| 摘要 |
<p>A method to improve packet loss concealment for generation of a synthetic speech signal in an algebraic code excited linear prediction decoder for a voice over packet network. One method improves features for coding gains in the decoder and for post-filtering of the signals. An alternative method uses a classification method for the signal based on the bitstream in the decoder. In a described example, a method of excitation signal level adjustment (80) after packet loss can be applied to fixed codebook gain (42) of the next good frame through multiplexer (82). During the packet loss, the pulse positions of fixed codebook (28) are unknown, thus it can be difficult to predict them correctly. Wrong pulse locations within a large gain (42) can cause severe distortion on synthesized signals of lost frames and the contiguous good frames in the rest of speech frames. Therefore, zero fixed codebook gain is used in lost frames, which is the standard recommendation in G.729. To composite the fixed codebook contribution, the beginning of the next good frame will adjust the excitation signal level based on the current codebook gain and lost frame duration. The excitation signal level adjustment is applied to adjust the gain error. Further embodiments of improving the PLC strategy in decoder is the excitation signal level adjustment (80) applied to the fixed codebook (28) gain (42).</p> |
