| 摘要 |
<p>A method and apparatus which is used to precondition a speech signal such that the signal has relatively low power at predetermined points which form the boundaries of DFT blocks in a coder. The method and apparatus is particularly effective when the filter bank operates on a linear-prediction residual (150). The requirement of having low energy at the block boundary is well approximated by a requirement of having a pitch pulse near the center (520) of the block. The method and apparatus makes it possible to make the difference between the original speech signal (120) and the pre-processed speech signal (280) inaudible or nearly inaudible. An AE coder (110) which follows the pre-processor (100), therefore, reconstructs a quantized version of the pre-processed speech. The present invention differs from earlier pre-processors in its operation, in the properties of the modified speech signal, and in the fact that it is compatible with a sinusoidal or waveform-interpolation type of speech coder.</p> |
