media/video/video_receive_thread.cpp

src/media/video/video_receive_thread.h

src/media/video/video_rtp_session.cpp

src/media/video/video_rtp_session.h