Image sub-sampling apparatus

Details Image sub-sampling apparatus Image sub-sampling apparatus

1995-08-10

1996-10-15

Chin, Tommy P.

Television

Bandwidth reduction system

Data rate reduction

348392, 348405, H04N 724, H04N 730

Patent

active

055659250

ABSTRACT:
A quantization coefficient is inputted to an inverse quantization circuit. The coefficient is multiplied by a quantization step size stored in a quantization table. Resultant data is delivered to an inverse discrete cosine transformation circuit. The quantization step size is attained by replacing each value of a high-frequency portion of the quantization table with "0" by a masking circuit. As a consequence, each value of inversely quantized data associated with the portion is set to "0". Data inversely transformed according to a transformation expression is fed to a sub-sampling circuit. Based on an n specification signal, the data is sub-sampled such that a dot is extracted for every n dots, thereby generating a compressed image signal. Aliasing noise is prevented by the masking a portion of the quantization table, and the sub-sampling ratio can be varied.

REFERENCES:
patent: 5018010 (1991-05-01), Masumoto
patent: 5072295 (1991-12-01), Murakami et al.
patent: 5369502 (1994-11-01), Fukuda et al.
patent: 5371549 (1994-12-01), Park
Patent Abstracts of Japan, vol. 17, No. 393, Jul. 1993.
Wallace et al., "The JPEG Still Picture Compression Standard", IEEE Transactions on Consumer Electronics, vol. 38, No. 1, Feb. 1992, pp. xviii-xxxiv.
Patent Abstracts of Japan, vol. 16, No. 326, Jul. 1992.
Patent Abstracts of Japan, Katsutoshi, vol. 16, No. 326, Jul. 16, 1992.

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