| 摘要 |
PURPOSE:To obtain a differential pulse modulation system with excellent coding efficiency by adding the polarity to a threshold value based on the polarity decision of a differential signal between a forecast error signal and a threshold value and applying the correction to the difference signal based on the polar threshold value so as to apply quantization. CONSTITUTION:A subtracter 1 calculates a forecast error signal S2 being a difference between an input signal S1 and a forecast signal S9, and a change detection circuit 2 outputs a change detection signal S3 and a difference signal S4 based on the signal S2 and a threshold value T from a threshold value generating circuit 9. A threshold value generating circuit 18 outputs a polar threshold value T1 and a correction difference signal S15 from the signals S3, S4. The signal S15 goes to a quantized signal S5 by a quantization circuit 3 and the signal S5 is outputted to a variable length coding circuit 4 and a local decoding circuit 6. With the signal S3 effective, the circuit 4 fetches the threshold value T, the signal S3 is subject to run length coding, a short code is assigned to a numeral close to '0' where the frequency of the signal S5 is high, the code is stored in a transmission buffer circuit 5 to send a coded signal to a transmission line. The circuit 9 supervises the data storage of the circuit 5, generates a proper threshold value T thereby controlling the generation amount of the coded data. |
