Quantization step is a key parameter in quantization modulation method,but now there is no theoretical method to decide its value.To solve this problem,a quantitative estimation method of quantization step based on Peak Signal-to-Noise Ratio(PSNR) was proposed.In this method,dither quantization modulation method was chosen as research object,and wavelet coefficients were regarded as quantization coefficients.According to the distribution of quantization error,it firstly gave an estimating quantization error method based on quantization step.Then it deduced the quantitative relationship equation of quantization step,watermark sequence length and PSNR on the basis of some properties of wavelet transform.The experimental results show that PSNR values calculated through quantitative equation are in good agreement with those obtained from experiments when the values of their quantization step are the same.It demonstrates that the deduced quantitative relationship equations are accurate.%量化步长是量化调制方法中的重要参量,但是目前无法定量计算.针对这个问题,以抖动量化调制方法为研究对象,以小波变换系数为量化系数,提出了基于峰值信噪比(PSNR)的量化步长定量估算方法.首先根据量化误差的分布情况给出了基于量化步长的量化误差定量估算方法,然后根据小波变换的性质推导出了量化步长、水印序列长度与PSNR之间的定量关系式.实验结果显示,量化步长取值相同时实验测得的PSNR值和定量关系式计算出的PSNR值基本一致,验证了推导的定量关系式.
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