| 摘要 |
<p>A bi-directional pitch enhancement system for speech coding systems. As speech data applications continue to operate in areas having intrinsic bandwidth limitations, the perceptual quality of reproduced speech data in typical speech coding systems suffers significantly. The present invention employs forward pitch enhancement and backward pitch enhancement to maintain a high perceptual quality in reproduced speech. In certain embodiments of the invention, the forward pitch enhancement and the backward pitch enhancement are performed in a single portion of the entire speech coding system. For example, in speech codecs, the forward and the backward pitch enhancement are performed only in the speech codec's encoder, or alternatively, only in the speech codec's decoder. If desired, the forward and the backward pitch enhancement are performed in a distributed manner, each being performed, at least in part, in each one of the encoder and the decoder of the speech codec. If desired, the backward pitch enhancement is generated using the forward pitch enhancement itself. The backward pitch enhancement is a mirror image of the forward pitch enhancement that is previously generated; the backward pitch enhancement is generated dependent on the forward pitch enhancement. Alternatively, in other embodiments of the invention, the backward pitch enhancement is generated independent of the forward pitch enhancement; the backward pitch enhancement is generated irrespective of the forward pitch enhancement that has previously been generated. The backward pitch enhancement is usually performed on the fixed codebook in code excited linear prediction (CELP) or is performed as post-processing in the decoder.</p> |
