Abstract:
Methods and apparatus for quickly selecting an optimal excitation waveform from a codebook are presented herein. In encoding schemes that use forward and backward pitch enhancement, storage and processor load is reduced by approximating a two-dimensional autocorrelation matrix with a one-dimensional autocorrelation vector. The approximation is possible when a cross-correlation element is configured to determine the autocorrelation matrix of an impulse response and a pulse energy determination element is configured to determine the energy of a pulse code vector that incorporates secondary pulse positions.
Abstract:
It is an objective of the present invention to provide an optimized method of selection of the encoding mode that provides rate efficient coding of input speech. A rate determination logic element (14) selects a rate at which to encode speech. The rate selected is based upon the target matching signal to noise ration computed by a TMSNR computation element (2), normalized autocorrelation computed by a NACF computation element (4), a zero crossings count determined by a zero crossings counter (6), the prediction gain differential computed by a PGD computation element (8) and the interframe energy differential computed by a frame energy differential element (10).
Abstract:
A speech processing system modifies various aspects of input speech according to a user-selected one of various preprogrammed voice fonts. Initially, the speech converter receives a formants signal representing an input speech signal and a pitch signal representing the input signal's fundamental frequency. One or both of the following may also be received: a voicing signal comprising an indication of whether the input speech signal is voiced, unvoiced, or mixed, and/or a gain signal representing the input speech signal's energy. The speech converter also receives user selection of one of multiple preprogrammed voice fonts, each specifying a manner of modifying one or more of the received signals (i.e., formants, voicing, pitch, gain). The speech converter modifies at least one of the formants, voicing, pitch, and/or gain signals as specified by the selectedvoice font.
Abstract:
A method and apparatus for enhancing coding efficiency by reducing illegal or other undesirable packet generation while encoding a signal. The probiability of generating illegal or other undesirable packets while encoding a signal is reduced by first analyzing a history of the frequency of codebook values selected while quantizing speech parameters. Codebook entries are then reordered so that the index/indices that create illegal or ther undesirable packets contain the least frequently used entry/entries. Reordering multiple codebooks for various parameters further reduces the probability, that an illegal or ther undesirable packet will be created during signal encoding. The method and apparatus may be applied to reduce the probability of generating illegal null traffic channel data packets while encoding eight rate speech.
Abstract:
A method and an accompanying apparatus provide for a distributed voice recognition (VR) capability in a remote device (201). Remote device (201) decides and controls what portions of the VR processing may take place at remote device (201) and what other portions may take place at a base station (202) in wireless communication with remote device (201).
Abstract:
The cellular telephone (10) includes an equalization filter (54) for adjusting the frequency response pattern of an audio signal provided to the speaker (24). The equalization filter (54) operates in response to user control to allow the user to adjust the frequency response pattern as desired. In one specific embodiment, the cellular telephone (10) includes an equalization filter table (56) for storing sets of audio frequency filter parameters, and the user merely selects one of the sets of filter parameters by pressing a corresponding button on a front control panel (11) of the cellular telephone (10). In other embodiments, the cellular telephone (10) includes an equalizer scroll bar allowing a large number of sets of filter parameters to be accessed. The equalization filter (54) and the filter table (56) may form part of a digital signal processing unit (42) also including vocoder encoders (50) and decoders (52). By providing an equalization filter (54), a cellular telephone (10) user may adjust the frequency response pattern of received signals to compensate, for example, for local noise or for hearing abnormalities to thereby allow the user to hear the other party to a telephone call more clearly. Even in the absence of any significant noise and even for a user having normal hearing, the user may still gain at least a perceived listening improvement.
Abstract:
Methods and apparatus for quickly selecting an optimal excitation waveform from a codebook are presented herein. To reduce the number of computations required to choose the optimal codebook vector, a subset of codevectors are selected based upon optimal pulse locations (425), wherein the subset of codevectors form a subcodebook. Rather than searching the entire codebook, only the entries of the subcodebook are searched (400).
Abstract:
A call setup procedure is presented to permit vocoder bypass, which will allow the transmission of wideband speech packets between wideband terminals over narrowband transmission constraints. In addition, methods and apparatus are presented that allow the conversion between a wideband tandem-free operation, a narrowband tandem-free operation, and a standard tandem operation.
Abstract:
Method and apparatus for selecting a code vector in an algebraic codebook wherein the analysis window for the coder is extended beyond the length of the target speech frame. An input signal is filtered by a perceptual weighting filter (76). Then, the filter is set to ring out for a number of samples equal to the length of the perceptual weighting filter (76), while a zero input vector is applied as input. By extending the analysis window, the two dimensional impulse response matrix can be stored as a one dimensional autocorrelation matrix in memory (60, 80), greatly saving on the computational complexity and memory required for the search.
Abstract:
A first remote vocoder (15) receives analog voice (170) and produces packetized vocoder data (190) which is transmitted over a wireless link (20). A first local vocoder (35) receives the packetized vocoder data (190) from the wireless link (20). The first local vocoder (35) converts the packetized data (190) to a multibit PCM output (120). The first local vocoder (35) also adds a detection code to one of the least significant bits (LSB) of the PCM output (210). The first local vocoder (35) passes the PCM signal (210) to the PSTN (40). The first local vocoder (210) also receives PCM input (120) over the PSTN (40). The first local vocoder (35) constantly monitors the least significant bit of the PCM input (120) for a detection code indicating that a second local vocoder (55) is connected at the receiving end. If the first local vocoder (35) detects the detection code from the second local vocoder (55), it begins to substitute packetized data and a redundancy check for a second one of the LSB's of the outgoing PCM (210). The first local vocoder (35) also begins to monitor the second one of the LSB's of the incoming PCM (120). If the redundancy check indicates that valid packetized data has been received, the first local vocoder (35) stops converting the PCM output (120) into packetized data and simply passes the packetized data on the second one of the LSB's to the first remote vocoder (15) as packets (100). If at any time the redundancy check fails and the detection code is not detected, the first local vocoder (35) returns to converting the incoming PCM (190) to packetized data. In this way, the tandem vocoding arrangement is avoided.