| 摘要 |
<p>A multi-rate speech codec supports a number of encoding bit rate modes by adaptively selecting encoding bit rate modes to match communication channel restrictions. In higher bit rate encoding modes, an accurate representation of speech through CELP (code-excited linear prediction) and other associated modeling parameters are generated for higher quality decoding and reproduction. To achieve high quality in high lower bit rate encoding modes, the speech encoder departs from the strict waveform matching criteria of regular CELP coders and strives to identify significant perceptual features of the input signal. To support lower bit rate encoding modes, a variety of techniques are applied, many of which involve the classification of the input signal. For each of the bit rate modes selected, a number of fixed or innovation sub-codebooks are selected in use in generating innovation vectors.</p> |
