A New DCT-Domain Distortion Model for MB-Level Quality Control

For many applications like video surveillance and digital cinema, it is desirable to encode video content with constant video quality. However, although constant quantization parameter is used in video encoder, quality fluctuation in macroblock level is still very large and standard deviation of PSNR is typically about 1.8 dB. Since distortion is introduced in the process of quantization of DCT coefficients, we propose a new DCT-domain distortion model which utilizes the truncated tailing bits in quantization to estimate distortion in macroblock level, and QP of each block is determined by the estimated PSNR. Experimental results show that our proposed model can accurately estimate distortion of each MB before implementing quantization and the corresponding RMSE is only about 0.3 dB (less than 1% of the actual value). Compared with previous works, our proposed algorithm can achieve 0.57 dB enhancement in quality stabilization.