apparatus and method for decoding a signal

专利摘要:
APPLIANCE FOR THE DECODING OF A SIGN UNDERSTANDING TRANSIENTS USING A COMBINATION UNIT AND A MIXER. An apparatus for generating a de-correlated signal comprising a transient separator (310; 410; 510; 610; 710; 910), a transient de-correlator (320; 420; 520; 620; 720; 920), a second de-correlator (330 ; 430; 530; 630; 730; 930), a combination unit (340, 440, 540, 640, 740, 940) and a mixer (450; 552; 752; 952), in which the transientess separator (310 ; 410; 510; 610; 710; 910 is adapted to separate an input signal for a first signal component and for a second signal component such that the first signal component comprises transient signal portions of the input signal and such that the second signal component comprises non-transient signal portions of the input signal The combination unit (340; 440; 540; 640; 740; 940) and the mixer (450; 552; 752; 952) are arranged so that a signal decoupled from a combination unit is fed to the mixer (450; 552; 752; 952) as an e signal entry. Figure. 4.
公开号:BR112013004365B1
申请号:R112013004365-2
申请日:2011-07-06
公开日:2021-01-12
发明作者:Sascha Disch；Achim Kuntz；Jürgen Herre；Fabian Kuech；Johannes Hilpert
申请人:Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.；
IPC主号:

专利说明:

[0001] [001] The present invention relates to the field of audio processing and audio decoding, in particular, for decoding a signal comprising transients.
[0002] [002] Audio processing and / or decoding has advanced in many ways. In particular, spatial audio applications have become increasingly important. Audio signal processing is often used to de-correlate or reproduce signals. In addition, signal de-correlation and reproduction are used in the mono to stereo conversion, mono to multi-channel stereo conversion, artificial reverb, stereo enlargement or interactive user mix / playback.
[0003] [003] Various audio signal processing systems employ de-correlation devices. An important example is the application of decorrelation systems in parametric spatial audio decoders to restore the specific properties of decorrelation between two or more signals that are reconstructed from one or more mixing signals. The application of de-correlation devices significantly improves the perceived quality of the output signal, for example, when compared to the stereo intensity. Specifically, the use of de-correlation devices allows the adequate synthesis of spatial sound with a wide sound image, several simultaneous sound objects or environment. However, it is known that the correlation devices also introduce errors such as changes in the structure of the temporal signal, timbre, etc.
[0004] [004] Other examples of application of de-correlation devices in audio processing are, for example, the generation of artificial reverberation to change the spatial impression or the use of de-correlation devices in multi-channel acoustic echo cancellation systems to improve the convergence behavior.
[0005] [005] A typical state-of-the-art application of a de-correlation device in a mono to stereo converter, used for example in Parametric Stereo (PS), is illustrated in Fig. 1, where a mono input signal M (a signal "dry") is provided for a de-correlation device 110. De-correlation device 110 de-correlates the input signal M according to a de-correlation method to provide a de-correlated signal D (a "wet" signal) at its output. The de-correlated signal D is fed to a mixer 120 as a first input signal from the mixer, together with the dry mono signal M as a second input signal from the mixer. In addition, a mixing control unit 130 feeds the conversion control parameters at the input of mixer 120. Mixer 120 then generates two output channels L and R (L = left stereo output channel; R = right output channel stereo) according to an H mix matrix. The mix matrix coefficients can be corrected depending on the signal or with user control.
[0006] [006] Alternatively, the mix matrix is controlled by the additional information that is transmitted along with the mix containing a parametric description of how to convert the mix signals to form the desired multi-channel output. This spatial information is normally generated during the mono mixing process in a concordant signal encoder.
[0007] [007] This principle is widely applied in spatial audio coding as Parametric Stereo, see for example, J. Breebaart, S. van de Par, A. Kohlrausch, E. Schuijers, "High-Quality Parametric Spatial Audio Coding at Low Bit Rates ”(" High Quality Parametric Spatial Audio Coding at Low Transfer Rates ") in Proceedings of AES Convention 116, Berlin, Preprint 6072, May 2004.
[0008] [008] A state of the art typical of the structure of a parametric stereo decoder is illustrated in Fig. 2, where a de-correlation process is carried out in a transformation domain. A set of analysis filters 210 transforms a mono input signal to a transformation domain, for example, a frequency domain. The de-correlation of the transformed mono input signal M is then carried out by the de-correlation device 220 which generates a de-correlated signal D. Both the transformed mono input signal M and the de-correlated signal D are fed into the mixing matrix 230. The mixing matrix 230 it then generates two output signals L and R using conversion parameters, which are provided by the parameter modification unit 240, which has spatial parameters and which is connected to the parameter control unit 250. In Fig. 2, the parameters Spatial can be modified by a user or with additional tools, for example, from post-processing to processing / presentation for a perception of sound in both ears. In this example, the conversion parameters are combined with the parameters of the binaural filters to form the input parameters for the conversion matrix. Finally, the output signals generated by the mixing matrix 230 are fed into a set of synthesis filters 260, which determine the stereo output signal.
[0009] [009] The output L (left) / R (right) of the mixing matrix 230 is calculated from the mono input signal M and the de-correlated signal D according to the mixing rule, for example, by applying the following formula:
[0010] [010] In the mixing matrix, the amount of decorrelated sound fed to the output is controlled according to transmission parameters, for example, the Correlation / Coherence between Channels (ICC) and / or fixed or user-defined settings.
[0011] [011] By concept, the output signal of the output D uncorrelator replaces a residual signal that ideally would allow a perfect decoding of the original L (left) / R (right) signals. The use of output de-correlator D in place of a residual signal in the converter results in savings in the bit transfer rate that would be required to transmit the residual signal. The purpose of the decorrelator is therefore to generate a D signal from the mono signal M, which exhibits similar properties, such as the residual signal, which is replaced by D.
[0012] [012] Correspondingly, in the aspect of the encoder, two types of spatial parameters are extracted: a first group of parameters contains correlation / coherence parameters (for example, ICCs = Correlation / Coherence parameters between Channels) that represent coherence or the cross-correlation between the two input channels that must be encoded. A second group of parameters includes level difference parameters (for example, ILDs = Level Difference parameters between Channels) that represent the level difference between the two input channels.
[0013] [013] In addition, a mixing signal is generated by mixing the two input channels. In addition, a residual signal is generated. Residual signals are signals that can be used to regenerate the original signals by additional use of the mixing signal and a mixing matrix. When, for example, N signals are mixed to form a signal, the mixture is typically one of the N components that result from mapping the N input signals. The remaining components resulting from the mapping (for example, N-1 components) are the residual signals and allow to reconstruct the original N signals through an inverse mapping. This mapping can, for example, be a rotation. The mapping must be carried out in such a way that the mixing signal is maximized and the residual signals are minimized, for example, similar to a transformation of the main axis. For example, the energy of the mix signal must be maximized and the energies of the residual signals must be minimized. When the mixture of two signals generates a signal, the mixture is normally one of the two components that result from the mapping of the two input signals. The remainder of the component resulting from the mapping is the residual signal and allows to reconstruct the 2 original signals by means of an inverse mapping.
[0014] [014] In some cases, the residual signal may represent an error associated with the representation of the two signals by mixing them and the associated parameters. For example, the residual signal can be an error signal, which represents the error between the original channels L, R and channels L ', R', resulting from the conversion of the mixing signal that was generated based on channels L and R. originals.
[0015] [015] In other words, a residual signal can be considered as a signal in the time domain or in the frequency domain of one or a subband domain, which together with the mixing signal alone or with the combination between the mixing signal and parametric information allows a correct or almost correct reconstruction of an original channel. The definition of the term "almost correct" has to be understood in such a way that the reconstruction with the residual signal with an energy greater than zero is somewhat closer to the original channel compared to a reconstruction using a mixture without the residual signal or using the mixture and parametric information without the residual signal.
[0016] [016] Considering the MPEG Surround (MPS) format, PS-like structures called one-to-two boxes (OTT boxes) are used in the spatial audio decoding trees. This can be seen as a generalization of the concept from mono to stereo conversion schemes to spatial audio encoding / decoding schemes. In the MPS format, two-to-three conversion systems (TTT boxes) can also apply de-correlators, depending on the TTT operating mode. Details are described in the document J. Herre, K. Kjorling, J. Breebaart, et al., “MPEG surround — the ISO / MPEG standard for efficient and compatible multi-channel audio coding,” ("MPEG surround format - the standard ISO / MPEG for compatible and efficient multi-channel audio coding ", in Proceedings of the AES 122th Vienna Convention, Austria, May 2007.
[0017] [017] As for Directional Audio Coding (DirAC), DirAC concerns a parametric sound field coding scheme that is not linked to a fixed number of audio output channels with fixed speaker positions. Dirac applies decorrelators in the Dirac processor, that is, in the spatial audio decoder to synthesize non-coherent components of sound fields. More information regarding directional audio coding can be found at Pulkki, Ville: “Spatial Sound Reproduction with Directional Audio Coding”, in J. Audio Eng. Soe., Vol 55, No. 6, 2007.
[0018] [018] In relation to state-of-the-art decelators in spatial audio decoders, reference is made to the International Standard ISO / IEC “Information Technology-MPEG audio technologies - Part1: MPEG Surround” ("Information Technology - MPEG Audio Technology - Part 1: MPEG Surround "), ISO / IEC 23003-1: 2007 and also for J. Engdegard, H. Purnhagen, J. Roden, L.Liljeryd “Synthetic Ambience in Parametric Stereo Coding” in the procedures of AES Convention 116, Berlin, prepress, May 2004. Filter structures infinite time response (IIR) that pass all frequencies equally are used as decorrelators in spatial audio decoders such as the MPS format, as described in J. Herre, K. Kjörling, J. Breebaart, et al. "MPEG surround — the ISO / MPEG standard for efficient and compatible multi-channel audio coding,” ("MPEG Surround format - the ISO / MPEG standard for compatible and efficient multi-channel audio coding"), in the AES Proceedings, Convention 122 in Vienna, Austria, May 2007, and as described in the international ISO / IEC standard "Information Technology- MPEG audio technologies - Part 1: MPEG Surround” ("Information Technology - MPEG audio technologies - Part 1: MPEG Surround" ) ISO / IEC 23003-1: 2007. Other de-correlators with this state of the art apply (potentially frequency-dependent) delays to the de-correlated signals or promote convolution of the input signals, for example, with exponentially decomposing noise peaks. For an overview of decelators with this state of the art for spatial audio conversion systems, see "Synthetic Ambience in Parametric Stereo Coding" in the AES Convention 116 Annals, Berlin, prepress, May 2004.
[0019] [019] Another signal processing technique is "semantic conversion processing". Semantic conversion processing is a technique to decompose the signals into components with different semantic properties (ie, signal classes) and to apply different conversion strategies to the different signal components. The different conversion algorithms can be optimized according to the different semantic properties, in order to improve the overall signal processing scheme. This concept is described in WO / 2010/017967, "An apparatus for determining a spatial output multichannel-channel audio signal", International patent application, PCT / EP2009 / 005828, 11.8.2009, 2010/11/06 (FH090802PCT).
[0020] [020] An additional spatial audio coding scheme is the "time permutation method", as described by Hotho, G., van de Par, S., and Breebaart, J .: "Multichannel coding of applause signals" ( "The multi-channel coding of applause signals"), EURASIP Journal on Advances in Signal Processing, January 2008, art.10. DOI = http://dx.doi.org/10.1155/2008/. In this document, a spatial audio coding scheme is proposed, adapted for the coding / decoding of signals as applause.
[0021] [021] This scheme is based on the perceptual similarity of segments of a monophonic audio signal, specifically a mixing signal from a spatial audio encoder. The monophonic audio signal is segmented into overlapping time segments. These segments are temporarily pseudo-randomly exchanged (mutually independent for n-output channels) within a "super" -block, to form the uncorrelated output channels.
[0022] [022] An additional spatial audio coding technique is "time delay and switching method". In Patent DE 10 2007 0180 32 A: 20070417, Erzeugungng dekorrelierter Signale, 2007/04/17, 2008/10/23 (FH070414PDE), a scheme is proposed that is also adapted for the encoding / decoding of signals such as applause, for binaural presentation. This scheme also depends on the similarity in the perception of segments of a monophonic audio signal and delays in the output channels in relation to the other signal. In order to avoid a deviation of location for the main channel, guide and delay channels are changed periodically.
[0023] [023] In general, applause-like multichannel or stereo signals encoded / decoded in spatial audio encoders are responsible for reducing signal quality (see, for example, Hotho, G., van de Par, S., and Breebaart, J .: “Multichannel coding of applause signals” (EURASIP Journal on Advances in Signal Processing), January 2008, art.10 DOI = http : //dx.doi.org/10.1155/2008/531693, see also DE 10 2007 0180 32 A). Applause-like signs are characterized by temporarily dense mixtures of transients from different directions. Examples of such signs are applause, the sound of rain, galloping horses, etc. Applause-like signals often also contain components of sound from distant sound sources, which are perceptibly merged into a background noise sounding like soft noise.
[0024] [024] State-of-the-art de-correlation techniques employed in spatial audio decoders such as MPEG Surround contain pass-through structures. These act as artificial reverberation generators and are, therefore, well suited to generate immersion sounds such as soft, homogeneous noises (such as room reverberation tails). However, there are examples of acoustic fields with an inhomogeneous temporal space structure that are still involving the listener: a prominent example is applause-like sound fields that create a wrap around the listener, not only by homogeneous noise fields, but also by rather dense sequences of individual palms from different directions. Thus, the non-homogeneous component of the applause sound can be characterized by a spatially distributed mixture of transients. Obviously, these distinct applause are by no means homogeneous or subdued.
[0025] [025] Due to the reverberation behavior, the frequency-passing de-correlation devices are unable to generate an immersive sound field with the characteristics, for example, of applause. Instead, when applied to applause-like signals, they tend to spread the transients temporarily over the signals. The undesirable result is a surround sound field without the distinctive temporal space structure of applause-like sound fields. Other transient events, such as a single palm, could trigger sound error from the defrost filters.
[0026] [026] A system according to Hotho, G., van de Par, S., and Breebaart, J .: "Multichannel coding of applause signals”, "EURASIP Journal on Advances in Signal Processing, Jan. 2008, art.10 DOI = http://dx.doi.org/10.1155/2008/531693, will expose the noticeable degradation of the output sound, due to a certain repetitive quality in the audio signal of This is due to the fact that one and the same segment of the input signal appears unchanged on each output channel (albeit at a different point in time) .In addition, to avoid the increased density of applause, some original channels have to be dropped in the conversion and thus some important auditory event can be lost in the resulting conversion. The method is only applicable if it is possible to find signal segments that share the same perceptual properties, that is: signal segments that look similar. , in general, alters the temporal structure of the signals, which and it may be acceptable only for very few signs. In the case of applying the scheme for applause-like signs (for example, due to signal classification error), temporal permutation will most often lead to unacceptable results. Temporal permutation further limits the applicability to cases where several signal segments can be mixed without error such as echoes or comb filter. Similar drawbacks apply to the method described in DE 10 2007 0180 32 A.
[0027] [027] The processing of the semantic conversion described in WO / 2010/017967 separates the transient components of signals before the application of the decorrelators. The remaining (transient-free) signal is fed to the conventional de-correlation and to the conversion processor, while the transient signals are treated differently: the latter are (for example, randomly) distributed to different stereo channels for multi-channel output signal by applying amplitude balance techniques. The amplitude balance shows several disadvantages:
[0028] [028] The amplitude balance does not necessarily produce an output signal that is similar to the original. The output signal can only be close to the original if the distribution of the transients in the original signal can be described by amplitude balance laws. In other words, the amplitude balance can only reproduce purely balanced amplitude events correctly, but not the phase or time differences between the transient components in different output channels.
[0029] [029] Furthermore, the application of the amplitude balance approach in MPS would require a deviation not only from the decorrelator but also from the conversion matrix. Since the conversion matrix reflects the spatial parameters (Correlations between channels: ICCs, Level differences between channels: ILDs) that are needed to synthesize a conversion output that shows the correct spatial properties, the balance system itself has to apply some rule to synthesize the output signals with the correct spatial properties. A general rule for doing this is not known. In addition, this structure increases the complexity since the spatial parameters have to be checked in two moments: first for the non-transient part of the signal and, second, for the balanced transient part of the signal amplitude.
[0030] [030] It is, therefore, an object of the present invention to offer an improved concept for generating a decorrelated signal to decode a signal. The object of the present invention is solved by a device for generating and decoding a signal according to claim 1, through a method for decoding a signal according to claim 13 and by a computer program according to claim 14.
[0031] [031] An apparatus according to a characterization comprising a transient separator for separating an input signal for a first signal component and for a second signal component such that the first signal component comprises portions of the signal's transient signal input and such that the second signal component comprises non-transient signal portions of the input signal. The transient separator can separate the different signal components from one another to allow the signal components that comprise the transients to be processed differently than the signal components that do not contain transients.
[0032] [032] The apparatus further comprises a transient de-correlator for de-correlating signal components containing the transients according to a de-correlation method, which is particularly suitable for de-correlating the signal components comprising transients. In addition, the apparatus comprises a second de-correlator for de-correlating signal components that do not comprise transients.
[0033] [033] Thus, the device is capable of processing either signal components using a standard decelelerator or, alternatively, processing the signal components using the transient decelerator particularly suitable for processing transient signal components. In a characterization, the transient separator decides whether a signal component is fed to a standard de-correlator or to a transient de-correlator.
[0034] [034] In addition, the apparatus can be adapted to separate a signal component in such a way that the signal component is partially fed to a transient de-correlator and partially fed to a second de-correlator.
[0035] [035] In addition, the apparatus comprises a combining unit for combining the output signal components by the standard de-correlator and the transient de-correlator to generate a de-correlated combination signal.
[0036] [036] In a characterization, the device comprises a mixer, being adapted to receive input signals and, furthermore, being adapted to generate output signals based on the input signals and the mixing rule. An input signal from the apparatus is fed into a transient separator and then de-correlated by a transient separator and / or a second de-correlator as described above. The combining unit and the mixer can be arranged so that the uncorrelated combination signal is fed to the mixer, as a first input signal from the mixer. A second input signal from the mixer can be the input signal from the device or a signal derived from the input signal from the device. Since the de-correlation process is already complete when the de-correlated combination signal is fed into the mixer, the transient de-correlation does not need to be taken into account by the mixer. Therefore, a conventional mixer can be employed.
[0037] [037] In another characterization, the mixer is adapted to receive correlation / coherence parameter data indicating a correlation or coherence between the two signals and is adapted to generate the output signals based on the correlation / coherence parameter data. In another embodiment, the mixer is adapted to receive level difference parameter data indicating a power difference between the two signals and is adapted to generate the output signals based on the level difference parameter data. In such a characterization, the transient de-correlator, the second de-correlator and the combining unit do not have to be adapted to process such parameter data, as the mixer will process the corresponding data. On the other hand, a conventional mixer with conventional correlation / coherence and level difference parameter processing can be employed in such characterization.
[0038] [038] In a characterization, the transient separator is adapted to feed a portion of the signal considered from an input signal from the apparatus to the transient de-correlator or to feed the portion of the signal considered in the second de-correlator, depending on the transient separation information , which indicates that the considered signal portion comprises a transient or indicates that the considered signal portion does not comprise a transient. This characterization allows for easy processing of transient separation information.
[0039] [039] In another characterization, the transient separator is adapted to partially feed a portion of the signal considered from an input signal of the apparatus to a transient de-correlator and to partially feed the portion of the signal considered in the second de-correlator. The amount of the considered signal portion that is fed into the transient separator and the amount of the considered signal portion that is fed to the second de-correlator depends on the transient separation information. Therefore, the strength of a transient can be taken into account.
[0040] [040] In another characterization, the transient separator is adapted to separate an input signal from a device that is represented in a frequency domain. This allows for frequency-dependent transient processing (separation and de-correlation). Thus, certain components of the signal from a first frequency band can be processed according to a transient de-correlation method, while signal components from another frequency band can be processed according to another method, for example, a method conventional de-correlation. Thus, in a characterization, the transient separator is adapted to separate an input signal from an apparatus based on the frequency-dependent transient separation information. However, in an alternative characterization, the transient separator is adapted to separate an apparatus input signal based on the frequency independent separation information. This allows for more efficient transient signal processing.
[0041] [041] In another characterization, the transient separator can be adapted to separate an input signal from a device that is represented in a frequency domain, in such a way that all parts of the device's input signal within a first range of frequencies are fed to a second de-correlator. A corresponding apparatus is therefore adapted to restrict the transient signal processing for signal components with signal frequencies in a second frequency range, while no signal components with signal frequencies in the first frequency range are fed into the decelector transient (but instead for the second decelerator).
[0042] [042] In an additional characterization, the transient de-correlator can be adapted to de-correlate the first signal component by applying phase information that represents the phase difference between a residual signal and a mixing signal. In the aspect of the encoder, a "reverse" mixing matrix can be used to create a mixing signal and a residual signal, for example, from the two channels of a stereo signal, as explained above. While the mixing signal can be transmitted to the decoder, the residual signal can be discarded. According to a characterization, the phase difference employed by the transient decoupler can be the phase difference between the residual signal and the mixing signal. It may thus be possible to reconstruct an "artificial" residual signal, by applying the initial phase of the residual in the mixture. In a characterization, the phase difference can be related to a certain frequency band, that is, it can be dependent on the frequency. Alternatively, a phase difference does not refer to certain frequency bands, but it can be applied as a frequency independent broadband parameter.
[0043] [043] In a characterization, the apparatus comprises a receiving unit for receiving phase information, in which the transient decelerator is adapted to apply the phase information to the first signal component. The phase information can be generated by a suitable encoder.
[0044] [044] In a further characterization, a phase condition can be applied to the first signal component by multiplying the phase condition with the first signal component.
[0045] [045] In a further characterization, the second de-correlator can be a conventional de-correlator, for example, a de-correlator with infinite time response filter (IIR) structures.
[0046] [046] The characterizations are now explained in more detail with reference to the figures, in which: Fig. 1 illustrates a state of the art application of a de-correlator in a mono to stereo converter. Fig. 2 illustrates another application of the state of the art of a de-correlator in a mono to stereo mixing unit. Fig. 3 illustrates an apparatus for generating a decorrelated signal according to a characterization. Fig. 4 illustrates an apparatus for decoding a signal according to a characterization; Fig. 5 is an overview of the one-to-two system (OTT) according to a characterization. Fig. 6 illustrates an apparatus for generating a decorrelated signal comprising a receiving unit according to another characterization; Fig. 7 is an overview of the one-to-two system according to another form of characterization; Fig. 8 illustrates examples of mappings of phase consistency measurements to a transient separation resistance; Fig. 9 is an overview of the one-to-two system according to another additional characterization; Fig. 10 illustrates an apparatus for encoding an audio signal that has a plurality of channels according to a characterization.
[0047] [047] Fig. 3 illustrates an apparatus for generating a decorrelated signal according to a characterization. The apparatus comprises a transient separator 310, a transient de-correlator 320, a conventional de-correlator 330 and a combination unit 340. The transient treatment approach of this characterization is intended to generate applause signals that are decorrelated from applause-like audio signals. , for example, for the application in the conversion process of spatial audio decoders.
[0048] [048] In Fig. 3, an input signal is supplied to a transient separator 310. The input signal may have been transformed into a frequency domain, for example, by applying a set of QMF hybrid filters. The transient separator 310 can decide for each signal component considered in the input signal whether it contains a transient. In addition, the transient separator 310 can be arranged to feed the considered signal portion to either the transient decelerator 320, if the signal portion considered contains a transient (signal component s1), or it can feed the portion of the signal considered in the conventional decorrelator 330, if the signal portion considered does not contain a transient (signal component s2). The transient separator 310 can also be arranged so as to divide the part of the considered signal depending on the existence of a transient in the considered portion of the signal and to supply them partially to the decelerator 320 and partially to the conventional decelerator 330.
[0049] [049] In a characterization, the transient decelrelator 320 decelelates the signal component s1 according to a transient decelelation method that is particularly suitable for decelrelating the transient signal components. For example, the de-correlation of the components of the transient signal can be performed by applying phase information, for example, by applying phase conditions. A method where the phase de-correlation conditions are applied to the transient signal components is explained below in relation to the characterization of Fig. 5. Such a de-correlation method can also be used as a transient de-correlation method of the transient de-correlator 320 of the characterization of Fig. 3.
[0050] [050] The signal component s2, which comprises non-transient signal portions, is fed to the conventional de-correlator 330. The conventional de-correlator 330 can then de-correlate the signal component s2 according to a conventional method of de-correlation, for example, through the application of frequency passing structures, for example, an IIR filter (infinite impulse response).
[0051] [051] After having been de-correlated by the conventional de-correlator 330, the de-correlated signal component from the conventional de-correlator 330 is fed to the combination unit 340. The de-correlated transient signal component from the transient de-correlator 320 is also fed into the unit combination unit 340. The combination unit 340 then combines both components of the de-correlated signal, for example, by adding both signal components, to obtain a de-correlated combination signal.
[0052] [052] In general, a method that de-correlates a signal containing transients according to a characterization can be performed as follows:
[0053] [053] In a separation step, the input signal is separated into two components: a component s1 containing the transients of the input signal, another component s2 containing the remaining (non-transient) part of the input signal. The non-transient component s2 of the signal can be processed as in systems without the application of the transient de-correlation de-correlation method of this characterization. In other words: the transient-free signal s2 can be fed to one or more conventional deceleration signal processing structures as structures similar to IIR frequency pass structures (infinite impulse response).
[0054] [054] In addition, the signal component containing the transients (the transient flow s1) is fed into a "transient de-correlator" structure that de-correlates the transient flow, maintaining the special signal properties better than conventional structures de-correlation. The de-correlation of the transient flow is carried out by applying information in a high temporal resolution. Preferably, the phase information comprises the conditions of the phase. In addition, it is preferable that the phase information is provided by an encoder.
[0055] [055] In addition, the output signals from both the conventional decelerator and the transient decelerator are combined to form the decorrelated signal that can be used in the conversion process of the spatial audio encoders. The elements (h11, h12, h21, h22) of the mixing matrix (Mmix) of the spatial audio decoder can remain unchanged.
[0056] [056] Fig. 4 illustrates an apparatus for decoding an apparatus input signal according to a characterization, where the apparatus input signal is fed to the transient separator 410. The apparatus comprises the transient separator 410, a transient de-correlator 420, a conventional de-correlator 430, a combination unit 440 and a mixer 450. The transient separator 410, the transient de-correlator 420, the conventional de-correlator 430 and the combination unit 440 of this characterization may be similar to the separator of transients transients 310, transient de-correlator 320, conventional de-correlator 330 and combination unit 340 of the characterization of Fig. 3, respectively. A de-correlated combination signal generated by the combination unit 440 is fed to a mixer 450 as a first input signal from the mixer. In addition, the input signal from an apparatus, which has been fed to the transient separator 410, is also fed to the mixer 450, as a second input signal from the mixer. Alternatively, the device input signal is not fed directly to the mixer 450, but a signal derived from the device input signal is fed to the mixer 450. A signal can be derived from the device input signal, for example example, by applying a conventional signal processing method to the device's input signal, for example, by applying a filter. The mixer 450 of the characterization of FIG. 4 is adapted to generate output signals based on the input signals and a mixing rule. Such a mixing rule can be, for example, to multiply the input signals and a mixing matrix, for example, by applying the formula:
[0057] [057] The mixer 450 can generate the output channels L, R, based on the data of correlation / coherence parameters, for example, the Correlation / Coherence between Channels (ICC), and / or the data of difference parameters of level, for example, a Level Difference Between Channels (ILD). For example, the coefficients of a mixture matrix may depend on the correlation / coherence parameter data and / or the level difference parameter data. In the characterization of Fig. 4, mixer 450 generates two output channels L and R. However, in alternative characterizations, the mixer can generate a plurality of output signals, for example, 3, 4, 5 or 9 output signals. , which can be engaging beeps.
[0058] [058] Fig. 5 shows a system overview of the transient treatment approach in a 1 to 2 conversion (OTT) system of a characterization, for example, a 1-to-2 box of a spatial audio decoder MPS (MPEG Surround). The parallel signal path for the separate transients according to a characterization is constituted in the U-shaped transient handling box. An input signal from the DMX device is supplied to a transient separator 510. The input signal from the device can be represented by a frequency domain. For example, a time domain input signal may have been transformed into a frequency domain by applying a set of QMF filters, as used in the MPEG Surround format. The transient separator 510 can then supply the input signal components of the DMX apparatus to a transient de-correlator 520 and / or an IIR (infinite time response) frequency-pass de-correlator. The input signal components of the device are then de-correlated by the transient de-correlator 520 and / or by the IIR (infinite time response) 530. Then the de-correlated signal components D1 and D2 are combined by a combination unit 540, for example. example, by adding both signal components, to obtain a de-correlated combination signal D. The de-correlated combination signal is fed to a mixer 552, as a first input signal from mixer D. In addition, the input signal of the mixer DMX device (or, alternatively: a signal derived from the input signal of the DMX device) is also fed into the mixer 552, as a second input signal from the mixer. The mixer 552 then generates a first and a second "dry" signal, depending on the input signal of the DMX device. Mixer 552 also generates a first and second "wet" signal, depending on the combination of the de-correlated signal D. The signals, generated by mixer 552, can also be generated based on the transmitted parameters, for example, the correlation parameter data / coherence, for example, Correlation / Coherence between Channels (ICC), and / or the data of the level difference parameters, for example, Level Difference between Channels (ILD). In a characterization, the signals generated by the mixer 552 can be supplied to a modeling unit 554, which models the supplied signals based on the provided temporal modeling data. In other characterizations, no signal modeling is performed. The generated signals are then supplied to a first 556 or second 558 addition unit that combine the supplied signals to generate a first output signal L and a second output signal R, respectively.
[0059] [059] The processing principles, represented in Fig. 5, can be applied in mono-to-stereo conversion systems (for example, stereo audio encoders), as well as in multiple channel configurations (for example, MPEG Surround format ). In characterizations, the proposed transient treatment scheme can be applied as an enhancement to existing conversion systems without major conceptual modifications to the conversion system, since only a parallel decelerator signal path is introduced, without changing the conversion process. in itself.
[0060] [060] The signal separation in the transient and non-transient component is controlled by the parameters that can be generated in an encoder and / or in the spatial audio decoder. The transient de-correlator 520 uses the phase information, for example, the phase conditions that can be obtained from the spatial audio encoder or decoder. Possible variants for obtaining transient handling parameters (ie: transient separation parameters as transient positions or the separation force and transient de-correlation parameters as phase information) are described below.
[0061] [061] The input signal can be represented in a frequency domain. For example, a signal may have been transformed into a frequency domain using a set of analysis filters. A set of QMF filters can be applied to obtain a plurality of subband signals from a time domain signal.
[0062] [062] For better quality of perception, transient signal processing may preferably be restricted to signal frequencies in the limited frequency range. An example would be to limit the processing range of the frequency band to the k = 8 indices of a set of hybrid QMF filters, as used in the MPS format, similar to the frequency band limitation of guided envelope modeling (GES) in MPS format.
[0063] [063] In the following, characterizations of a 520 transient separator are explained in more detail. The transient separator 510 divides the DMX input signal into transient and non-transient components S1 and S2, respectively. The transient separator 510 can employ transient separation information to divide the DMX input signal, for example a transient separation parameter β [n]. The division of the DMX input signal can be done in such a way that the sum of the component, s1 + s2, is equal to the DMX input signal: s1 [n] = DMX [n] · β [n] s2 [n] = DMX [n] - (1 - β [n]) where n is the time index of the subband signals with data size reduction and the valid values for the parameter β [n] of the transient separation with time variant are in the range [0, 1]. β [n] can be an independent parameter of frequency. A transient separator 510 that is adapted to separate an instrument input signal based on a frequency independent separation parameter can feed all subband signal portions with time index n, either to the transient de-correlator 520 or for the second de-correlator depending on the value of β [n].
[0064] [064] Alternatively, β [n] can be a frequency-dependent parameter. A transient separator 510, which is adapted to separate an input signal from device l based on frequency-dependent transient separation information, can process portions subband signal with the same time index but differently, if the corresponding transient separation information differs.
[0065] [065] In addition, frequency dependency can, for example, be used to limit the frequency range of transient processing as mentioned in the previous section.
[0066] [066] In a characterization, the transient separation information can be a parameter that indicates that the considered portion of a DMX input signal contains a transient or that the considered portion of the signal does not contain a transient. The transient separator 510 feeds the signal portion considered for the transient de-correlator 520, if the transient separation information indicates that the considered signal portion contains a transient. Alternatively, the transient separator 510 feeds the signal portion considered in the second de-correlator, for example, in the IIR (infinite time response) de-correlator 530, if the transient separation information indicates that the considered portion of the signal contains a transient.
[0067] [067] For example, a transient separation parameter β [n] can be used as transient separation information that can be a binary parameter. n is the time index of a considered input signal portion of the DMX input signal. β [n] can be 1 (indicating that the signal part considered must be fed into the transient de-correlator) or 0 (indicating that the signal part considered must be fed into the second de-correlator). Restricting β [n] to β ∈ {0, 1} results in difficult decisions between transients / non-transients, that is: components that are treated as transients are completely separated from the input (β = 1).
[0068] [068] In another characterization, the transient separator 510 is adapted to partially feed a portion of the signal considered from the input signal of the apparatus to the transient de-correlator 520 and to partially feed the portion of the signal considered in the second de-correlator 530. The value of part of the signal considered that is fed into the transient separator 520 and the amount of the part of the signal considered that is fed to the second de-correlator 530 depends on the information of the transient separation. In a characterization, β [n] must be in the range [0, 1]. In another characterization, β [n] can be limited to β [n] [0, max β], where max β <1 results in a partial separation of the transients, leading to a less pronounced effect of the transient treatment scheme. Therefore, changing βmax allows the transition between the output of conventional conversion processing without transient manipulation and the conversion processing including the treatment of transients.
[0069] [069] In the following, a transient de-correlator 520 according to a characterization is explained in more detail.
[0070] [070] A transient de-correlator 520, according to a characterization, creates an output signal that is sufficiently de-correlated at the input. This does not change the temporal structure of individual / transient applause (without temporal spread, without delay). Instead, it leads to a spatial distribution of the transient signal components (after the conversion process), which is similar to the spatial distribution in the original (uncoded) signal. Transient uncorrelator 520 can allow exchanges between bit rate and quality (for example, a totally random spatial transient distribution if there is low bit transfer ↔ close to the original (almost transparent) with high bit transfer rate). In addition, this is achieved with low computational complexity.
[0071] [071] As explained above, in the aspect of the encoder, a "reverse" mixing matrix can be used to create a mixing signal and a residual signal, for example, from the two channels of a stereo signal. While the mixing signal can be transmitted to the decoder, the residual signal can be discarded. According to a characterization, the phase difference between the residual signal and the mixing signal can be determined, for example, by an encoder, and can be used by a decoder when performing the signal de-correlation. Therefore, it may then be possible to reconstruct an "artificial" residual signal by applying the original phase of the residual in the mixture.
[0072] [002] A corresponding method of 520 transient de-correlation according to a characterization will be explained below:
[0073] [001] According to a transient de-correlation method, a phase condition can be employed. The de-correlation is achieved by simply multiplying the transient current of phase conditions in high temporal resolution, for example, the time resolution of the subband signal in the transformation domain, such as MPS systems: D1 [n] = s1 [n] · ejΔ [n]
[0074] [002] In this equation, n is the time index of the subband signals with data size reduction. Δφ ideally reflects the phase difference between the mixture and the residual. Therefore, the transient residues are replaced with a copy of the mixture's transients, modified in such a way that they exhibit the original phase.
[0075] [003] Applying the phase information inherently results in a balance of the transients for the mixing process. As an illustrative example, consider the case ICC = 0, ILD = 0: the transient part of the output signals is then read as: L [n] = c · (s [n] + D1l [n]) = c · s [n] (1 + ej · Δφ [n]) R [n] = c · (s [n] - D1 [n]) = c · s [n] · (1 - ej.Δφ [n])
[0076] [004] For Δφ = 0, this results in L = 2c * s, R = 0, while Δφ = π, leads to L = 0, R = 2-C * s. Other values of Δφ, ICC, and ILD lead to different levels and phase relationships between the reproduced transients.
[0077] [005] The Δφ [n] values can be applied as parameters of the independent broadband frequency, or as frequency dependent parameters. In the case of signs similar to applause without tonal components, the Δφ [n] bandwidth values can be advantageous due to the lower data rate requirement and consistent manipulation of broadband transients (consistency across the frequency).
[0078] [006] The transient handling structure of Fig. 5 is arranged in such a way that only the conventional 530 de-correlator is offset in relation to the transient signal components while the mixing matrix remains unchanged. Thus, spatial parameters (ICC, ILD) are inherently also taken into account for transient signals, for example: the ICC automatically controls the width of the reproduced transient distribution.
[0079] [007] Considering the aspect of how to obtain phase information, in a characterization, the phase information can be received from an encoder.
[0080] [008] Fig. 6 illustrates a characterization of an apparatus for generating a de-correlated signal. The apparatus comprises a transient separator 610, a transient de-correlator 620, a conventional de-correlator 630, a combination unit 640 and a receiving unit 650. The transient separator 610, the conventional de-correlator 630 and the combination unit 640 are similar to the transient separator 310, the conventional de-correlator 330 and the combination unit 340 of the characterization shown in Fig. 3. However, Fig. 6 further illustrates a receiving unit 650, which is adapted to receive phase information . The phase information may have been transmitted by an encoder (not shown). For example, an encoder may have calculated the phase difference between residual and mix signals (relative phase of the residual signal with respect to a mix). The phase difference may have been calculated for certain frequency or broadband bands (for example, in a time domain). The encoder can appropriately encode the values of the uniform or non-uniform quantization phase, and potentially encode lossless. The encoder can then transmit the encoded phase values to the spatial audio decoding system. Obtaining the phase information from an encoder is advantageous since the information of the original phase is then possible in a decoder (except for the quantization error).
[0081] [009] The receiving unit 650 feeds the phase information to the transient de-correlator 620 which uses the phase information when a signal component is de-correlated. For example, the phase information can be a condition of the phase and the transient de-correlator 620 can multiply a received transient signal component by the condition of the phase.
[0082] [010] In the case of transmission of the Δφ [n] phase information from the encoder to the decoder, the required data rate can be reduced as follows:
[0083] [011] The phase information Δφ [n] can be applied only to the transient signal components in the decoder. Therefore, the phase information only needs to be available in the decoder while there are transient components in the signal to be decorrelated. The transmission of the phase information can thus be limited by the encoder such that only the necessary information is transmitted to the decoder. This can be done by applying a transient detection to the encoder, as described below. The Δ fase [n] phase information is transmitted only to points in time n, for which transients have been detected in the encoder.
[0084] [012] Considering the aspect of transient separation, in a characterization, the transient separation can be triggered by an encoder.
[0085] [013] According to a characterization, the transient separation information (also referred to as "the transient information") can be obtained from an encoder. The encoder can apply transient detection methods, as described by Andreas Walther, Christian Uhle, Sascha Disch "Using Transient Suppression in Blind Multi-channel Up-mix Algorithms” ("Using Transient Suppression in Blind Multi-Channel Conversion Algorithms" ") in Proc. 122 AES Vienna Convention, Austria, May 2007, either for the encoder input signals or for the mixing signals. The transient information is then transmitted to the decoder and preferably obtained, for example, from time resolution of subband signals with reduced data size.
[0086] [014] The transient information can preferably comprise a simple binary decision (transient / non-transient) for each signal sample over time. This information can preferably also be represented by the positions of the transients in time and the durations of the transients.
[0087] [015] Transient information can be encoded without loss (for example, with encoding with data sequence compression, independent compression of characteristics) to reduce the data rate that is required to transmit transient information from the encoder to the decoder .
[0088] [016] Transient information can be transmitted as broadband information, or as frequency-dependent information at a given frequency resolution. The transmission of transient information as broadband parameters reduces the data rate of transient information and potentially improves audio quality due to the consistent handling of broadband transients.
[0089] [017] Instead of the binary decision (transient / non-transient), the strength of the transients can be transmitted, that is, quantified in two or four steps. The force of transients can then control the separation of the transients in the spatial audio decoder as follows: the strong transients are completely separated from the input of the IIR decoder, while the weaker transients are only partially separated.
[0090] [018] Transient information can only be transmitted if the encoder detects applause-like signals, for example, using applause detection systems, as described by Christian Uhle, "Applause Sound Detection with Low Latency" with Low Latency "), Convention 127 of the" Audio Engineering Society ", New York, 2009.
[0091] [019] The detection result for the similarity between the input signal to applause signals can also be transmitted with a lower time resolution (for example, the spatial parameter update rate in MPS) to the decoder to control the force transient separation. The result of the applause detection can be transmitted as a binary parameter (that is, as a difficult decision), or as a non-binary parameter (that is, as an easy decision). This parameter controls the separation force in the spatial audio decoder. Therefore, it allows (hardly or gradually) to turn on / off the handling of transients in the decoder. This makes it possible to avoid errors that may occur, for example, when applying a transient handling scheme for signals containing tonal components.
[0092] [020] Fig. 7 illustrates an apparatus for decoding a signal according to a characterization. The apparatus comprises a transient separator 710, a transient de-correlator 720, an IIR 730 de-correlator, a combination unit 740, a mixer 752, an optional modeling unit 754, a first addition unit 756 and a second addition unit 758 , which correspond to the transient separator 510, the transient de-correlator 520, the de-correlator IIR 530, the combination unit 540, the mixer 552, the optional modeling unit 554, the first addition unit 556 and the second addition unit 558 of characterization of fig. 5, respectively. In the characterization of Fig. 7, an encoder obtains the phase information and the information about the position of the transients and transmits the information to a decoding device. No residual signal is transmitted. Fig. 7 illustrates a 1-to-2 conversion configuration as an OTT box in MPS format. It can be applied in a stereo codec (encoder decoder) system for conversion from a mono mix to a stereo output according to a characterization. In the characterization of Fig. 7, three transient handling parameters are transmitted as frequency independent parameters from the encoder to the decoder, as can be seen in Fig. 7:
[0093] [021] A first transient handling parameter to be transmitted is the transient / non-transient binary decision of a transient detector operating on the encoder. It is used to control the separation of transients in the decoder. In a simple scheme, the transient / non-transient binary decision can be transmitted as a binary flag per subband time sample without additional coding.
[0094] [022] An additional transient handling parameter to be transmitted is the phase value (or phase values) Δφ [n] required for the transient decelerator. Δφ is transmitted only for times n, for which transients are detected in the encoder. The Δφ values are transmitted as indices of a quantizer with a resolution of, for example, 3 bits per sample.
[0095] [023] Another parameter of transient handling to be transmitted is the separation force (that is, the intensity of the effect of the transient handling regime). This information is transmitted with the same spatial temporal resolution as the spatial parameters ILD, ICC.
[0096] [024] The bit rate required for the transmission of transient separation and broadband phase information decisions from the encoder to the decoder can be estimated for MPS-type systems such as:
[0097] [003] BR = BRsin alignersofthese transients + BRΔφ ≈ (fs / 64) + σ · Q · fs / 64 = (1 + σ · Q) · fs / 64
[0098] [004] where σ is the density of transients (fraction of time intervals (= subband time samples) that are marked as transients), Q is the number of bits per transmitted phase value, and fs is the sampling frequency. Note that (fs / 64) is the sample rate of the subband signals with reduced data size.
[0099] [001] E {σ} <0.25 was measured by a set of various items representing applause, where E {.} Indicates the average over the duration of the item. A reasonable compromise between the accuracy of the phase values and the bit rate of the parameters is Q = 3. To reduce the data rate of the parameters, ICCs and ILDs can be transmitted as broadband signals. The transmission of ICCs and ILDs as broadband lanes is especially applicable for non-tonal signals such as applause.
[0100] [002] In addition, the parameters that signal the separation force are transmitted at the update rate of the ICCs / ILDs. For long spatial frames in MPS (32 times 64 samples) and separation forces quantified in 4 steps, this results in an additional bit rate of: BR transceiverparationforces (fs / (64 · 32)) · 2
[0101] [003] The separation force parameter can be derived from an encoder from the results of signal analysis algorithms that assess the similarity of applause signals, such as tonality, or other signal characteristics that indicate potential benefits or problems when characterization transient de-correlation applies.
[0102] [004] The transmission parameters for handling transients may be subject to lossless coding to reduce redundancy, resulting in a lower bit rate parameter (for example, with encoding with data sequence compression, independent compression of characteristics) .
[0103] [005] Returning to the aspect of obtaining phase information, in a characterization, the phase information can be obtained in a decoder.
[0104] [006] In such a characterization, the device for decoding does not receive the phase information from an encoder, but can determine the phase information alone. Therefore, it is not necessary to transmit phase information, which results in a reduced overall transmission rate.
[0105] [007] In a characterization, the phase information is obtained in an MPS decoder based on the GES data ("Guided Envelope Modeling"). This is only applicable if the GES data is transmitted, that is, if the GES feature is activated in an encoder. The GES function is available, for example, in MPS systems. The ratio of the GES envelope values between the output channels reflects balance positions for high resolution transients. The GES envelope ratio (GESR) can be mapped to the phase information required for handling transients. In GES, the mapping can be performed according to a mapping rule obtained empirically from the statistics of the GESR distribution phase for a representative set of appropriate test signals. Determining the mapping rule is a step in the design of the transient handling system, not a time execution process when applying the transient handling system. Therefore, it is advantageous that there is no need for additional transmission costs for the phase data, if the GES data is necessary for the application of the GES function in any way. Backward compatibility with bitstream is achieved with MPS bitstream decoders. However, the phase information extracted from the GES data is not as accurate (for example: the estimated phase signal is unknown) as the phase information that can be obtained from the encoder.
[0106] [008] In another characterization, the phase information can also be obtained from a decoder, but from residues transmitted from non-total band. This is the case, for example, if residual limited band signals are transmitted (usually covering a range of frequencies above a transition frequency) in an MPS encoding regime. In such a characterization, the phase relationship between the mixture and the residual signal transmitted in the residual band is calculated, that is, for frequencies to which the residual signals are transmitted. In addition, the information from the residual band phase to the non-residual band is extrapolated (and / or, eventually, interpolated). One possibility is to map the phase relation obtained in the residual band to a relation of the global independent frequency phase which is then used for the transient de-correlator. This results in the advantage that there are no additional transmission costs for the phase data, if the non-complete band waste is transmitted in any way. However, it must be considered that the accuracy of the phase estimate depends on the frequency bandwidth over which the residual signals are transmitted. The accuracy of the calculated phase also depends on the consistency of the phase relationship between the mixture and the residual signal along the frequency axis. For clearly transient signals, high consistency is usually found.
[0107] [009] In another form of characterization, the phase information is obtained with a decoder using additional correction information transmitted from the encoder. This characterization is similar to the two previous characterizations (GES phase, phase from residuals), but, in addition, it is necessary to generate correction data in the encoder transmitted to the decoder. The correction data allows to reduce the phase estimation error that can occur in the two variants described above (GES phase, phase from residuals). In addition, correction data can be derived from estimates of the estimated error of the decoder phase in the encoder. The correction data can be this estimated (potentially coded) estimation error. In addition, with respect to the GES data phase estimation approach, the correction data can simply be the correct signal of the phase values generated by the encoder. This allows the generation of phase conditions with the correct signal in the decoder. The benefit of this approach is that, due to the correction data, the accuracy of the recoverable phase information in the decoder is much closer than the phase information generated by the encoder. However, the independent compression of the correction information data is less than the independent compression of the information data of the correct phase itself. Thus, the bit rate parameter is reduced when compared to the direct transmission of the phase information obtained in the encoder.
[0108] [010] In another form of characterization, the information / conditions of the phase are obtained from a random (pseudo) process in a decoder. The benefit of this approach is that there is no need to transmit any phase information with high temporal resolution. This results in a reduced data rate. In a characterization, a simple method to generate phase values with a uniform random distribution in the range [- 180 °, 180 °].
[0109] [011] In an additional characterization, the statistical properties of the phase distribution in the encoder are measured. These properties are encoded and transmitted (in a low time resolution) to the decoder. The random phase values are generated in the decoder and are subject to statistical transmission properties. These properties can be the mean, variants, or other statistical measures of the statistical phase distribution.
[0110] [012] When more than one de-correlator is running in parallel (for example, for a multi-channel conversion), care must be taken to ensure mutually de-correlated de-correlator outputs. In a characterization, in which multiple vectors of random (pseudo) phase values (instead of a single vector) are generated for all but the first decorrelator, a set of vectors is selected that results in the lowest correlation of the phase value on all decelelators.
[0111] [013] In the case of transmission of phase correction information from the encoder to the decoder, the required data rate can be reduced as follows:
[0112] [014] The phase correction information only needs to be available in the decoder while there are transient components in the signal to be decorrelated. The transmission of the phase correction information can thus be limited by the encoder in such a way that only the necessary information is transmitted to the decoder. This can be done by applying a transient detection to the encoder as described above. The phase correction information is only transmitted to points in time n, for which transients have been detected in the encoder.
[0113] [015] Returning to the aspect of transient separation, in a characterization, the separation of transients can be conducted by the decoder.
[0114] [016] In such a characterization, the transient separation information can also be obtained in the decoder, for example, by applying a transient detection method, as described by Andreas Walther, Christian Uhle, Sascha Disch "Using Transient Suppression in Blind" Multi-channel Up-mix Algorithms ”(" Using Transient Suppression in Blind Multi-Channel Conversion Algorithms ") in AES Convention Procedures 122 Vienna, Austria, May 2007 for the mix signal that is available on the audio decoder space before conversion to a stereo multichannel output signal, in which case no transient information has to be transmitted, which saves the transmission data rate.
[0115] [017] However, performing transient detection in decoding can cause problems when, for example, the transient handling scheme is standardized: for example, it can be difficult to find a transient detection algorithm that results in the same results accurate detection of transients when implemented in different architectures / platforms involving different numerical precision, rounding schemes, etc. Such predictable decoder behavior is often mandatory for standardization. In addition, the standardized transient detection algorithm may fail for some input signals, causing intolerable distortions in the output signals. It can then be difficult to correct the failed algorithm after standardization without building a decoder that does not conform to the standard. This problem can be less severe if at least one transient separation force control parameter is transmitted with a lower time resolution (for example, at an MPS spatial parameter update rate) from the encoder to the decoder.
[0116] [018] In an additional characterization, the separation of transients is also triggered by the decoder and non-full band residuals are transmitted. In this characterization, the decoder-driven transient separation can be refined using phase estimates obtained from residuals transmitted from the unfilled band (see above). Note that this enhancement can be applied to the decoder without transmitting additional data from the encoder to the decoder.
[0117] [019] In this characterization, the phase conditions that are applied in a transient de-correlator are obtained by extrapolating the values of the correction phase to the residual bands for frequencies where there are no residues available. One method is to calculate the weighted phase value (for example, an energy signal) from the phase values that can be calculated for those frequencies where residual signals are available. The average value of the phase can then be applied as a frequency independent parameter in the transient de-correlator.
[0118] [020] As long as the correct phase relationship between the mixture and the residual is independent of frequency, the average phase value represents a good estimate of the correct phase value. However, in the case of a phase relationship that is not consistent across the frequency axis, the average phase value may be a less accurate estimate, which can lead to incorrect phase values and audible errors.
[0119] [021] The consistency of the phase relationship between the mixture and the residual transmitted along the frequency axis can thus be used as a reliable measure of extrapolated phase estimation that is applied to the transient decelator. To decrease the risk of audible errors, the measure of consistency obtained in the decoder can be used to control the transient separation force in the decoder, for example, as follows:
[0120] [022] The transients, for which the corresponding phase information (that is, the phase information for the same time as the index n) is consistent across the frequency, are completely separate from the input of the conventional decoupler and are fully fed into the transient decorrelator. Since large phase estimation errors are unlikely, the full potential of transient handling is used.
[0121] [023] Transients, for which the corresponding phase information is less consistent over the frequency, are only partially separated, leading to a less prominent effect of the transient treatment regime.
[0122] [024] The transients, for which the information of the corresponding phase is very inconsistent over the frequency, are not separated, leading to the normal behavior of a conventional conversion system, without the proposed transient treatment. Thus, no error occurs due to large phase estimation errors.
[0123] [025] The measures for the consistency of the phase information can be deduced, for example, from the variance (potentially a power signal) of the standard deviation of the phase information along the frequency.
[0124] [026] Since only a few frequencies may be available to which residual signals are transmitted, the measure of consistency may have to be estimated from only a few samples across the frequency, leading to a measure of consistency that is only rarely seen. reaches extreme values ("perfectly compatible", or "perfectly inconsistent"). Thus, the consistency measure can have linear or non-linear distortion before being used to control the force of transient separation. In a characterization, the threshold characteristic is implemented as shown in Fig. 8, example on the right.
[0125] [027] Fig. 8 shows different examples of mappings of measures of consistency of the phase of separation of transient forces, which illustrates the impact of variants to obtain transient handling parameters on the robustness to transient classification errors. The variants for obtaining the transient separation information and the phase information listed above differ in the parameter data rate and therefore represent different operating points in terms of the total bit rate or a codec (decoder encoder) of application of the proposed technique for transient treatment. In addition, the choice of source for obtaining phase information also affects aspects such as robustness against false transient classifications: the treatment of a non-transient signal results in a transient with much less audible distortion if the correct phase information is applied to the transient treatment. Thus, a signal classification error causes less serious errors in the transmitted phase value scenario when compared to the random phase generation scenario in the decoder.
[0126] [028] Fig. 9 is an overview of the one-to-two system, with transient treatment according to an additional characterization, in which the narrowband residual signals are transmitted. The Δφ data phase is estimated from the phase relationship between the mixture (DMX) and the residual signal in the frequency range of the residual signal. Optionally, the phase correction data is transmitted to reduce the phase estimation error.
[0127] [029] Fig. 9 illustrates a transient separator 910, a de-correlator 920, a de-correlator IIR 930, a combination unit 940, a mixer 952, an optional modeling unit 954, a first addition unit 956 and a second unit addition 958, which correspond to transient separator 510, transient de-correlator 520, IIR 530 de-correlator, combination unit 540, mixer 552 of optional modeling unit 554, first addition unit 556 and second addition 558 in the characterization of Fig. 5, respectively. The characterization form of Fig. 8 also contains a 960 phase estimation unit. The 960 phase estimation unit receives a DMX input signal, a residual signal residual and, optionally, phase correction data. Based on the information received, the phase information unit calculates the phase data Δφ. Optionally, the phase estimation unit also determines the phase consistency information and passes the phase consistency information to the 910 transient separator. For example, the phase coherence information can be used by the transient separator to control the transient separation force.
[0128] [030] The characterization of Fig. 9 applies the conclusion that, if the residues are transmitted within the coding scheme in a non-full band way, the difference in the average phase of the power signal between the residual and the mixture (Δφ residualbands) can be applied to the broadband phase information for separate transients (Δφ = Δφ residual_bands) In this case, no additional phase information has to be transmitted, reducing the demand for bit rate for the treatment of transients. In the characterization of Fig. 9, the phase estimate from the residual bands can deviate considerably from the more accurate estimate of the broadband phase that is available in the encoder. Therefore, one option is to transmit the phase correction data (for example, Δφ correction Δφ-Δφ residual_bands) so that the correct Δφ is available in the decoder. However, since the Δφ correction may show a lower data compression than Δφ, the required data rate parameter may be lower than the rate that would be required for Δφ transmission. (This concept is similar to the general use of forecasting in coding: instead of encoding the data directly, a forecasting error with less data compression is coded. In the characterization of Fig. 9, the forecasting step is the extrapolation of the phase from residual frequency bands to non-residual bands). The consistency of the phase difference in residual frequency bands (Δφ residual_bands) along the frequency axis can be used to control the transient separation force.
[0129] [031] In characterizations, a decoder can receive phase information from an encoder, or the decoder can itself determine the phase information. In addition, the decoder can receive transient separation information from an encoder, or the decoder can itself determine the transient separation information.
[0130] [032] In characterizations, an aspect of transient treatment is the application of "semantic de-correlation", a concept described in Patent WO / 2010/017967, together with the "transient de-correlator" which is based on multiplying the input by the conditions of the phase. The quality of perception of the signals similar to reproduced applause improves since both processing steps avoid changing the temporal structure of the transient signals. In addition, the spatial distribution of the transients, as well as the phase relationships between the transients, are reconstructed in the output channels. In addition, characterizations are also efficient by computer, and can be easily integrated into PS or MPS conversion systems. In characterizations, the transient treatment does not affect the mixing matrix process, so that all the spatial reproduction properties that are defined by the mixing matrix are also used for the transient signal.
[0131] [033] In characterizations, a new de-correlation system is applied, which is particularly suitable for application in conversion systems, which is particularly suitable for the application of spatial audio coding systems such as PS or MPS and which improves the quality of perception of the output signal in the case of signals such as applause, that is, signals that contain dense mixes of spatially distributed transients and / or can be seen as a particularly improved application of the generic "semantic correlation" structure. In addition, a new de-correlation scheme comprises the reconstruction of the spatial / temporal distribution of the transients similar to the distribution of the original signal, preserving the temporal structure of the transient signals and allowing to vary the transmission speed while there is an exchange with the quality parameter and / or is suitable for a combination of MPS functions such as non-full band residuals or GES. The combinations are complementary, that is: the information of standard MPS characteristics is reused for the treatment of transients.
[0132] [034] Fig. 10 illustrates an apparatus for encoding an audio signal with a plurality of channels. Two input channels L, R feed a mixer 1010 and a residual signal calculator 1020. In other characterizations, a plurality of channels are fed into the mixer 1010 and the residual signal calculator 1020, for example, 3, 5 or 9 surround channels. The mixer 1010 then mixes the two channels L, R, to obtain a mixing signal. For example, mixer 1010 can employ a mixing matrix and perform matrix multiplication of the mixing matrix and the two input channels L, R, to obtain the mixing signal. The mix signal can be transmitted to a decoder.
[0133] [035] In addition, the residual signal generator 1020 is adapted to calculate an additional signal, which is known as the residual signal. Residual signals are signals that can be used to regenerate the original signals by using the mixing signal and a mixing matrix. When, for example, N signals are mixed into one signal, the mixture is typically one of the N components that result from the mapping of the N input signals. The remaining components resulting from the mapping (for example, N-1 components) are the residual signals and allow to reconstruct the original signal N by an inverse mapping. This mapping can, for example, be a rotation. The mapping must be carried out in such a way that the mixing signal is maximized and the residual signals are minimized, for example, in a similar way to a transformation of the main axis. For example, the energy of the mix signal must be maximized and the energies of the residual signals must be minimized. When converting two signals into one signal, the mix is usually one of the two components that result from mapping the two input signals. The remainder of the component resulting from the mapping is the residual signal and allows to reconstruct the 2 original signals by an inverse mapping.
[0134] [036] In some cases, the residual signal may represent an error associated with the representation of two signals by their mixtures and the associated parameters. For example, the residual signal can be an error signal, which represents the error between the original L, R channels and the L ', R' channels, resulting from mixing the mixing signal that was generated based on the origin of L channels and R.
[0135] [037] In other words, a residual signal can be considered as a signal in the time domain or in the frequency domain or in the subband domain, which together with the mixing signal, alone or with the mixing signal and parametric information allows a correct or almost correct reconstruction of an original channel. For the term "almost correct" it must be understood that the reconstruction of the residual signal with an energy greater than zero is closer to the original channel compared to a reconstruction using the mixture without the residual signal or using the mixture and the parametric information , without the residual signal.
[0136] [038] In addition, the encoder comprises a 1030 phase information calculator. The mixing signal and the residual signal are fed into the 1030 phase information calculator. The phase information calculator then calculates the information about the difference in phase between the mixture and the residual signal to obtain the phase information. For example, the phase information calculator can apply functions that calculate the cross-correlation of the mixture and the residual signal.
[0137] [039] In addition, the encoder comprises an output generator 1040. The phase information generated by the phase information calculator 1030 is fed to the output generator 1040. The output generator 1040 then generates the phase information.
[0138] [040] In a characterization, the device also comprises a phase information quantifier to quantify the phase information. The phase information generated by the phase information calculator can be fed to the phase information quantifier. The phase information quantifier then quantifies the phase information. For example, the phase information can be mapped to eight different values, for example, one of the values 0, 1, 2, 3, 4, 5, 6 or 7. The values can represent the differences in phase 0, π / 4 , π / 2, 3π / 4, π, 5π / 4, 3π / 2 and 7π / 4, respectively. The quantified phase information can then be fed to the output generator 1040.
[0139] [041] In another characterization, the device also comprises a lossless encoder. The phase information from the 1040 phase information calculator or the quantified phase information from the phase information quantizer can be fed to the lossless encoder. The lossless encoder is adapted to encode the phase information through the application of lossless coding. Any type of lossless coding scheme can be employed. For example, the encoder may employ arithmetic coding. The lossless encoder then feeds the lossless encoded phase information to output generator 1040.
[0140] [042] With regard to the decoder and encoder and the methods of the described characterizations, the following is mentioned:
[0141] [043] Although some aspects have been described in the context of an apparatus, it is evident that these aspects also represent a description of the corresponding method, in which a block or a device corresponds to a method step or a characteristic of a method step. Similarly, the aspects described in the context of a method step also represent a description of a corresponding block or item or characteristic of a corresponding device.
[0142] [044] Depending on the requirements of certain applications, the characterizations of the invention can be implemented in hardware or in software. The application can be performed using a digital storage medium, for example, a floppy disk, a DVD, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having readable electronic signals of stored control that cooperate ( or are able to cooperate) with a programmable computer system so that the corresponding method is carried out.
[0143] [045] Some characterizations according to the invention comprise a data loader with electronically readable control signals, which are capable of cooperating with a programmable computer system, so that one of the methods described here is carried out.
[0144] [046] Generally, the characterizations of the present invention can be implemented as a computer program product with a program code, the program code being operative to perform one of the methods in which the computer program product operates on a computer. The program code, for example, can be stored in an optical reader.
[0145] [047] Other characterizations include the computer program for the execution of one of the methods described in this document, stored in an optical reader or a non-transitory storage medium.
[0146] [048] In other words, one way of characterizing the method of the invention is, therefore, a computer program with a program code to perform one of the methods described here, when the computer program is executed on a computer.
[0147] [049] Another way of characterizing the methods of the invention is, therefore, a data loader (or a digital storage medium, or a computer-readable medium), containing the computer program for carrying out one of the methods here described.
[0148] [050] Another characterization of the method of the invention is, therefore, a data stream or a sequence of signals representing the computer program for carrying out one of the methods described herein. The data stream or signal sequence can, for example, be configured to be transferred over a data communication link, for example over the Internet.
[0149] [051] A characterization further comprises a processing medium, for example a computer or a programmable logic device, configured for or adapted to perform one of the methods described herein.
[0150] [052] Another characterization comprises a computer, having a computer program installed in it to execute one of the methods described here.
[0151] [053] In some characterizations, a programmable logic device (for example, an infinite number of ports that are programmable in the field) that can be used to execute part or all of the functionalities of the methods described here. In some characterizations, a multitude of programmable ports in the field can cooperate with a microprocessor in order to execute one of the methods described here. Generally, the methods are preferably performed by any hardware device.
[0152] [054] The characterizations described above are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described here will be evident to other specialists on the subject. It is, therefore, intended to be limited only to the scope of the pending patent claims and not to the specific details presented by way of description and explanation of the characterizations of the present invention.

权利要求:
Claims (13)
[0001]
Apparatus for decoding a signal, characterized by comprising: a transient separator (310; 410; 510; 610; 710; 910) for separating an input signal from an apparatus to a first signal component and a second signal component such that the first signal component comprises transient signal portions of the input signal and such that the second signal component comprises non-transient signal portions of the input signal; a transient de-correlator (320; 420; 520; 620, 720, 920) for de-correlating the first signal component according to a first de-correlation method to obtain a first de-correlated signal component; an additional second de-correlator (330; 430; 530; 630; 730; 930) to de-correlate the second signal component according to a second de-correlation method to obtain a second de-correlated signal component, wherein the second de-correlation method is different the first method of de-correlation; a combining unit (340, 440; 540; 640; 740; 940) for combining the first de-correlated signal component and the second de-correlated signal component to obtain a de-correlated combination signal; and a mixer (450; 552; 752; 952), being adapted to receive input signals from the mixer and being adapted to generate output signals based on the input signals of the mixer and a mixing rule; wherein the combining unit (340, 440; 540; 640; 740; 940) and the mixer (450; 552; 752; 952) are arranged so that the de-correlated combination signal is fed to the mixer (450; 552; 752; 952) as a first input signal from the mixer, and that the input signal from a device or a signal derived from the device input signal is fed into the mixer (450; 552; 752; 952) as a second mixer input signal.
[0002]
Apparatus according to claim 1, characterized in that the mixer (450; 552; 752; 952) is also adapted to receive the correlation / coherence parameter data that indicate a correlation or coherence between the two signals, and in that the mixer ( 450, 552, 752, 952) furthermore be adapted to generate output signals from the data of correlation / coherence parameters.
[0003]
Apparatus according to claim 1 or 2, characterized in that the mixer (450; 552; 752; 952) is also adapted to receive level difference parameter data indicating a power difference between two signals and that the mixer (450 ; 552; 752; 952) also be adapted to generate the output signal based on the level difference parameter data.
[0004]
Apparatus according to any one of claims 1 to 3, characterized in that the mixer (450; 552; 752; 952) is adapted to use a mixing rule that comprises the rule for multiplying the first and second input signal of the mixer by a mixing matrix.
[0005]
Apparatus according to any one of claims 1 to 4, characterized in that the combination unit (340, 440; 540; 640; 740; 940) is adapted to combine the first de-correlated signal component and the second de-correlated signal component by adding the first de-correlated signal component and the second de-correlated signal component.
[0006]
Apparatus according to any one of claims 1 to 5, characterized in that the transient separator (310; 410; 510; 610; 710; 910) is adapted to supply a portion of the signal considered from the input signal to the apparatus for de-correlating transient (320; 420; 520; 620, 720, 920) or to feed the portion of the signal considered to the second decoupler (330; 430; 530; 630; 730; 930), depending on the transient separation information, which indicates that the signal portion considered comprises a transient or that it indicates that the signal portion considered contains a transient.
[0007]
Apparatus according to any one of claims 1 to 5, characterized in that the transient separator (310; 410; 510; 610; 710; 910) is adapted to partially supply a portion of the signal considered from the input signal to the apparatus for the transient de-correlator (320; 420; 520; 620, 720, 920) and to partially feed the portion of the signal considered in the second de-correlator (330; 430; 530; 630; 730; 930), and by the quantity of the signal portion it is considered that it is fed to the transient separator and the amount of the part of the signal considered that is fed to the second de-correlator depends on the transient separation information.
[0008]
Apparatus according to any one of claims 1 to 7, characterized in that the transient separator (310; 410; 510; 610; 710; 910) is adapted to separate an input signal from an apparatus which is represented in a frequency domain .
[0009]
Apparatus according to any one of claims 1 to 8, characterized in that the transient separator (310; 410; 510; 610; 710; 910) is adapted to separate the input signal from the apparatus to a first signal component and a second signal component based on independent frequency transient separation information.
[0010]
Apparatus according to any one of claims 1 to 9, characterized in that the transient separator (310; 410; 510; 610; 710; 910) is adapted to separate the input signal from an apparatus to a first signal component and to a second signal component based on frequency dependent transient separation information.
[0011]
Apparatus according to any one of claims 1 to 10, characterized in that the apparatus further comprises a receiver unit (650), which is adapted to receive the phase information from an encoder, and in that the transient de-correlator (320; 420; 520 620, 720, 920) be adapted to apply the encoder phase information to the first signal component.
[0012]
Apparatus according to any one of claims 1 to 11, characterized in that the second de-correlator (330; 430; 530; 630; 730; 930) is an IIR de-correlator.
[0013]
Method for decoding a signal characterized by comprising: separating an input signal from an apparatus to a first signal component and a second signal component such that the first signal component comprises transient signal portions of the input signal of the apparatus and such that the second signal component comprises non-transient signal portions of the apparatus input signal; de-correlating the first signal component by a transient de-correlator according to a first de-correlating method to obtain a first de-correlated signal component; de-correlation of the second signal component via an additional second de-correlator according to a second de-correlation method to obtain a second de-correlated signal component, wherein the second de-correlation method is different from the first de-correlation method; combining the first de-correlated signal component and the second de-correlated signal component to obtain a de-correlated combination signal; and generation of output signals based on a mixing rule, the decorrelated combination signal and the device input signal.

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法律状态:
2020-06-23| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2020-07-07| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-11-03| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-01-12| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 06/07/2011, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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US37698010P| true| 2010-08-25|2010-08-25|

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US61/376,980|2010-08-25|

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PCT/EP2011/061360|WO2012025282A1|2010-08-25|2011-07-06|Apparatus for decoding a signal comprising transients using a combining unit and a mixer|

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