Method and device for encoding data

Abstract

DCT coefficient data obtained by transforming inputted picture data at a DCT (Discrete Cosine Transform) circuit is quantized by selected one of plural quantizers at a quantizing circuit to allow the quantized data to undergo variable length encoding at a variable length encoding circuit to output it. A class designation circuit compares DCT coefficient data from the DCT circuit with threshold values Th , Th , Th in macro block units to carry out class designation to output activity code AT. A code quantity estimation section estimates total encoded data quantity when data corresponding to 1 video segment which is 5 macro blocks of DCT coefficient data which have been read out from a zigzag read-out circuit is quantized by respective quantizers to allow the quantized data thus obtained to undergo variable length encoding to send, to the quantizing circuit quantizer number for determining an optimum one of the quantizers in which the estimated data quantity is reference value or less. Any different one of reference values of the code quantity estimation section and threshold values Th , Th , Th of the class designation circuit are read out from the compression factor table in dependency upon information of a desired compression factor from a terminal Thus, a desired compression factor can be easily obtained in compression-encoding.