Apparatus for reducing quantization noise in image signals

摘要

An apparatus for decoding a discrete cosine transform coded image signal includes an image restoration circuit which comprises a first conversion block for converting the reconstructed image signal into its frequency domain image signal including image signal phase components and image signal amplitude components thereof; a predictive quantization noise generation block for responding to the quantization parameter and for generating a predictive quantization noise having a known probability density function; a second conversion block for converting the predictive quantization noise into its frequency domain noise including noise phase components and noise amplitude components; an adder circuit for generating compensated amplitude components representative of the difference between the image signal amplitude components and the noise amplitude components; and a inverse conversion block responsive to the image signal phase components and the compensated amplitude components for converting them to restore the image signal, free of the quantization noise, in the time domain to thereby improve the quality of the displayed image.