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二、模数变换实现模拟电视的数字化,必须先将模拟电视经过A/D变换器变成数字信号,把连续变化的信号变为二进制信号,必须经过抽样、量化、编码三个过程才能完成,这三个过程一般集中在A/D芯片中一次完成。量化可分为舍入量化和截尾量化。舍入量化即是用四舍五入来处理被量化信号与预置量化级数电平之间的差值,如图1所示。截尾量化,即把高于预置量化级数电平的尾数部分全部舍去,如图2所示。从图中可以看出,截尾量化误差比舍入量化误差大一倍,因此在实际使用中一般只采用舍入量化
Second, the analog-to-digital conversion Analog TV, analog TV must first A / D converter into a digital signal, the continuous change of the signal into a binary signal, you must go through the sampling, quantization, encoding three processes can be completed, The three processes are generally concentrated in the A / D chip to complete. Quantization can be divided into rounding quantization and truncation quantization. Rounding quantization refers to rounding off the difference between the quantized signal and the level of the preset quantization level, as shown in FIG. 1. Truncated quantification, that is, the mantissa above the level of the number of pre-quantified part of all rounded off, as shown in Figure 2. As can be seen from the figure, the truncated quantization error is two times larger than the rounding quantization error, so in actual use, only rounding quantization