Video codecs that use motion compensation benefit greatly from the development of algorithms for near-optimal intra/inter mode switching within a rate-distortion framework. A separate development has involved the use of multiple-frame prediction, in which more than one past reference frame is available for motion estimation. In this paper, we show that using a dual-frame buffer (one short-term frame and one long-term frame available for prediction) together with intra/inter mode switching improves the compression performance of the coder. We improve the mode-switching algorithm with the use of half-pel motion vectors. In addition, we investigate the effect of feedback in making more informed and effective mode-switching decisions. Feedback information is used to limit drift errors due to packet losses by synchronizing the long-term frame buffers of both the encoder and the decoder.

Video codecs that use motion compensation have recently achieved performance improvements from the use of intra/inter mode switching decisions within a ratedistortion framework. A separate development has involved the use of multiple frame prediction, in which more than one past reference frame is available for motion estimation. In this paper, we show that using a dual frame buffer (one short term frame and one long term frame available for prediction) together with intra/inter mode switching improves the compression performance of the coder. Also, we improve the mode switching algorithm with the use of half-pel motion vectors.

Real-time video applications require tight bounds on end-to-end delay. Hierarchical bidirectional prediction requires buffering frames in the encoder input buffer, thereby contributing to encoder input delay. Long-term frame prediction with pulsed quality requires buffering at the encoder output, increasing the output buffer delay. Both hierarchical B-pictures and pulsed-quality coders involve uneven bit-rate allocation. Both the encoder and decoder buffering requirements depend on the rate allocation. We derive an efficient rate allocation for hierarchical B-pictures using the power spectral density of a wide-sense stationary process. In addition, we discuss important aspects of hierarchical predictive coding, such as the effect of the temporal prediction distance and delay tradeoffs for prediction branch truncation. Finally, we investigate experimentally the tradeoff between delay and compression efficiency.

No abstract

A dual-frame video coder employs two past reference frames for motion compensated prediction. Compared to conventional single frame prediction, the dual-frame encoder can have advantages both in distortion-rate performance and in error resilience. In previous work, it was shown that optimal mode selection can enhance the performance of a dual-frame encoder. In another strand of previous work, it was shown that uneven assignment of quality to frames, to create high-quality (HQ) long-term reference frames, can enhance the performance of a dual-frame encoder. In this letter, we combine these two strands and demonstrate the performance advantages of optimal mode selection among HQ frames for video transmission over noisy channels.