Time recovery scheme for package language in multiplexed language environment with data applications

摘要

Multiple speech bit-stream frame buffers 11, 35 are used between the controller 30 and the speech decoder 10. Whenever excessive or missing speech packages are detected, the speech decoder 10 switches to a special corrective mode. If there is too much, the buffered frames are played out fast; if there is too little the buffered frames are played out slowly. For the fast play, some speech information has to be discarded, while for the slow play some speech-like information has to be synthesized. The speech may be handled in sub-frame units, which may be 52 samples at a time. Low energy, silent or unvoiced sub-frames, which also indicate non-periodicity, are detected and manipulated 129, 130. Moreover, the decoded signal is manipulated at the excitation phase 125, 130 before the final LPC synthesis filter 140, resulting in a transparent perceptual effect on the manipulated speech quality. Additionally, the buffers 11 are enlarged such that the problem caused by controller 30 asynchronicity is eliminated. Further, for bulk delay caused by multiplexing data and speech transmissions, the buffers 11 maintain the smallest number of speech packets 32 necessary to prevent buffer 11 underflow during a data packet transmission while minimizing speech delay and preserving data transmission efficiency.