| 摘要 |
Voice compression is performed in multiple stages (12, 14) to increase the overall compression between the incoming analog voice signal (15) and the resulting digitized voice signal (80) over that which would be obtained if only a single stage of compression were to be used. A first type of compression is performed on a voice signal (15) to produce an intermediate signal (44) that is compressed with respect to the voice signal (15), and a second, different type of compression is performed on the intermediate signal (40) to produce an output signal (42) that is compressed still further. As a result, compression better than 1920 bits per second (and approaching 960 bits per second) are obtained without sacrificing the intelligibility of the subsequently reconstructed analog voice signal (15). Voice compression is also performed by recognizing redundant portions of said voice signal (15), such as silence, and replacing such redundant portions with a special code in said compressed signal (40). Among other advantages, the higher total compression allows speech to be transmitted in far less time than would otherwise be possible, thereby reducing expense.
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