Abstract: A signal modification technique facilitates compact voice coding by employing a continuous, rather than piece-wise continuous, time warp contour to modify an original residual signal to match an idealized contour, avoiding edge effects caused by prior art techniques. Warping is executed using a continuous warp contour lacking spatial discontinuities which does not invert or overly distend the positions of adjacent end points in adjacent frames. The linear shift implemented by the warp contour is derived via quadratic approximation or other method, to reduce the complexity of coding to allow for practical and economical implementation. In particular, the algorithm for determining the warp contour uses only a subset of possible contours contained within a sub-range of the range of possible contours. The relative correlation strengths from these contours are modeled as points on a polynomial trace and the optimum warp contour is calculated by maximizing the modeling function.

Abstract: A signal modification technique facilitates compact voice coding by employing a continuous, rather than piece-wise continuous, time warp contour to modify an original residual signal to match an idealized contour, avoiding edge effects caused by prior art techniques. Warping is executed using a continuous warp contour lacking spatial discontinuities which does not invert or overly distend the positions of adjacent end points in adjacent frames. The linear shift implemented by the warp contour is derived via quadratic approximation or other method, to reduce the complexity of coding to allow for practical and economical implementation. In particular, the algorithm for determining the warp contour uses only a subset of possible contours contained within a sub-range of the range of possible contours. The relative correlation strengths from these contours are modeled as points on a polynomial trace and the optimum warp contour is calculated by maximizing the modeling function.

Abstract: A variable bit rate coder, and an associated method, for encoding a frame of speech, such as frames of data generated during operation of a communication station operable in a cellular communication system. Selection of the coding rate is made responsive to indicia of actual coding performance of a coder at more than one coding rate.

Abstract: A signal modification technique facilitates compact voice coding by employing a continuous, rather than piece-wise continuous, time warp contour to modify an original residual signal to match an idealized contour, avoiding edge effects caused by prior art techniques. Warping is executed using a continuous warp contour lacking spatial discontinuities which does not invert or overly distend the positions of adjacent end points in adjacent frames. The linear shift implemented by the warp contour is derived via quadratic approximation or other method, to reduce the complexity of coding to allow for practical and economical implementation. In particular, the algorithm for determining the warp contour uses only a subset of possible contours contained within a sub-range of the range of possible contours. The relative correlation strengths from these contours are modeled as points on a polynomial trace and the optimum warp contour is calculated by maximizing the modeling function.

Abstract: A speech coder and a method for speech coding wherein the speech signal is represented by an excitation signal applied to a synthesis filter. The speech is partitioned into frames and subframes. A classifier identifies which of several categories the speech frame belongs to, and a different coding method is applied to represent the excitation for each category. For some categories, one or more windows are identified for the frame where all or most of the excitation signal samples are assigned by a coding scheme. Performance is enhanced by coding the important segments of the excitation more accurately. The window locations are determined from a linear prediction residual by identifying peaks of the smoothed residual energy contour. The method adjusts the frame and subframe boundaries so that each window is located entirely within a modified subframe or frame.

Abstract: To overcome the problem of poor representation of the background noise, the present invention includes a noise parameter generator (40) which uses a weighted average of auto-correlation values of the input signal generated during the noise-analysis phase. The weighting function gives less weight to the auto-correlations during the first few frames (as they may contain speech) and more weight to frames towards the end of this phase. Also included, to overcome the bursty nature of comfort noise, is a comfort noise generator (50) which gradually changes the nature of the signal from speech to pseudo-random noise after the speech-burst. The comfort noise generator (50) of the present invention excites the auto-regressive filter corresponding to the noise model with a weighted combination of the past excitation and pseudo-random noise.

Abstract: To overcome the problem of poor representation of the background noise, the present invention includes a noise parameter generator (40) which uses a weighted average of auto-correlation values of the input signal generated during the noise-analysis phase. The weighting function gives less weight to the auto-correlations during the first few frames (as they may contain speech) and more weight to frames towards the end of this phase. Also included, to overcome the bursty nature of comfort noise, is a comfort noise generator (50) which gradually changes the nature of the signal from speech to pseudo-random noise after the speech-burst The comfort noise generator (50) of the present invention excites the auto-regressive filter corresponding to the noise model with a weighted combination of the past excitation and pseudo-random noise.

Abstract: To overcome the problem of poor representation of the background noise, the present invention includes a noise parameter generator (40) which uses a weighted average of auto-correlation values of the input signal generated during the noise-analysis phase. The weighting function gives less weight to the auto-correlations during the first few frames (as they may contain speech) and more weight to frames towards the end of this phase. Also included, to overcome the bursty nature of comfort noise, is a comfort noise generator (50) which gradually changes the nature of the signal from speech to pseudo-random noise after the speech-burst. The comfort noise generator (50) of the present invention excites the auto-regressive filter corresponding to the noise model with a weighted combination of the past excitation and pseudo-random noise.