Modified TMN8 Rate Control for Low-Delay Video Communications

Abstract

The existing macroblock-layer rate control schemes in the literature calculates quantization parameters of all macroblocks (MB) in a frame in a raster scan order, and then encodes the MBs in the same order. Actually, the quantization distortion is heavily dependent upon the coding order of MBs. This work investigates the relationship of quantization distortion and the coding order. Then we present a scheme where we modify the encoding order of MBs in TMN8 to favor the more complex MBs. We implement TMN8 and the modified version in H.263 video codec. The experimental results indicate that our scheme achieves average PSNR gain of 1.05 dB over TMN8. In addition, the buffer occupancy is steadier and average bit rate achieved is closer to the target channel rate. The new rate control scheme is fully compliant to H.263 coding standard.