Predictive skip mode based all zero block detection for AVS encoder

The sufficient condition is derived for all zero block detection. We use the condition that the maximum sum of absolute difference of all zero block as the checking threshold for AVS. Then we incorporate all zero block detection technique into predictive skip mode algorithm. It avoids lots of computation for transform, quantization, Zig-zag scans, inverse transform, inverse quantization and reconstruction. The experimental results show that the proposed methods provide about 30%-70% reduction in computational complexity while maintaining coding rate and quality.