【摘要】 本文对CCITT H.261建议的具体应用进行了深入探讨,提出了在不同意义下与H.261兼容的改进型H.261编码方案,并在两方面对H.261进行了充实和修正。1)自适应缓冲存储器控制策略,提出新的量化级控制方法——“g跳变法”,使码率较低(p=1,2)时的图像质量明显提高。2)字长有规律的可变字长偏码,提出码字长度为4比特的整倍数并且具有奇偶校验能力的DCT系数码表构造,使误码率较高时系统的抗干扰能力显著增强。在现有ASIC芯片和DSP芯片条件下,改进型H.261易于实时实现。在传输码率为96kbit/s、误码率为1×10~4情况下,本文对一些国际通用序列图像数据进行了计算机模拟测试,得到了令人满意的结果。更多还原

【Abstract】 The practical application of CCITT Rec. H. 261 is discussed in this paper. An improved Scheme of H. 261 for videoconference image coding is proposed which it compatible with H. 261 in different levels. There are two improvements:1) to improve the picture quality at low bltrate (p = 1, 2), a new control strategy for quantization is proposed; 2) to improve a powerful noise immunity at higher orror bit rate, a new code table for DCT coefficients is set, where the codeword length is an integer multiple of four bits, and odd-ever check function is provided. It’s easy for this scheme to implement in real time with existing ASIC chips and general purpose DSP chips. The simulation result obtained at bitrate of 96kb/s and error bit rate of 1×10-4 is satisfactory.更多还原