Television – Bandwidth reduction system – Data rate reduction
Patent
1994-01-31
1995-07-11
Kuntz, Curtis
Television
Bandwidth reduction system
Data rate reduction
348420, 348390, 382251, 358432, H04N 712
Patent
active
054325560
ABSTRACT:
A coding apparatus reduces a digital image signal. The coding apparatus includes a block formatting circuit for dividing the digital image signal into blocks of a plurality of picture elements, an orthogonal transforming circuit for transforming the blocks of plurality of picture elements into a plurality of coefficients, an adaptive quantizing unit for quantizing the plurality of coefficients with a quantization table, a calculating circuit that divides each block of the digital image signal into a plurality of sub-blocks and obtains a plurality of indexes, and a detecting circuit that obtains a maximum index and a minimum index from the plurality of indexes. Each index indicates a degree of change between the picture elements in a sub-block of the plurality of sub-blocks. The coding apparatus further includes a subtracting unit that obtains a difference between the maximum index and the minimum index, and a selecting unit that obtains the quantization table from a plurality of quantization tables according to the minimum index and the difference. As a result, the image quality of the background having little change in the signal is kept good.
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Hatano Yoshiko
Onishi Ken
Kuntz Curtis
Mitsubishi Denki & Kabushiki Kaisha
Oh Minsun
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