A transform unit obtains a discrete cosine coefficient by processing an image signal in a discrete cosine transform fashion per unit of a predetermined data amount. A memory includes therein a plurality of quantization tables corresponding to quantization accuracies different from each other, and a memory...http://www.google.com.hk/patents/US5440404?utm_source=gb-gplus-share專利 US5440404 - Image signal compression apparatus and method using variable length encoding
