EP1979899B1 - Verfahren und anordnungen zur audiosignalkodierung - Google Patents

Verfahren und anordnungen zur audiosignalkodierung Download PDF

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EP1979899B1
EP1979899B1 EP06706507.8A EP06706507A EP1979899B1 EP 1979899 B1 EP1979899 B1 EP 1979899B1 EP 06706507 A EP06706507 A EP 06706507A EP 1979899 B1 EP1979899 B1 EP 1979899B1
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Prior art keywords
excitation signal
audio
exc
excitation
band
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German (de)
English (en)
French (fr)
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EP1979899A1 (de
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Bernd Geiser
Peter Jax
Stefan Schandl
Hervé TADDEI
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Unify GmbH and Co KG
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Unify GmbH and Co KG
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Processing of the speech or voice signal to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
    • G10L21/038—Speech enhancement, e.g. noise reduction or echo cancellation using band spreading techniques
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
    • G10L19/08—Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters
    • G10L19/12—Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L2019/0001—Codebooks

Definitions

  • the invention relates to a method and arrangements for audio signal coding.
  • the invention relates to a method and an excitation signal generator for forming an excitation signal for exciting an audio synthesis filter and an audio signal encoder and an audio signal decoder.
  • Efficient compression of audio signals is also an important consideration in the context of storage or archival of audio signals.
  • Coding methods in which an audio signal to be transmitted is adjusted on a time-frame basis to an audio signal synthesized by an audio synthesis filter by optimization of filter parameters prove to be particularly efficient.
  • a Such a procedure is often referred to as analysis-by-synthesis.
  • the audio synthesis filter is excited by a preferably also to be optimized excitation signal.
  • Filtering is often referred to as formant synthesis.
  • LPC coefficients LPC: Linear Predictive Coding
  • parameters specifying a spectral and / or temporal envelope of the audio signal can be used as filter parameters.
  • the optimized filter parameters as well as the parameters specifying the excitation signal are then transmitted to the receiver on a timely basis in order to form a synthetic audio signal there by means of an audio synthesis filter provided on the receiver side, which is as similar as possible to the original audio signal with regard to the subjective auditory impression.
  • Such an audio coding method is known from ITU-T Recommendation G.729.
  • a real-time audio signal with a bandwidth of 4 kHz can be reduced to a transmission rate of 8 kbit / s.
  • the excitation signal is generated by means of a so-called adaptive codebook in cooperation with a so-called fixed codebook.
  • the fixed codebook a plurality of predetermined excitation signal sequences are permanently stored, which are retrievable on the basis of a codebook index.
  • already generated excitation signal sequences are stored in the adaptive codebook.
  • a respective sequence of the excitation signal is generated by mixing a sequence from the adaptive codebook with a sequence from the fixed codebook.
  • both the fixed and the adaptive codebook are searched for excitation signal sequences for each time frame, which allow the best possible approximation of the synthetic audio signal to the audio signal to be transmitted.
  • parameters specifying the excitation signal become access information transferred to the sequences found to be optimal from the fixed and the adaptive codebook to the receiver. At the receiver these parameters are used to reconstruct an excitation signal by means of a fixed and an adaptive codebook of the receiver.
  • EP 0 883 107 A1 For example, a CELP (Code-Excited Linear Prediction) type coder / decoder is described, wherein a random codevector reading section and a random codebook of a conventional speech codec / decoder are respectively output by an oscillator for outputting different vector streams according to values of input, and a seed memory section be replaced for storing a variety of seeds.
  • a CELP Code-Excited Linear Prediction
  • Such a bandwidth extension of the synthesized audio signal can be achieved by constructing from a narrow-band excitation signal, eg with a bandwidth of 4 kHz, a suitable excitation signal of higher bandwidth, for example 8 kHz bandwidth, in order to excite the audio synthesis filter in a broadband manner.
  • a broadband excitation signal can be generated by squaring the narrow-band excitation signal in the time domain or by generating an enhancement band by shifting or mirroring the frequency spectrum of the narrow-band excitation signal.
  • the methods mentioned above distort the spectrum of the excitation signal anharmonically and / or cause a considerable, audible phase error in the spectrum.
  • the excitation signal is formed as a consequence of excitation samples.
  • Already formed excitation samples are stored temporally consecutively in an adaptive codebook.
  • a noise generator is provided by which random sampling values are generated continuously. From the adaptive codebook, a sequence of the stored excitation samples is selected based on an input audio fundamental frequency parameter, by which a time interval of the sequence to be selected is specified for the current time reference.
  • the audio basic frequency parameter specifies a time interval which is not an integer multiple of a predetermined sampling interval of a narrow-band excitation signal to be generated separately is interpolated between the excitation samples and / or between the random samples dependent on the audio fundamental frequency parameter such that a sample spacing of the samples is less than the sample interval of the narrowband excitation signal, whereby the excitation signal is additional frequency components of an extension band to the narrowband excitation signal having.
  • the excitation signal is formed by mixing the selected sequence with a random sequence comprising current random samples of the noise generator.
  • a fixed codebook for filling the adaptive codebook can be dispensed with. Accordingly, it is not necessary to provide or transmit codebook indices for selecting predetermined sample sequences stored in a fixed codebook. Since such codebook indices for a fixed codebook occupy a considerable proportion of the audio data to be transmitted in known methods, the transmission rate can generally be considerably reduced by the invention. The saved transmission bandwidth can be used accordingly for other purposes or to increase the transmission quality.
  • a noise component contained in audio signals or speech signals can generally be better modeled than by means of a fixed code book containing only fixed predetermined sample sequences.
  • a harmonic fine structure of the audio or speech signals can be well reproduced from the adaptive codebook by the selection of a sample sequence dependent on the audio basic frequency parameter.
  • a noise generator is naturally well scalable to different frequency ranges, bandwidth extensions can be realized with little effort.
  • a coding residual error is transmitted in a bandwidth extension in an extension band.
  • narrow-band excitation signal is provided to insert intermediate samples between the excitation samples and / or between the random samples depending on the audio basic frequency parameter.
  • the insertion is preferably such that a sampling interval of the resulting samples is less than the sampling interval of the narrow-band excitation signal.
  • the invention can be advantageously used both in the encoding and in the decoding of an audio signal.
  • a Audio signal encoder can be excited by an excitation signal generator according to the invention an audio synthesis filter whose output audio signal is compared with a respective current frame of the audio signal to be transmitted.
  • the comparison of the current frame is preferably performed for different selections of sequences stored in the adaptive codebook from previous excitation samples.
  • the timing of the sample sequence within the adaptive codebook where the comparison indicates optimal match may be expressed by a corresponding audio ground frequency parameter, which may then be transmitted to a receiver.
  • a search of another, fixed codebook and an additional transmission of codebook indices are not required.
  • an audio stimulus signal generator in an audio signal decoder, can be controlled by a respective received audio basic frequency parameter so that it generates an excitation signal which harmonically corresponds to the audio fundamental frequency parameter, without having to rely on codebook indices to be transmitted additionally.
  • the excitation signal thus generated can be used to excite an audio synthesis filter in order to produce a synthetic audio signal which is very similar to the original audio signal in terms of the audio impression.
  • the audio synthesis filters in the audio signal encoder and / or audio signal decoder can be used, for example, as an LPC filter, Wiener FIR filter, as a filter for shaping a temporal or spectral Envelopes of the audio signal or as a combination of these filters can be realized.
  • the method according to the invention can preferably be carried out by a signal processor.
  • the excitation samples and / or the random samples may be processed on a time frame basis, the length of the selected sequence and / or the length of the random sequence corresponding to a predetermined length of a time frame.
  • the selected sequence may be selected according to a first intensity parameter and / or the random sequence according to a first intensity parameter second intensity parameters are amplified.
  • the first and the second intensity parameters, as well as the audio basic frequency parameters, can preferably be derived and transmitted on a timely basis from the audio signal to be transmitted.
  • the excitation signal can be formed with a smaller sampling interval compared with a narrow-band excitation signal to be generated separately, as a result of which the excitation signal has subtractive frequency components of an extension band relative to the narrow-band excitation signal.
  • the audio basic frequency parameter and the first and / or second intensity parameter can be derived from audio synthesis parameters which are actually intended to generate the narrow-band excitation signal.
  • the audio basic frequency parameter as well as the first and / or the second intensity parameter can be derived from a narrowband component of an audio signal to be transmitted.
  • the audio base frequency parameter as well as the first and / or second parameters of interest can thus be derived from narrowband audio parameters, but applied to the extension band. This is advantageous in that no additional audio synthesis parameters are required for the bandwidth expansion of the excitation signal except for the audio synthesis parameters provided for generating the narrow-band excitation signal.
  • the intended for generating the narrow-band excitation signal audio synthesis parameters can be provided by existing narrow-band audio codecs, such as, for example, according to G.729 recommendation.
  • the audio basic frequency parameter is often more accurately determined than the sampling interval of the narrow-band excitation signal. Frequently, an accuracy of e.g.
  • the audio basic frequency parameter provided for the narrow-band excitation signal can generally be used directly or substantially unchanged for generating the bandwidth-expanded excitation signal.
  • the first and / or the second intensity parameter may each be derived from the corresponding narrowband intensity parameters by applying a predetermined function, e.g. emphasize a noise component versus a harmonic component in the extension band of an audio signal.
  • a portion of the excitation signal attributable to the denial band may be combined with the separately generated narrow-band excitation signal to produce a broadband excitation signal, e.g. in the frequency range from 0 to 8 kHz, to excite the audio synthesis filter.
  • FIG. 1 illustrates an audio signal sampled at different sample rates. Individual samples are represented here as points which have different amplitudes illustrated by vertical lines. The different sampling rates are illustrated by different sampling intervals between the sampling values. Both subfigures have a common time axis T.
  • the upper part of the figure illustrates the audio signal sampled at a sample rate of, for example, 8 kHz.
  • the sampling rate of 8 kHz corresponds to a sampling interval DT1 of 1/8000 s.
  • audio signals can essentially be represented up to a frequency of 4 kHz according to a fundamental sampling theorem. This frequency range is referred to below as narrowband.
  • the lower part of the figure shows the audio signal sampled at a sampling rate of 16 kHz.
  • the sampling distance DT2 in the lower part of the figure is half of the sampling distance DT1, ie here 1/16000 s.
  • an audio signal can be represented substantially up to a frequency of 8kHz.
  • the above frequency range is also referred to as broadband in the following. It goes without saying that the terms narrow-band and broad-band are not limited to the frequency ranges only by way of example, but are generalizable to arbitrary frequency ranges insofar as the term broadband is to specify a larger frequency range than the term narrow-band.
  • FIGS. 2a and 2b show a schematic representation of various embodiments of an excitation signal generator.
  • the illustrated excitation basic generators comprise as function components in each case a noise generator NOISE, an adaptive codebook ACB and a mixer MIX.
  • the random number generator NOISE is used for the continuous generation of Züfalls samples with a given sampling interval.
  • the respective noise generator NOISE generates random sampling values with a narrow-band sampling rate, ie, for example, 8 kHz. Random sampled values are understood to be sampled values which are generated by the noise generator chronologically, randomly or quasi-randomly and, in particular, are not predetermined or are selected from predefined values.
  • the random samples are generated independently of an audio signal to be encoded or decoded by the respective excitation signal generator.
  • NOISE requires no supply or transmission of specific access parameters as with a fixed code book according to the prior art.
  • fixed codebook fixed predetermined deterministic sampling sequences are stored, for their timely fetch codebook indices are to be supplied continuously, which usually takes a significant share of the transmission bandwidth.
  • a noise signal formed by the random samples has a substantially white or flat frequency spectrum.
  • the excitation signal generator shown there can generally be used for audio and / or speech coding.
  • Both the noise generator NOISE and the adaptive codebook ACB output samples on a time frame basis, that is to say as a sequence of time frames of predefined length containing samples.
  • a time frame of, for example, 5 ms in length contains at a sampling rate of eg 8 kHz corresponding to 40 samples. With a sampling rate of 16 kHz, such a time frame contains correspondingly 80 samples.
  • the adaptive code book ACB continuously outputs sequences ie time frames EXC_P of stored excitation samples.
  • the random sequences EXC_N and the sequences EXC_P output by the adaptive codebook ACB are forwarded to the mixer MIX, which is also supplied with time-frame-wise intensity control parameters G_N for level control of the random sequences EXC_N and intensity parameters G_P for level control of the sequences EXC_P coming from the adaptive codebook ACB.
  • the random samples of a respective random sequence EXC_N having a respective intensity parameter G_N and the samples of a respective sequence EXC_P output by the adaptive code book ACB are time-frame multiplied, ie amplified, by a respective intensity parameter G_P.
  • the multiple cations are in FIG. 2a indicated by circles provided with multiplication signs.
  • the according to the intensity parameters G_N and G_P amplified sample sequences are added on a time-frame basis by the mixer MIX and the resulting sum signal is output as excitation signal EXC in the form of a sequence of excitation samples.
  • the addition is in FIG. 2a illustrated by a plus sign circle.
  • the formed excitation signal EXC is outputted and stored in parallel in temporal succession in the adaptive codebook ACB.
  • the excitation signal EXC is therefore to some extent fed back from the output of the mixer MIX to the adaptive codebook ACB.
  • the adaptive codebook ACB acts in a similar way as a shift register in which currently formed sequences of the excitation signal EXC are stored, successively shifting backwards previously formed sequences of the excitation signal while maintaining the chronological order.
  • the output of the sequences EXC_P of stored excitation samples is controlled by the adaptive codebook ACB in timed audio basic frequency parameters PITCH.
  • the sequences EXP to be output by the adaptive codebook ACB are selected from the stored excitation sample values. The selection is made by means of a selector SEL of the adaptive codebook ACB.
  • Such an audio basic frequency parameter PITCH is often referred to in the art as "pitch lag".
  • the audio basic frequency parameters PITCH are each given in units of a narrow-band sampling interval, here for example 1/8000 s at a narrow-band sampling rate of 8 kHz.
  • the audio basic frequency parameters PITCH each time frame, a period a fundamental frequency of the audio signal to be transmitted or synthesized.
  • the fundamental frequency periods of an audio signal are often measured or provided at a higher resolution than corresponds to a sampling interval used in each case.
  • precise audio basic frequency parameters can thus also assume non-integer values in units of the sampling interval.
  • Such a non-integer audio basic frequency parameter PITCH contains information about higher frequency components than actually corresponds to the sampling interval. While such higher frequency components are filtered out in known audio encoders, eg according to the G.729 recommendation, the information about the higher frequency components in audio signal generators according to the invention can be used in a simple way to improve the quality of the audio synthesis.
  • FIG. 3 illustrates the selection of a sample sequence EXC_P from the adaptive codebook ACB based on the audio basic frequency parameter PITCH supplied to the selector SEL.
  • FIG. 3 shows a section of the in the adaptive codebook ACB temporally continuously stored excitation samples.
  • the stored excitation samples are indicated by dots provided with vertical lines, the length of a respective line illustrating a respective amplitude of an excitation sample.
  • the time course is indicated by a time axis.
  • a current time reference T0 is in FIG. 3 . indicated by a vertical line indicating the location in the adaptive codebook at which a respective currently formed time frame of the excitation signal is newly stored in the adaptive codebook ACB.
  • the storage takes place here temporally or logically adjacent to an immediately prior stored time frame of the excitation signal.
  • a timeframe includes FIG. 3 only four samples. A generalization of the FIG. 3 illustrated relationships on time frames of any given length is evident.
  • sequence EXC_P of stored excitation samples is selected for output, the beginning of which has a time interval corresponding to the audio basic frequency parameter PITCH from the current time reference T0 and whose length corresponds to the predetermined length of a time frame.
  • the time interval is calculated backwards from the current time reference T0. It has since been pointed out that the beginning of the selected sequence EXC_P need not fall on a time frame boundary, but may possibly fall within given limits to any stored excitation sample.
  • FIG. 3 By way of example, it is assumed that a time interval of six sampling intervals is specified by the audio basic frequency parameter PITCH transmitted with the current time frame.
  • the output time frame EXC_P is in FIG. 3 indicated by a dashed rectangle.
  • the adaptive code book ACB When the excitation signal generator is switched on, the adaptive code book ACB is initially empty, in order then to be filled successively with generated excitation sample values of the output excitation signal EXC. Since the adaptive codebook ACB is initially empty, the excitation signal EXC initially fed only by the noise generator NOISE as the only signal source. This means that the adaptive code break ACB is first filled with non-periodic random samples. In this scenario, the question arises as to how ACB can obtain periodic signal components by means of the adaptive codebook, since only a non-periodic noise generator NOISE is available as the original signal source. In fact, according to previous ideas, it was considered necessary, in addition to an adaptive codebook, also to provide a fixed codebook in order to fill the adaptive codebook ACB with deterministic signal sequences stored in the fixed codebook.
  • an excitation signal with a harmonic fine structure can be generated from the adaptive codebook ACB by continuously suitable selection of sample sequences EXC_P.
  • EXC_P sample sequences
  • the current time frame is stored with a specified by the audio basic frequency parameter PITCH distance to the previously issued sequence EXC_P.
  • a periodic signal portion whose period is determined by the audio basic frequency parameter PITCH is successively formed in the adaptive codebook ACB.
  • the periodic share of Total excitation signal EXC is controlled by the intensity parameters G_N and G_P.
  • the noise generator NOISE instead of a fixed codebook, transmission of codebook indices for a fixed codebook can be dispensed with. In this way, the transmission rate or bandwidth for the transmission of audio signals can be significantly reduced. In addition, by using the noise generator NOISE a better listening experience can be achieved, especially when playing non-harmonic or noisy audio components.
  • FIG. 2b An embodiment of the excitation signal generator according to the invention for generating a bandwidth-extended excitation signal EXC is explained below.
  • the output excitation signal EXC is generated with a bandwidth expanded by a bandwidth expansion factor N.
  • FIG. 2a used reference numbers FIG. 2b its meaning.
  • the adaptive code book ACB and the mixer MIX use the 16 kHz wide-band sampling rate.
  • an interpolator INT_N is connected between these and the noise generator NOISE.
  • the interpolator INT_N receives the noise generator NOISE For each of the values of the bandwidth expansion factor N, N-1 intermediate samples, each having an amplitude of 0, between each two instances, are analogously set to N-1 intermediate samples, each outputted at a narrow-band sampling rate -Sampled values inserted. In this way, a narrow-band white noise spectrum of the noise generator NOISE is converted to a broadband white spectrum.
  • the audio basic frequency parameter PITCH is supplied in units of the narrow-band sampling interval. Let it further be assumed that the audio basic frequency parameter PITCH in these units is provided exactly to at least a fractional part 1 / N, that is to say exactly here to 1/2.
  • the adaptive codebook ACB uses a sampling interval halved with respect to the narrow-band sampling interval or divided by N.
  • the audio basic-frequency parameter PITCH is first multiplied by N.
  • excitation signal generator can be easily generated a bandwidth-expanded excitation signal EXC whose harmonic fine structure in the extension band by using the fractional portion of the audio basic frequency parameter PITCH better modeled can.
  • the harmonic fine structure of the excitation signal in the narrow band frequency range can be continued harmoniously and consistently into the grant band.
  • an inventive audio signal decoder for receiving an audio signal to be transmitted is shown schematically.
  • the audio signal decoder comprises an audio synthesis filter ASYN, which is excited by a broadband excitation signal S_EXC, for example in the frequency range from 0 to 8 kHz, and generates a synthetic audio signal SAS by filtering.
  • the audio synthesis filter ASYN is supplied with spectral parameters F_ENV specifying a spectral envelope of the audio signal to be transmitted and timing parameters T_ENV specifying a temporal envelope of the audio signal.
  • the audio synthesis filter ASYN forms the spectral and temporal envelope of the audio signal SAS to be synthesized on the basis of the supplied parameters F_ENV and T_ENV.
  • the parameters F_ENV and T_ENV are timed by the transmitter of the audio signal to be transmitted and transmitted to the receiver or audio signal decoder.
  • the generation of the broadband excitation signal S_EXC is divided into different layers, namely a layer for the narrowband frequency range, here from 0 to 4 kHz, and a layer for the extension band, here from 4 to 8 kHz.
  • the audio signal decoder has for generating a narrow-band excitation signal N_EXC, here in the frequency range of 0 to 4 kHz, a narrow-band excitation signal generator NBC and for generating a frequency-expanded excitation signal E_EXC, here in the frequency range of 4 to 8 kHz, according to an excitation signal generator EBC FIG. 2b for the extension tape on.
  • the narrowband excitation signal generator NBC can be used as in FIG. 2a illustrated excitation signal generator or as a herkömmli-rather, be equipped with adaptive and fixed codebook excitation signal generator, eg according to G.729 recommendation, designed.
  • the narrow-band excitation signal generator NBC is supplied with the audio basic frequency parameter PITCH as well as the intensity parameters G_N and G_P on a time frame basis. Instead of the intensity parameters G_N and G_P, a sum parameter G_S + G_N and a ratio parameter G_S / G_N or its reciprocal can also be supplied.
  • the narrow-band excitation signal generator NBC Based on the supplied parameters PITCH, G_S and G_N, the narrow-band excitation signal generator NBC generates the narrow-band excitation signal N_EXC.
  • the parameters PITCH, G_S and G_N used by the narrow-band excitation signal generator NBC are supplied. If necessary, the intensity parameters G_S and G_N are converted by a predetermined function before they are used in the mixer MIX of the excitation signal generator EBC for level control.
  • the excitation signal EXC which initially has a bandwidth of 0 to 8 kHz. Since the excitation signal generator EBC should only be responsible for the expansion band in the illustrated audio signal decoder, the excitation signal EXC is supplied to a high-pass filter HP. This essentially only allows frequencies of the extension band of 4 to 8 kHz to pass and outputs a frequency-expanded excitation signal E_EXC.
  • the frequency-expanded excitation signal E_EXC is used with the narrow-band excitation signal N_EXC, as in FIG. 4 indicated by a plus sign combined to form the broadband excitation signal S_EXC. The latter is finally fed to the audio synthesis filter ASYN.
  • the audio parameters PITCH, G_S and G_N are required to generate the bandwidth-expanded excitation signal E_EXC and thus to generate the broadband excitation signal S_EXC, which signals are transmitted anyway for generating the narrowband excitation signal or are provided by a narrowband excitation signal generator.
  • the audio parameters PITCH, G_N and G_P can therefore advantageously be derived from the narrowband frequency range of the audio signal to be transmitted or from parameters of a narrowband codec in order then to be applied to an extension band to be added.
  • no additional audio parameters are to be transmitted in comparison to generation of the narrowband excitation signal N_EXC.
  • an additional transmission of codebook indices can be dispensed with. Additional information about an audio structure in the extension band can be transmitted via the parameters F_ENV and T_ENV.
  • the in FIG. 4 shown audio signal decoder can be extended to an audio signal encoder according to the analysis-by-synthesis principle.
  • the synthesized audio signal SAS is compared by a comparison device with the audio signal to be encoded and adjusted by varying the audio synthesis parameters PITCH, G_S, G_N, F_ENV and T_ENV.
  • a combination of audio signal decoder and audio signal encoder is often referred to as a codec.
EP06706507.8A 2006-01-31 2006-01-31 Verfahren und anordnungen zur audiosignalkodierung Active EP1979899B1 (de)

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US20090012782A1 (en) 2009-01-08
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US8135584B2 (en) 2012-03-13
CN101336449A (zh) 2008-12-31
EP1979899A1 (de) 2008-10-15

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