US 5,708,509 A · Digital data processing device

Abstract

A digital data processing device has a DCT processing circuit in which image data is discrete cosine transformed, so that DCT coefficients can be obtained. The DCT coefficients are quantized using a quantization table in a quantization processing circuit to obtain quantized DCT coefficients. The quantized DCT coefficients are inversely quantized by the quantization table in an inverse quantization processing circuit to obtain inversely quantized coefficients. Optimum quantization coefficients are obtained by determining a minimum value for the sum of the squares of differences between the DCT coefficients and corresponding inversely quantized coefficients. The image data are then encoded using a Huffman encoding processing circuit. The encoded image data and the optimum quantization coefficients are then recorded to a recording medium.

Claims21

Dependent claims

A device for processing digital data, comprising:

quantization means for quantizing input data to obtain first quantized data using a first quantization table containing a plurality of first quantization coefficients;
inverse quantization means for inversely quantizing said first quantized data to obtain inversely quantized data;
and
generating means for generating a second quantization table, based on said input data and said inversely quantized data, containing a plurality of second quantization coefficients which are obtained in such a manner that a second inversely quantized data have values closer to said input data in comparison with said first quantization coefficients.

1 more element

A device for processing digital data, comprising:

quantization means for quantizing input data to obtain first quantized data using a first quantization table containing a plurality of first quantization coefficients and for quantizing said input data to obtain second quantized data using a second quantization table containing a plurality of second quantization coefficients having values different than said first quantization coefficients;
each of said coefficients having a data length related to a number of bits in an encoded binary value of each of said coefficients;
classifying means for classifying each said coefficient included in each of said first quantized data and said second quantized data in accordance with said data length of each said coefficient to determine a group to which each said coefficient belongs;
and
changing means for changing said second quantized data to obtain third quantized data in such a manner that a group to which a coefficient of said third quantized data belongs does not have a data length longer than that of a group to which a corresponding coefficient of said first quantized data belongs.

2 more elements

Dependencies are inferred from the claim text.

Digital data processing device

Life of this patent

Digital data processing device

Life of this patent

Abstract

Claims21