Quantizing and dequantizing circuitry for an image data companding device

摘要

In quantizing and dequantizing circuity for an image data companding device, a selective inputting circuit selects either of image data undergone orthogonal transform and data undergone decoding. A multiplier multiplies the data selected by the inputting circuit by quantization coefficients or reciprocals thereof for dequantization or quantization. The quantization coefficients or the reciprocals thereof are rewritably stored in a RAM (Random Access Memory) in matching relation to input data and transferred from the RAM to the multiplier. The quantization coefficients are read out of a look-up table which stores a plurality of kinds of quantization coefficients. A ROM (Read Only Memory) stores the reciprocals of quantization coefficients beforehand. In the event of quantization, particular reciprocals matching quantization coefficients fed from the outside are read out of the ROM and transferred to the RAM. At the time of dequantization, the quantization coefficients fed from the outside are directly written to the RAM. Such hardware processing using multiplication implements quantization and dequantization with a common circuit at high speed.