RTP/RTCP Reception Hint Tracks for Video Call Recording and Playback

This paper proposes to use RTP (Real-time Transport Protocol) Reception Hint Tracks for convenient recording and playback of a video call in MP4 format. The feasibility of RTP Reception Hint Tracks is validated as a part of an implemented end-to-end video call system. The proposed approach records a bidirectional Linphone video call and multiplexes it as MP4 RTP Reception Hint Tracks with the L-SMASH software library. It also stores RTCP (RTP Control Protocol) Reception Hint Tracks for additional timing information. Playback of the MP4 file is performed with VLC Media Player that is made compatible with RTP Reception Hint Tracks. The proposed proof-of-concept setup meets particularly well the needs of multi-codec solutions where different audio and video codecs can be used for a video call recording and playback. According to our analysis, recording RTP reception Hint Tracks increases the Linphone CPU time by under 1% and the bitrate by under 2% over the bare bitrate of the recorded RTP packets.