A Bitrate-Conservative Fast-Adjusting Rate Controller for Video Conferencing

Widely-used Rate Control (RC) algorithms, such as those in the H.264 encoder, have certain shortcomings for time-sensitive applications such as High Definition Video Conferencing (HDVC): they either respond too slowly to available bandwidth variations, causing degradation in the perceived quality of the video session, or do not optimize video quality for a given available bandwidth. To overcome these shortcomings, we propose Dynamic Rate Control (DRC) which: 1- can adjust the bitrate of the video within a fast 4 frames or so 2- is conservative and does not waste bandwidth by unnecessarily increasing the video quality, instead saving the bandwidth as bursts for future frames, and 3- uses a moving window to limit the effect of past bursts on current bitrate. We implemented DRC in the x264 codec and used it in an actual video conferencing product from Magor Corp. The results showed that, compared to the widely-used ABR and CRF rate controllers, DRC provides better video quality and user experience, while adjusting the video bitrate faster.