| 摘要 |
PROBLEM TO BE SOLVED: To send an image with sufficient image quality by allowing a difference pulse modulation coder to conduct encoding without causing an overflow. SOLUTION: A danger of overflowing a storage circuit 25 is caused by a very long word length and an insufficient transmission rate depending on a transmission channel. The information is informed via occupied information generated by an occupancy measurement circuit 45 connecting to a buffer storage circuit 25. In order to prevent the overflow, a synthesizer 50 is provided, to receive activity information and occupancy information and to send control information. The synthesizer 50 is made up of comparators 32, 34 and two multipliers 52, 54, and the multipliers multiply two preset threshold levels S1 , S2 by a coefficientαto provide threshold levels SP1 =αS1 and SP2 =αS2 to other input terminals of the comparators. The coefficientαis an attenuation coefficient, a degree of storage is evaluated by an arithmetic circuit 60 and an image is sent without overflow depending on the degree of storage. |
