Complexity and memory efficient GOP structures supporting VCR functionalities in H.264/AVC

Supporting digital video cassette recording (VCR) trick-play functionalities (e.g. random access, fast-forward play, fast-reverse play) is desirable for compressed video streams. However, due to strong inter-frame dependencies introduced by motion compensated prediction (MCP), the computational complexity and memory requirement is drastically increased. Tradeoffs between coding efficiency and decoding complexity can be made with different group of pictures (GOP) structures. In this paper, we investigate two flexible GOP structures, named G-group and binary reference GOP structure (BRGS), which can achieve trick-play functionalities while keeping low decoder complexity and memory requirement for the state-of-the-art H.264/AVC video coding standard. The schemes are drift-free since they utilize the compression and memory management tools adopted in H.264/AVC. Our analysis and experimental results show that they can greatly reduce the decoder complexity and buffer size while introducing only about 4.0%-7.6% bitrate increase on average. The computational complexity saving for the worst case and average case can be up to 77.8% and 62.5%, respectively. The memory buffer for the fast-reverse play mode can be reduced to 33.3% compared to the conventional scheme. Moreover, the schemes are flexible and can be easily adapted to achieve a good tradeoff between compression performance and complexity saving for the trick-play modes.