Adaptive quantizer
First Claim
1. An adaptive quantizer, for which a color image signal is color-separated into a plurality of color components to obtain an input picture element value for each color component of each picture element, and said input picture element values are divided into blocks consisting of a plurality of adjacent picture element values for each color component, comprising:
- means (11) for obtaining estimation error between said input picture element value and a quantized estimation value of said input picture element value;
a quantizer (31) for quantizing said estimation error by using a selected quantization characteristic from one of a plurality of quantization characteristics provided for each color component and having quantization steps suitably determined for a respective color component;
a quantization characteristic determining unit (32,
33) receiving the output of said quantizer for determining a quantization characteristic to be used for the next block according to the distribution of quantization level values provided when said estimation error in one block is quantized according to said selected quantization characteristic;
a quantization characteristic selector (35) receiving an output of said quantization characteristic determining unit for selecting said selected quantization characteristic; and
means (14,
15) for estimating a quantized estimation value of said input picture element value from a plurality of quantized estimation errors of other input picture element values.
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Abstract
An adaptative quantizer for use with color images separates each color component for separate quantization and breaks up the input image into a plurality of blocks. A quantization characteristic determining unit determines the characteristic to be used for a given block according to the distribution of quantization level values obtained when an estimation error in a preceding block is quantized according to a particular quantization characteristic. The characteristic may be changed when the distribution of quantization level values is smaller than or exceeds given threshold values.
32 Citations
7 Claims
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1. An adaptive quantizer, for which a color image signal is color-separated into a plurality of color components to obtain an input picture element value for each color component of each picture element, and said input picture element values are divided into blocks consisting of a plurality of adjacent picture element values for each color component, comprising:
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means (11) for obtaining estimation error between said input picture element value and a quantized estimation value of said input picture element value; a quantizer (31) for quantizing said estimation error by using a selected quantization characteristic from one of a plurality of quantization characteristics provided for each color component and having quantization steps suitably determined for a respective color component; a quantization characteristic determining unit (32,
33) receiving the output of said quantizer for determining a quantization characteristic to be used for the next block according to the distribution of quantization level values provided when said estimation error in one block is quantized according to said selected quantization characteristic;a quantization characteristic selector (35) receiving an output of said quantization characteristic determining unit for selecting said selected quantization characteristic; and means (14,
15) for estimating a quantized estimation value of said input picture element value from a plurality of quantized estimation errors of other input picture element values. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification