To improve the efficiency of progressive transmission coding of image data, one needs to consider both the bit rate and the image quality in each state of transmission. But this point has been overlooked in most known methods.
In this thesis, a simple progressive transmission coding is proposed for a very low bandwidth channel. For simplicity, a single uniform quantizer is used for all DCT coefficients, and the thresholds for progressive build up is decided from the probability distribution of DCT coefficients.
Two methods are investigated in choosing the thresholds : taking after quantization, and before quantization.
Computer simulation shows that proposed method results in good quality at low rate of 0.5 (or 0.75) bpp.
