TWI467979B - Systems, methods, and apparatus for signal change detection - Google Patents

Description

System, method and device for signal change detection

This disclosure relates to signal processing.

Voice transmission by digital technology has become commonplace, particularly in long distance telephones, packet switched telephones such as Voice over IP (VoIP), and digital wireless telephones such as cellular telephones. This growth has established an interest in reducing the amount of information used to transmit voice communications over the transmission channel while maintaining the perceived quality of reconstructed speech.

A device configured to compress speech by taking parameters associated with a human speech production model is referred to as a "speech encoder." Speech encoders typically include an encoder and a decoder. The encoder usually divides the incoming speech signal (the digital signal representing the audio information) into time segments called "frames", analyzes each frame to capture certain relevant parameters, and quantizes the parameters into two. A carry indicates, for example, a set of bit or binary data packets. The data packet is transmitted over a transmission channel (i.e., a wired or wireless network connection) to a receiver including a decoder. The decoder receives and processes the data packet, dequantizes it to generate the parameters, and re-establishes the voice frame using the inverse quantized parameters.

In a typical conversation, each speaker is silent for about sixty percent of the time. The speech encoder is typically configured to distinguish between frames containing speech in the speech signal ("active frame") and frames containing only silence or background noise in the speech signal ("inactive frame"). This encoder can be configured to encode active and inactive frames using different encoding modes and/or rates. For example, a speech encoder is typically configured to transmit an encoded inactive frame (also referred to as a "quiet descriptor", "silence description" or SID at a lower rate than the encoded active frame. ).

At any time during full duplex telephone communication, it may be expected that input to at least one of the speech encoders will be an inactive frame. It may be desirable for the encoder to transmit the SID for less than all of the inactive frames. This operation is also known as discontinuous transmission (DTX). In one example, the speech encoder performs DTX by transmitting one SID for each of the 32 consecutive inactive frames. Corresponding to the information in the SID of the decoder application, the noise generation model used by the comfort noise generation algorithm for synthesizing the inactive frame is updated.

A method of processing a speech signal according to a configuration includes generating a sequence of spectral tilt values for a plurality of inactive frames based on the speech signal. The method includes: calculating a change between at least two values of a sequence of spectral tilt values; and determining whether to transmit the description of the frame for one of the plurality of inactive frames. In this method, the description of whether to transmit the frame is based on the calculated change.

A computer program product according to another configuration includes a computer readable medium. The medium includes code for causing at least one computer to generate a sequence of spectral tilt values for a plurality of inactive frames based on the speech signal. The medium includes code for causing at least one computer to calculate a change between at least two values of a sequence of spectral tilt values; and for causing at least one computer to actuate one of the plurality of inactive frames and A method of determining whether to transmit the description of the frame is based on the calculated change.

An apparatus for processing a speech signal according to yet another configuration includes a sequence generator configured to generate a sequence of spectral tilt values for a plurality of inactive frames based on the speech signal. The apparatus includes: a calculator configured to calculate a change between at least two values of a sequence of spectral tilt values; and a comparator configured to target one of the plurality of inactive frames The activity frame and based on the calculated change determines whether to transmit the description of the frame.

An apparatus for processing a speech signal according to yet another configuration includes means for generating a sequence of spectral tilt values for a plurality of inactive frames based on the speech signal. The apparatus includes: means for calculating a change between at least two values of a sequence of spectral tilt values; and determining, for one of the plurality of inactive frames, an inactive frame and determining whether based on the calculated change The component that describes the description of the frame.

The configurations described herein include systems, methods, and apparatus for detecting changes in voice signals. For example, several configurations are disclosed for detecting changes during periods of inactivity of a signal and initiating an update to the signal description based on the detection. Such configurations are generally intended for use in packet switched networks (e.g., wired and/or wireless networks configured to carry voice transmissions according to protocols such as voice over IP or VoIP), although explicitly covered and thus disclosed Use in circuit switched networks.

The term "calculation" is used herein to indicate any of its ordinary meanings, such as calculation, evaluation, smoothing, and selection from a plurality of values, unless explicitly limited in its context. Where the term "comprising" is used in the context of the present description and claims, it does not exclude other elements or operations. The term "A based on B" is used to indicate either of its ordinary meanings, including the following: (i) "A is based on at least B", and (ii) "A is equal to B" (if appropriate in a particular context) ).

The encoder implementing DTX can be configured to discard (or "mask") most of the inactive frames according to the blanking scheme. An instance of the occlusion mechanism issues an update to the silence description at regular intervals (eg, every 16 or 32 consecutive inactive frames). Other occlusion mechanisms (also known as "smart occlusion" mechanisms) are configured to issue an update to the silence description upon detection of fluctuations in energy and/or spectral characteristics indicative of background noise changes.

An occlusion mechanism that relies solely on energy fluctuations may sometimes fail to detect perceptually significant background noise changes. In some cases, perceptually different inactive frames will have similar energy characteristics (typically encoded as gain values). Although background noise ("street noise") in a street, for example, may have a time-dependent energy distribution similar to the energy distribution of background noise ("babble noise") in a crowded space. , but these two types of noise are often perceived in very different ways. An occlusion mechanism that is indistinguishable from perceiving different types of noise may produce audible artifacts at the decoder. Since the active frame also includes, for example, background noise, audible discontinuities may occur when the decoder self-decoding active frame switches to comfort noise generated from improper SID.

An occlusion mechanism is needed to detect perceptually significant background noise changes. For example, an obscuration mechanism may be required to detect sudden changes in one or more spectral characteristics (eg, spectral tilt) of background noise. A method or apparatus as described herein can be used to implement this obscuration mechanism. Alternatively, a method or apparatus as described herein can be used to assist with another occlusion mechanism. For example, a speech coder or a speech encoding method can be as described in the method or apparatus described herein as described in US Patent Application Publication No. 2006/0171419 (Spindola et al., issued Aug. 3, 2006). The occlusion mechanism is combined with another occlusion mechanism configured to detect changes in frame energy and/or spectral characteristics of the speech signal, such as differences between line spectra and vectors.

Figure 1A shows a flow chart of a method M100 in accordance with a general configuration. Based on the plurality of inactive frames of the speech signal, task T200 generates a sequence of spectral tilt values. Task T400 calculates a change within the sequence of spectral tilt values (eg, a change between at least two values of the sequence). For one of the speech signals, the task T500 determines whether to transmit the description of the frame, wherein the decision is based on the calculated change. For example, the decision whether to transmit the description may be based on the relationship between (A) the calculated magnitude of the change and (B) the threshold.

In an exemplary embodiment of method M100, each of the sequence of spectral tilt values is based on a spectral tilt of the corresponding inactive frame. The spectral tilt of the frame of the speech signal is the value that describes the distribution of the energy within the frame over the frequency range. Typically, the spectral tilt indicates the slope of the spectrum of the signal on the corresponding frame and can be positive or negative. The act of generating a value below the spectral tilt sequence is also referred to as "updating" the sequence.

The values of the sequence of spectral tilt values are typically configured in chronological order such that successive values of the sequence correspond to temporally consecutive segments of the signal. The sequence of spectral tilt values configured in this manner can be said to represent a profile (i.e., a spectral tilt profile) that describes the change in the slope of the energy spectrum of the speech signal over time.

Task T200 can be implemented to generate a sequence of spectral tilt values in any of a number of different manners. For example, task T200 can be configured to self-store elements or arrays (eg, semiconductor memory cells or arrays), another task from a larger process (such as a speech encoding method), or from one of, for example, a speech encoder The components of the device receive this sequence. Alternatively, task T200 can be configured to calculate this sequence as described herein.

Task T200 can be configured to output a received or calculated sequence (also denoted herein as x) as a sequence of generated spectral tilt values. Alternatively, task T200 can be configured to generate a sequence of spectral tilt values y by performing one or more other operations on this sequence x. Such other operations may include selecting another sequence from the values of the sequence x: for example, every n values are selected (where n is an integer greater than 1), and/or only the values corresponding to the inactive frames are selected. As described herein, such other operations may also include smoothing the received, computed, or selected sequences.

The duration of each segment of the speech signal (also referred to as "fragment" or "frame") is typically chosen to be sufficiently short in time that the spectral envelope of the predictable signal remains relatively smooth. For example, a typical frame length is 20 milliseconds, which corresponds to 160 samples at a sampling rate of 8 kilohertz (kHz), although any frame length or sampling rate deemed appropriate for a particular application can be used. In some applications, frames are non-overlapping, while in other applications, overlapping frames are used. For example, speech encoders generally use an overlap frame mechanism at the encoder and a non-overlapping frame mechanism at the decoder.

In a typical application, the logic gate array is configured to perform one, more than one, or even all of the various tasks of method M100. For example, this or such tasks can be implemented as machine executable code to be executed by a programmable array, such as a processor. The task of method M100 can also be performed by more than one such array. In these or other embodiments, the tasks can be performed within a wireless communication device, such as a cellular telephone or other device having such communication capabilities. The device can be configured to communicate with the circuit switched and/or packet switched network (e.g., using one or more protocols such as VoIP). For example, the device can include an RF circuit configured to transmit the encoded active frame and SID. The method M100 can also be implemented as a machine readable product embodied in a computer program product (eg, one or more data storage media such as a magnetic disk, a flash memory card or other non-volatile memory card, a semiconductor memory chip, etc.) code.

In a typical application of method M100, task T400 iterates over a sequence of spectral tilt values generated by task T200 to calculate a series of changes based on successive pairs of spectral tilt values, and task T500 iterates over the series of changes to perform A series of transmission decisions. In general, task T200 is performed as a current process, and tasks T400 and T500 are iterated in a serial or parallel manner such that the spectral tilt value and the corresponding calculated change and transmission indication are for each inactive signal of the voice signal. The box is generated (eg, possibly after the initialization period of one or more inactive frames). It is also possible to implement method M100 such that task T200 generates a spectral tilt value less frequently (e.g., for every two or three frames) compared to each inactive frame, such that task T400 executes as frequently as task T200 Or less frequently than task T200 (eg, for every two or three iterations of task T200), and/or such task T500 is performed as frequently as task T400 or less frequently than task T400 ( For example, for every two or three iterations of task T400).

Figure 1B shows a block diagram of an apparatus A100 in accordance with a general configuration. Sequence generator 120 is configured to generate a sequence of spectral tilt values for a plurality of inactive frames based on the speech signal. For example, sequence generator 120 can be configured to perform an embodiment of task T200 as disclosed herein. The calculator 140 is configured to calculate a change between at least two values of the sequence of spectral tilt values. For example, the calculator 140 can be configured to perform an embodiment of the task T400 as disclosed herein. Comparator 150 is configured to determine whether to transmit a description of an inactive segment of the speech signal, wherein the decision is based on the calculated change (eg, based on (A) the calculated magnitude of the change and (B) the threshold Relationship). For example, comparator 150 can be configured to perform an embodiment of task T500 as disclosed herein. In a typical application, an embodiment of apparatus A100 is configured to process a sequence of spectral tilt values and generate a series of transmission decisions based on the sequence.

The various components of device A100 can be implemented as any combination of hardware, software, and/or firmware suitable for the application. For example, any of these elements can be implemented as one or more logic gate arrays. Either or both of these elements may be implemented in the same array or in several identical arrays. The array or arrays can be implemented in one or more wafers (eg, within a wafer set comprising two or more wafers). Any of the various components of apparatus A100 can also be implemented as one or more computers (eg, programmed to execute one or more sets of instructions or arrays of instructions, also referred to as "processors"), and such Any two or more of the components, or even all of them, may be implemented in the same computer or in several identical computers. The various components of device A100 can be included within a wireless communication device, such as a cellular telephone or other device having such communication capabilities. The device can be configured to communicate with the circuit switched and/or packet switched network (e.g., using one or more protocols such as VoIP). For example, the device can include a speech encoder configured to transmit the SID based on the results of the corresponding transmission decision, and/or an RF circuit configured to transmit the encoded active frame and SID.

An example of one of the parameters that can be used to indicate the spectral tilt of the frame is the first reflection coefficient k ₀ , and other such parameters are described below. Task T200 can be configured to receive a sequence of spectral tilt values from another task of a larger program, such as a speech encoding method. Alternatively, task T200 can be implemented to include task T210, which is configured to calculate this value, as described below. Likewise, sequence generator 120 can be configured to receive a sequence of spectral tilt values from another element of a larger device, such as a speech encoder or communication device. Alternatively, sequence generator 120 can be implemented to include a calculator 128 that is configured to calculate such values, as described below.

Task T200 can be implemented to include task T300, which smoothes the sequence of spectral tilt values. The exemplary embodiment of task T300 is configured to filter a sequence of spectral tilt values according to a self-regressive model, such as an infinite impulse response (IIR) filter. A particular instance of task T300 performs the first level IIR filtering operation described below to calculate each value of the smoothed sequence y as a weighted average of the current value of the input spectral tilt value sequence x and the previous value of the smoothed sequence y. : y [ n ]= ax [ n ]+(1- a ) y [ n -1], (1) where n denotes a sequential index. The gain factor a may have any value from 0 to 1 depending on the desired smoothness. In general, the gain factor a has a value of no more than 0.6. For example, the gain factor a can have a value in the range from 0.1 (or from 0.15) to 0.4 (or to 0.5). In a particular example, the sequence x is a series of values of the first reflection coefficient k ₀ and the gain factor a has a value of 0.2 (zero two). 1C shows a flowchart of an embodiment M101 of method M100 in which task T200 is implemented as task T300. 1D shows a block diagram of an embodiment A101 of apparatus A100 in which sequencer 120 is implemented as a smoother 130 configured to perform an embodiment of task T300.

2 shows a block diagram of one example of an embodiment 132 of smoother 130. The smoother 132 includes a first multiplier configured to apply a gain factor G10 to a current value x [ n ] of the input spectral tilt value sequence, and a second multiplier configured to apply the gain factor G20 to A value y [ n -1] preceding the sequence of smoothed spectral tilt values obtained from the delay element D; and an adder configured to output y [ n ] as the sum of the two products. It may be desirable (eg, for stability) that the gain factor G10 has a value a as described above with reference to task T300 and that the gain factor G20 is required to have a value (1- a ). In a particular example, the sequence x is a series of values of the first reflection coefficient k ₀ , the gain factor G10 has a value of 0.2 (zero two), and the gain factor G20 has a value of 0.8 (zero eight). As noted above, the smoother 132 can be implemented as any combination of hardware, software, and/or firmware suitable for the application.

Alternatively or additionally, task T300 can be configured to perform one or more other averaging, integrating, and/or low pass filtering operations by performing a sequence of spectral tilt values x (or a smoothing operation on sequence x ). The value of the smoothed spectral tilt value sequence y. For example, in an alternate embodiment of method M100, task T300 is configured to filter sequence x according to a moving average model, such as a finite impulse response (FIR) filter. In another alternate embodiment of method MlOO, task T300 is configured to filter sequence x according to a self-regressive moving average (ARMA) model. Similarly, smoother 130 can be implemented as an integrator or other low pass filter (such as an FIR or ARMA filter) configured to produce a smoothed value based on two or more input values.

Method M100 is typically implemented such that each value of the sequence of smoothed spectral tilt values x in task T300 corresponds to one of a plurality of consecutive frames of the speech signal. Similarly, device A100 is typically implemented such that each value of sequence x smoothed by smoother 130 corresponds to one of a plurality of consecutive frames of the speech signal. Note that these consecutive frames need not be coherent, as will be described in more detail below.

The voice signal will usually contain an active frame and an inactive frame. However, the energy distribution during the active frame is likely to be primarily due to factors other than background noise, so that the energy distribution values from the active frame are less likely to provide reliable information about background noise changes. Therefore, it may be desirable for the sequence of spectral tilt values x to include only values corresponding to inactive frames. In this case, the value of the sequence x may correspond to a discontinuous continuous (inactive) frame in the speech signal.

To illustrate this principle, Figure 3 shows an example in which each circle represents one of a series of consecutive frames in a speech signal over time. The circles indicating the inactive frames are each marked with an index number of a corresponding value in the sequence of spectral tilt values x . In this example, the values 74 and 75 are consecutive in the sequence. Although the inactive frames corresponding to values 74 and 75 are contiguous in the speech signal, they are separated by active frame blocks and are therefore not coherent with each other.

Method M100 can be configured such that task T300 receives only the spectral tilt values in sequence x corresponding to the inactive frame. Alternatively, task T300 can be implemented to select only those values corresponding to the inactive frames from the sequence of spectral tilt values corresponding to the consecutive frames. For example, this embodiment of task T300 can be configured to select a spectrum corresponding to an inactive frame based on a voice activity indication received from a speech encoder, a speech encoding method, or a voice activity detection task T100, as described below. The tilt value (and/or the value corresponding to the active frame).

Likewise, device A100 can be configured such that smoother 130 only receives spectral tilt values in sequence x that correspond to inactive frames. Alternatively, the smoother 130 can be implemented to select only the values corresponding to the inactive frames from the sequence of spectral tilt values corresponding to the consecutive frames. For example, this embodiment of smoother 130 can be configured to select an inactive frame based on a voice activity indication received from a speech encoder, a speech encoding method, or a voice activity detector 110, as described below. The spectral tilt value (and/or the value corresponding to the active frame).

Task T400 calculates a change between at least two values of the sequence of spectral tilt values produced by task T200. For example, task T400 can be configured to calculate a difference between consecutive values of the smoothed sequence y (also known as "Delta") based on an expression such as the following expression: z [ n ]= y [ n ]- by [ n -1], (2) where z represents the output and b represents the gain factor. 4 shows an embodiment 142 of the calculator 140, which may be used to perform a particular case where b is equal to 1 in this example of task T400 (ie, according to the first stage FIR high pass filtering operation z [ n ]= y [ n ] - y [ n -1]). Other embodiments of calculator 140 and/or task T400 can be configured to apply this filtering operation using different values of b. For example, the value of b can be selected based on the desired frequency response. For the case where task T200 is configured to generate sequence x , this embodiment of T400 or calculator 142 can be configured to be based on an expression such as z [ n ]= x [ n ] -x [ n -1] Calculate the difference. As noted above, the calculator 142 can be implemented as any combination of hardware, software, and/or firmware suitable for the application.

Alternatively or additionally, task T400 can be configured to perform one or more other differential operations on the generated sequence of spectral tilt values, such as different high pass filtering operations (eg, applying a first stage IIR high pass filter to the generated sequence) ), or otherwise calculate the distance or other change between the values of the resulting sequence. Similarly, calculator 140 may be implemented as a differentiator, difference calculator, or other high pass IIR or FIR filter configured to calculate a difference or other distance or change between two or more input values.

The change calculated by task T400 can be used to indicate the rate of change of the resulting sequence of spectral tilt values. For example, the magnitude of z [ n ] as described above can be used to indicate how much the spectral tilt profile of the background noise has changed from one inactive frame to the next inactive frame. Task T400 is typically configured to iteratively calculate a series of distances that represent the rate of change of the smoothed profile over the respective frame period.

Task T500 determines whether to transmit a description of the inactive segment of the speech signal, wherein the decision is based on the corresponding change computed by task T400. For example, task T500 can be configured to determine whether to transmit a description by comparing the calculated magnitude of the change to threshold value T. This embodiment of task T500 can be configured to set a binary flag based on the result of this comparison: The value of the flag p [ n ] indicates the result of the transmission decision. In this case, the p [ n ] value of one or logical TRUE is a positive transmission indication (ie, having a normal transmission indication, a transmission grant indication, an indication of a decision on transmission) indicating that it should be for the current frame. And transmitting an update to the silence description; and the p [ n ] value of the zero or logical FALSE is a negative transmission indication (ie, a negative transmission indication, a transmission disable indication, an indication of a decision not to transmit), Indicates that the update to the silence description should not be transmitted for the current frame. In an example, the threshold T has a value of 0.2. A lower threshold can be used to provide greater sensitivity to changes in the resulting sequence of spectral tilt values, while a higher threshold can be used to provide a larger removal of transients in the resulting sequence of spectral tilt values.

Those skilled in the art will recognize that in an alternate embodiment of method M100, task T400 can calculate the change as a magnitude based on an expression such as the following expression: z [ n ]=| y [ n ]- By [ n -1]|, and task T500 can be configured to set a binary flag based on the result of a comparison such as the comparison below:

Method M100 can also be implemented to include different variations of task T500, such as an average magnitude of both or more of the threshold and the calculated change (eg, the calculated change of the current and previous frames) The average amount) is compared to the examples.

FIG. 5 shows a block diagram of an embodiment 152 of comparator 150, which may be used to perform an embodiment of task T500. In this example, comparator 152 is configured to perform a transmission decision by calculating the magnitude of the calculated change and comparing the magnitude to threshold T10. In a particular example, threshold T10 has a value of 0.2 (zero two). 6 shows a block diagram of another embodiment 154 of comparator 150, which may be used to perform an embodiment of task T500. In this example, the comparator 154 is configured to compare the calculated positive and negative sign values with the positive threshold T10 and the negative threshold T20, respectively, and the calculated change is greater than (or, not less than The positive transmission indication is issued when the threshold T10 is less than (or not greater than) the threshold T20. In an example, threshold T20 has a value that is a negative value of threshold T10 such that comparators 152 and 154 are configured to produce the same result. However, the comparator 154 can also be implemented such that the threshold T20 has a different magnitude than the threshold T10 as needed.

Another embodiment of the comparator 150 is configured to receive the calculated change from the calculator 140 as a magnitude and compare the magnitude to the threshold T10. As discussed above, such embodiments of comparator 150 (i.e., including comparators 152 and 154) can be implemented as any combination of hardware, software, and/or firmware suitable for the application. 7A shows a block diagram of an embodiment A102 of apparatus A100 that is configured to perform various operations as described above on input signal x[n] to generate a corresponding transmission indication.

8A shows an example of a source code list of an instruction set that may be executed by an array of programmable logic elements or other state machine (eg, a computer or processor) to perform an embodiment of method M101, which includes Examples of tasks T300, T400, and T500. In this example, the variable k0 holds the spectral tilt value x [ n ] of the current frame, the variable y_current initially holds the most recent value of the smoothed spectral tilt value sequence y, and the flag p holds the state of the transmission indication. Part 1 (Part 1) performs task T300 by calculating the current value of the smoothed sequence y according to the above expression (1) using the value of the gain factor a of 0.2. Part 2 (Part 2) performs task T400 by calculating the change between the current value and the most recent value of the smoothed sequence y according to the above expression (2) using the value 1 of the gain factor b. Part 3 (Part 3) performs task T500 by setting the flag p based on the comparison result between the calculated change and the threshold using the threshold value 0.2. In a typical application, the set of instructions is executed in an iterative manner (eg, for each inactive frame) such that the initial value of the variable y_current for each iteration is the final value of the variable y_current calculated during the previous iteration.

As described above, task T300 can be configured to calculate the current of the smoothed sequence y based on one or more past values of the spectral tilt value sequence x and/or one or more past values of the smoothed spectral tilt value sequence y . value. However, for the initial value of the smoothed sequence y , the past value of the sequence x and/or the past value of the smoothed sequence y may not exist. If task T300 uses an arbitrary value or a zero value instead of the past value to calculate the value of the smoothed sequence y , the result can cause task T400 to output a calculated change that is too large, which in turn can cause task T500 to even be spectrally skewed. A positive transmission indication is also output in the case of a constant constant.

It may be desirable to initialize one or more variables (eg, data storage locations) configured to hold the sequence x and/or past values of the smoothed sequence y . This initialization may be performed prior to the first execution of task T300, and/or may be performed in task T300. For example, one or more such variables can be initialized to the current value of the sequence x . In a particular example, the variable configured to store the past value of the smoothed sequence ( y [ n -1] in expression (1) above) is initialized to the current value of the input sequence (the expression above) (1) in the x [ n ]). For the different instances in which task T400 is configured to calculate changes based on values x [ n ] and x [ n -1], variables configured to store past values x [ n -1] of the input sequence are initialized to inputs The current value of the sequence x [ n ]. Alternatively or additionally, method M100 can be configured to avoid outputting a positive transmission indication for the first few inactive frames (eg, by forcing task T500 to output a negative transmission indication for the frame). In this case, task T200 (which may include task T300) may be configured to use any value or zero value for each of one or more past values, rather than initializing their variables as described herein.

8B shows another example of a source code list of an instruction set that may be executed by an array of programmable logic elements or other state machine (eg, a processor) to perform an embodiment of method M101, the embodiment including tasks Embodiment T310 of T300 and embodiments of tasks T400 and T500. In this example, task T310 includes an initialization operation that uses the variable Y_VALID to indicate whether the instruction set has been previously called and thus indicates whether the value stored in the variable y_current is valid. In this case, the calling routine (eg, a larger program, such as a speech encoding method) will be configured to initialize the value of Y_VALID to FALSE before calling the instruction set. If the instruction set determines that the value of Y_VALID is FALSE (ie, if the instruction set is first executed), then the variable y_current is initialized to the current value of the variable k0.

The Silent Description (SID) usually includes a description of the spectral envelope of the frame and/or a description of the energy envelope of the frame. Such descriptions may be obtained from a current inactive frame and/or one or more previously inactive frames. The SID can also be called other names such as "Quiet Description Update", "Quiet Descriptor", "Quiet Insert Descriptor", "Comfort Noise Descriptor Frame" and "Comfort Noise Parameters". Specific to the Enhanced Variable Rate Codec (EVRC) as described in document 3GPP2 C.S0014-C Version 1.0 "Enhanced Variable Rate Codec, Speech Service Options 3, 68, and 70 for Wideband Spread Spectrum Digital Systems" In the example, the noise-stimulated linear prediction (NELP) coding mode is used to encode the SID at an eighth rate (16 bits per frame), while code-excited linear prediction (CELP), prototype pitch period (PPP) is used. Or NELP encoding mode encodes the active frame at full rate (171 bits per frame), half rate (80 bits per frame) or quarter rate (40 bits per frame) .

The spectral envelope description generally includes a set of coding parameters such as filter coefficients, reflection coefficients, line spectral frequency (LSF), line spectrum pair (LSP), impedance spectrum frequency (ISF), impedance spectrum pair (ISP), cepstral coefficient Or logarithmic area ratio. The set of encoding parameters configurable as one or more vectors is typically quantized as one or more indices into a corresponding lookup table or "codebook."

The typical length of the spectral envelope description within the SID is currently in the range of eight to 28 bits. In a specific example of EVRC as described in 3GPP2 C.S0014-C version 1.0, cited above, each 16-bit SID includes a four-bit index LSPIDX1 for low frequency information of the spectral envelope in the codebook, and The four-bit index LSPIDX2 of the high frequency information for the spectral envelope in the codebook. In a specific example of an adaptive multi-rate (AMR) speech codec as described in document ETSI TS 126 092 V6.0.0 (European Telecommunications Standards Institute (ETSI), Sophia Antipolis Cedex, FR, December 2004), Each 35-bit SID includes an 8-bit or 9-bit long index for each of the three LSF sub-vectors. In a specific example of the AMR wideband speech codec as described in the document ETSI TS 126 192 V6.0.0 (ETSI, December 2004), each 35-bit SID includes for each of the five ISF sub-vectors. One of the 5-bit or 6-bit long index.

The energy envelope description may include a gain value to be applied to the frame (also referred to as a "gain frame"). Alternatively or additionally, the energy envelope description may include a number of gain values (collectively referred to as "gain profiles") to be applied to each of a number of sub-frames of the frame. In general, the gain frame and/or gain profile may be quantized into the corresponding codebook as one or more indices, although in some cases an algorithm may be used to quantize and/or reverse without using the codebook. Quantize the gain frame and/or gain profile. The typical length of the energy envelope description within the SID is currently in the range of 5 to 8 bits. In a particular example of an EVRC as described above in 3GPP2 C.S0014-C v.1.0 (version 1.0), each 16-bit SID includes an 8-bit energy index FGIDX. In a specific example of the AMR speech codec as described in ETSI TS 126 092 V6.0.0, cited above, and the AMR wideband speech codec described in ETSI TS 126 192 V6.0.0 referenced above, each The 35-bit SID includes a 6-bit energy index.

Method M100 or device A100 can be used as an obstruction mechanism to support DTX. For example, a program including method M100 or a device including apparatus A100 can be configured to perform transmission of the SID only when the status of the transmission indication generated by task T500 is positive. Other obscuration mechanisms can also be used to support DTX. One such example is a method or apparatus that issues a positive SID transmission indication each time the number of consecutive inactive frames that occur after the most recent SID transmission reaches (or exceeds) the threshold DTX_MAX. Typical values for DTX_MAX include 16 and 32. Another example of an occlusion mechanism issues a positive SID transmission indication when the number of consecutive inactive frames that occur after the most recent active frame reaches (or exceeds) a threshold.

Other occlusion mechanisms that may be used to support DTX include mechanisms that are configured to issue a positive SID transmission indication upon detection of a change in the energy of the speech signal and/or a change in the spectral envelope description. For example, the mechanism can be configured to detect a distance between a spectral envelope description (eg, LSF, LSP, ISF, or ISP vector) of the frame and a spectral envelope description of the last transmitted SID that exceeds a threshold. (or, not less than the threshold) a positive SID transmission indication is issued indicating the decision to transmit the description of the currently inactive frame. It may be necessary to filter the spectral envelope description (eg, smoothing) before calculating the distance. A variant of this mechanism is configured to detect that the distance between the energy envelope description of the current inactive frame and the energy envelope description of the last transmitted SID exceeds a threshold (or, not less than a threshold) The positive SID transmission indication is issued. Another variation is configured to issue a positive SID transmission indication when it detects that any of these conditions are met. Other occlusion mechanisms that may be used include values configured to filter the value according to a threshold value and an average absolute value of the frame or the energy value of the frame (eg, the sum of the squares of the samples). Several mechanisms for issuing positive SID transmission indications are compared between comparisons.

Another example of an obscuration mechanism that can be used to support DTX is configured to be issued when it is detected that the Itakura distance between the last transmitted SID and the currently inactive frame exceeds a threshold (or, no less than a threshold) Positive SID transmission indication. A variant of this mechanism is configured to detect the Itakura distance between (A) the last transmitted SID and (B) the current inactive frame and the previous inactive frame exceeds the threshold (or, A positive SID transmission indication is issued when not less than the threshold. The Itakura distance is a measure of spectral change based on autocorrelation and residual energy values, and a description of this mechanism can be found in Annex B of the ITU-T Recommendation G.729 (International Telecommunication Union, Geneva, CH, October 1996).

The method of method M100 or apparatus A100 can be combined with one or more other occlusion mechanisms, such as one or more of the above-described occlusion mechanisms. For example, a device that includes or executes this embodiment can be configured to transmit a SID when any of its occlusion mechanisms issue a positive SID transmission indication for a frame. Figure 7B shows an embodiment of this example in which a number of different transmission indications are combined into a composite transmission indication using a logical OR operation.

As mentioned above, the SID can be derived from one or more inactive frames. For example, a device including device A100 or a program including method M100 may be required to calculate and transmit a SID representing an average of a number of encoded inactive frames instead of transmitting a SID in accordance with a single encoded inactive frame. This average may be calculated using FIR or IIR filtering operations and/or by using statistical methods such as median filtering, which may include discarding outliers or replacing outliers with median values. For example, the device or program can be configured to calculate the SID by statistically smoothing the energy and spectral envelope description of the current frame with the energy and spectral envelope descriptions of one or more previously inactive frames. The resulting SID thus contains the most frequently occurring gain and frequency values in the near future.

The number of frames for which the average value is calculated may be fixed or may vary depending on, for example, the measure of stationarity. An example of this measure is the distance between the spectral averages obtained on the different sets of frames (eg, Itakura distance). In one such example as described in Appendix B of G.729, cited above, an average of six past frames (including the current frame) and two past frames are calculated. If the distance between these two averages exceeds the threshold (or, not less than the threshold), the SID includes a spectral description that averages the two frames (eg, assuming the signal is partially unstable) . In other respects, the SID includes a spectral description that averages the six frames (eg, assuming the signal is locally stationary). In a specific example of the AMR wideband codec as described in ETSI TS 126 192 V6.0.0, referenced above, the SID includes a jitter indication, the state of the jitter indication being between the current frame and the seven previous frames. The sum of the spectral distances is set according to the distance between the energy of the current frame and the average energy value of the past frame.

Method MlOO can be implemented to cause task T200 to receive a sequence of spectral tilt values from another process, such as a speech encoding process. For example, a device or system configured to perform an embodiment of method M100 is also typically configured to perform a speech encoding method on a speech signal. The speech encoding method may include a linear predictive coding (LPC) analysis that computes a set of coefficients that model the sample of the speech signal at time t as a linear combination of samples of the speech signal at a time prior to t. The LPC analysis performed by a speech coder of a communication device (e.g., a cellular telephone) typically has a number of levels of four, six, eight, ten, twelve, 16, twenty, twenty, twenty or eight. For performing independent LPC analysis on different frequency bands of the speech signal, task T200 can be configured to receive based on a pair of low frequency bands (eg, including frequencies below 1 kHz) or a medium frequency band (eg, including at least 1 kHz and 2 kHz) A sequence of spectral tilt values for the analysis of the frequency).

Task T200 can be configured to receive a sequence of spectral tilt values as a sequence of reflection coefficients, such as a sequence of first or second reflection coefficients. The scope of the configurations disclosed herein includes several methods including a combination of method M100 and a speech encoding method (e.g., as described in FIG. 9), and a number of speech encoding methods including method M100.

Apparatus A100 can be implemented to cause sequence generator 120 to receive a sequence of spectral tilt values from another apparatus, such as a speech coder. For example, a device or system including an embodiment of apparatus A100 will typically also include a speech encoder that can be configured to perform LPC analysis on the speech signal. In this case, sequence generator 120 can be configured to receive a sequence of spectral tilt values as a sequence of reflection coefficients. The scope of the configurations disclosed herein includes several devices including a combination of device A100 and a speech encoder (e.g., as described in FIG. 10), and a number of speech encoders including device A100.

Alternatively, task T200 can be implemented to include task T210, which calculates a sequence of spectral tilt values based on a plurality of inactive frames of the speech signal. Task T210 can be configured to evaluate the spectral tilt of the signal for each of a series of frames, for example, according to one or more of a number of different techniques as described below. 11A shows a flowchart of an embodiment M200 of method M100, wherein embodiment M200 includes this embodiment T202 of task T200. Task T210 can also be configured to provide a sequence of calculated spectral tilt values to other tasks of a larger process, such as a speech encoding method. Method M100 can also be implemented such that task T200 is implemented as task T210.

11B shows a block diagram of an embodiment A200 of apparatus A100, wherein embodiment A200 includes an embodiment 122 of sequence generator 120. Sequence generator 122 includes a calculator 128 that is configured to calculate a sequence of spectral tilt values based on a plurality of inactive frames of the speech signal. For example, the calculator 128 can be configured to perform an embodiment of task T210 as disclosed herein. As with other components of device A200, calculator 128 can also be implemented as any combination of hardware, software, and/or firmware suitable for the application. The calculator 128 can also be configured to provide the calculated sequence of spectral tilt values to other tasks such as a larger device of the speech coder. Apparatus A100 can also be implemented such that sequence generator 120 is implemented as calculator 128.

The exemplary embodiment of task T210 is configured to calculate the spectral tilt as the first reflection coefficient of the corresponding frame of the speech signal. The first reflection coefficient of the frame (generally denoted as k ₀ ) can be calculated as the ratio R (1) / R (0) (ie, the normalized first autocorrelation value of the frame), for -1 to +1 The sample value in the range has a scalar value between -1 and +1 than R (1) / R (0). In this expression, R (1) represents the first autocorrelation coefficient of the frame (ie, the value of the autocorrelation function when the frame is delayed by one sample), and R (0) represents the zeroth of the frame. Autocorrelation coefficient (ie, the value of the autocorrelation function at the zero lag time frame).

In other embodiments, task T210 is configured to calculate the spectral tilt as the second reflection coefficient of the corresponding frame of the speech signal. The second reflection coefficient of the frame (usually expressed as k ₁ ) can be calculated as: Where R (2) represents the second autocorrelation coefficient of the frame (ie, the value of the autocorrelation function of the frame when the two samples are delayed). Task T210 can also be implemented to calculate one or more reflection coefficients (eg, first and/or second reflection coefficients) of a corresponding frame based on one or more other parameters, such as one or more LPC filter coefficients. .

The scope of the embodiment of task T210 is not limited to the embodiment in which the spectral tilt is calculated as the reflection coefficient. Alternatively or additionally, task T210 can be configured to perform one or more other spectrum estimation techniques to calculate the spectral tilt of one or more frames. Such spectrum estimation techniques may include calculating the spectral tilt of each frame as the ratio between the energy of the high band and the energy of the low band. This calculation may include performing a frequency transform on the segment, such as a discrete Fourier transform (DFT). Such spectral evaluation techniques may include calculating the spectral tilt as the number of zero crossings within each segment. In this case, a higher number of zero crossings can be used to indicate a larger amount of high frequency energy.

In calculating the sequence of spectral tilt values, task T210 can be configured to perform calculations based on the value of the autocorrelation function, such as calculating one or more reflection coefficients as described above. An autocorrelation method of calculating LPC model parameters, such as filtering or reflection coefficients, involves performing a series of iterations to solve an equation including a Toeplitz matrix. In some embodiments, task T210 is configured to perform an autocorrelation method according to any of the well-known Levinson and/or Durbin recursive algorithms for solving this equation. This algorithm typically calculates the reflection coefficient (also known as the partial correlation (PARCOR) coefficient, the negative PARCOR coefficient, or the Schur-Szego parameter) as an intermediate value in the process of generating a set of LPC filter coefficients.

In other embodiments, task T210 is configured to perform a series of iterations to calculate one or more reflection coefficients rather than a set of filter coefficients. For example, task T210 can be configured to acquire one or more reflection coefficients using an embodiment of the Leroux-Gueguen algorithm. Alternatively, task T210 can be configured to obtain one or more reflection coefficients from an autocorrelation value using an embodiment of another well-known iterative method, such as a Schur recursive algorithm (which can be configured for efficient parallel computation) Or Burg recursive algorithm.

Task T210 can be configured to calculate one or more values of the autocorrelation function of the corresponding frame of the speech signal. For example, task T210 can be configured to evaluate the autocorrelation function of the frame for a particular hysteresis value m (where m is an integer not less than zero) according to an expression such as the following expression: Where N is the number of samples in the frame. Alternatively, task T210 can be configured to receive values of the autocorrelation function (eg, from a speech coder, or a speech encoding method or other process).

The speech encoder or speech encoding method can be configured to use the value of the autocorrelation function in the encoding operation, such as calculating parameters (eg, filtering and/or reflection coefficients) of the LPC model. This speech coder or speech encoding method may be required to perform one or more pre-processing operations on the autocorrelation values. For example, the autocorrelation value R ( m ) can be spectrally smoothed by performing an operation such as the following:

In this scenario, task T210 can be configured to perform spectral smoothing or another pre-processing operation on autocorrelation values, and/or to calculate spectral tilt parameters using spectrally smoothed or otherwise pre-processed autocorrelation values. The value.

Before applying the autocorrelation function to the speech signal (eg, by task T210, or a speech coder or speech coding method), it may be desirable to apply the window function w [ n ] to the signal. For example, it may be desirable to zero the speech signal that is currently being applied to the frame of the autocorrelation function. In some cases, the window function w [ n ] is rectangular or triangular. It may be necessary to use a wedge window function with low sample weights at each end of the window, which can help reduce the effects of components outside the window. For example, a raised cosine window may be required, such as the Hamming window function described below: Where N is the number of samples in the frame.

Other wedge windows that may be used include Hanning, Blackman, Kaiser, and Bartlett windows. The window frame s _w [ n ] can be calculated from an expression such as the following expression:

The window function does not need to be symmetrical so that one half of the window can be weighted differently from the other half. You can also use a hybrid window, such as a Hamming cosine window, or a window with two halves of different windows (for example, two Hamming windows of different sizes). The sample value and/or the windowed value may be subjected to one of a perceptual weighting or a plurality of other pre-processing operations (e.g., by task T210 or a speech coder or speech encoding method) before the autocorrelation function is evaluated.

The window function w [ n ] can be configured to include samples of the current frame and samples from one or more adjacent frames. In some cases, the window includes samples from the current frame and the adjacent previous and subsequent frames (for example, 5-20-5 windows including 5 milliseconds immediately before and after the 20 millisecond frame), in other In this case, the window includes samples from only the current frame and adjacent previous frames (eg, 10-20 windows including the current 20 millisecond frame and the last 10 milliseconds of the previous frame).

For the case where a window function is applied to a speech signal (for example, by task T210 or a speech coder or speech coding method), the autocorrelation function of the frame can be calculated according to an expression such as the following expression:

As described above, it may be desirable for task T300 or smoother 130 to smooth a sequence that only includes values corresponding to inactive frames. In this case, method M100 or apparatus A100 can be configured to receive an indication of the level of voice activity in the frame (eg, from a speech coder or a speech encoding method). For example, this indication (also referred to as "voice activity indication") may have the form of a binary variable or flag indicating whether the corresponding frame is active or inactive.

The voice activity indication can be used to control the operation of the smoothing task T300. For example, the voice activity indication can be used to allow smoothed spectral tilt values to be generated from the corresponding inactive frame and/or to prevent smoothed spectral tilt values from being generated from the corresponding active frame. In one such example, the computer or processor is configured to control task T300 to smooth the spectral tilt value only when the voice activity indication indicates that the corresponding frame is an inactive frame. Alternatively, task T300 can include determining whether to generate a smoothed spectral tilt value or to determine whether to accept or remove the spectral tilt value based on the value of the corresponding voice activity detection. 12A shows a flowchart of an embodiment M110 of method M101, which includes an embodiment T320 of task T300.

The voice activity indication can be used to control the operation of the computing task T210. For example, the voice activity indication can be used to allow for the generation of a spectral tilt of the corresponding inactive frame and/or to prevent the spectral tilt of the corresponding active frame from being generated. In one such example, the processor is configured to control task T210 to calculate the spectral tilt only when the voice activity indication indicates that the current frame is an inactive frame. Alternatively, task T210 can be configured to include determining whether to generate a spectral tilt for a given frame, or can be configured to control its input (eg, accept or remove frames) and/or based on the value of the corresponding voice activity indication. Its output (for example, whether to release the spectral tilt value). 12B shows a flowchart of an embodiment M210 of method M200, which includes an embodiment T204 of task T202, wherein task T204 includes this embodiment T220 of task T210.

As an alternative to receiving a voice activity indication, method M100 can be implemented to include task T100 configured to indicate whether the frame is active or inactive. For example, task T100 can be configured to calculate a voice activity indication (VAI) as described above. 12C shows a flowchart of an embodiment M120 of method M101 that includes task T100, and FIG. 12D shows a flowchart of an embodiment M220 of method M200 that includes task T100. Task T100 can be configured to divide the frame into active or inactive based on one or more factors, such as full band energy, low band energy, high band energy, spectral parameters (eg, one or Multiple LSF and/or reflection coefficients), periodicity and zero crossing rate. For example, this classification may include comparing the value of such a characteristic to a fixed or adaptive threshold, and/or calculating a magnitude of the change in the value of such characteristic (eg, the amount of difference between two values) The value, or the magnitude of the difference between a value and a moving average, and compares the magnitude to a fixed or adaptive threshold.

Task T100 can be configured to evaluate the energy of the current frame in each of the low and high frequency bands, and the indication frame is when the energy in each frequency band is less than (or, not greater than) the respective threshold. Inactive. These thresholds can be fixed or adaptive. For example, each threshold can be based on the desired coding rate. An example of a pair of adaptive thresholds is described in Section 4.7 of C.S0014-C v.1.0, cited above. In this example, the threshold for each band is based on the anchor operating point (if obtained from the desired average data rate), the estimate of the background noise level in the previous band of the previous frame, and the previous frame. The signal-to-noise ratio in the band.

The transition from active speech to inactive speech usually occurs over a period of time with a number of frames, and in addition to background noise, the first few inactive frames after the transition from the active speech may also include residuals of pronunciation. The voicing remnant may cause the post-transition inactive frames to have a spectral tilt that is different from the spectral tilt of the background noise, and such differences may corrupt the sequence of spectral tilt values generated by task T200 and result in no The necessary SID transmission.

As noted above, task T200 may be required to generate a value based only on the sequence x of inactive frames. As such, task T300 may be required to generate a value based on the smoothed sequence y from one or more spectral tilt values of the inactive frame. It may also be desirable for embodiments of method M100 to avoid updating the spectral tilt profile using spectral tilt values from one or more post transition frames. This limitation can help reduce the likelihood that the decision task T500 will make an incorrect positive transmission indication.

Task T200 can be configured to generate one or more values of the generated sequence of spectral tilt values based on the temporal distance between the corresponding inactive frame and the previous active frame. For example, this embodiment of task T200 or task T300 can be configured to delay or temporarily suspend the beginning of a spectrally skewed profile update for one or more inactive frames after a transition from active speech. Figures 13A and 13B illustrate examples of this transition and the effects of this delay or temporary suspension, respectively. Figure 13A shows a sharp change in the amplitude of the smoothed spectral tilt profile caused by the residual of the sound in the post transition frame. This change can result in improper positive SID transmission decisions. In this particular example, the spectral tilt parameter is the first reflection coefficient k ₀ such that the pronunciation residual causes a sharp rise in the amplitude of the smoothed spectrally sloped profile, although the pronunciation residual can instead be caused by the use of another spectral tilt parameter. The amplitude is drastically reduced. By way of comparison, Figure 13B shows an example in which the application delay (also known as "delay") is used to update the smoothed contour during the post transition frame. In this case, the sharp rise seen in Fig. 13A does not occur. In a particular example, the delay of five frames is used after transitioning from active speech to inactive speech.

14 shows an example of a source code list of an instruction set executable by an array of programmable logic elements or other state machine (eg, a processor) to perform an embodiment of method M100, the embodiment including task T310 Embodiment T312 and embodiments of tasks T400 and T500. In this example, task T312 reads the variable FRAME_ACTIVE that stores the current state of the voice activity indication. If the value of FRAME_ACTIVE is TRUE (this indicates that the current frame is active), the delay count is stored to the variable hangover_1 and the instruction set is terminated. In this particular example, the delay count is 5, although any other positive integer value can be used. When the value of FRAME_ACTIVE changes to FALSE (this indicates that the current frame is inactive), each subsequent iteration of the instruction set decrements the value of the variable hangover_1 and terminates early when the value of the variable hangover_1 reaches zero. In this example, tasks T400 and T500 are implemented using instructions as described above with reference to Figure 8B.

Examples of method M100 and apparatus A100 include several embodiments configured to control the update of the spectral tilt profile in accordance with the state of an update control signal. This signal can be based on a voice activity indication as described above. The variable FRAME_ACTIVE shown in Fig. 14 is an example of an update control signal (specifically, an update disable signal). Delay logic circuit 50 can be used to calculate an update control signal by delaying the transition from active to inactive in the voice behavior indication. 15 shows an embodiment 52 of delay logic circuit 50, which is configured to generate an update control signal (specifically, an update enable signal). In this figure, the state of the voice activity indication is low for the inactive frame and high for the active frame, and the sub-sampling delay line with three delay elements is used to implement the delay of the three frames, and the logic The "or" operation is used to combine the current and deferred voice activity indications. In other examples, the status of the voice activity indication may be high for the inactive frame and low for the active frame, and in this case, the current and deferred speech may be combined using a logical "and" operation. Activity instructions. In the case of a subsampling delay line, other examples of this circuit may use any number of delay elements depending on the desired delay duration. Alternatively, delay logic circuit 50 may be implemented to count down (or up count) using a delay counter from active to inactive transition, and/or to calculate an update disable signal instead of an update enable signal.

The sequence generator 120 can be configured to generate one or more values of the generated sequence of spectral tilt values based on the temporal distance between the corresponding inactive frame and the previous active frame. For example, sequence generator 120 or smoother 130 can be configured to temporarily suspend the beginning of a spectrally skewed profile update after a transition to active to inactive based on the desired delay. This embodiment of sequence generator 120 or smoother 130 can be configured to include embodiments of delay logic circuit 50 as described above. FIG. 16A shows one such embodiment 134 of smoother 132. In this example, the selector (e.g., multiplexer) is at the current value of the sequence (i.e., x [ n ]) and the previous value of the smoothed spectral slope profile based on the state of the update control signal (i.e., y [ Switch the input of the smoother between n -1]). Alternatively, an embodiment of smoother 110 can be configured to store the current value x [ n ] when the update control signal is high and to use this stored value for input when the update control signal is low.

FIG. 16B shows another embodiment 136 of smoother 132, which includes an embodiment of delay logic circuit 50 as described above. This example includes two selectors (eg, multiplexers) that are configured to output different gain factors depending on the state of the update control signal. The first selector outputs a gain factor to be applied to x [ n ]. When the state of the update control signal is high, the selector outputs a gain factor F10, and when the state of the update control signal is low, the selector outputs a gain factor F12. The second selector outputs a gain factor to be applied to y [ n -1]. When the state of the update control signal is high, the selector outputs a gain factor F20, and when the state of the update control signal is low, the selector outputs a gain factor F22. In one example, gain factors F10 and F12 have values of 0.2 and 0, respectively, and gain factors F20 and F22 have values of 0.8 and 1.0, respectively.

Another embodiment of smoother 136 can be configured to select between more than two values of each gain factor, thereby making the smoother transition from temporary suspension to normal operation more gradual. For example, instead of a delay logic circuit that produces a two-state control signal, the smoother can include an embodiment of the delay logic circuit 50 configured to generate a control signal having more than two states. This embodiment of delay logic circuit 50 can be configured to generate an update control signal that experiences c states in response to an active to inactive transition, where c is an integer greater than two. In this case, the two selectors of smoother 136 can be configured such that, in response to the transition and over a series of c frames, the gain factor applied to x [ n ] experiences from a minimum to a maximum The c values are (for example, from 0.0 to 0.2), and the gain factors applied to y [ n -1] are subjected to c values from the maximum value to the minimum value (for example, from 1.0 to 0.8).

The coding gain metric describes the relationship between the energy of the signal received by the speech coder (or speech coding method) and the energy of the corresponding coding error. In general, a speech coder or speech coding method encodes an active frame more efficiently than an inactive frame such that the coding gain metric is higher for the active frame than the inactive frame. An example of a coding gain metric of a frame is the ratio of the initial signal energy E _in (eg, the energy of the window frame) to the coded residual energy E _err . In such cases, the energy of each signal is typically calculated as the sum of the magnitudes of the samples. Another common coding gain metric for LPC analysis is the prediction gain, which can be calculated as (1- The inverse of the product of the product, for all i j (or, for all i, 1< i j )), where j is the number of stages of the LPC analysis and k _i indicates the ith reflection coefficient.

The degree of coding gain achieved by a speech coder or speech coding method tends to vary frame by frame as the signal changes. However, during a series of inactive frames, the signal may be expected to be relatively smooth so that its statistics do not change significantly. Accordingly, coding gain can be expected metric value of G _c also remains relatively constant even during significant changes in the perceived background noise.

Changing the value of the larger coding gain G _c of the metric may be indicative of a speech signal due to the factors other than the background noise changes changed. This may be a factor contributing to change the value of G _c is a threshold value in the detection of the voice activity detector of the encoder of the speech activity. In this case, a larger change can also occur in the spectral tilt value, causing the task T500 to make a positive SID transmission decision even if the background noise has not changed significantly.

Method M100 may be required to implement the coding gain taking into account the value of the metric spectral tilt change associated with a change of G _c. For example, embodiments of task T200 or T230 of task T300 T330 embodiments may be configured based on a measure of coding gain change value G _c of the magnitude of the energized or de-energized profile updating.

In some cases, the coding gain metric can be calculated based on the coding error, as in the following expression:

Similarly, the prediction gain can also be calculated as the prediction error, as in the following expression: For all, i j (or, for all, 1< i j )).

The coding gain metric can also be calculated from other expressions, such as the following products, for example: , for all, i j (or, for all, 1< i j )), or include the ratio between E _in and E _err as a factor or term.

The coding gain metric can be represented on a linear scale or in another domain, such as on a logarithmic scale. Examples of such expressions include the following expressions:

Coding gain metrics are typically evaluated for each frame, but may be less frequent (eg, for every two or every three frames) and/or at longer intervals (eg, in one or three Evaluation on the frame.

In a typical configuration, task T230 or task T330 is configured to dissipate the generated spectrum when the value G _{c changes} from an inactive frame to a next inactive frame by more than a threshold amount (or no less than a threshold amount). The update of the skewed outline. In a particular example, task T330 is configured to update the smoothed contour when the value of the predicted gain changes from the previous inactive frame to the current inactive frame by more than 0.72 dB. Embodiments of task T230 or task T330 can be configured to apply a delay to extend this de-enforcement to one or more subsequent frames. Another embodiment of task T230 or task T330 can also be configured to apply a delay after the transition from a live voice as described above (eg, with reference to Figures 13A-16B).

Embodiment of apparatus A100 may be necessary to account for the measure of coding gain (such as one of those above example) the spectrum change of the value of G _c of the associated inclined profile changes. For example, apparatus A100 can be implemented to include a control signal generator 60 configured to generate an update control signal whose state is based on a magnitude of a change in predicted gain. FIG. 17A shows a block diagram of an example 62 of control signal generator 60. Control signal generator 60 may also be implemented to apply delays as in the example of control signal generator 64 shown in Figure 17B. In a particular example, the value of threshold T30 is 0.72 dB. Embodiments of smoother 134 or 136 may include embodiments of control signal generator 60 instead of or in addition to the circuitry configured to delay the transition from active to inactive in the voice activity indication. For example, this embodiment can include a control signal generator 66 as shown in FIG. 18 that combines the operation of delay logic circuit 62 with control signal generator 64.

Embodiments of method M100 can be configured to control the generation of SID transmission indications based on changes in the value of the coding gain metric. For example, an embodiment of method M100 can include an embodiment of task T400, the embodiment of task T400 being configured to encode a gain metric (eg, predictive gain) from one inactive frame to the next. The output distance is zero when the active frame changes beyond the threshold amount (or, not less than the threshold amount). Additionally or in the alternative, an embodiment of method M100 can include an embodiment of task T500, the embodiment of task T500 being configured to energize or de-energize a positive SID transmission indication based on a magnitude of a change in predicted gain. produce. One such embodiment T510 of task T500 is configured to disable the generation of a positive SID transmission indication unless the predicted gain changes from a previous inactive frame to a current inactive frame less than (or does not exceed) a threshold. In one particular example, the threshold is 0.65 dB. In addition to controlling the update of the spectral tilt profile or as an alternative to controlling the update of the spectral tilt profile, control of the generation of the transmission indication can be performed.

Example of apparatus A100 may be configured to change the value of G _c according to the measure of coding gain is controlled to produce an indication of the SID transmission. 19A shows a block diagram of an example 72 of a transmission indication control circuit 70 that is configured to gate a positive SID transmission indication based on a relationship between a threshold value T40 and a magnitude of a predicted gain change. In a particular example, the value of threshold T40 is 0.65 dB. 19B shows a block diagram of an embodiment 156 of comparator 152, which includes transmission indication control circuitry 72.

Example of apparatus A100 may be configured to change the value of a coding gain based on a measure of G _c and the control of the update control signal is generated indicative of the SID transmission. 20 shows a block diagram of an example 82 of control circuit 80 configured to perform such operations. This circuit can be configured to receive a SID transmission indication from comparator 150 and provide an update control signal to smoother 130. This circuit can also be implemented in smoother 130 or comparator 150. For example, in smoother 134 or 136, control circuit 82 can be configured to replace delay logic circuit 52 and gate the SID transmission indication from comparator 150 based on the predicted gain. In another example, control circuit 82 can be configured in comparator 152 to gate the SID transmission indication based on the predicted gain and also provide an update control signal to smoother 130.

21 shows an example of a source code list of an instruction set that may be executed by an array of programmable logic elements or other state machine (eg, a processor) to perform an embodiment of method M100, which includes task T312 Embodiments of Embodiment T332 of T330, Embodiment T510 of Task T500, and Task T400. In this example, the state of the variable FRAME_ACTIVE indicates whether the current frame is active or inactive, and the state of the variable Y_VALID indicates whether the instruction set has been previously called (and thus indicates whether the value stored in the variable y_current is valid), and The value of the variable Gc indicates the predicted gain of the current frame.

If the instruction set determines that the value of Y_VALID is FALSE (ie, if the instruction set is first executed), the variable Gc_current is initialized to the current value of the variable Gc. The absolute difference between the current value of Gc and the past value is stored to the variable Gc_diff, and if the difference is greater than the threshold, the delay of the two frames is applied. In Part 3, the flag p is set only when the value of Gc_diff is less than the threshold.

The specific examples of the logical embodiments described herein are set forth to explain the present disclosure and are not to be construed as limiting the scope of the invention. For example, the selection logic implemented in one context as a "and" gate configured to generate an active high signal only when all of its inputs are high may be implemented in another context to be configured only at all The OR gate of the active low signal is generated when the input is low. The countdown from the first value to the second value can also be implemented as an incremental count from the second value to the first value, and vice versa. A positive or TRUE indication can be represented by a binary high value in one context and a binary low value in another context. It is contemplated and thus disclosed that such and other embodiments are also within the scope of the present disclosure.

In the above example, it is assumed that the sequence of spectral tilt values includes the value of each of a series of consecutive inactive frames. However, it is also contemplated that method M100 and apparatus A100 can be implemented such that the sequence of spectral tilt values includes less than one value for each of a series of consecutive inactive frames. For example, the sequence can include values for every other frame (or every two frames, etc.) in the series. This sequence can be obtained by ignoring the intermediate frame or discarding the values from such frames, or by averaging the values of each pair (three, etc.) frames. Other or additional, these principles can be applied to other sequences, such as a sequence of coding gain metric values.

Those skilled in the art will appreciate that information and signals can be represented by any of a variety of different techniques and techniques. For example, the materials, instructions, commands, information, signals, bits, and symbols that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields, or magnetic particles, light fields, or optical particles, or any combination thereof. . Although the signal from which the resulting sequence of spectral tilt values is derived is referred to as a "speech signal," it is also contemplated and thus disclosed that the signal can also carry music or other non-speech information content in the active frame.

Elements of various embodiments of apparatus A100 as described herein can be fabricated as electronic and/or optical devices residing, for example, on the same wafer or between two or more wafers of a wafer set. An example of such a device is an array of fixed or programmable logic elements, such as a transistor or gate. One or more elements of various embodiments of apparatus A100 as described herein may also be implemented in whole or in part as one or more sets of instructions that are configured to be executed in one or more fixed or Array of stylized logic elements such as microprocessors, embedded processors, IP cores, digital signal processors, field programmable gate arrays (FPGAs), application specific standard products (ASSPs), and special application integrated circuits (ASICs) ).

One or more elements of an embodiment of apparatus A100 may be used to perform tasks that are not directly related to the operation of the apparatus or to perform other sets of instructions that are not directly related to the operation of the apparatus, such as with a device or system in which the apparatus is embedded. Another operation related task. One or more of the elements of the apparatus A100 may also have a common structure (eg, a processor for executing portions of the code corresponding to different elements at different times, executed to perform at different times corresponding to different The set of instructions for the task of the component, or the configuration of electronic and/or optical devices that perform operations on different components at different times). In one such example, smoother 130, calculator 140, and comparator 150 are implemented as a set of instructions configured to execute on the same processor. In another such example, sequence generator 120 and even a speech encoder (which may include device A100) are implemented to be configured to execute on one or more sets of instructions on the processor.

The above statements of the configurations are provided to enable those skilled in the art to make or use the methods and other structures disclosed herein. The flowcharts and other structures shown and described herein are merely examples, and other variations of such structures are also within the scope of the present disclosure. Many modifications to these configurations are possible, and the general principles described herein can also be applied to other configurations.

The configuration described herein may be implemented partially or entirely as a hardwired circuit, as a circuit configuration fabricated into a special application integrated circuit, or as a firmware loaded into a non-volatile memory or as The machine readable code is a software program loaded from a data storage medium or loaded into a data storage medium, the machine readable code being an instruction executable by an array of logic elements, such as a microprocessor or other digital signal processing unit. The data storage medium can be an array of storage elements, such as semiconductor memory (which can include, but is not limited to, dynamic or static RAM (random access memory), ROM (read only memory), and/or Flash RAM); or ferroelectric, magnetoresistive, bidirectional, polymeric or phase change memory; or disc media such as disk or optical disc. The term "software" shall be taken to include a source code, a combined language code, a machine code, a binary code, a firmware, a macro code, a microcode, any one or more instruction sets or sequences of instructions executable by an array of logic elements, and the like. Any combination of examples.

The methods disclosed herein may also be embodied (eg, in one or more of the data storage media listed above) as one or more sets of instructions, which may include an array of logic elements (eg, Machine reading and/or execution by a processor, microprocessor, microcontroller or other finite state machine. Therefore, the present disclosure is not intended to be limited to the configuration shown above, but is intended to be in accord with the broadest scope of the principles and novel features disclosed herein. The scope of the additional patent application forms part of the original disclosure.

Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and operations described in connection with the configurations disclosed herein can be implemented as an electronic hardware, a computer software, or a combination of both. Such logic blocks, modules, circuits, and operations may use general purpose processors, digital signal processors (DSPs), ASICs, FPGAs, or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or The design is implemented or performed in any combination of the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a combination of a plurality of microprocessors, a combination of one or more microprocessors and a DSP core, or any other such configuration. .

The methods and algorithms described herein can be implemented directly in software, in a software module executable by a processor, or in a combination of the two. The software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, scratchpad, hard disk, removable disk, CD-ROM, or known in the art. Any other form of storage media. The illustrative storage medium is coupled to the processor such that the processor can read information from the storage medium and write information to the storage medium. In the alternative, the storage medium can be integrated into the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in the user terminal. In the alternative, the processor and the storage medium may reside as discrete components in the user terminal.

50,52. . . Delay logic

62,64,66. . . Control signal generator

72. . . Transmission indication control circuit

82. . . Control circuit

120,122. . . Sequence generator

128,140,142. . . Calculator

130,132,134,136. . . Smoother

150,152,154,156. . . Comparators

A100, A101, A102, A200. . . Device

G10, G20, F10, F12, F20, F22. . . Gain factor

T10, T20, T30, T40. . . Threshold

Figure 1A shows a flow chart of a method M100 in accordance with a configuration.

Figure 1B shows a block diagram of an apparatus A100 in accordance with a configuration.

1C shows a flow chart of an embodiment M101 of method M100.

1D shows a block diagram of an embodiment A101 of apparatus A100.

2 shows a block diagram of an embodiment 132 of smoother 130.

3 shows an illustrative example in which each circle represents one of a series of consecutive frames in a speech signal over time.

4 shows a block diagram of an embodiment 142 of the calculator 140.

FIG. 5 shows a block diagram of an embodiment 152 of comparator 150.

FIG. 6 shows a block diagram of an embodiment 154 of comparator 150.

FIG. 7A shows a block diagram of an embodiment A102 of apparatus A100.

Figure 7B shows an example of combining several different transmission indications into a composite transmission indication.

FIG. 8A shows a list of source code that can be executed to execute an instruction set of an embodiment of method M100.

FIG. 8B shows a list of source code that can be executed to execute an instruction set of another embodiment of method M100.

9 shows a flow chart of a method including a combination of method M101 and a speech encoding method.

Figure 10 shows a block diagram of an apparatus comprising a combination of apparatus A 101 and a speech coder.

11A shows a flowchart of an embodiment M200 of method M100.

11B shows a flowchart of an embodiment A200 of apparatus A100.

Figure 12A shows a flow diagram of an embodiment M110 of method M101.

FIG. 12B shows a flowchart of an embodiment M210 of method M200.

Figure 12C shows a flow chart of an embodiment M120 of method M101.

12D shows a flowchart of an embodiment M220 of method M200.

Figures 13A and 13B show examples of smoothed spectral tilt profiles, respectively, with and without application delay.

14 shows a source code listing of an instruction set that can be executed to perform another embodiment of method MlOO.

Figure 15 shows a block diagram of an example of a delay logic circuit.

FIG. 16A shows a block diagram of an embodiment 134 of smoother 132.

16B shows a block diagram of an embodiment 136 of smoother 132.

17A shows a block diagram of an example 62 of control signal generator 60, where instance 62 is configured to generate an update control signal based on the predicted gain.

17B shows a block diagram of an example 64 of control signal generator 62, where instance 64 is configured to apply a delay.

18 shows a block diagram of an embodiment 66 of control signal generator 64, wherein embodiment 66 also includes delay logic circuit 52.

19A shows a block diagram of an example 72 of a transmission indication control circuit 70.

19B shows a block diagram of an embodiment 156 of comparator 152.

20 shows a block diagram of an example 82 of control circuit 80, where instance 82 is configured to generate an update control signal and gate the SID transmission indication.

21 shows a source code listing of an instruction set that can be executed to perform another embodiment of method MlOO.

(no component symbol description)

Claims (46)

A method for processing a speech signal, the method comprising: generating a sequence of spectral tilt values based on a plurality of inactive frames of the speech signal, wherein the sequence of spectral tilt values comprises a sequence of reflection coefficients, wherein the spectral tilt values are Each of the at least one reflection coefficient of the inactive frame corresponding to one of the voice signals, the at least one reflection coefficient comprising a first reflection coefficient of the corresponding inactive frame or the corresponding inactive frame At least one of a second reflection coefficient; calculating a change between at least two values of the spectral tilt values based on the reflection coefficient; and determining whether one of the plurality of inactive frames is an inactive frame A description of one of the frames is transmitted, wherein the description of whether to transmit the frame is based on the calculated change. A method of processing a speech signal according to claim 1, wherein the generating the sequence of spectral tilt values comprises smoothing another sequence of spectral tilt values to generate the sequence of spectral tilt values, wherein each of the spectral tilt values of the another sequence The indicator indicates that one of the plurality of inactive frames is spectrally tilted. A method of processing a speech signal according to claim 1, wherein each of the plurality of spectral tilt values is based on another spectral tilt value in the sequence of spectral tilt values. A method for processing a speech signal according to claim 1, wherein each of the plurality of spectral tilt values is based on (A) one of the plurality of inactive frames One of the corresponding ones is spectrally tilted and (B) is another spectral tilt value in the sequence of spectral tilt values. A method of processing a speech signal according to claim 1, wherein the calculated change is based on a difference between consecutive values in the sequence of spectral tilt values. A method of processing a speech signal according to claim 1, wherein the calculating the change comprises calculating a distance between adjacent values in the sequence of spectral tilt values. A method of processing a speech signal of claim 1, wherein the determining whether to transmit the frame comprises comparing the calculated change to a threshold. A method of processing a speech signal according to claim 1, wherein the result of the description of whether to transmit the frame is based on (A) a value of the calculated change and (B) a threshold value a relationship. A method for processing a voice signal according to claim 1, wherein the method includes transmitting a silence description if a result of the determining whether to transmit the frame is a decision to transmit the description of the frame, The silence description includes at least one of a spectral envelope description and an energy envelope description. A method of processing a speech signal according to claim 9, wherein the method comprises: (A) a spectral envelope description of each of the plurality of inactive frames and (B) an energy of each of the plurality of inactive frames The silence description is calculated by at least one of the envelope descriptions. A method of processing a speech signal according to claim 1, wherein the description of whether to transmit the frame is based on at least one of the following: (A) a vector describing the spectral envelope of one of the frames, (B) a residual energy of the frame, (C) a description of one of the inactive frames, a time distance of the most recent transmission, (D) The time distance to one of the most recent active frames, (E) one of the energy envelopes of the frame, (F) the average absolute value of one of the frames, and (G) the energy value of one of the frames. A method for processing a voice signal according to claim 11, wherein the method includes transmitting a silence description if a result of the determining whether to transmit the frame is a decision to transmit the description of the frame, The silence description includes at least one of a spectral envelope description and an energy envelope description. The method of claim 1, wherein the determining whether to transmit the frame comprises determining not to transmit the frame in response to detecting that one of the coding gain metrics changes by more than a threshold. description. A method of processing a speech signal according to claim 13, wherein each value of the coding gain metric is based on a value of a plurality of reflection coefficients of one of the speech signals corresponding to the inactive frame. A method of processing a speech signal according to claim 1, wherein the method comprises calculating at least one of the spectral tilt value and the spectral tilt value sequence for each of the plurality of the spectral tilt values in the sequence of spectral tilt values a change between one of the other spectral tilt values, and wherein the method includes determining, for each of the plurality of inactive frames of the voice signal, whether to transmit the frame, and wherein, for the other For each of a plurality of inactive frames, a result of the determination to determine whether to transmit the frame is based on at least one of the calculated changes. The method of claim 15 for processing a voice signal, wherein, for at least some of the inactive frames in the other plurality of inactive frames, a result of the determining whether to transmit the frame is not transmitted. The description of the description of the frame. The method of claim 15 for processing a voice signal, wherein, for each of the other plurality of inactive frames, the determining whether to transmit the frame comprises responding to detecting a coding gain metric. The description of the frame is not transmitted as soon as the change exceeds a threshold. A method of processing a speech signal according to claim 17, wherein for each of the other plurality of inactive frames, the change in a coding gain metric is based on (A) the speech signal is before the frame a value of the coded gain metric of a first inactive frame and (B) the second inactive frame of the voice signal that precedes the frame and is different from one of the first inactive frames A value that encodes the gain metric. The method of claim 1 for processing a speech signal, wherein the generating the sequence of spectral tilt values comprises at least some inactive frames for the plurality of inactive frames, according to the inactive frame and one of the voice signals A time interval between the active frames produces a spectral tilt value corresponding to one of the sequence of spectral tilt values. The method of claim 19, wherein the generating a spectral tilt value corresponding to one of the sequence of spectral tilt values comprises the time between the inactive frame and a previous active frame of the voice signal. When the distance is less than a threshold, the spectral tilt value is set to one of the previous spectral tilt values of the sequence of spectral tilt values. The method of claim 1 for processing a speech signal, wherein the generating the sequence of spectral tilt values comprises at least some inactive frames for the plurality of inactive frames, and calculating according to a coding gain metric of one of the inactive frames One of the spectral tilt value sequences corresponds to a spectral tilt value. A method for processing a speech signal according to claim 1, wherein the generating the sequence of spectral tilt values comprises, for at least one of the sequence of spectral tilt values, in response to detecting that one of the coding gain metrics changes by more than a threshold value. The spectral tilt value is set to one of the previous spectral tilt values of the sequence of spectral tilt values. The method of claim 1, further comprising: combining the plurality of transmission indications into a composite transmission indication, wherein each transmission indication is generated from a different blanking algorithm; and determining whether based on the composite transmission indication Transmit a description of one of the inactive frames. A non-transitory computer readable medium, the medium comprising a plurality of instructions for causing at least one computer to: generate a sequence of spectral tilt values of a plurality of inactive frames based on a speech signal, wherein the spectral tilt value The sequence includes a sequence of reflection coefficients, wherein each of the spectral tilt values is based on at least one reflection coefficient of the inactive frame corresponding to one of the voice signals, the at least one reflection coefficient including the corresponding inactive frame At least one of a first reflection coefficient or a second reflection coefficient of the corresponding inactive frame; calculating at least two values of the spectral tilt values based on the reflection coefficient a change between the two; and an inactive frame for the one of the plurality of inactive frames and determining whether to transmit a description of the frame based on the calculated change. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to generate the sequence of spectral tilt values are configured such that the at least one computer is based on another spectral tilt value in the sequence of spectral tilt values Each of the plurality of spectral slope values is generated. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to calculate the change are configured to cause the at least one computer to base a difference between consecutive values in the sequence of spectral tilt values Calculate the change. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to determine whether to transmit the description of the frame are configured to cause the at least one computer to be based on (A) one of the calculated changes The relationship between the magnitude and (B) a threshold determines whether or not to transmit the description of the frame. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to determine whether to transmit the description of the frame comprise causing the at least one computer to respond to a threshold of a coding gain exceeding a threshold One of the changes determines that several instructions of the description of the frame are not transmitted. The computer readable medium of claim 24, wherein the instructions for causing at least one computer to calculate a change are configured to cause the at least one computer to target a plurality of the spectral tilt values in the sequence of spectral tilt values Calculating the change between the spectral tilt value and at least one other spectral tilt value in the sequence of spectral tilt values, and The instructions for causing at least one computer to determine whether to transmit the description of the frame are configured to cause the at least one computer to determine whether to transmit for each of the other plurality of inactive frames of the voice signal The description of the frame, and wherein the instructions for causing the at least one computer to determine whether to transmit the description of the frame are configured to cause transmission for each of the other plurality of inactive frames The determination of the description of the frame is based on at least one of the calculated changes. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to generate the sequence of spectral tilt values include at least some inactive frames for the at least one computer to target the plurality of inactive frames And generating, according to a time distance between the inactive frame and the previous active frame of the one of the voice signals, a plurality of instructions for generating a spectral tilt value corresponding to one of the sequence of spectral tilt values. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to generate the sequence of spectral tilt values are configured to cause the at least one computer to respond to the at least one of the sequence of spectral tilt values A spectral gain metric is detected to change beyond a threshold to set the spectral tilt value to a previous spectral tilt value in the sequence of spectral tilt values. The computer readable medium of claim 24, wherein the instructions for causing the at least one computer to generate the sequence of spectral tilt values are configured to cause the at least one computer to smooth another sequence of spectral tilt values to generate the sequence of spectral tilt values , Each of the spectral tilt values of the another sequence indicates that one of the plurality of inactive frames is spectrally tilted. An apparatus for processing a speech signal, the apparatus comprising: a sequence generator configured to generate a sequence of spectral tilt values of a plurality of inactive frames based on the speech signal, wherein the sequence of spectral tilt values comprises a sequence of reflection coefficients, wherein each of the spectral tilt values is based on at least one reflection coefficient of the inactive frame corresponding to one of the voice signals, the at least one reflection coefficient including one of the corresponding inactive frames a reflection coefficient or at least one of a second reflection coefficient of the corresponding inactive frame; a calculator configured to calculate a value between the at least two values of the spectral tilt values based on the reflection coefficient And a comparator configured to determine whether to transmit a description of the frame based on the one of the plurality of inactive frames and based on the calculated change. The apparatus of claim 33 for processing a voice signal, wherein the comparator is configured to determine based on a relationship between (A) the calculated magnitude of the change and (B) a threshold value. Whether to transmit the description of the frame. A device for processing a voice signal according to claim 33, wherein the device comprises a wireless communication device, the device comprising the sequence generator, the calculator and the comparator, and wherein the device is configured to respond to the A silence description is transmitted by the comparator to transmit the description of the frame, the silence description including at least one of a spectral envelope description and an energy envelope description. The apparatus of claim 33 for processing a voice signal, wherein the comparator is configured to determine not to transmit the description of the frame in response to a change in a coding gain metric exceeding a threshold. The apparatus of claim 33 for processing a speech signal, wherein the calculator is configured to calculate the spectral tilt value and the spectrum for each of the plurality of spectral tilt values in the sequence of spectral tilt values a change between at least one other spectral tilt value in the sequence of skew values, and wherein the comparator is configured to decide whether to transmit the frame for each of the other plurality of inactive frames of the voice signal The description, and wherein the comparator is configured such that for each of the other plurality of inactive frames, the determination of whether to transmit the description of the frame is based on the calculated changes At least one. The apparatus of claim 33 for processing a voice signal, wherein the sequence generator is configured to act on the inactive frame and the voice signal for at least some of the inactive frames of the plurality of inactive frames A time interval between the previous active frames produces a spectral tilt value corresponding to one of the sequence of spectral tilt values. An apparatus for processing a speech signal according to claim 33, wherein the sequence generator is configured to respond to detecting that one of the coding gain metrics changes by more than one threshold for at least one of the sequence of spectral tilt values The value is used to set the spectral tilt value to the previous spectral tilt value of the sequence of spectral tilt values. An apparatus for processing a speech signal as claimed in claim 33, wherein the sequence generator is configured to generate the sequence by smoothing another sequence of spectral tilt values A sequence of spectral tilt values, wherein each of the spectral tilt values of the another sequence indicates a spectral tilt of one of the plurality of inactive frames. An apparatus for processing a speech signal, the apparatus comprising: means for generating a sequence of spectral tilt values of a plurality of inactive frames based on the speech signal, wherein the sequence of spectral tilt values comprises a sequence of reflection coefficients, wherein Each of the spectral tilt values is based on at least one reflection coefficient of the inactive frame corresponding to one of the voice signals, the at least one reflection coefficient including a first reflection coefficient of the corresponding inactive frame or the corresponding At least one of a second reflection coefficient of one of the inactive frames; a means for calculating a change between the at least two values of the spectral tilt values based on the reflection coefficient; and for inactive for the plurality of One of the frames is inactive and determines whether to transmit the component described by one of the frames based on the calculated change. An apparatus for processing a voice signal according to claim 41, wherein the apparatus includes means for transmitting a silence description in response to a decision made by the means for determining the component to transmit the description of the frame, The silence description includes at least one of a spectral envelope description and an energy envelope description. An apparatus for processing a speech signal according to claim 41, wherein the means for generating the sequence of spectral tilt values is configured to act on the at least some inactive frames of the plurality of inactive frames according to the inactivity Frame and A temporal distance between one of the previously active frames of the speech signal produces a spectral tilt value corresponding to one of the sequence of spectral tilt values. An apparatus for processing a speech signal of claim 41, wherein the means for generating the sequence of spectral tilt values is configured to respond to detecting a coding gain metric for at least one of the sequence of spectral tilt values One of the changes exceeds a threshold to set the spectral tilt value to one of the previous spectral tilt values of the sequence of spectral tilt values. An apparatus for processing a speech signal according to claim 41, wherein the means for generating the sequence of spectral tilt values is configured to generate the sequence of spectral tilt values by smoothing another sequence of spectral tilt values, wherein the other Each of the sequence of the spectral tilt values indicates that one of the plurality of inactive frames is spectrally tilted. A method for processing a speech signal, the method comprising: generating, by a sequence generator of a computer, a sequence of spectral tilt values of a plurality of inactive frames based on the speech signal, wherein the sequence of spectral tilt values comprises a reflection coefficient a sequence, wherein each of the spectral tilt values is based on at least one reflection coefficient of an inactive frame corresponding to one of the voice signals, the at least one reflection coefficient including a first reflection coefficient of the corresponding inactive frame Or at least one of the second reflection coefficients of the corresponding inactive frame; calculating, by the calculator of the computer, a change between the at least two values of the spectral tilt values based on the reflection coefficient; A comparator of the computer determines whether to transmit a description of the frame for one of the plurality of inactive frames. The determining whether to transmit the frame is based on the calculated change, and wherein the generating the sequence of spectral tilt values comprises at least some inactive frames for the plurality of inactive frames, according to the inactive message A time interval between the frame and one of the previously active frames of the speech signal produces a spectral tilt value corresponding to one of the sequence of spectral tilt values.