| 摘要 |
PURPOSE:To obtain good transmission efficiency by determining the most suitable transmission mode for transmitting an input signal, for every block which is divided with regard to a time. CONSTITUTION:In an in-block maximum value detecting and comparing circuit 3, the maximum absolute value in a word data in each mode in one block, that is to say, the maximum absolute value in data (peak value data) W1-Wn-1 in a general PCM mode, the maximum absolute value in differential data D1-Dn-1 in a differential PCM mode, and the maximum absolute value in sum data A1- An-1 in a sum PCM mode are detected respectively, each maximum absolute value of these three modes is compared, and a mode having the smallest maximum absolute value is decided to be a mode having a high compression efficiency, which is capable of taking widely a dynamic range by said the equal number of bits, and this mode information and the maximum absolute value of this mode are sent to a mode selecting adaptive information calculating circuit 41. Accordingly, the error propagation in the differential PCM mode or the sum PCM mode can be terminated in a short time. |
