| 摘要 |
PURPOSE:To prevent degradation of reproduced sound by using the coefficient and gain of a synthetic filter by replacing them by the values corresponding to one vector just before and performing decoding without performing a post filter processing when a flag showing an error does not exist. CONSTITUTION:The vector (b) that a exciting VQ code book 1 outputs is made into vectors (c) and (f) by the gain adjuster 2 of gain (e) and a synthetic filter 4 and the vectors are outputted to backward gain and synthetic filter adapters 3 and 5. By the gain (d) and the synthetic filter coefficient (g) that the adapters 3 and 5 predict and calculate, gain and synthetic filter coefficient control circuits 8 and 9 control the adjuster 2 and the filter 4. The circuit 9 holds or updates the coefficient (g) based on the error detection flag (k) that a radio line control processor 10 outputs and makes the filter 4 correspond to the next input vector by an output (h). After the vector (f) is processed by a post filter 6 based on the flag (k), the vector (f) is outputted as a PCM output (j) by a PCM conversion circuit 7. Thus, degradation of reproduced sound quality is prevented and an effective error countermeasure is taken. |
