PURPOSE: To attain video communication with high quality by monitoring an idle band of a packet network and an idle buffer quantity of a video coder and controlling dynamically a prediction method and a quantization degree.

CONSTITUTION: A video signal from a video source 20 is inputted to a video coder 1, the information is compressed by compressors 5, 6 and the result is packet-processed by a packet processing section 7 and stored in a 1st or a 2nd buffer 8 or 9. An adjustment device 10 is used to gives a command to the buffer 8 or 9 by using a transmission enable signal 151 or 152. After the buffer 8 or 9 receives the signal 151 or 152 and sends a packet to a congestion avoidance variable speed network 40. When an idle capacity in the buffer 8 or 9 is increased and a congestion notice signal from the variable speed network 40 is received by the adjustment device 10, the prediction method having a refresh effect is commanded to a prediction method selector 2 by using a prediction method designation signal 12. Simultaneously a quantization degree designation signal 11 is used to command the reduction in the quantization steps to a quantization device 5 in order to reduce quantity of produced packets.