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本文提出的开关型自适应帧内DPCM图象编码的要点是:(1)由前一象素的活动函数值,预报当前象素为非活动象素或活动象索,并选用两个预测器中的某个。(2)由前一象素与其邻近象素的最小差值方向,确定预测器中需选用的4组预测系数中的某组。(3)对应非活动象素和活动象素的两个预测器,由主观实验确定各自的非线性量化器。 对四幅测试图象作的计算表明:本文提出的开关型自适应预测器之预测误差(无量化器),与典型的固定系数二维DPCM预测器相比,其直方图在e=0附近更为集中;其熵值之平均改善量为0.2比特/象素。 用三组序列图象(抽样频率10MHz),通过计算机模拟作主观实验,测定了掩盖函数,并用最小量化分层数目的准则,设计非线性量化器。主观实验结果表明:本文方案之复原图象,与原始图象相比看不出明显差别时,所需之最小量化分层数目,比已发表的工作有一定改善。 本文结果用于亮度信号(抽样频率10MHz)的DPCM编码时,则传输PAL广播电视信号(包括色度信号、双伴音及纠错码)可符合PCM三次群的要求(34.368 Mbits/s)。
The main points of this paper are: (1) Predict the current pixel as the inactive pixel or active image from the activity value of the previous pixel, and choose two predictor Someone in the world (2) From the direction of the minimum difference between the previous pixel and its neighboring pixels, one of the four prediction coefficients to be used in the predictor is selected. (3) Two predictors corresponding to inactive pixels and active pixels, each of which is determined by a subjective experiment. The calculation of the four test images shows that the prediction errors (quantizers) of switched adaptive predictor proposed in this paper, compared with the typical fixed-coefficient two-dimensional DPCM predictor, have a histogram near e = 0 More concentrated; its average improvement in entropy was 0.2 bits per pixel. Three sets of sequence images (sampling frequency of 10MHz) were used to make subjective experiments by computer simulation. The masking function was determined and the criterion of minimizing the number of layers was used to design a nonlinear quantizer. The results of subjective experiments show that the minimum number of layers required for the reconstructed image in this paper can not be obviously changed compared with the original image, which is better than the published work. The results of this paper are for the DPCM encoding of luminance signals (sampling frequency 10 MHz), and the transmission of PAL broadcast television signals (including chrominance signals, double audio and error correction codes) complies with the requirements of PCM cubic subgroups (34.368 Mbits / s).