An Adaptive Strategy for Hybrid Image Coding

In hybrid coding technique, the sampled data are divided into blocks of samples. Next, each block is transformed to generate a one-dimensional transform of each line in the block. The transform coefficients are then processed by a block of DPCM encoders which uncorrelate the data in the second dimension and qnantize the uncorrelated samples using appropriate quantizers. In this study an adaptive hybrid coding technique is proposed based on using a single quantizer (A/D converter) to quantize the transform coefficients and using a variable-rate algorithm for coding the quantized coefficients. The accuracy of the A/D converter (number of bits per sample) determines the fidelity of the system. The buffercontrol algorithm controls the accuracy of the A/D converter for each block resulting in a fixed-rate encoder system. Experimental results have shown a stable buffer condition and reconstructed images with a higher fidelity than nonadaptive hybrid systems.