Signal generation system and signal generation method

Abstract

The present invention provides an efficient scheme for improved cross-product high frequency reconstruction (HFR), where a new frequency component of Q Ω + r Ω 0 is generated based on the existing components Ω and Ω + Ω 0.SOLUTION: The present invention performs a block-wise harmonic transposition, wherein time blocks of complex subband samples are processed with a common phase modification. The superposition of the modified samples has the advantageous effect of limiting unwanted intermodulation products, thereby allowing a coarser frequency resolution and / or a lower degree of oversampling to be used. The present invention in one embodiment uses a window function suitable for use with an improved block-based cross product HFR. A hardware embodiment of the present invention includes an analysis filter bank (101), a subband processor (102) configured by control data (104), and a synthesis filter bank (103).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an audio source coding system that uses a harmonic transposition method for high-frequency reconstruction (HFR) in a digital effects processor, such as an exciter that introduces resulting harmonic distortion into the luminance of the processed signal, or a time stretcher or time expander that extends the signal duration while preserving the spectral content. [Background technology]

[0002] Patent Document 1 describes the concept of transposition as a method for constructing high-frequency bands from low-frequency bands of an audio signal. Using this concept in audio coding can save significant bitrate. In an HFR-based audio coding system, a narrow-bandwidth signal is fed to a core waveform encoder, and higher frequencies are reconstructed using very low-bitrate additional side information (information describing the target spectral waveform at the decoder) and transposition. At low bitrates, the bandwidth of the core coded signal is narrow, and it becomes increasingly important to reconstruct a perceptually pleasing high band. The harmonic transposition disclosed in Patent Document 1 works very well for complex music signals in situations where the crossover frequency is low. The principle of harmonic transposition is to transpose a sine wave with frequency ω onto a signal with frequency Q. φ is to map or correspond to a sinusoidal wave of ω, Q φ>1 is an integer that determines the transposition order. In contrast, HFR, based on single sideband modulation (SSB), maps a sine wave of frequency ω to a sine wave of frequency ω + Δω, where Δω is a constant frequency deviation or shift. For low-bandwidth core signals, SSB transposition can cause unpleasant ringing artifacts.

[0003] To achieve the best possible audio quality, modern high-quality HFR methods use complex modulation frequency banks with a large degree of oversampling and very fine frequency resolution to obtain the required audio quality. Fine resolution is necessary to avoid unwanted intermodulation distortions arising from nonlinearities inherent in the synthesis of sine waves. For sufficiently narrow subbands, high-quality methods aim to have at most one sine wave per subband. A large degree of oversampling in time is necessary to avoid aliasing distortions, and some oversampling in frequency is also necessary to avoid pre-echoes of transient signals. The obvious drawback is that this approach can be very computationally intensive.

[0004] Another common drawback associated with harmonic transposition becomes apparent in the case of signals with a pronounced periodic structure. Such signals are superpositions of harmonics with frequencies Ω, 2Ω, 3Ω, ..., where Ω is the fundamental frequency. φ For harmonic transposition where , the output sinusoids are φ Ω, 2Q φ Ω, 3Q φ Ω, ... and Q φ >1, they are a subset of the complete set of harmonics desired. In terms of the resulting audio quality, the transposed fundamental frequency Q φIt is common to perceive a "ghost" pitch corresponding to Ω. Harmonic transposition often introduces a "metallic" sounding character into the encoded and decoded audio signal.

[0005] In US Pat. No. 6,269,499, which is incorporated herein by reference, the cross-product method is improved to address the problem of ghost pitches that arise in the case of high-quality transposition. A nonlinear combination of at least two different analysis subbands, complemented by a nonlinear subband correction, transmits full or partial information about the fundamental frequency values ​​of the dominant harmonic components of the transposed signal with high fidelity. As a result, missing components are reconstructed in the transposed output, but at the expense of considerable computational overhead. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above-mentioned drawbacks of existing available HFR schemes, it is an object of the present invention to provide an improved and more effective cross-product HFR scheme, and in particular to provide a method that allows for superior audio reproduction with a reduced computational burden compared to existing schemes.

[0007] The present invention aims to alleviate or eliminate at least one of the above problems by the inventions set forth in the claims. [Means for solving the problem]

[0008] The signal processing system according to the disclosed invention comprises: 1. A signal generation system for generating a time-warped and / or frequency-transposed signal from an input signal, comprising: an analysis filter bank for deriving, from the input signal, Y analysis subband signals, each of which has a plurality of complex analysis samples having a phase and an amplitude, where Y≧1; a subband processing unit that generates a synthesis subband signal from the Y analysis subband signals using a subband transposition factor Q and a subband stretch factor S; a synthesis filter bank for generating the time-warped and / or frequency-transposed signals from the synthesis subband signals; wherein at least one of Q and S is greater than 1, and the subband processing unit includes a block extraction unit, a nonlinear frame processing unit, and an overlap addition unit; The block extraction unit i) generating Y frames from L input samples, each of the frames being extracted from a plurality of complex analysis samples of an analysis subband signal, and the length of the frames being L (L>1); ii) generating frames of input samples by applying a block hop size of h samples to the plurality of complex analysis samples before generating a subsequent frame of L input samples; The non-linear frame processor generates a frame of processed samples based on the Y corresponding frames of input samples generated by the block extractor by determining a phase and amplitude of each processed sample of the frame, and for at least one processed sample: i) the phase of the processed samples is based on the phase of each corresponding input sample in each of the Y frames of input samples; ii) the amplitudes of the processed samples are based on the phases of corresponding input samples in each of the Y frames of input samples; the overlap-add unit generates the composite subband signal by overlapping and adding samples of a series of frames of processed samples; The signal generation system is a signal generation system that operates at least when Y=2. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 illustrates the principle of subband block-based harmonic transposition. [Figure 2] FIG. 1 is a diagram showing nonlinear subband block processing for one subband input. [Figure 3] FIG. 1 is a diagram showing nonlinear subband block processing for two subband inputs. [Figure 4] 10A and 10B are diagrams illustrating the operation of harmonic transposition based on improved cross-product subband blocks. [Figure 5] 1 illustrates an application of subband block-based transposition using several orders of transposition in an improved HFR audio coder. [Figure 6] 1 shows an application of multi-order subband block-based transposition using a 64-band QMF analysis filter bank. [Figure 7] 10A and 10B are diagrams illustrating the results of using the disclosed subband block-based transposition method. [Figure 8] 10A and 10B are diagrams illustrating the results of using the disclosed subband block-based transposition method. [Figure 9] 3 is a diagram showing in detail the nonlinear processing unit (including a pre-normalization unit and a multiplication unit) shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Summary of the Invention> A signal generating system according to a first embodiment of the disclosed invention comprises: 1. A signal generation system for generating a time-warped and / or frequency-transposed signal from an input signal, comprising: an analysis filter bank for deriving, from the input signal, Y analysis subband signals, each of which has a plurality of complex analysis samples having a phase and an amplitude, where Y≧1; a subband processing unit that generates a synthesis subband signal from the Y analysis subband signals using a subband transposition factor Q and a subband stretch factor S; a synthesis filter bank for generating the time-warped and / or frequency-transposed signals from the synthesis subband signals; wherein at least one of Q and S is greater than 1, and the subband processing unit includes a block extraction unit, a nonlinear frame processing unit, and an overlap addition unit; The block extraction unit i) generating Y frames from L input samples, each of the frames being extracted from a plurality of complex analysis samples of an analysis subband signal, and the length of the frames being L (L>1); ii) generating frames of input samples by applying a block hop size of h samples to the plurality of complex analysis samples before generating a subsequent frame of L input samples; The non-linear frame processor generates a frame of processed samples based on the Y corresponding frames of input samples generated by the block extractor by determining a phase and amplitude of each processed sample of the frame, and for at least one processed sample: i) the phase of the processed samples is based on the phase of each corresponding input sample in each of the Y frames of input samples; ii) the amplitudes of the processed samples are based on the phases of corresponding input samples in each of the Y frames of input samples; the overlap-add unit generates the composite subband signal by overlapping and adding samples of a series of frames of processed samples; The signal generation system is a signal generation system that operates at least when Y=2.

[0011] A signal generation method according to a second embodiment of the disclosed invention includes: 1. A signal generation method for generating a time-warped and / or frequency-transposed signal from an input signal, comprising the steps of: deriving Y (Y≧2) analysis subband signals from the input signal, each of the analysis subband signals having a plurality of complex analysis samples having a phase and an amplitude; forming Y frames of L input samples, each frame being extracted from said plurality of complex analysis samples of an analysis subband signal, said frames having a length of L; applying a block hop size of h samples to the plurality of analysis samples before deriving a subsequent frame of L input samples to generate a sequence of frames of input samples; generating frames of processed samples by determining a phase and an amplitude for each processed sample of the frame based on Y corresponding frames of input samples, wherein for at least one processed frame, i) the phase of the processed sample is based on each of the phases of corresponding input samples in each of the Y frames of input samples, and ii) the amplitude of the processed sample is based on each of the amplitudes of corresponding input samples in each of the Y frames of input samples; determining a composite subband signal by overlappingly adding samples in a sequence of frames of processed samples; generating the time-warped and / or frequency-transposed signal from the synthesized subband signals; A signal generation method comprising:

[0012] In this case, Y is any integer greater than 1. The signal generation system according to the first embodiment performs the above method at least when Y=2.

[0013] A third embodiment of the disclosed invention is a computer program or software having software instructions for causing a programmable computer to carry out the signal generation method according to the second embodiment.

[0014] A fourth embodiment of the disclosed invention is a storage medium (or data carrier) storing software instructions for causing a programmable computer to carry out the signal generation method according to the second embodiment.

[0015] The present invention recognizes that the general concept of enhanced cross-product HFR provides superior results when data is arranged and processed in blocks of complex subband samples. Among other things, it allows for frame-by-frame phase offsets to be applied to the samples. Amplitude or magnitude adjustments are also possible, with similar benefits. An embodiment of the cross-product enhanced HFR in accordance with the present invention performs subband block-based harmonic transposition, significantly reducing intermodulation. This allows for the use of filter banks with coarser frequency resolution and / or less oversampling (e.g., QMF filter banks) while maintaining excellent output quality. In the case of subband block-based processing, time blocks of complex subband samples are processed with a common phase correction value, and the overlap of multiple corrected samples to form output subband samples has the effect of reducing intermodulation products that would otherwise occur when the input subband signal consists of multiple sinusoids. Block-based transposition requires a much lower computational burden than high-resolution transposers, and can achieve nearly the same high quality for many signals.

[0016] For the sake of convenience, it should be noted that in this embodiment, Y≧2, and the nonlinear processing unit uses Y “corresponding” frames of input samples as input, meaning that the frames are synchronized or nearly synchronized. For example, the samples in each frame are associated with time intervals that have a significant temporal overlap (or overlap or overlap) between the frames. The term “corresponding” is used to indicate that they are synchronized or approximately so. Furthermore, the term “frame” may be used interchangeably with “block.” Thus, the “block hop size” may be equal to or shorter than the frame length (adjusted for downsampling, if applicable), meaning that the input samples may belong to more than one frame. By determining the phase and amplitude based on the phase and amplitude of all Y corresponding frames of input samples, the system does not need to generate all processed samples in a frame; without departing from the invention, the system may generate the phase and / or amplitude of some processed samples based on a smaller number of corresponding input samples or based on only one sample.

[0017] In one embodiment, the analysis filter bank is a quadrature mirror filter (QMF) bank or pseudo-QMF bank with any number of taps and points. It may be, for example, a 64-point QMF bank. The analysis filter bank may be selected from classes such as windowed discrete Fourier transform or wavelet transform. Advantageously, the synthesis filter bank matches the analysis filter bank with an inverse QMF bank, an inverse pseudo-QMF bank, etc. It is noted that such filters may have a relatively coarse frequency resolution and / or a relatively low degree of oversampling. Unlike the prior art, the present invention can be implemented using such relatively simple components without suffering from output degradation, and such embodiments of the present invention exhibit greater economy than the prior art.

[0018] In one embodiment, one or more of the following holds for the analysis filter bank: ●Analysis time progression width is Δt A is; ●Analysis frequency interval is Δf A is; ● The analysis filter bank has N>1 analysis subbands, and the analysis subbands are specified by analysis subband indices, n=0,...,N-1; • Analysis subbands are associated with frequency bands of the input signal.

[0019] In one embodiment, one or more of the following holds for the synthesis filter bank: ●The composite time progression width is Δt s is; ●The synthetic frequency interval is Δf s is; ● The synthesis filter bank has M>1 synthesis subbands, and the synthesis subbands are specified by synthesis subband indices m=0,...,M-1; The synthesis subbands are associated with a time stretched signal and / or a frequency transposed signal.

[0020] In one embodiment, a nonlinear processing unit is applied to two input frames (Y=2) to generate one processed frame, and the subband processing unit includes a cross-processing control unit that generates cross-processing control data. By clarifying the qualitative and / or quantitative nature of the subband processing, the present invention allows for greater flexibility and applicability. The control data specifies (e.g., is specified by index) subbands that differ in frequency by the fundamental frequency of the input signal. In other words, the indices specifying the subbands may differ by integers that approximate the ratio of such fundamental frequency divided by the analysis frequency interval. Because the new spectral components generated by harmonic transposition are comparable to naturally occurring harmonics, this results in a more psychologically pleasing audio output.

[0021] According to a further improvement to the above embodiment, the (input) analysis and (output) synthesis subband indices are selected to satisfy Equation (16), below. The parameter σ in this equation allows for both odd-numbered and even-numbered filter banks to be applied. If the subband indices are specified as an approximate solution (e.g., least squares error) to Equation (16), the new spectral components obtained by harmonic transposition will resemble the natural series of harmonics. Thus, HFR provides a faithful reconstruction of the original signal with high-frequency components removed.

[0022] A further improvement to the above embodiment provides a method for selecting the parameter r, which appears in equation (16) and represents the order of the cross-product transposition. For a given output subband index m, each value of the transposition order r determines two analysis subband indices n1 and n2. This further improvement evaluates the magnitudes or amplitudes of the two subbands for multiple choices of r and selects the value that maximizes the smaller of the two analysis subband amplitudes. This index selection method eliminates the need to restore multiple amplitudes by amplifying weaker components of the input signal (which would result in poor output quality). In this regard, the subband magnitudes or amplitudes may be calculated in a known manner, e.g., by taking the square root of the input samples forming a frame (block) or part of a frame. The subband magnitudes or amplitudes may be calculated as the amplitude of a central or near-central sample within the frame. Such a calculation easily yields the appropriate amplitude measure.

[0023] According to a further improvement to the above embodiment, the analysis subbands receive contributions from harmonic transposition instances according to both direct processing and cross-product-based processing. In this regard, a criterion is applied to determine whether a particular possibility of regenerating missing parts according to cross-product-based processing is used. For example, this improvement may be configured to refrain from using one or more cross-subband processing units if any of the following conditions (a) to (c) is met:

[0024] The condition (a) is that the amplitude M S and the minimum amplitude value M for the optimal pair of cross source terms resulting in the composite subband. C and the ratio is greater than a predetermined value q, The condition (b) is that the synthesis subband receives a large contribution from the direct processing unit. The condition in (c) is that the fundamental frequency Ω0 is equal to the spacing Δf A It is something smaller.

[0025] In one embodiment, the present invention may perform downsampling or decimation of the input signal. Indeed, one or more frames of input samples may be determined by downsampling the complex analysis samples in the subbands, as performed by a block extractor.

[0026] According to a further improvement to the above embodiment, the downsampling factors applied satisfy Equation (15) described below. It is not permitted for all of the downsampling factors to be zero, as this corresponds to a trivial or insignificant case. Equation (15) not only defines the relationship between the downsampling factors D1 and D2, the subband stretching factor S, and the subband transposition factor Q, but also defines the relationship between the phase coefficients T1 and T2 appearing in Equation (13), which determine the phase of the processed sample (processed sample). This ensures that the phase of the processed sample matches with other components of the input signal to which the processed sample is added.

[0027] In one embodiment, a window function is applied to the frames of samples to be processed (windowed) before the frames are overlap-added. The windower applies a finite length window function to the frames of samples to be processed. Suitable window functions are defined in the appended claims.

[0028] The inventors recognized that cross-product methods of the type described in U.S. Patent No. 6,277,623 are not perfectly suited to subband block-based processing schemes from the outset. While such methods may be satisfactorily applied to any subband samples of a block, extending them directly to other samples within the block introduces aliasing artifacts. Therefore, in one embodiment, a windowing function is applied that includes window samples that fit a substantially constant sequence (when weighted with a complex weight and shifted by a hop size). The hop size may be the product of the block hop size h and the subband stretching factor S. The use of such a windowing function can significantly reduce aliasing artifacts. Alternatively or additionally, such a windowing function also reduces artifacts related to other quantities, such as phase rotation of the processed samples.

[0029] Preferably, the set of complex weights or weighting coefficients applied to evaluate the state for the window samples differ by a constant phase rotation angle. More preferably, the constant phase rotation angle is proportional to the fundamental frequency of the input signal. The phase rotation angle may be proportional to the order of the applied cross-product transposition and / or the difference in downsampling factors and / or the analysis time advance. The phase rotation angle may be given, at least approximately, by equation (21).

[0030] The present invention, according to one embodiment, allows for cross-product enhanced harmonic transposition by varying synthesis windowing depending on fundamental frequency parameters.

[0031] In one embodiment, a series of frames of samples to be processed are added with a certain degree of overlap or overlap. To achieve the proper overlap, frames belonging to the processed samples are appropriately shifted (displaced) by a hop size, which is the block size h upscaled or stretched by a subband stretch factor S. If the overlap of a series of frames belonging to the input samples is Lh, then the overlap of consecutive frames belonging to the processed samples will be S(Lh).

[0032] In one embodiment, the system according to the present invention can generate processed samples not only based on Y=2 input samples but also based on only Y=1 samples. That is, the system can restore or regenerate missing portions not only by a cross-product method (e.g., Equation (13) or the like) but also by a direct sub-band method (e.g., Equation (5) or (11) or the like). Preferably, a control unit controls the operation of the system, and the control includes specifying which method should be used to restore a particular missing portion.

[0033] A system according to a further improvement to the above embodiment generates a processed sample based on more than three samples (i.e., Y≧3). For example, the processed sample may be obtained by multiple harmonic transpositions based on cross products contributing to the processed sample, multiple direct subband processings, or a combination of cross product transposition and direct transposition. This method of applying transposition methods results in a powerful and versatile HFR. That is, the embodiment is operable to perform the method according to the second embodiment for Y=3, 4, 5, etc.

[0034] In one embodiment, a processed sample is determined as a complex number having an amplitude, which is the average of the amplitude values ​​of the corresponding input samples. The average may be a (weighted) arithmetic mean, a (weighted) geometric mean, or a (weighted) harmonic mean of two or more samples. When Y=2, the average is based on two complex input samples. Preferably, the amplitude of the processed sample is a weighted geometric mean. More preferably, the geometric mean is weighted by parameters ρ and 1−ρ as shown in Equation (13). In this case, the weighting parameter ρ of the geometric mean is a real number that is inversely proportional to the subband transposition factor Q. The parameter ρ may be inversely proportional to the warping factor S.

[0035] In one embodiment, the system determines a processed sample as a complex number having a phase, which is a linear combination of the phases of corresponding input samples in the frame of input samples. In particular, the linear combination may be the phase associated with two input samples (Y=2). The linear combination of the two phases may use non-zero integer coefficients, the sum of which is equal to the warping factor S multiplied by the subband transposition factor Q. Alternatively, the phase obtained by such a linear combination may be further adjusted by a constant phase correction parameter. The phase of the processed sample may be given by Equation (13):

[0036] In one embodiment, the block extractor (or a corresponding step in the method according to the invention) may interpolate two or more analysis samples in the analysis subband signal to obtain one input sample to be comprised in a frame (block). Such interpolation allows downmixing of the input signal by a non-integer factor. The interpolated analysis samples may or may not be contiguous.

[0037] In one embodiment, the configuration of the subband processing may be controlled by control data provided by an external means for controlling the processing. The control data relates to the current acoustic characteristics of the input signal. For example, the system itself may have means for determining the current acoustic characteristics of the signal (e.g., the (dominant) fundamental frequency of the signal). Knowledge of the fundamental frequency provides a basis or guidance for selecting the analysis subbands from which the processing samples are taken. Preferably, the spacing of the analysis subbands is proportional to such fundamental frequency of the input signal. Alternatively, the control data is provided externally to the system and is preferably included in an encoding format suitable for communication as a bitstream over a digital communications network. In addition to the control data, such an encoding format may also include information about the low-frequency components of the signal (e.g., the frequency components at 701 in FIG. 7). However, from the viewpoint of economical use of bandwidth, it is preferable that the encoding format does not include complete information about the high-frequency components (702 in FIG. 7) from which the high-frequency components are reconstructed in the present invention. In particular, the present invention provides a decoding system having a control data receiver adapted to receive such control data, which may be included in the received bitstream encoding the input signal or may be received as a separate signal or bitstream.

[0038] One embodiment provides a technique for efficiently performing the operations performed in the method according to the invention. To this end, the hardware implementation comprises a pre-normalizer or pre-normalizer that rescales (rescalates) the amplitude of the corresponding input stream in the part of the Y frame on which the frame of processed samples is based. After such rescaling, the processed samples can be calculated as a (weighted) complex product of the rescaled or possibly unrescaled input samples. Input samples that appear as rescaled factors in the product usually do not need to appear as unrescaled factors. With the possible exception of the phase correction parameter θ, it is possible to calculate equation (13) as a product of (possibly rescaled) complex input samples. This is advantageous in terms of computational effort compared to treating the amplitude and phase of the processed samples separately.

[0039] In one embodiment, the system is set with Y=2, which has two block extractors working in parallel to form one frame of input samples.

[0040] In another embodiment where Y≧3, the system includes multiple subband processors, each of which determines an intermediate synthesis subband signal using various subband transposition factors and / or various subband stretch factors and / or a cross-product-based or other transition method different from direct. The multiple subband processors may be arranged in parallel and operate in parallel. In this embodiment, the system further includes a synthesis unit arranged downstream of the subband processors and upstream of the synthesis filter bank. The synthesis unit combines (e.g., combines together) the associated intermediate synthesis subband signals to generate a synthesis subband signal. As described above, the intermediate synthesis subbands may be obtained by both direct and cross-product-based harmonic transposition. The system according to one embodiment may also include a core decoder for decoding the bitstream into the input signal. This forms an HFR processor configured to apply spectral band information, particularly by performing spectral shaping. The operation of the HFR processor may be controlled by information encoded in the bitstream.

[0041] One embodiment provides HFR of multidimensional signals in a system that reproduces audio signals in a stereo format forming Z channels, e.g., left, right, center, surround, etc. In one embodiment that processes an input signal with multiple channels, the warping factor S and transposition factor Q for each band may differ between channels, but are based on the same number of input samples as the processed samples for each channel. To this end, the embodiment includes an analysis filterbank that generates Y analog subband signals from each channel, a subband processing unit that generates Z subband signals, and Z time-warped and frequency-transposed signals that form the output signal.

[0042] In variations on the above embodiments, the output signal may have a different number of output channels based on the analysis subband signals, for example, it may be desirable to allocate more computational resources to the HFR of acoustically prominent channels, e.g., multiple channels reproduced from an audio source in front of the listener may be surround or near surround channels.

[0043] It is to be expressly noted that the invention relates to all combinations of the above features, even if they are recited in different claims.

[0044] <Overview of the drawings> Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, which do not limit the scope and spirit of the present invention.

[0045] FIG. 1 shows the principle of subband block based harmonic transposition.

[0046] Figure 2 shows the nonlinear subband block processing for one subband input.

[0047] FIG. 3 shows the nonlinear subband block processing for two subband inputs.

[0048] FIG. 4 illustrates the operation of harmonic transposition based on the cross product enhanced subband block.

[0049] FIG. 5 shows an example application of subband block-based transposition using several orders of transposition in an improved HFR audio coder.

[0050] FIG. 6 shows an example application of multi-order subband block based transposition using a 64-band QMF analysis filter bank.

[0051] FIG. 7 is a diagram illustrating the results of using the disclosed subband block-based transposition method.

[0052] FIG. 8 is a diagram illustrating the results of using the disclosed subband block-based transposition method.

[0053] FIG. 9 shows in detail the nonlinear processing section (including the pre-normalization section and the multiplication section) shown in FIG.

[0054] <Description of the Preferred Embodiment> The embodiments described below merely illustrate the principles of the present invention for improved cross-product subband block-based harmonic transposition. It will be understood that variations and modifications to the apparatus, methods, and specific details described herein will be apparent to those skilled in the art. Accordingly, it is intended that the present invention be defined solely by the appended claims, and not by the specific details presented in the specification and drawing description.

[0055] FIG. 1 illustrates the operating principles of subband-block-based transposition, time warping, or a combination of transposition and time warping. An input time-domain signal is applied to an analysis filter bank 101, which provides a plurality of complex-valued subband signals. These are applied to a subband processor 102, whose operation is controlled by control data 104. Each output subband may be obtained by processing one input subband or two input subbands, or may be obtained as a superposition of several subbands so processed. The plurality of complex-valued output subbands are applied to a synthesis filter bank 103, which outputs a modified time-domain signal. Optional control data 104 indicates the manner and parameters of the subband processing performed on the transposed signal. In the case of the improved cross-product transposition, the data includes information about the dominant fundamental frequency.

[0056] Figure 2 is a diagram illustrating the operation of nonlinear subband block processing when there is one subband input. Using physical time warping and transposition target values ​​(target values) and physical parameters of the analysis filter bank 101 and synthesis filter bank 103, not only subband time warping and transposition parameters but also source subband indices are derived for each target subband index. The purpose of the subband block processing is to perform transposition, time warping, or a combination of transposition and time warping corresponding to the complex-valued source subband signal to generate a target subband signal.

[0057] The block extractor 201 samples a finite number of frames from the input complex signal. The frames are defined by the input pointer position and the subband transposition factor. The frames are then nonlinearly processed by the processor 202 and then windowed with a finite, possible variable length by the window processor 213. The resulting samples are pre-added to the output samples in the overlap adder 204, with the output frame position defined by the output pointer position. The input pointer is incremented by a fixed value, and the output pointer is incremented by the fixed value multiplied by the subband stretch factor. This repeated process produces an output signal with a complex frequency transposed by the subband transposition position and a duration equal to the subband stretch factor multiplied by the input subband signal period, within the length of the synthesis window. The control signal 104 influences (controls) each of the three processors 201, 202, and 203.

[0058] 3 is a diagram illustrating the operation of nonlinear subband block processing when there are two subband inputs. Using physical time warping and transposition target values ​​and physical parameters of the analysis filter bank 101 and synthesis filter bank 103, not only subband time warping and transposition parameters but also source subband indices are derived for each target subband index. If the nonlinear subband block processing is for generating missing parts by cross product addition, not only the settings of processing units 301-1, 301-2, 302, and 303 but also the values ​​of the two source band indices depend on the output 403 of a cross processing control unit 404. The purpose of the subband block processing is to perform corresponding transposition, time warping, or a combination of transposition and time warping on two complex source subband signals to generate a target subband signal. The first block extractor 301-1 samples a finite time frame from the first complex source band, and the second block extractor 301-2 samples a finite frame from the second complex source band. The frames are defined by a common input pointer position and a subband transposition factor. The two frames pass through a nonlinear processor 302 and are then windowed by a finite-length window processor 303. The overlap adder 204 is the same as or similar to that shown in FIG. 2. This series of processes is repeated to produce an output signal whose duration is equal to the longer of the two subband signals (but within the length of the synthesis window) multiplied by the subband stretch factor. If the two input subband signals have the same frequency, the output signal will have a complex frequency transposed by the subband transition factor. If the two subband signals have different frequencies, the window processor 303 can be used to generate an output signal with a target frequency suitable for generating the missing portion of the transposed signal.

[0059] Fig. 4 is a diagram for explaining the principle of transposition, time warping, or a combination of transposition and time warping based on an improved cross-product subband block. The direct sub-band processing unit 401 may be the one already described with reference to Fig. 2 (processing unit 202) or Fig. 3. The cross sub-band processing unit 402 performs nonlinear sub-band block processing on the two sub-band inputs shown in Fig. 3, and the output target sub-band is summed with that from the direct sub-band processing unit 401 in the summation unit. The cross processing control data 403 is different for each input pointer position, and A selected list of target subband indices, A pair of source subband indices for each selected target subband index, and Finite length synthesis window The information includes at least information indicating the above.

[0060] The cross processing control unit 404 provides cross processing control data 403 based in part on control data 104 indicative of the plurality of complex subband signals and fundamental frequencies output from the analysis filter bank 101. The control data 104 also includes other signal-dependent configuration parameters that affect the cross-product processing.

[0061] The principles of improved cross-product subband block based time warping and transposition will now be described with reference to FIGS. 1-4 along with appropriate mathematical techniques.

[0062] The two main setting parameters for the harmonic transposer and / or overall time warping are: ·S φ : the desired physical time warping factor, and Q φ : the desired physical transposition factor is.

[0063] The filter banks 101, 103 may be of any complex exponential modulated type, such as QMF, windowed DFT, or wavelet transform. The analysis filter bank 101 and synthesis filter bank 103 may be stacked in even or odd bands during modulation, and may be defined from a wider range of prototype filters and / or windows. While all of these second-order choices affect subsequent design details such as phase correction, subband mapping management, etc., the main system design parameters for subband processing are generally determined by the following four filter bank parameters (all measured in physical units): Δt s / Δt A and Δf s / Δf A In the above quotient, Δt A is the subband sample time step or temporal stride of the analysis filter bank 101 (e.g., measured in seconds), Δf A is the subband frequency spacing of the analysis filter bank 101 (e.g., measured in Hertz [1 / s]), Δt s is the subband sample time step or temporal stride of the synthesis filter bank 103 (e.g., measured in seconds); Δf s is the subband frequency spacing of the synthesis filter bank 103 (eg, measured in Hertz [1 / s]).

[0064] Depending on the configuration of the subband processing unit 102, the following parameters should be calculated: S: Subband scaling factor. The subband scaling factor is applied to the subband processing unit 102 as a ratio of input and time samples, S φ This is to perform a global physical time warping of the time domain signal by

[0065] Q: Subband transposition factor. The subband transposition factor is applied to the subband processing unit 102, and the factor Q φ for performing a global physical frequency transposition of a time domain signal by

[0066] The correspondence between source and target subband indices, where n denotes the index of the analysis subband entering the subband processing unit 102 and m denotes the index of the corresponding synthesis subband at the output of the subband processing unit 102.

[0067] To determine the subband stretching factor S, the input signal to the analysis subband of physical duration D is multiplied by the number of analysis subband samples at the input to the subband processing unit 102, D / Δt A Check that these correspond to D / Δt A The samples are then scaled by a subband processing unit 102 that applies a subband scaling factor S to the sample. A At the output of the synthesis filter bank 103, these S·D / Δt A The samples are s ·S·D / Δt A The latter period is S φ Therefore, the time domain output signal period must match a specific value of the physical time stretch factor S φ Since the time domain input signal should be stretched by:

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[0071] 2 for one source subband will now be described as a function of the subband processing parameters S and Q. Let x(k) be the input signal to the block extractor 201 and h be the stride, step, or step size of the input block. That is, x(k) is the complex analysis subband signal of the analysis subband with index n. The block extracted by the block extractor 201 is generally lossless, since it can be considered to be defined by L=R1+R2 samples.

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[0073] An interesting special case of equation (4) is when R1=0 and R2=1, where the extracted block consists of one sample, ie the block length L is L=1.

[0074] In the polar coordinate representation of a complex number z=|z|exp(j∠z), where |z| denotes the amplitude of the complex number and ∠z denotes the phase or phase angle of the complex number, the nonlinear processing unit 202 that generates the output frame yl from the input frame xl is advantageously defined by a phase correction factor T=SQ according to the following formula:

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[0076] Equation (5) above indicates that the phase of an output frame sample is determined by shifting the phase of the corresponding input sample by a constant offset value. The constant offset value depends on a correction factor T, which itself depends on the subband warp factor and / or the subband transposition factor. Furthermore, the constant offset value depends on the phase of a sample of a particular input frame among the input frames. This particular input frame sample is kept fixed when determining the phases of all output frame samples of a given block. In equation (5), the phase of the center sample of the input frame is used as the phase of the particular input frame sample.

[0077] The second line of Equation (5) indicates that the amplitude of a sample in the output frame depends on the amplitude of the corresponding sample in the input frame. Furthermore, the amplitude of a sample in the output frame may depend on the amplitude of a particular input frame sample. That particular input frame sample may be used in determining the amplitudes of all output frame samples. For Equation (5), the center sample of the input frame is used as the particular input frame sample. In one embodiment, the amplitude of a sample in the output frame may correspond to the geometric mean of the amplitudes of the corresponding sample in the input frame and the particular input frame sample.

[0078] In the windowing unit 203, a window w of length L is applied to the output frame, resulting in the following windowed output frame:

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[0081] If a complex sinusoid is used as input to the subband processing unit 102, the analysis subband signal corresponds to the complex sinusoid.

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[0086] Below, the explanation of the subband processing section will be expanded so that it can be applied to the case of Figure 3 where there are two subband inputs. (1) (k) is the input subband signal to the first block extractor 301-1, and x (2) Let (k) be the input subband signal to the second block extractor 301-2. Since each extractor can use a different downsampling factor, the extracted blocks will be:

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[0089] The definition of the non-negative real parameters D1, D2, ρ, the non-negative integer parameters T1, T2, and the synthesis window w depends on the desired mode of operation. If the same subband is applied to both inputs, then x (1) (k)=x (2) It should be noted that when (k), D1=Q, D2=0, T1=1, and T2=T-1, the processing for equations (12) and (13) reduces to equations (4) and (5) for the one-input case.

[0090] In one embodiment, the frequency spacing Δf of the synthesis filter bank 103 s and the frequency interval Δf of the analysis filter bank 101 AWhen the ratio of (a) to (b) is different from the desired physical transposition factor Q, it is useful to determine the synthesis subband sample with index m from two analysis subbands with indices n and n+1, respectively. For a given index m, the corresponding index n is given by an integer value obtained by truncating the analysis index value n given by Equation (3). For example, one analysis subband signal, such as the analysis subband signal corresponding to index n, is provided to the first block extractor 301-1, and the other analysis subband signal, such as the analysis subband signal corresponding to index n+1, is provided to the second block extractor 301-2. Based on these two analysis subband signals, the synthesis subband signal corresponding to index m is determined according to the above process. The manner in which the analysis subband signals adjacent to the two block extractors 301-1 and 301-2 are designated may be based on the remainder obtained when truncating the index values ​​in Equation (3), i.e., based on the difference between the extracted index value given by Equation (3) and the truncated integer value n obtained from Equation (3). If the remainder is greater than 0.5, the analysis subband signal corresponding to index n may be assigned to the second block extractor 301-2, otherwise the analysis subband signal may be assigned to the first block extractor 301-1. In this operation mode, the parameters are designed so that the input subband signals share the same complex frequency.

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[0093] The following describes a method for cross processing control 404. Given an output subband index m, parameters r=1,...,Q φ For −1 and the fundamental frequency Ω 0 , approximate source subband indices n 1 and n 2 can be approximated by approximately solving the following equations:

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[0095] With these definitions, the following equation holds:

[0096] p=Ω0 / Δf A : the fundamental frequency measured in units of the frequency interval of the analysis filter bank, F=Δf s / Δf A : the quotient of the frequency spacing of the synthesis filter bank to the frequency spacing of the analysis filter bank, n f =[(m+σ)F-rp] / Q φ - σ: Real-valued target for integer-valued low source index.

[0097] A specific example of a favorable approximation to equation (16) is f Let n2 be the integer closest to n f +p is the nearest integer.

[0098] If the fundamental frequency is smaller than the analysis filterbank spacing, ie, p<1, it is advantageous to cancel or offset the addition of the cross products.

[0099] As taught in the patent application WO 2005 / 023990, cross products should not be added to output subbands that already have a significantly larger contribution from transposition without cross products. Furthermore, in at most one case, r=1,...,Q φ -1 should contribute to the cross-product output. Here, these rules may be achieved by performing the following three steps for each of the target output subband indexes m: 1. The amplitude |x of the candidate source subband calculated at the center time slot k=hk (1) | and |x (2) for all r=1,...,Q with the minimum of | φ Maximum value M out of -1 C Calculate the source subband x (1) and x (2) are given as indices n1 and n2 in equation (16).

[0100] 2. Index n ≒ (F / Q φ ) m (see Equation 3) together with the corresponding magnitude or amplitude Ms for the direct source term |x| obtained from the source subbands.

[0101] 3. If and only if Mc>qMs, then M is obtained at point 1 (step 1) above. C Select a cross term from the winning candidates for q, where q is a predetermined threshold.

[0102] Variations on the above procedure are desirable depending on the specific system configuration parameters. One such variation is to change the fixed threshold at point 3 (step 3) to M C / M S Another variation is to replace the maximization at point 1 (step 1) with a relaxed rule that depends on the quotient of Q φ A further variation is to extend the range beyond -1, for example to a finite list of candidate values ​​for the fundamental frequency measured in analysis frequency interval units p. Yet another variation is to use other quantities for the amplitude of the subbands, for example the amplitude of a fixed sample, the maximum amplitude, the mean amplitude, l p The amplitude by norm, etc. may also be used.

[0103] The list of target subbands m selected to add to the cross-product along with the values ​​of n1 and n2 form the main part of the cross-processing control data 403. The remaining discussion relates to the setting or configuration parameters D1, D2, ρ, the phase rotation (13) and the non-negative integer parameters T1, T2, which appear in (13), and the synthesis window w used in the cross-subband processing unit 402. Using a sinusoidal model for the cross-product situation, the following source band signals are obtained:

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[0109] It should be noted that the above algorithm for calculating cross-processing control data 403 based on input parameters such as target output subband index m and fundamental frequency Ω is merely illustrative of the nature of the present invention and is not intended to limit the scope of the present invention. Variations of this disclosure, such as alternative subband block processing methods that provide an output-like signal (18) in response to an input signal (17), are within the scope of the present invention, as determined by the common general knowledge and everyday experience of those skilled in the art.

[0110] Figure 5 shows an example of applying subband block-based transposition using any order of transposition in an improved HFR audio codec. The transmitted bitstream is received by a core decoder 501, which provides a low-bandwidth decoded core signal at a sampling frequency of fs. The low-bandwidth decoded core signal is resampled to an output sampling frequency of 2fs by a complex-modulated 32-band QMF analysis bank 502, which is followed (via an HFR processing unit) by a 64-band QMF synthesis bank (inverse QMF, IQMF) 505. The two filter banks 502 and 505 have the same physical parameters Δt s =Δt A and Δf s =Δf A , and the HFR processor 504 passes unmodified low sub-bands corresponding to the low bandwidth core signal. The spectral shaping and modification performed by the HFR processor 504 obtains the high frequency components of the output signal by providing high frequency sub-bands of the 64QMF synthesis bank 505 together with the output bands from the multiple transposer processor 503. The multiple transposer processor 503 takes the decoded core signal as input and outputs multiple sub-band signals, which represent the 64QAM band analysis by superposition or summation of several transposed signal components. The goal or objective is to allow each of the signal components to undergo an integer physical transposition (QMF) without time warping of the core signal when the HFR processing is bypassed or circumvented. φ = 2, 3, ... and S φ =1). In an embodiment of the present invention, the transposer control signal 404 includes data indicative of the fundamental frequency. This data may be transmitted in the bitstream from the corresponding audio encoder (the decoder performs pitch detection), or may be obtained from a combination of transmitted and detected information.

[0111] FIG. 6 is a diagram illustrating the operation of multi-order subband block-based transposition using a single 64-band QMF analysis filter bank. Three transposition orders, or Q φ =2,3,4 are generated and given in the domain of a 64-band QMF operating at an output sampling rate of 2fs.

[0112] The multiplexer, synthesizer, or combiner 603 selects and synthesizes related subbands from one transposition factor branch among multiple QMF subbands provided to the HFR processor. φ , the series of processes in the 64-band QMF synthesis unit 505 is φ = 1 (i.e., no stretching) with Q φ By identifying these three blocks along with 101, 102, and 103 in Figure 1, we can determine the physical transposition of Δt s / Δt A = 1 / 2 and F = Δf s / Δf A Δt = 2 A =64f s and Δf A =f s / 128. 602-Q φ The specific setting parameters for Q φ = 2, 3, and 4 are discussed separately. For all cases, the analysis stride is chosen to be h = 1, and the normalized fundamental frequency parameter p = Ω / Δf A =128Ω0 / f s is assumed to be known.

[0113] First, Q φConsider the case of r = 2. In this case, 602-2 must perform a subband stretch of S = 2 and a subband transposition of Q = 1 (i.e., no stretching), and the correspondence between the source n and target subband m is given by n = m for direct subband processing. During the cross-product summation process, there is only one cross product to consider (i.e., r = 1) (see equation (15) above), and equation (20) simplifies to T1 = T2 = 1 and D1 + D2 = 1. An example solution is to select D1 = 0 and D2 = 1. For the direct processing synthesis window, a rectangular window of length L = 10 with R1 = R2 = 5 may be used to satisfy condition (10). For the cross-processing synthesis window, a short tap window of L = 2 with R1 = R2 = 1 is used to minimize the additional complexity of the cross-product summation. The beneficial effect of using long blocks for subband processing is most pronounced in the case of complex audio signals, where unwanted intermodulation terms are suppressed and the dominant pitch has a low probability of producing such artifacts. A tap window of L=2 is the smallest possible to satisfy equation (10), since h=1 and S=2. However, the present invention can also satisfy equation (21), where the parameters are defined as follows:

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[0115] Q φ When r=3, the specification or operation of 602-3 according to equations (1)-(3) is to perform subband expansion of S=2 and subband transposition of Q=3 / 2, and the relationship between the target m subband and the source n subband for processing the direct terms is given by n≈2m / 3. There are two kinds of cross-product terms r=1, 2, and equation (20) is simplified as follows:

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[0117] D1=0 ​​and D2=3 / 2 (when r=1) D1=3 / 2 and D2=0 (when r=2) For the direct processing synthesis window, a rectangular window of length L=8 may be used with R1=R2=4. For the cross processing synthesis window, a short window of L=2 taps may be used with R1=R2=1, satisfying the following equation:

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[0119] Q φ When r = 4, the specification or operation of 602-4 according to equations (1)-(3) is to perform subband expansion of S = 2 and subband transposition of Q = 2, and the relationship between the target m subband and the source n subband for processing the direct terms is given by n ≈ 2m. There are three kinds of cross-product terms r = 1, 2, 3, and equation (20) is simplified as follows:

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[0121] D1=0 ​​and D2=2 (when r=1) D1=0 ​​and D2=1 (when r=2) D1=2 and D2=0 (when r=3) For the direct processing synthesis window, a rectangular window of length L=6 may be used with R1=R2=3. For the cross processing synthesis window, a short window of L=2 taps may be used with R1=R2=1, satisfying the following equation:

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[0123] In each of the above examples where values ​​of r greater than 1 are applicable, there are options similar to the three-step procedure described above, for example, in equation (17).

[0124] Figure 7 shows the amplitude spectrum of a harmonic signal with fundamental frequency Ω = 564.7 Hz. The low-frequency part 701 of this signal is used as input to several transposers. The purpose of the transposers is to generate a signal that is as close as possible to the high-frequency part 702 of the input signal, so that transmission of the high-frequency part 702 is not necessary and so that the available bit rate can be used economically.

[0125] Figure 8 shows the amplitude spectrum of the output from a transposer having as input the low-frequency component 701 of the signal in Figure 7. Following the description of Figure 5, multiple transposers have been constructed using a 64-band QMF filter bank with an input sampling frequency fs = 14400 Hz. However, for simplicity, we use two transposition orders Q φ Only =2,3 is considered. Three different spectra 801-803 represent the final output obtained using different settings of the cross-processing control data.

[0126] The upper spectrum 801 shows the output spectrum obtained when all cross processing is cancelled and only direct subband processing 401 is performed. This is the case when the cross processing control data 404 receives p=0 (no pitch indication). φ A =2 transposition produces an output in the 4 to 8 kHz range, with a Q φ A transposition of ≠3 produces an output in the 8-12 kHz range. As can be seen, the generated portions are far apart, and the output deviates significantly from the (intrinsic) high frequency portion 702. Audible double and triple "ghost pitch" artifacts appear in the resulting audio output.

[0127] The middle spectrum 802 shows cross-processing with pitch parameter p=5 (approximately equal to 128Ω / fs=5.0196), but a simple two-tap synthesis window with w(0)=w(-1)=1, which satisfies equation (10), is used for cross-subband processing. This is a direct combination of subband block-based processing and improved cross-product harmonic transposition. As shown, additional output signal components not present in 801 do not align with the desired harmonic sequence. This indicates that using the procedure described above, the cross-product processing can result in insufficient audio quality to offset the impact of direct subband processing design.

[0128] The spectrum 803 in the bottom row shows an output spectrum similar to the spectrum 802 in the middle row, but with a Q φ = 2,3, a cross-subband processing synthesis window is used. That is, a two-tap window with w(0) = 1 and w(-1) = exp(iα) satisfies equation (21), using the inventive feature that depends on the value of p. As can be seen, the synthesized output signal is well matched to the desired harmonic content 702.

[0129] 9 shows a nonlinear processing frame processor 202, which receives two input samples u1 and u2 and generates a processed sample (processed sample) w based on them, where the amplitude of the processed sample is given by the geometric mean of the amplitudes of the input samples, and the phase of the processed sample is a linear combination of the phases of the input samples, which can be expressed as follows:

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[0131] Further embodiments of the present invention will be apparent to those skilled in the art upon reading the above description. While the description and drawings show embodiments and examples, the present invention is not limited to those specific examples. Numerous modifications and variations are possible without departing from the scope of the present invention, which is defined by the appended claims.

[0132] The systems and methods disclosed herein may be implemented as software, firmware, hardware, or a combination thereof. All or some of the elements may be implemented as software executed by a digital signal processor or microprocessor, or as hardware or an application-specific integrated circuit. Such software may be stored on a computer-readable storage medium. While storage media include computer-readable media (or non-transitory media), the concept of the medium itself includes communication media (transitory media). As known to those skilled in the art, computer storage media include volatile media, non-volatile media, removable media, and non-removable media, and are implemented in any method or technique for storing information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media may be, but are not limited to, RAM, ROM, EEPROM, flash memory, or other types of memory, CD-ROM, digital versatile disks (DVDs), or other optical disk media, magnetic cassettes, magnetic tapes, magnetic disk storage, or other magnetic storage devices, or any other medium usable for storing desired information and accessible by a computer. Furthermore, those skilled in the art will appreciate that communication media may typically be embodied by computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or transmission medium and may include any information delivery mechanism. [Prior art documents] [Patent documents]

[0133] [Patent Document 1] International Publication No. 98 / 57436 [Patent Document 2] International Publication No. 2010 / 081892 [Patent Document 3] International Publication No. 2004 / 097794 [Patent Document 4] International Publication No. 2007 / 085275

[0134] (Appendix 1) 1. A signal generation system for generating a time-warped and / or frequency-transposed signal from an input signal, comprising: an analysis filter bank for deriving, from the input signal, Y analysis subband signals, each of which has a plurality of complex analysis samples having a phase and an amplitude, where Y≧1; a subband processing unit that generates a synthesis subband signal from the Y analysis subband signals using a subband transposition factor Q and a subband stretch factor S; a synthesis filter bank for generating the time-warped and / or frequency-transposed signals from the synthesis subband signals; wherein at least one of Q and S is greater than 1, and the subband processing unit includes a block extraction unit, a nonlinear frame processing unit, and an overlap addition unit; The block extraction unit i) generating Y frames from L input samples, each of the frames being extracted from a plurality of complex analysis samples of an analysis subband signal, and the length of the frames being L (L>1); ii) generating frames of input samples by applying a block hop size of h samples to the plurality of complex analysis samples before generating a subsequent frame of L input samples; The non-linear frame processor generates a frame of processed samples based on the Y corresponding frames of input samples generated by the block extractor by determining a phase and amplitude of each processed sample of the frame, and for at least one processed sample: i) the phase of the processed samples is based on the phase of each corresponding input sample in each of the Y frames of input samples; ii) the amplitudes of the processed samples are based on the phases of corresponding input samples in each of the Y frames of input samples; the overlap-add unit generates the composite subband signal by overlapping and adding samples of a series of frames of processed samples; A signal generation system, wherein the signal generation system operates at least when Y=2. (Appendix 2) the analysis filter bank is one of a quadrature mirror filter bank, a windowed discrete Fourier transform, or a wavelet transform; 2. The signal generation system of claim 1, wherein the synthesis filter bank is a corresponding inverse filter bank or transform. (Appendix 3) 3. The signal generation system of claim 2, wherein the analysis filter bank is a 64-point quadrature mirror filter bank and the synthesis filter bank is an inverse 64-point quadrature mirror filter bank. (Appendix 4) The analysis filter bank has an analysis time progression width Δt A applying to the input signal; The analysis filter bank has an analysis frequency interval Δf A Use n=0,...,N-1 are analysis subband indices, and the analysis filter bank has N analysis subbands; an analysis subband among the N analysis subbands is associated with a frequency band of the input signal; The synthesis filter bank has a synthesis time progression Δt sapplying to the synthesis subband signal; The synthesis filter bank has a synthesis frequency interval Δf s Use m=0,...,M-1 are synthesis subband indices, and the synthesis filter bank has M synthesis subbands; 4. A signal generation system according to any one of claims 1 to 3, wherein a synthesis subband among the M synthesis subbands is associated with a frequency band of the time-warped signal and / or the frequency-transposed signal. (Appendix 5) The subband processing unit is formed for Y=2 and further includes a cross processing control unit, the cross processing control unit being configured to determine the fundamental frequency Ω of the input signal and the analysis frequency interval Δf A 5. The signal generation system of claim 4, wherein the signal generation system generates cross-processing control data that defines subband indexes n1, n2 associated with the analysis subband signals such that the subband indexes differ by an integer p that is an approximation of the ratio of (Appendix 6) the subband processing unit is configured for Y=2 and further comprises a cross-processing controller, the cross-processing controller generating cross-processing control data defining subband indices n1, n2 related to the analysis subband signal and analysis subband index m, the subband indices being related to an approximate solution of the following equation:

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Claims

1. 1. A system configured to generate a time-warped and / or frequency-transposed signal from an input signal, the system comprising: a control data receiver; an analysis filterbank; a subband processor; and a synthesis filterbank; the control data receiver configured to receive control data; the analysis filter bank is configured to derive Y (Y≧2) analysis subband signals from the input signal, each analysis subband signal having a plurality of complex analysis samples each having a phase and an amplitude; the subband processing unit is configured to generate a synthesis subband signal from the Y analysis subband signals using a subband transposition factor Q and a subband stretch factor S, where at least one of Q and S is greater than 1, and the subband processing unit is configured to determine the synthesis subband signal taking into account the control data, the subband processing unit comprising: a block extraction unit; a nonlinear frame processing unit; and an overlap-add unit; the block extractor is configured to form Y frames of L input samples, each frame extracted from the plurality of complex analysis samples of an analysis subband signal, where L is a frame length greater than 1, and the block extractor is configured to apply a block hop size of h samples to the plurality of complex analysis samples before forming a subsequent frame of L input samples to generate a sequence of frames of input samples; The non-linear frame processor is configured to generate a frame of processed samples based on Y corresponding frames of input samples formed by the block extractor by determining a phase and an amplitude of each processed sample of the frame, wherein for at least one processed sample: i) the phase of the processed sample is based on the phase of each corresponding input sample in each of the Y frames of input samples; and ii) the amplitudes of the processed samples are based on amplitudes of corresponding input samples in each of the Y frames of input samples; the overlap-add unit is configured to determine the composite subband signal by overlapping and adding samples of a sequence of frames of processed samples; the synthesis filterbank configured to generate the time-warped and / or frequency-transposed signal from the synthesis subband signals; The system, wherein the block extractor is configured to derive at least one frame of input samples by downsampling the complex analysis samples of an analysis subband signal.

2. The analysis filter bank has an analysis time progression width Δt Ａ applying to the input signal; The analysis filter bank has an analysis frequency interval Δf Ａ Use n=0 , . . . , N−1 are analysis subband indices, and the analysis filter bank has N analysis subbands, where N>1; an analysis subband of the N analysis subbands is associated with a frequency band of the input signal; The synthesis filter bank has a synthesis time progression Δt Ｓ applying to the synthesis subband signal; The synthesis filter bank has a synthesis frequency interval Δf Ｓ Use m=0 , . . . , M−1 are synthesis subband indices, and the synthesis filter bank has M synthesis subbands, where M>1; The system of claim 1 , wherein a composite subband of the M composite subbands is associated with a frequency band of the time-warped signal and / or the frequency-transposed signal.

3. The subband processing unit is configured for Y=2 and further comprises a cross-processing control unit, the cross-processing control unit being configured to calculate a subband index n associated with the analysis subband signal and an analysis subband index m. １ , n ２ wherein the subband indices are associated with approximate integer solutions of the following equation: [Equation 1] Ω ０ is the fundamental frequency belonging to the dominant pitch component of the input signal, Ω is the frequency of the input signal to the analysis filterbank, σ=0 or ½, Q = (Δt Ｓ / Δt Ａ ) Q φ and Q φ is a transposition factor, r is 1≦r≦Q φ The system according to claim 2, wherein the integer satisfies −1.

4. The value of r that maximizes the minimum amplitude of the subbands of two samples formed by extracting analysis samples from the analysis subband signal is determined by the subband index n. １ , n ２ The system of claim 3 , wherein the cross-processing control is configured to generate cross-processing control data based on:

5. 5. The system of claim 4, wherein the amplitude of the subbands in each frame of L input samples is the amplitude of a central or near-central sample.

6. the signal generation system further comprises a plurality of subband processing units and a synthesis unit provided downstream of the plurality of subband processing units and upstream of the synthesis filter bank; each of the plurality of subband processing units is configured to determine an intermediate synthesis subband signal using a different value of the subband transposition factor Q and / or the subband stretch factor S; 6. The system of claim 1, wherein the synthesis unit is configured to synthesize corresponding intermediate synthesis subband signals to determine the synthesis subband signal.

7. the analysis filter bank is configured to form Y×Z analysis subband signals from the input signal; the subband processing unit generates Z synthesis subband signals from the Y×Z analysis subband signals, and applies a pair of values ​​of S and Q to each group of Y analysis subband signals underlying a synthesis subband signal; 7. The system of claim 1, wherein the synthesis filter bank is configured to generate Z time-warped and / or frequency-transposed signals from the Z synthesis subband signals.

8. 1. A method for generating a time-warped and / or frequency-transposed signal from an input signal, comprising the steps of: receiving control data; deriving Y (Y≧2) analysis subband signals from the input signal, each analysis subband signal having a plurality of complex analysis samples each having a phase and an amplitude; forming Y frames of L input samples, each frame extracted from said plurality of complex analysis samples of an analysis subband signal, where L is a frame length greater than 1; applying a block hop size of h samples to the plurality of complex analysis samples before deriving a subsequent frame of L input samples to generate a sequence of frames of input samples; generating a frame of processed samples based on Y corresponding frames of input samples and taking into account the control data by determining a phase and amplitude of each processed sample of the frame, wherein for at least one processed sample: i) the phase of the processed sample is based on the phase of each corresponding input sample in each of the Y frames of input samples; and ii) the amplitudes of the processed samples are based on the amplitudes of corresponding input samples in each of the Y frames of input samples; determining a composite subband signal by overlapping and adding samples of a sequence of frames of processed samples; and generating the time-warped and / or frequency-transposed signal from the synthesis subband signals, wherein forming the frames of input samples comprises downsampling the complex analysis samples of analysis subband signals; A method comprising:

9. A non-transitory data carrier storing computer readable instructions for performing the method of claim 8.

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