| 摘要 |
PURPOSE:To suppress the deterioration of a decoding error rate when a transmission line state is deteriorated. CONSTITUTION:A transmission speed selection circuit 54 selects transmission speed corresponding to the transmission error rate. A quantization circuit 56 and a variable length encoding circuit 58 execute quantization with a quantization coefficient corresponding to selected transmission speed and execute variable length-encoding. A data synthesis circuit 62 adds an error correction code to encoded picture data and output data by two phases P and Q. Variable roll-off filters 66 and 68 set an optimum pass frequency band and a roll-off coefficient alpha in accordance with selected transmission speed. A clock generation circuit 64 generates the clock of a frequency corresponding to selected transmission speed. A modulation circuit 70 modulates a carrier generated inside by the output of the synthesis circuit 62 through the variable roll-off filters 66 and 68. |
