Delay-Constrained and R-D Optimized Transrating for High-Definition Video Streaming Over WLANs

In this study, we propose bit-rate adaptation techniques for compressed high-definition video transmission over wireless home networks. Application-layer methods are developed to minimize quality impairments caused by wireless channel degradations. A transrater located at a home video server adjusts the transmission rate of the video stream based on bandwidth measurements. We consider delay constraints of multiple video frames across various time scales, and dynamically select an appropriate time scale for bit-rate adjustments. This novel feature prevents playout buffer underflows and avoids unnecessary rate reductions. Furthermore, distortion due to transrating is minimized by coding type-dependent rate allocation among the frames to be transmitted in the projected time scale. Using a realistic simulation setup, we demonstrated that the proposed technique significantly reduces video glitches. Up to 3.12 dB average PSNR improvement is achieved, compared to a non-delay constrained rate adaptation method, which also utilizes bandwidth measurements. Our approach maintains compliance with existing wireless local area (WLAN) devices and standards, as well as consumer video standards and applications.