Complexity controllable DCT for real-time H.264 encoder

A new integer 4x4 transform is adopted in the new video coding standard H.264/AVC. It consumes a big account of computation of a real-time encoder. To reduce the computation load of the new transform, pruned DCT algorithm is applied. To avoid serious encoding performance loss, a new condition is derived based on statistical sum of absolute value test(SSAVT) to identify pruned block adaptively. Considering the variance of DCT coefficients' contribution, a novel efficient model based on statistical analysis is proposed. To achieve further control on DCT complexity and a good tradeoff between performance and computation load, a scheme to control the complexity of DCT is presented. Simulation results show that the novel statistical model can save more computation, so it is chose to control DCT complexity. Simulation results show that the complexity controllable scheme can control the complexity of DCT within the specified target with negligible encoding performance loss.