Early Detection of All-Zero Coefficients in H.263

We characterize H.263 bitstreams to determine the distribution of inter-macroblocks whose quantized DCT coefficients are completely zero. Based on this analysis, we propose a new H.263-compatible algorithm that predicts blocks with all-zero quantized DCT coefficients, which eliminates the DCT and quantization computation for those blocks. Simulation results show that, relative to the base H.263 encoder, our early-detection mechanism can reduce the computational requirements of the DCT/Quantizer by as much as 81% while simultaneously reducing the bit rate, with virtually no visible change in video fidelity. We analyze the performance of this enhancement using different types of motion searches.