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This paper presents an overview of the transform and quantization designs in H.264. Unlike the popular 8 8 discrete cosine transform used in previous standards, the 4 4 transforms in H.264 can be computed exactly in integer arithmetic, thus avoiding inverse transform mismatch problems. The new transforms can also be computed without multiplications, just additions and shifts, in 16-bit arithmetic, thus minimizing computational complexity, especially for low-end processors. By using short tables, the new quantization formulas use multiplications but avoid divisions.

This paper discusses two new frame types, SP-frames and SI-frames, defined in the emerging video coding standard, known as ITU-T Rec. H.264 or ISO/IEC MPEG-4/Part 10-AVC. The main feature of SP-frames is that identical SP-frames can be reconstructed even when different reference frames are used for their prediction. This property allows them to replace I-frames in applications such as splicing, random access, and error recovery/resilience. We also include a description of SI-frames, which are used in conjunction with SP-frames. Finally, simulation results illustrating the coding efficiency of SP-frames are provided. It is shown that SP-frames have significantly better coding efficiency than I-frames while providing similar functionalities.

In this paper, a novel intra coding scheme is proposed. The proposed scheme improves H.264 intra coding from three aspects: 1) H.264 intra prediction is enhanced with additional bi-directional intra prediction modes; 2) H.264 integer transform is supplemented with directional transforms for some prediction modes; and 3) residual coefficient coding in CAVLC is improved. Compared to H.264, together the improvements can bring on average 7% and 10% coding gain for CABAC and for CAVLC, respectively, with average coding gain of 12% for HD sequences.

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