Adaptive rate control for H.264 based video conferencing over a low bandwidth wired and wireless channel

This paper presents a method for adaptive rate control in a video conferencing solution over a variable bandwidth channel. The bandwidth is estimated using the round-trip delay of probe packets. Based on the estimated bandwidth, the video rate adaptation is done in two folds; one in the H.264 video encoder based on adaptive basic unit selection and the other by generation of fragments for encoding data and controlling the transmission delay of the same. The audio adaptation is done with the voice activity detection (VAD) of NB-AMR speech codec. System architecture is proposed for a generic video conferencing solution to implement the multimode adaptive rate control for a variable quality of service (QoS) wired channel and a low bandwidth wireless channel. The implementation is tested with ADSL and CDMA 1xRTT channels. The proposed method gives an improvement in image quality (PSNR) compared to the reference H.264 (JM9.5) encoder demonstrating an improved adaptive rate control behavior in the heterogeneous network.