KR101239812B1 - Apparatus and method for generating a bandwidth extended signal - Google Patents

Abstract

An apparatus for generating a bandwidth extension signal from an input signal includes a patch generator and a combiner. The input signal is represented in the first band by the first resolution data and in the second band by the second resolution data, and the second resolution is lower than the first resolution. The patch generator generates a first patch from the first band of the input signal according to the first patching algorithm and generates a second patch from the first band of the input signal according to the second patching algorithm. The combiner combines the first patch, the second patch and the first band of the input signal to obtain a bandwidth extension signal. An apparatus for generating a bandwidth extension signal scales an input signal different to the first patching algorithm and the second patching algorithm, or scales the first patch and the second patch, so that the bandwidth extension signal meets the spectral envelope criterion.

Description

Apparatus and method for generating a bandwidth extension signal {APPARATUS AND METHOD FOR GENERATING A BANDWIDTH EXTENDED SIGNAL}

Embodiments according to the present invention relate to audio signal processing, and in particular, an apparatus and method for generating a bandwidth extended signal from an input signal, and a bandwidth reduced signal based on the input signal and the audio signal. And apparatus and method for providing the same.

Perceptually adapted coding of audio signals, which provides substantial data rate reduction for efficient storage and transmission of audio signals, is widely applied in many fields. For example, many coding algorithms are known, such as MPEG ½ Layer 3 (“MP3”) or MPEG 4 AAC (Advanced Audio Coding). However, the coding used for this, especially when operating at the lowest bit rate, can lead to a reduction in the subjective audio quality caused by the encoder side, which is primarily a limitation of the bandwidth of the transmitted audio signal.

In WO 98 57436 it is known that in such a situation on the decoder side the audio signal is band-limited and only encodes the lower band of the audio signal by a high quality audio encoder ("core coder"). However, the upper band is only roughly characterized, for example by a parameter set that reproduces the spectral envelope of the upper band. On the decoder side, the upper band is then synthesized. For this purpose, a harmonic transposition is proposed in which the lower band of the decoded audio signal is provided to a filterbank. The lower band filterbank channel is connected to, or "patched" to, the upper band filterbank channel, and each patched bandpass signal is subject to envelope adjustment. A synthesis filterbank belonging to a particular analysis filterbank receives the bandpass signal of the audio signal in the lower band and the envelope-adjusted bandpass signal of the lower band which is patched with harmonics into the upper band. The output signal of the synthesis filterbank is an extended audio signal with respect to its original bandwidth transmitted from the encoder side to the decoder side by a core coder operating at a very low data rate. In particular, filterbank calculation and patching in the filterbank domain can be a high computational effort.

The complexity-reduced method for bandwidth expansion of band-limited audio signals uses instead a copying function of the low frequency signal portion into the high frequency range to approximate missing information due to band limitation. do. Such methods are described in M. Dietz, L. Liljeryd, K. Kjand 0. Kunz, "Spectral Band Replication, a novel approach in audio coding," in 112th AES Convention, Munich , May 2002; S. Meltzer, R. Band F. Henn, "SBR enhanced audio codecs for digital broadcasting such as" Digital Radio Mondiale "(DRM)," 112th AES Convention, Munich, May 2002; T. Ziegler, A. Ehret, P. Ekstrand and M. Lutzky, "Enhancing mp3 with SBR: Features and Capabilities of the new mp3PRO Algorithm," in 112th AES Convention, Munich, May 2002; International Standard ISO / IEC 14496-3: 2001 / FPDAM, "Bandwidth Extension," ISO / IEC, 2002, or "Speech bandwidth extension method and apparatus", Vasu Iyengar et al. US Pat. No. 5,455,888.

In this way, no harmonic prediction is performed, but the continuous bandpass signal of the lower band is introduced into the continuous filterbank channel of the upper band. This achieves a rough approximation of the upper band of the audio signal. In the following step, then this coarse approximation of the signal is homogenized with respect to the original by post-processing using control information obtained from the original signal. Here, for example, the scale factor helps to apply spectral envelope, inverse filtering, and the addition of the noise floor is also described in the MPEG-4 High Efficiency Advanced Audio Coding (HE-AAC) standard. As such, it helps to apply a complement of sinusoidal signal portions for tonality and missing harmonics.

Apart from this, another method uses a phase vocoder for bandwidth extension. When applying a phase vocoder for spectral expansion, the frequency lines move further apart from each other. If a gap exists in the spectrum, for example by quantization, the same is increased by expansion. In energy adaptation, the remaining lines in the spectrum receive too much energy compared to each line of the original signal.

13 shows a schematic diagram 1300 of bandwidth extension using a phase vocoder. In this embodiment, two patches 1312 and 1314 are added to the low frequency band 1302 of the signal. The upper cut-off frequency 1320, also called the crossover frequency, is the low-end frequency of the neighboring patch 1312 and twice the crossover frequency. The upper limit frequency of the neighboring patch 1312 and the lower limit frequency of the next patch 1314. The phase vocoder doubles the frequency of the frequency line of the low frequency band 1302 of the signal to obtain a neighboring patch 1312 and then the frequency of the low frequency band 1302 of the signal to obtain a patch 1314. Triple the frequency of the line. Therefore, the spectral density of the neighboring patch 1312 is only half the spectral density of the low frequency band 1302 of the signal and the spectral density of the next patch 1314 is only the spectral density of the low frequency band 1302 of the signal. .

The concentration of energy in the band for only a few frequency lines results in a substantial change in timbre that is different from the original. The energy of the previous more bands (frequency lines) is added to the remaining less lines.

Some embodiments for phase vocoders and their applications are described in "Frederik Nagel and Sascha Disch, Harmonic Bandwidth Extension Method for Audio Codecs,"ICASSP'09 and "M. Puckette. Phase-locked Vocoder. IEEE ASSP Comference on Applications of Signal Processing to Audio and Acoustics, Mohink 1995. ", Robel, A .: Transient detection and preservation in the phase vocoder; citeseer. ist.psu.edu/679246.html ', "Laroche L., Dolson M .: Improved phase vocoder timescale modification of audio", IEEE Trams.Speech and Audio Processing, Vol. 7 , No. 3, pp. 323-332 "and US Pat. No. 6,549,884.

One approach to filling the gap is shown in WO 00/45379. It includes methods and apparatus for enhancement of a source coding system that uses high frequency reproduction. It addresses the problem of insufficient noise content in the reproduced high band by adaptive noise-floor addition. The addition of noise can fill the gap, but the audio quality or the subjective quality cannot be sufficiently increased.

It is an object of the present invention to provide a concept for bandwidth extension of an audio signal which increases the subjective quality of the bandwidth extension signal.

This object is solved by an apparatus according to claims 1 and 11, an audio signal according to claim 14 and a method according to claims 15 and 16.

An embodiment of the present invention provides an apparatus for generating a bandwidth extension signal from an input signal. The input signal is represented by a first band by first resolution data and a second band by second resolution data, the second resolution being lower than the first resolution. The device includes a patch generator and a combiner. The patch generator is set to generate a first patch from a first band of the input signal according to the first patching algorithem and to generate a second patch from a second band of the input signal according to the second patching algorithm. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm. The combiner is set to combine the first patch, the second patch and the first band of the input signal to obtain a bandwidth extension signal. The apparatus for generating the bandwidth extension signal is configured to scale the input signal according to the first patching algorithm and the second patching algorithm or to scale the first patch and the second patch, so that the bandwidth extension signal is a spectral envelope reference. satisfies the spectral envelope criterion

Embodiments in accordance with the present invention provide a patch having a low spectral density in order to expand the bandwidth of the input signal (e.g., that the patch contains a difference compared to the low frequency band of the input signal). It is based on a central idea that combines with a patch (e.g., a patch means little or no difference compared to the low frequency band of the input signal). Since both patches are based on the input signal, the high frequency bandwidth extension of the low frequency band of the input signal can provide an approximation of the superiority of the original audio signal. In addition, the first and second patches can be scaled before or after generation (by the scale of the input signal) to meet the spectral envelope criteria, since the spectral envelope of the original audio signal is reproduced in the high frequency band of the input signal. For it is considered. In this way, the subjective or audio quality of the bandwidth extension signal can be significantly increased.

In some embodiments according to the present invention, the first patching algorithm is a harmonic patching algorithm. In other words, the first patch is generated so that a frequency that is only an integer multiple of the frequency of the first band of the input signal is included by the first patch. In addition, the second patching algorithm may be a mixed patching algorithm. This means, for example, that a second patch can be generated to include frequencies that are multiple integers of the frequencies of the first band of the input signal and frequencies that are not multiple integers of the frequencies of the first band of the input signal. Therefore, the spectral density of the second patch is higher than the spectral density of the first patch. By combining the first patch and the second patch, the missing frequency line of the first patch is filled by the frequency line of the second patch. In this way, the gap of harmonic bandwidth extension according to the first patching algorithm can be filled by the second patch and the audio quality of the bandwidth extension signal can be significantly improved.

Some embodiments according to the present invention relate to an apparatus for providing a bandwidth reduction signal based on an input signal. The apparatus includes a spectral envelope data determiner, a patch scaling control data generator, and an output interface. The spectral envelope data determiner is set to determine the spectral envelope data based on the high frequency band of the input signal. The patch scaling control data generator is configured to generate a patch scaling control data to scale the bandwidth reduction signal at the decoder or to scale the first and second patches by the decoder, thus extending the bandwidth generated by the decoder. The signal meets the spectral envelope criteria. Spectral envelope criteria are based on spectral envelope data. The first patch is generated from the low frequency band of the bandwidth reduction signal according to the first patch algorithm and the second patch is generated from the low frequency band of the bandwidth reduction signal according to the second patching algorithm. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm. The output interface is configured to combine the low frequency band, spectral envelope data, and power scaling control data of the input signal to obtain a bandwidth reduction signal. Moreover, the output interface is configured to provide a bandwidth reduction signal for transmission or storage.

Some subsequent embodiments according to the invention are directed to an audio signal comprising a first band and a second band. The first band is represented by the first resolution data and the second band is represented by the second resolution data. The second resolution data is lower than the first resolution data. The second resolution data is based on spectral envelope data in the second band and patch-scaling control data in the second band to scale the audio signal at the decoder or to scale the first patch and the second patch by the decoder, Thus, the bandwidth extension signal generated by the decoder satisfies the spectral envelope criterion. Spectral envelope criteria are based on spectral envelope data. The first patch is generated from the first band of the audio signal according to the first patch algorithm and the second patch is generated from the first band of the audio signal according to the second patching algorithm. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generator according to the first patching algorithm.

Embodiments according to the present invention will be described in detail with reference to the accompanying drawings that follow:
1 is a block diagram of an apparatus for generating a bandwidth extension signal from an input signal;
2A is a schematic diagram of the generated first patch;
2B is a schematic view of the generated first and second patches;
3A is a block diagram of an apparatus for generating a bandwidth extension signal from an input signal;
3B is a schematic diagram of a clipped sinusoidal input signal;
3C is a schematic diagram of a half-wave rectified sinusoidal input signal;
3D is a schematic diagram of a clipped and full-wave rectified sinusoidal input signal;
4 is a block diagram of an apparatus for generating a bandwidth extension signal from an input signal;
5A is a schematic diagram of a filterbank implementation of a phase vocoder;
FIG. 5B is a detail view of the filter of FIG. 5A; FIG.
FIG. 5C is a schematic diagram for manipulation of magnitude and frequency signals in the filter channel of FIG. 5A; FIG.
6 is a schematic diagram of a switching implementation of a phase vocoder;
7 is a block diagram of an apparatus for generating a bandwidth extension signal from an input signal;
8 is a block diagram of an apparatus for generating a bandwidth extension signal from an input signal;
9 is a block diagram of an apparatus for generating a bandwidth extension signal from an input signal;
10 is a block diagram of an apparatus for providing a bandwidth reduction signal from an input signal;
11 is a flowchart of a method for generating a bandwidth extension signal from an input signal;
12 is a flowchart of a method for providing a bandwidth reduction signal based on an input signal; And
13 is a schematic diagram of a known bandwidth extension algorithm.

In the following, the same reference numerals are used for objects and functional units having the same or similar functional properties and their descriptions in connection with the drawings will also apply to the other drawings in order to avoid duplication in the embodiments.

1 shows a block diagram of an apparatus 100 for generating a bandwidth extension signal 122 for an input signal 102 according to an embodiment of the present invention. The input signal is represented in the first band by the first resolution data and in the second band by the second resolution data, and the second resolution data is lower than the first resolution data. Device 100 includes a patch generator 110 coupled with combiner 120. The patch generator 120 generates a first patch from the first band of the input signal 102 according to the first patching algorithm and generates a second patch from the first band of the input signal 102 according to the second patching algorithm. . The spectral density of the second patch 114 generated according to the second patching algorithm is higher than the spectral density of the first patch 112 generated according to the first patching algorithm. The combiner 120 combines the first band of the first patch 112, the second patch 114 and the input signal 102 to obtain the bandwidth extension signal 122. In addition, the apparatus 100 for generating the bandwidth extension signal 122 may scale the input signal according to the first and second patching algorithms or the first patch 112 to satisfy the spectral envelope criterion. ) And the second patch 114.

The spectral density means, for example, the density of different frequencies or frequency lines in a frequency band. For example, a frequency band from 0H to 10 kHz that includes a frequency portion with frequencies of 4 kHz and 8 kHz may have a lower spectral density than the same frequency band that includes a frequency portion with frequencies of 2 kHz, 4 kHz, 6 kHz, 8 kHz and 10 kHz. Have Since the spectral density of the first patch 112 is lower than the spectral density of the second patch 114, the first patch 112 includes a gap as compared to the second patch 114. Therefore, the second patch 114 can be used to fill this gap. Since both patches are based on the first band of the input signal 102, the two patches are related to the characteristics of the original signal corresponding to the input signal 102. Therefore, the bandwidth extension signal 122 can be an approximation of the superiority of the original signal and the subjective quality or the audio quality of the bandwidth extension signal 122 can be significantly improved using the described concepts. In this way, more energy can be distributed between the remaining lines, for example, unnatural sounds can be prevented.

For example, the first patching algorithm may be a harmonic patching algorithm. Therefore, the patch generator 110 may generate a first patch 112 that includes only frequencies that are multiple integers of the frequencies of the first band of the input signal 102. Harmonic bandwidth extension can provide an approximation of the goodness of the tonal structure of the original signal. This gap can be filled by the second patch. For example, the second patching algorithm may be a mixed patching algorithm, where the patch generator 110 may input multiple signals of the frequency of the first band of the input signal 102 (harmonic frequency) and the input signal 102 (non-harmonic frequency). This means that a second patch 114 can be generated that includes frequencies that are not multiple integers of the frequencies of the first band. The non-harmonic frequency can be used to fill the gap of the first patch 112. It may also be possible to combine the entire second patch (including harmonic frequencies) with the first patch 112. In this example, the amplification of the harmonic frequencies due to the combination of harmonic frequency portions of the first patch 112 and the second patch 114 properly scales the first patch 112 and / or the second patch 114. Can be considered.

The first patch 112 and the second patch 114 comprise at least partially the same frequency range. For example, the first patch 112 includes a frequency band from 4 kHz to 8 kHz and the second patch 114 includes a frequency band from 6 kHz to 10 kHz. In some embodiments according to the present invention, the lower cut of the frequency of the first patch 112 is equal to the lower limit of the frequency of the second patch 114 and the upper cut of the frequency of the first patch 112. ) Is equal to the upper limit of the frequency of the second patch 114. For example, both patches cover a frequency band from 4 kHz to 8 kHz.

2A and 2B illustrate embodiments of the first patch 112 according to the first patching algorithm 212 and the second patch 114 according to the second patching algorithm 214. For better explanation, FIG. 2A shows only the first patch 112 and FIG. 2B shows the first patch 112 and the corresponding second patch 114. 2A illustrates an example 200 for two first patches 112 generated according to the first band 202 and the first patching algorithm 212 of the input signal 102. In this example, the patch includes the same bandwidth as the first band 202 of the input signal 102. The bandwidth can also be different. The upper limit frequency 220 of the first band 202 of the input signal 102 is represented by a 'crossover' frequency. In the example shown in FIG. 2A, the patch starts at the same frequency as multiple of the crossover frequency 220. The frequency lines in the first patch 112 are multiple integers of the frequency lines of the first band 202 of the input signal 102 and can be generated, for example, by a phase vocoder. This first patch 112 includes a gap in terms of missing frequency lines compared to the first band 202 of the input signal 102.

2B additionally shows an example 250 for two corresponding second patches 114. This patch is generated according to the second patching algorithm 214 and includes harmonic and non-harmonic frequencies. The non-harmonic frequency line can be used to fill the gap of the first patch 112. The frequency line of the second patch 114 may be generated by, for example, non-linear distortion.

In this way, the gap cannot be filled arbitrarily, for example, filling a gap with noise. The gap is filled based on the first resolution data of the first band of the input signal and thus the original signal.

The first band of the input signal 102 may, for example, represent a low frequency band of the original audio signal encoded with high resolution. The second band of the input signal 102 can represent, for example, the high frequency band of the original audio signal and can be, for example, one such as spectral envelope data, noise data and / or missing harmonic data with low resolution. Or may be quantized by more parameters. The original audio signal may be, for example, a signal recorded by a microphone prior to processing or encoding.

Scaling an input signal according to a first patching algorithm and a second patching algorithm is, for example, an input signal in which the input signal is once scaled by the first patching algorithm before the first patch is generated and then the first patch is scaled. Is generated based on the first patch, and the input signal is first scaled by the second patching algorithm before the second patch is generated and then the second patch is generated based on the scaled input signal, thus the first patch. After combining the second band and the first band of the input signal, the bandwidth extension signal satisfies the spectral envelope criterion. Alternatively, scaling of the input signal according to the first and second patching algorithms in combination with the scaling of the first and second patches may be possible.

The combiner 120 may be, for example, an adder and the bandwidth extension signal 122 is a weight of the first band of the first patch 112, the second patch 114, and the input signal 102. It may be a weighted sum.

Satisfying the spectral envelope criterion means, for example, that the spectral envelope of the bandwidth extension signal is based on the spectral envelope data included by the input signal. The spectral envelope data may be generated by the encoder and may indicate a second band of the original signal. In this way, the spectral envelope of the bandwidth extension signal may be an approximation of the superiority of the spectral envelope of the original signal.

Apparatus 100 may also include a core decoder for decoding the first band of input signal 102.

Patch generator 110 and combiner 120 may be specially designed hardware or part of a processor or microcontroller, or may be a computer program configured to run on a computer or microcontroller. The device 100 may be part of a decoder or an audio decoder.

3A shows a block diagram of an apparatus 300 for generating a bandwidth extension signal 122 from an input signal 102 according to an embodiment of the present invention. In this embodiment, the patch generator 110 includes a phase vocoder 310 for generating the first patch and an amplitude clipper 320 for generating the second patch 114. Phase vocoder 310 and amplitude clipper 320 are coupled to combiner 120. The phase vocoder 310 may spread the first band of the input audio signal 102 to produce a first patch 112 that includes harmonic frequencies. In the non-linear processing step, the amplitude clipper 320 may clip the input signal 102 to produce a second patch 114 that includes harmonic and non-harmonic frequencies. As an alternative to amplitude clipper 320, half-wave rectifiers, full-wave rectifiers, mixers, or diodes used in the secondary region of the characteristic curve are also non-linear processing. Can be used to generate a non-harmonic frequency based on the input signal 102 by step.

3B, 3C and 3D show an embodiment of an input signal 102 that has been clipped and / or calibrated to produce a non-harmonic frequency. 3B shows a schematic diagram 350 of a clipped sunusoidal input signal 102. By clipping the signal, a discontinuous point in the form of a sudden change in signal slope 380 is created and a non-harmonic portion with harmonics and high frequencies is created.

Alternatively, FIG. 3C shows a schematic diagram 360 of the half-wave rectified sinusoidal input signal 102, which also results in a discontinuity point 380.

In addition, a combination of clipping and correction may be possible. 3D shows a schematic diagram 370 of the clipped and full-wave rectified sinusoidal input signal 102 resulting in another discontinuity point 380.

By applying different methods of nonlinear processing to clip and / or correct or create discrete points 380, a broad spectrum of different frequencies can be generated. Therefore, a patch generated according to such a patching algorithm may include high spectral density.

4 shows a block diagram of an apparatus 400 for generating a bandwidth extension signal 122 from an input signal 102 according to an embodiment of the present invention. Device 400 is similar to the device shown in FIG. 3A but additionally includes a spectral line selector 410. Phase vocoder 310 and amplitude clipper 320 are connected to spectral line selector 410 and spectral line selector 410 is coupled to combiner 120. The spectral line selector 410 may select a plurality of frequency lines of the second patch 114 to obtain a modified second patch 414 that may be complementary to the first patch. If the corresponding frequency line of the first patch 112 is missing, the frequency line of the second patch 114 can be selected. In other words, the spectral line selector 410 selects the frequency line of the second patch 114 to fill the gap of the first patch 112 and the second patch 114 already included by the first patch 112. The frequency of can be ignored. In this way, the modified second patch 414 may include a gap at the frequency already included by the first patch 112.

In this embodiment, the combiner 120 combines the first patch 112, the modified second patch 414, and the first band of the input signal 102.

The spectral line selector 410 may be part of a patch generator 110 (as shown in FIG. 4) or a separate unit, for example.

In the following, with reference to FIGS. 5 and 6, a possible implementation of a phase vocoder according to the invention is described. 5 shows a filterbank implementation of a phase vocoder in which an audio signal is supplied to input 500 and obtained at output 510. In particular, each channel of the filter bank shown in FIG. 5A includes a bandpass filter 501 and a downstream oscillator 502. The output signals of all oscillators from all channels are combined by a combiner, represented as 503, for example, implemented as an adder to obtain an output signal. Each filter 501 is implemented as it provides an amplitude signal on the one hand and a frequency signal on the other. The amplitude signal and the frequency signal are time signals describing the development of the amplitude in the filter 501 over time, while the frequency signal represents the development of the frequency of the signal filtered by the filter 501.

The schematic setting of the filter 501 is described in FIG. 5B. Each filter in FIG. 5A can be set as in FIG. 5B, but only the frequency f _i provided to the two input mixers 551 and adder 552 is different from channel to channel. The mixer output signal of mixer 551 is all lowpass filtered by lowpass 553, which is at a local oscillator frequency (LO frequency) where they are phase inverted by 90 °. As long as they are generated, they are different. The upper low pass filter 553 provides a quadrature signal, while the lower filter 553 provides an in-phase signal. These two signals, such as Q and I, are provided to a coordinate transformer that produces a magnitude phase representation from the rectangular representation. Each progress signal or amplitude signal in FIG. 5A over time is an output at output 557. The phase signal is provided to a phase unwrapper 558. At the output of component 558, there are no more phase values, always between 0 ° and 360 °, but the phase values increase linearly. This “ubwrapped” phase value is, for example, current point in time to obtain a frequency value relative to the current point in time or any other means for obtaining an approximation of a phase derivative. Provided to phase / frequency converter 559 is implemented as a simple phase difference calculator that subtracts the phase of the current point in time from the phase in. This frequency value is added to a constant frequency value f _i of the filter channel i to obtain a frequency value that is temporarily changed at the output 560. The frequency value at output 560 is a direct component = f _i And an alternative component = frequency deviation at which the current frequency of the signal in the filter channel deviates from the average frequency f _i .

Thus, as described in Figures 5A and 5B, the phase vocoder achieves separation of spectral information and temporal information. Spectral information is contained in a particular channel or frequency f _i that provides a direct portion of the frequency for each channel, while temporal information is included in frequency deviation or magnitude evolution over time, respectively.

FIG. 5C illustrates an operation, such as performed for the creation of a first patch according to the present invention, in particular using a phase vocoder 310, more specifically inserted at the position of the dashed line of the circuit described in FIG. 5A. do.

For time scaling, for example, the magnitude signal A (t) in each channel or the frequency signal f (t) in each channel can be removed or interpolated. For the purpose of transposition, interpolation, as is useful for the present invention, for example, the transient expansion or spreading of signals A (t) and f (t), is the spreading signals A '(t) and f' (t). Is performed to obtain the interpolation controlled by the spreading factor 598. For example, a spreading factor may be selected for the phase vocoder to generate harmonic frequencies. The frequency of each individual vibrator 502 in FIG. 5A is not changed by interpolation of the phase change, for example, a value before addition of a constant frequency by the adder 552. However, with factor 2, for example, the temporal change of the entire audio signal is slowed down. The result is a temporarily spreading tone with an original pitch, for example the original fundamental wave with harmonics.

By performing the signal processing described in FIG. 5C, the audio signal can be reduced back to the original period, for example by elimination of factor 2, while all frequencies are doubled simultaneously. This leads to a pitch transposition by factor 2, but an audio signal having the same length as the original audio signal, for example the same number of samples, is obtained.

As an alternative to the filterband implementation described in FIG. 5A, a transform implementation of a phase vocoder such as described in FIG. 6 may also be used. Here, the audio signal 698 is provided into the FFT processor, or more generally, into the Short-Time-Fourier-Transformation (STFT) processor 600 as a sequence of time samples. The FFT processor 600 is then implemented to perform temporary windowing of the audio signal to calculate two magnitude spectra and also phase spectra by the next FFT, which calculation is strongly overlapping the audio signal. This is done for a continuous spectrum of blocks of.

In the extreme case, a new spectrum can be calculated for every new audio signal, which can also be calculated for each 20th new sample, for example. The distance 'a' in the sample between the two spectra is preferably given by the controller 602. The controller 602 is further implemented to provide an IFFT processor 604 that is implemented to operate in an overlap-add manner. In particular, the IFFT processor 604 is implemented to perform an inverse short time Fourier transform by executing one IFFT per spectrum based on the magnitude spectrum and the phase spectrum, in order to implement a superposition-addition scheme for obtaining the resulting time signal. . The overlap addition scheme is set to eliminate the blocking effect by the analysis window.

Temporal spreading of the time signals is achieved by the distance 'b' between the two spectra, which is greater than the distance 'a' between the spectra used in the generation of the FFT spectrum, since they are processed by the IFFT processor 604. The basic idea is to spread the audio signal by an inverse FFT farther than the analysis FFT. As a result, the spectral change in the synthesized audio signal occurs more slowly than the original audio signal.

However, without phase rescaling at block 606, this may lead to frequency artifacts. When one single frequency bin is taken into account, for example, to realize a continuous phase value by 45 °, the signal in the filterbank is the ratio of the period of the period in phase by, for example, 45 ° per time interval. , Where the time interval is the time interval between successive FFTs. If the inverse FFTs are now located farther apart from each other, this means that a 45 ° phase increase occurs over a long time interval. This means that the frequency of this signal portion has been inadvertently changed. To remove this artifact, the phase is rescaled by exactly the same elements by which the audio signal is spread over time. Thus the phase of each of the FFT spectral values is increased by the b / a factor, thus eliminating unintended frequency changes.

In the embodiment described in FIG. 5C, in the filterbank implementation of FIG. 5A, diffusion by interpolation of the magnitude / frequency control signal is achieved for one signal oscillator, whereas the diffusion in FIG. This is achieved by the distance between two IFFT spectra larger than 'a' and greater than the distance between two FFT spectra, but phase rescaling is performed according to the 'b / a' ratio for artifact prevention. The distance 'b' may be chosen, for example, by the phase vocoder to produce a high frequency frequency.

7 shows a block diagram of an apparatus 700 for generating a bandwidth extension signal 122 from an input signal 102 in accordance with an embodiment of the present invention. The device 700 is similar to the device shown in FIG. 1, but includes a power controller 710, a first power regulation means 730, and a second power regulation means 730. The power controller 710 is connected to the first power adjusting means 730 and to the second power adjusting means 730. The first power adjusting means 730 and the second power adjusting means 730 are connected to the patch generator 110. The power controller 710 may control scaling of the input signal according to the first and second patching algorithms based on the spectral envelope data included by the input signal and the patch scaling control data included by the input signal. Alternatively, at least one patch scaling control parameter may be used instead of the patch scaling control data included by the input signal. The patch scaling control parameter may be stored by the patch-scaling control parameter memory, which may be part or separate unit of the power controller 710. The first power adjusting means 720 may scale the input signal 102 according to the first patching algorithm and the second power adjusting means 730 may scale the input signal 102 according to the second patching algorithm. . In other words, the input signal 102 can be preprocessed, so that first and second patches can be generated, so that the bandwidth extension signal meets the spectral envelope criteria. To this end, the spectral envelope data may define the spectral envelope of the bandwidth extension signal 122 and the patch scaling data or patch scaling control parameter may set the ratio between the first patch 112 and the second patch 114 or Alternatively, an absolute value between the first patch 112 and / or the second patch 114 may be set. The first power adjusting means 720 and the second power adjusting means 730 may be part of the power controller 710 or may be separate units as shown in FIG. 7. The power controller 710 may be part of the patch generator 110 or may also be a separate unit as shown in FIG. 7. The power regulating means 720, 730 may be, for example, an amplifier or a filter controlled by the power controller 710.

Alternatively, scaling occurs after the creation of the patch. Suitably, FIG. 8 shows a block diagram of an apparatus 800 for generating a bandwidth extension signal 122 from an input signal 102 in accordance with an embodiment of the present invention. The device 800 is similar to the device shown in FIG. 7, but power adjusting means 720, 730 are arranged between the patch generator 110 and the combiner 120. In this embodiment, the patch generator 110 is connected with the first power adjusting means 720 and the second power adjusting means 730. The first power adjusting means 720 and the second power adjusting means 730 are connected to the combiner 120. In this way, the first patch 112 may be scaled by the first power adjusting means 720 according to the first patching algorithm and the second patch 114 may be scaled by the second power adjusting means according to the second patching algorithm. 730. The power adjusting means is again controlled by the power controller 710 based on spectral envelope data and patch scaling control data or by patch scaling control parameters as described above.

Alternatively, scale only one of the two patches or scale the power after combining the patches by combiner 120 and scaling the combined patches before combining the combined patches with the first band of input signal 102. It may be possible to. In other words, the first one patch can be scaled to achieve a predefined ratio between the two patches (eg, based on patch scaling control data) and then the combined patches meet the spectral envelope criteria. To scale (eg, based on spectral envelope data).

Patch scaling control data may include, for example, simple coefficients or a plurality of parameters for power distribution scaling. The patch scaling control data may be, for example, a power ratio between the first patch and the second patch for the entire second band or the entire high band or the first pitch and / or the first for the entire first band and / or the entire high band. It can represent an absolute value for power of two pitches and can be represented by at least one parameter. Alternatively, patch scaling data may also indicate the transmission function of the filter. For example, a parameter of the transmission function of the filter for scaling the first patch and / or a parameter of the transmission function of the filter for scaling the second patch may be included in the input signal. In this way, the parameter can indicate the function of the frequency. Another alternative may be a patch scaling control parameter that indicates the differential function of the first patch and the second patch. According to this embodiment, scaling of the input signal or scaling of the first patch and the second patch may be based on patch scaling control data including at least one parameter.

9 shows a block diagram of an apparatus for generating a bandwidth extension signal 122 from an input signal 102 in accordance with an embodiment of the present invention. The device 900 is similar to the device shown in FIG. 8, but additionally a noise adder 910, a missing harmonic adder 920, a noise power adjustment mean 940 and a missing one. Harmonic power adjusting means 950. The noise adder 910 is connected to the noise power adjusting means 940, which is connected to the combiner 120. The missing harmonic adder 920 is connected with the missing harmonic power adjusting means 950, which is connected with the combiner 120. In addition, the power controller 710 is connected with the noise power adjusting means 940 and the missing harmonic power adjusting means 950. The noise adder 910 can generate a noise patch 912 based on the noise data included by the input signal 102.

The noise patch 912 can be scaled by the noise power adjusting means 940. The power controller 710 may control the noise power adjusting means 940 based on the spectral envelope data and / or the noise scaling data included in the input signal 102. In this way, the noise of the original signal can be approached to improve the audio quality of the bandwidth extension signal.

The missing harmonic adder 920 may generate the missing harmonic patch 922 based on the missing harmonic data included in the input signal. The missing harmonic patch 922 may include a harmonic frequency, which may only occur in the high frequency band of the original signal, and thus, in relation to the first band of the input signal 102 of the low frequency band of the original signal. If only information is available, it cannot be reproduced. Missing harmonic data can provide information about these missing harmonics. The missing harmonic patch 922 can be scaled by the missing harmonic power adjusting means 950. The power controller 710 may control the missing harmonic power adjusting means 950 based on the spectral envelope data or based on the missing harmonic scaling data included by the input signal 102.

Combiner 120 receives first patch 112, second patch 114, first band of input signal 102, noise patch 912, and missing harmonic patches to obtain bandwidth extension signal 122. 922 may be combined. The power controller 710 in combination with the power adjusting means comprises a first patch 112, a second patch 114, a first band of the input signal 102, a noise patch 912 and omission based on spectral envelope data. Harmonic patch 922 can be scaled, thus meeting spectral envelope criteria.

10 shows a block diagram of an apparatus 1000 for providing a bandwidth reduction signal 1032 based on an input signal 102 in accordance with an embodiment of the present invention. Apparatus 1000 includes a spectral envelope data determiner 1010, a patch scaling data generator 1020, and an output interface 1030. The spectral envelope data determiner 1010 and the patch scaling data generator 1020 are connected to the output interface 1030. The spectral envelope data determiner 1010 may determine the spectral envelope data 1012 based on the high frequency band of the input signal 1002. The patch scaling data generator 1020 may be configured to scale the bandwidth reduction signal 1032 at the decoder so that the bandwidth extension signal by the decoder satisfies the spectral envelope criterion or to scale the first patch and the second patch by the decoder. Control data 1022 may be generated. Spectral envelope criteria are based on spectral envelope data. The first patch is generated from the first band of bandwidth reduction signal 1032 according to the first patching algorithm and the second patch is generated from the first band of bandwidth reduction signal 1032 according to the second patching algorithm. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm. The output interface 1030 combines the low frequency band, spectral envelope data 1012 and patch scaling control data 1022 of the input signal 1002 to obtain a bandwidth reduction signal 1032. Besides. Output interface 1030 provides a bandwidth reduction signal 1032 for transmission and storage.

Apparatus 1000 may also include a core coder to encode the low frequency band of the input signal. The core coder may be, for example, a differential encoder, an entropy encoder or a perceptual audio encoder.

Apparatus 1000 may be part of an encoder configured to provide a signal for the decoder described above. Patch scaling control data 1022 may include, for example, simple coefficients or a plurality of parameters for power distribution scaling. The patch scaling control data may represent, for example, the power ratio between the first patch and the second patch for the entire high frequency band or the absolute value for the power of the first pitch and / or the second pitch for the entire high frequency band. It may be represented by at least one parameter. Alternatively, the patch scaling data includes coefficients determined for each of the plurality of subbands that together make up the high frequency band, similar to spectral envelope data per subband in spectral bandwidth replication applications, for example. For example, the parameter of the transmission function of the filter for scaling the first patch and / or the parameter of the transmission function of the filter for scaling the second patch may be determined to generate patch scaling control data. In this way, parameters can be generated based on the function of the frequency. Another alternative may be to generate patch scaling control parameters indicative of the differential function of the first patch and the second patch.

The patch scaling control data 1022 analyzes the input signal 1002 and uses the patch scaling control parameters stored in the patch scaling control parameter memory based on the analysis of the input signal 1002 to obtain the patch scaling control data 1002. Can be generated by selection.

Alternatively, the generation of patch scaling control data 1022 can be realized by analysis by a synthesis approach. For example, patch scaling control data generator 1020 may additionally include a patch generator (as described for the decoder) and a comparator. The patch generator may generate a first patch from a low frequency band of the input signal 1002 according to the first patching algorithm and generate a second patch from a low frequency band of the input signal 1002 according to the second patching algorithm. have. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm. The comparator may compare the high frequency band of the first patch, the second patch and the input signal to obtain the patch scaling control data 1022. In other words, the concepts described above also apply to apparatus 1000. In this manner, apparatus 1000 may extract patch scaling control data 1022 by comparing a patch combined with an input signal, which may be a patch or an original input signal, for example. In addition, the apparatus 1000 may also include a spectral line selector, power controller, noise adder, and / or missing harmonic adder as described above. In this way, also noise data, noise patch scaling control data and missing harmonic patch scaling control data can be extracted by analysis by the synthesis approach.

Some embodiments according to the invention relate to an audio signal comprising a first band and a second band. The first band is represented by the first resolution data and the second band is represented by the second resolution data, wherein the second resolution is lower than the first resolution. The second resolution data is based on the spectral envelope data of the second band and the patch scaling control data of the second band for scaling the first and second patches by the decoder or for scaling the audio signal at the decoder, Thus, the bandwidth extension signal by the decoder satisfies the spectral envelope criterion. Spectral envelope criteria are based on spectral envelope data. The first patch is generated from a first band of audio signal according to the first patching algorithm and the second patch is generated from a first band of audio signal according to the second patching algorithm. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm.

The audio signal may be, for example, a bandwidth reduction signal based on the original audio signal. The first band of the audio signal may represent a low frequency band of the original audio signal encoded with high resolution. The second band of the audio signal may represent a high frequency band of the original audio signal and is quantized by at least two parameters, a spectral envelope parameter represented by the spectral envelope data and a patch scaling control parameter represented by the patch scaling control data. Based on such an audio signal, a decoder according to the concepts described above can generate a bandwidth extension signal that provides an approximation of the superiority of the original audio signal with improved audio quality compared to known concepts.

11 illustrates a flowchart of a method 1100 for generating a bandwidth extension signal from an input signal according to an embodiment of the present invention. The first signal is represented by the first resolution data and the second band is represented by the second resolution data, and the second resolution is lower than the first resolution. The method 1100 may include generating a first patch 1110, generating a second patch 1120, scaling an input signal 1130, or scaling a first patch and a second patch 1130. And combining 1140 a first band of the first patch, the second patch and the input signal to obtain a bandwidth extension signal. The first patch is generated from a first band of the input signal according to the first patching algorithm (1110) and the second band is generated from a first band of the input signal according to the second patching algorithm (1120). The spectral density of the second patch generated 1120 according to the second patching algorithm is higher than the spectral density of the first patch generated 1110 according to the first patching algorithm. The input signal can be scaled according to the first and second patching algorithms (1130) or the first and second patches can be scaled (1130), so that the bandwidth extension signal meets the spectral envelope criterion.

In addition, the method 1100 may be extended by steps in accordance with the concepts described above. The method 1100 may be implemented, for example, with a computer program running on a computer or microcontroller.

12 illustrates a flowchart of a method 1200 for providing a bandwidth reduction signal based on an input signal according to an embodiment of the present invention. The method 1200 includes determining spectral envelope data based on the high frequency band of the input signal 1210, generating patch scaling control data 1220, low frequency of the input signal to obtain a bandwidth reduction signal. Combining 1230 band, spectral envelope data and patch scaling control data and providing a bandwidth reduction signal 1240 for transmission and storage. The patch scaling control data is generated 1220 in order for the bandwidth extension signal generated by the decoder to scale the bandwidth reduction signal at the decoder or to scale the first and second patches by the decoder so as to meet the spectral envelope criteria. Spectral envelope criteria are based on spectral envelope data. The first patch is generated from the low frequency band of the bandwidth reduction signal according to the first patching algorithm and the second patch is generated from the low frequency band of the bandwidth reduction signal according to the second patching algorithm. The spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm.

In addition, the method 1200 may be extended by steps in accordance with the concepts described above. The method 1200 may be implemented, for example, with a computer program running on a computer or microcontroller.

Some embodiments according to the present invention are directed to an apparatus for generating a bandwidth extension signal using a phase vocoder for bandwidth extension combined with non-linear distortion or noise-charging for higher density spectrum. When applying a phase vocoder for spread spectrum, the frequency lines move further apart. If there is a gap in the spectrum, for example by quantization, the same is increased by diffusion. In energy adaptation, the remaining lines in the spectrum receive too much energy. This is prevented by filling the gap by subsequent harmonics which can be obtained either by noise or by non-linear distortion of the signal. In this way, more energy is distributed between the remaining lines. The concentration of energy in the band for very few frequency lines results in an unnatural or metallic sound. The energy of the previous more bands is combined into the remaining bands.

If there is no gap in the spectrum, but at least noise is present, some of the energy remains in the noise floor. By applying non-linear distortion, it can again be densified by the noise produced by the distortion, on the other hand by the subsequent harmonic portions, which are steered by the proper selection of the signal portion to be distorted.

The bandwidth extension signal can then be, for example, a weighted sum of the signal generated with the aid of the filtered distorted signal and the phase vocoder. In other words, the bandwidth extension signal may be a weighted sum of the first patch, the second patch and the first band of the input signal.

Some embodiments according to the present invention relate to concepts suitable for all audio applications where full bandwidth is not available. For example, for the broadcast of audio content using digital radio services, internet streaming or other audio communication applications, the described concepts may be applied.

While the invention has been described in connection with some embodiments, changes, substitutions, and equivalents exist without departing from the scope of the invention. It should also be noted that there are many alternative ways of implementing the methods and configurations of the present invention. Therefore, the appended claims should be construed as including all such alterations, substitutions, and equivalents without departing from the true spirit and scope of the invention.

In particular, depending on the state, the inventive arrangements can also be implemented in software. Implementation of digital storage media. In particular, it may be on a CD (CD) with electronically readable control signals that can cooperate with a programmable computer system to cause a floppy disk or a corresponding method to be executed. In general, the present invention thus consists of a computer program product having a program code stored on a machine-readable carrier when the computer program product is executed on a computer and also for carrying out the method of the present invention. In other words, the present invention can thus be realized as a computer program having a program code for executing the method of the present invention when the computer program product is executed on a computer.

100: device
102: input signal
110: patch generator
112: the first patch
114: second patch
120: combiner
122: bandwidth extension signal
202: first band
212: first patching algorithm
214: second patching algorithm
220: upper limit frequency of the first band
300: device
310: phase vocoder
320: amplitude clipper
380 discontinuity
400: device
410: Spectrum Line Selector
414: the second patch
500: input
501: bandpass filter
502: downstream oscillator
503: Combiner
510: output
551: Mixer
552: adder
553 low pass
557: output
558: phase unwrapper
559 phase / frequency converter
560: output
598 diffusion factor
600: short time Fourier transform
602 controller
604: IFFT Processor
698: audio signal
700: device
710: Power Controller
720: first power control means
730: second power control means
800: device
900: device
910: Noise Adder
912: Noise Patch
920: missing harmonic adder
922: Missing Harmonic Patch
940: noise power control means
950: missing harmonic power adjusting means
1000: device
1002: input signal
1010 spectral envelope data
1012 spectral envelope data
1020: Patch Scaling Data Generator
1022 patch scaling control data
1030: output interface
1032: bandwidth reduction signal
1302: low frequency band
1312: neighboring patches
1314: the next patch
1320: upper limit frequency

Claims (17)

Bandwidth extension signal from input signal 102, characterized in that the input signal is represented by the first resolution data in the first band and the second resolution data is represented in the second band and the second resolution is lower than the first resolution. In an apparatus (100; 300; 400; 700; 800; 900) for generating 122:
Generate a first patch 112 from a first band of the input signal 102 according to the first patching algorithm and replace the second patch 114 from a second band of the input signal 102 according to the second patching algorithm. And the spectral density of the second patch 114 generated according to the second patching algorithm is higher than the spectral density of the first patch 112 generated according to the first patching algorithm. ); And
A combiner 120 configured to combine the first patch 112, the second patch 114, and the first band of the input signal 102 to obtain a bandwidth extension signal 122,
The apparatus for generating the bandwidth extension signal is set to scale the input signal 102 or scale the first patch 112 and the second patch 114 according to the first patching algorithm and the second patching algorithm. And the bandwidth extension signal satisfies the spectral envelope criterion.
2. The first patching algorithm of claim 1, wherein the first patching algorithm is a harmonic patching algorithm and the patch generator 110 is set to produce a first patch 112, thus allowing the first patch 112 to generate a first signal of the input signal 102. A device comprising only frequencies that are multiple integers of one band of frequencies.
The method of claim 1, wherein the second patching algorithm is a mixed patching algorithm, and the patch generator 110 is set to produce a second patch 114, so that the second patch 114 is configured to generate the first signal of the input signal 102. And a frequency that is a multiple integer of a frequency of one band and a frequency that is not a multiple integer of the frequency of a first band of the input signal (102).
The lower limit frequency of the first patch 112 is equal to the lower limit frequency of the second patch 114, and the upper limit frequency of the first patch 112 is the upper limit frequency of the second patch 114. Device characterized in that the same as.
2. The apparatus of claim 1, comprising a phase vocoder (310) set to produce a first patch (112) according to the first patching algorithm.
2. The apparatus of claim 1, comprising an amplitude clipper (320) configured to generate a second patch (114) according to the second patching algorithm by clipping the first band of the input signal (102).
2. The apparatus of claim 1, comprising a spectral line selector 410 set to select a plurality of frequency lines of the second patch 114 to obtain a modified second patch 414, wherein the frequency line is a first patch if Selected if the corresponding frequency line of 112 is missing, the combiner 120 is set to combine the first patch 112, the modified second patch 414, and the first band of the input signal 102. Apparatus characterized in that the.
The power controller of claim 1, wherein the power controller is configured to control the scaling of the input signal 102 according to the first and second patching algorithms or to control the scaling of the first patch 112 and the second patch 114. 710, the power controller 710 based on the spectral envelope data included by the input signal 102 and at least one stored patch scaling control parameter or patch scaling control data included by the input signal 102. And control scaling.
9. An input according to claim 8, comprising first power adjusting means (720) set to scale an input signal (102) according to a first patching algorithm or to scale a first patch (112). Second power adjusting means 730 configured to scale the signal 102 or to scale the second patch 114, wherein the power controller 710 comprises a first power adjusting means 720 and a second power adjusting. Apparatus characterized in that it is configured to control the means (730).
9. The noise patch 912 of claim 8, comprising a noise adder 910, a missing harmonic adder 920, wherein the noise adder 910 is based on noise data contained by the input signal 102. The missing harmonic adder 920 is set to generate a missing harmonic patch 922 based on the missing harmonic data contained by the input signal 102 and the power controller 710. ) Is set to control the scaling of the noise patch 912 and the missing harmonic patch 922 based on the spectral envelope data, and the combiner 120 is configured to obtain a first bandwidth extension signal 122 to obtain a bandwidth extension signal 122. The patch 112, the second patch 114, the first band of the input signal 102, the noise patch 912, and the missing harmonic patch 922 are set to combine, the power controller 710 being a spectral envelope. First patch 112, second patch 114 based on data , Controlling the scaling of the first band of the input signal (102), the noise patch (912) and the missing harmonic patch (922), thus satisfying the spectral envelope criterion.
In the apparatus 1000 for providing a bandwidth extension signal 1032 based on an input signal 1002:
A spectral envelope data determiner 1010 set to determine spectral envelope data 1012 based on the high frequency band of the input signal 1002;
The bandwidth extension signal by the decoder to generate patch scaling control data 1022 to scale the bandwidth reduction signal 1032 at the decoder to meet the spectral envelope criteria or to scale the first and second patches by the decoder. Wherein the spectral envelope criterion is based on spectral envelope data 1012 and the first patch is generated from a first band of bandwidth reduction signal 1032 according to a first patching algorithm and the second patch is a second patching algorithm. Spectral density of the second patch generated from the first band of the bandwidth reduction signal 1032 according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm. A patch scaling data generator 1020;
Configured to combine the low frequency band, spectral envelope data 1012 and patch scaling control data 1022 of the input signal 1002 to obtain a bandwidth reduction signal 1032 and a bandwidth reduction signal 1032 for transmission and storage. And an output interface (1030) set to provide a.
12. The system of claim 11 wherein the patch scaling data generator is:
Set to generate a first patch from a low frequency band of the input signal 1002 according to the first patching algorithm and set to generate a second patch from a low frequency band of the input signal 1002 according to the second patching algorithm, wherein A patch generator, wherein the spectral density of the second patch generated according to the second patching algorithm is higher than the spectral density of the first patch generated according to the first patching algorithm; And
And a comparator set to compare the high frequency band of the first patch, the second patch, and the input signal (1002) to obtain patch scaling control data (1022).
12. The apparatus of claim 11, further comprising a patch scaling control parameter memory configured to store and provide a plurality of patch scaling control data, wherein the patch scaling data control data generator 1020 is configured to analyze the input signal 1002 and input signal. And generate patch scaling control data (1022) based on the selected patch scaling control parameter based on the analysis of (1002).
A first band represented by the first resolution data; And
A second band represented by second resolution data:
The second resolution is lower than the first resolution, and the second resolution data is used to scale the audio signal at the spectral envelope data and the decoder of the second band or to scale the first patch and the second patch by the decoder. Based on the patch scaling control data of the second band, so that the bandwidth extension signal by the decoder satisfies the spectral envelope criterion, the spectral envelope criterion based on the spectral envelope data, and the first patch is a first patching algorithm. Is generated from the first band of the audio signal according to the second patch and the second patch is generated from the first band of the audio signal according to the second patching algorithm and the spectral density of the second patch generated according to the second patching algorithm is first patched. Higher than the spectral density of the first patch generated according to the algorithm Computer-readable medium having stored thereon an audio signal.
A method for generating a bandwidth extension signal from an input signal wherein the input signal is represented by a first band by first resolution data and a second band by second resolution data, the second resolution being less than the first resolution; For 1100:
Generating (1110) a first patch from a first band of the input signal according to the first patching algorithm;
The spectral density of the second patch generated 1120 according to the second patching algorithm is higher than the spectral density of the first patch generated 1110 according to the first patching algorithm. Generating 1120 a second patch of a first band from a first band of;
Scaling 1130 or scaling the first and second patches according to the first and second patching algorithms, where the bandwidth extension signal meets the spectral envelope criteria; And
Combining 1140 a first patch, a second patch and a first band of an input signal to obtain a bandwidth extension signal;
A method 1200 for generating a bandwidth reduction signal from an input signal:
Determining 1210 spectral envelope data based on the high frequency band of the input signal;
The spectral envelope criterion is based on spectral envelope data, wherein the first patch is generated from the low frequency band of the bandwidth reduction signal according to the first patching algorithm and the second patch is from the low frequency band of the bandwidth reduction signal according to the second patching algorithm. Wherein the spectral density of the second patch generated in accordance with the second patching algorithm is higher than the spectral density of the first patch generated in accordance with the first patching algorithm. Generating 1220 patch scaling control data to scale a bandwidth reduction signal at a decoder to satisfy an envelope criterion or to scale a first patch and a second patch by a decoder;
Combining (1230) the low frequency band, spectral envelope data and patch scaling control data of the input signal to obtain a bandwidth reduction signal; And
Providing (1240) a bandwidth reduction signal for transmission and storage.
A computer readable medium having stored thereon a computer program having program code for executing the method according to claim 15 when the computer program runs on a computer or a microcontroller.

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