METHOD FOR GENERATING AN AUDIO SUBFRAME FOR BLINDING, DECODING DEVICE, AND COMPUTER-READABLE MEDIA

Abstract

A method and a decoding device are provided for generating an audio subframe of an audio signal. The method comprises generating frequency spectra based on subframes wherein consecutive subframes of the audio signal have a property that an applied window format of the first subframe of consecutive subframes is a mirrored or temporally inverted version of a second subframe of consecutive subframes. The peaks of a signal spectrum of a previously received audio signal are detected for an audio subframe, and a phase of each of the peaks is estimated. A temporally inverted phase adjustment is derived based on the estimated phase and applied to the peaks of the signal spectrum to form temporally inverted phase-adjusted peaks.

Description

1 / 40 METHOD FOR GENERATING AN AUDIO SUBFRAME FOR BLINDING, DECODING DEVICE, AND COMPUTER-READABLE MEDIA FIELD OF TECHNIQUE

[001] The present description refers generally to communications, and more particularly to methods and apparatus for controlling packet loss concealment for encoding and decoding single-channel, stereo or multi-channel audio. FUNDAMENTALS

[002] Modern telecommunications services generally provide reliable connections between end users. However, such services still need to deal with variable channel conditions where occasional data packets may be lost due to, for example, network congestion or weak cellular coverage. To overcome the problem of transmission errors and packet loss, telecommunications services can make use of Packet Loss Control (PLC) techniques. In the case of data packet loss due to poor connection, network congestion, etc., the lost packet information on the receiving side can be replaced in the decoder by a synthetic signal. PLC techniques can often be closely linked to the decoder, where internal states can be used to produce a continuation or extrapolation of the signal to cover packet loss.For a multimode codec with multiple operating modes for different signal types, there are usually several PLC technologies to handle concealment. There are many different terms used for packet loss concealment techniques, including Frame Error Concealment (FEC), Frame Loss Concealment (FLC), and Error Concealment Unit (ECU).

[003] For linear prediction (LP) modes based on speech code conversion, PLC may be based on adjusting glottal pulse positions using estimated end-of-frame step and information. Petition 870260054451, dated 05 / 06 / 2026, page 14 / 111 2 / 40 replication of the previous frame step cycle [1]. The long-term predictor (LTP) gain converges to zero with speed depending on the number of consecutively lost frames and the stability of the last well, i.e., error-free frame [2]. Frequency domain (FD) based code conversion modes are designed to handle general or complex signals, such as music. Different techniques can be used depending on the characteristics of the last received frame. Such analysis may include the number of tonal components detected and the periodicity of the signal. If frame loss occurs during a highly periodic signal, such as active speech or single instrumental music, a time-domain PLC, similar to LP-based PLC, may be suitable. In this case, the FD PLC can mimic an LP decoder by estimating LP parameters and an excitation signal based on the last received frame [2].If the lost frame occurs during a non-periodic or noise-like signal, the last received frame can be repeated in the spectral domain where the coefficients are multiplied for a random signal to reduce the metallic sound of a repeated signal. For a stationary tonal signal, it was considered advantageous to use an approach based on the prediction and extrapolation of the detected tonal components. More details on the aforementioned techniques can be found in [1][2][3].

[004] A generic error concealment method that operates in the frequency domain is the phase ECU (Error Hide Unit) [4]. The phase ECU is a stand-alone tool that operates on a temporary storage of the previously decoded and reconstructed time-domain signal. The structure of the phase ECU is based on sinusoidal analysis and the synthesis paradigm. In this method, the sinusoidal components of the last good frame can be extracted and the phase can be shifted. When a frame is lost, the sinusoidal frequencies are Petition 870260054451, dated 05 / 06 / 2026, page 15 / 111 3 / 40 obtained in the DFT (Discrete Fourier Transform) domain from the synthesis decoded in the past. First, the corresponding frequency bins are identified by finding the peaks in the magnitude spectrum plane. Then, the fractional frequencies of the peaks are estimated using frequency peak bins. The frequency bins corresponding to the peaks along with their neighbors are phase-shifted using fractional frequencies. For the remainder of the frame, the magnitude of the past synthesis is maintained while the phase is random. The overflow error is also handled in such a way that the estimated signal is smoothly muted as it converges to zero. More details on the phase ECU can be found in [4].

[005] The phase ECU concept can be used in decoders that operate in the frequency domain. This concept includes encoding and decoding systems that perform decoding in the frequency domain, as illustrated in Figure 1, but also decoders that perform decoding in the time domain with additional processing in the frequency domain, as illustrated in Figure 2. In Figure 1, the time domain audio signal input (sub)frames are windowed 100 and transformed into frequency domain by the DFT 101. An encoder 102 performs encoding in the frequency domain and provides encoded parameters for transmission 103. A decoder 104 decodes the received frames or applies PLC 109 in case of frame loss. In constructing the concealment frame, PLC can use a memory 108 of previously decoded frames.The decoded or hidden frame is transformed in the time domain by the inverse DFT 110, and the output audio signal is then reconstructed by the superposition-addition operation 111. Figure 2 illustrates an encoder and decoder pair where the decoder applies a DFT transform to facilitate processing in the frequency domain. The signal. Petition 870260054451, dated 05 / 06 / 2026, page 16 / 111 4 / 40 received and decoded from time domain is first (sub)frame in windowed mode 105 and then transformed into frequency domain by the DFT 106 for frequency domain processing 107 which can be done before or after the PLC 109 (in case of frame loss).

[006] Since a frequency domain spectrum is already produced for each frame, the raw material for the phase ECU can be easily obtained by simply storing the last decoded spectrum in memory. However, if the decoded spectra correspond to time domain signal frames with different windowing functions (see Figure 1), the efficiency of the algorithm may be reduced. This can happen when the decoder divides the synthesis frames into shorter subframes, for example, to handle transient sounds that require higher time resolution. To achieve good results, the ECU must produce the desired window shape for each frame, or there may be transition artifacts at each frame boundary. One solution is to store the spectrum of each frame corresponding to a given window and apply the ECU to them individually.Another solution could be to store a single spectrum for the ECU and correct the windowing in the time domain. This can be implemented by applying an inverse window and then reapplying a window with the desired shape. These solutions have some drawbacks which are discussed below.

[007] One disadvantage of applying frequency domain ECU to individual subframes is that there may be differences between the subframes that will be replicated for each subframe during the lost frame. For consecutive frame losses, this can lead to a repetitive artifact, since each subframe may have a slightly different spectral signature. Another problem is that the memory requirement is increased, since a spectrum of each subframe needs to be stored.

[008] The window rearrangement solution in which the windowing is Petition 870260054451, dated 05 / 06 / 2026, page 17 / 111 The inverted and reapplied 5 / 40 window overcomes the issue of different spectral signatures since the ECU can be based on a single subframe. However, applying the inverted window and then applying a new window involves splitting and multiplying for each sample, where splitting is a computationally complex and expensive operation. This solution could be improved by storing a pre-computed rearrangement window in memory, but this would increase the required desktop memory. If the ECU is applied to a sub-part of the spectrum, it may additionally require the entire spectrum to be rearranged, as the entire spectrum needs to have the same window format. SUMMARY

[009] According to a first aspect, it is proven that a method generates a hidden audio subframe from an audio signal in a decoding device. The method comprises generating frequency spectra based on subframes wherein consecutive subframes of the audio signal have the property that an applied window format of the first subframe of the consecutive subframes is a mirrored version or a time-inverted version of a second subframe of the consecutive subframes. The method further includes detecting peaks in a signal spectrum of a previously received audio signal on a fractional frequency scale, estimating a phase of each of the peaks, and deriving a time-inverted phase adjustment to apply to the peaks of the signal spectrum based on the estimated phase to form time-inverted phase-adjusted peaks. The method further includes applying a time inversion to the hiding audio subframe.

[0010] A potential advantage is that a multi-subframe ECU is generated from a single subframe spectrum by applying inverted time synthesis. This generation may be suitable for cases where the subframe windows are time-inverted versions of each other. A Petition 870260054451, dated 05 / 06 / 2026, p. 18 / 111 Generating all ECU frames from a single stored decoded frame ensures that subframes have a similar spectral signature, while keeping memory footprint and computational complexity to a minimum.

[0011] According to a second aspect, a decoding device configured to generate a hidden audio subframe from an audio signal is demonstrated. The decoding device is configured to generate frequency spectra based on subframes wherein consecutive subframes of the audio signal have the property that an applied window format of the first subframe of the consecutive subframes is a mirrored version or a time-inverted version of a second subframe of the consecutive subframes. The decoding device is further configured to detect peaks in a signal spectrum of a previously received audio signal on a fractional frequency scale and to estimate the phase of each of the peaks.The decoder device is further configured to derive a time-inverted phase adjustment to apply to the signal spectrum peaks based on the estimated phase, and to form time-inverted phase-adjusted peaks by applying the time-inverted phase adjustment to the signal spectrum peaks. The decoder device is further configured to apply a time inversion to the occultation audio subframe.

[0012] According to a third aspect, a computer program is provided. The computer program comprises the program code to be executed through the processing circuit of a decoder device configured to operate on a communication network, where the execution of the program code causes the decoder device to perform operations according to the first aspect.

[0013] According to a fourth aspect, a product is provided of Petition 870260054451, dated 05 / 06 / 2026, page 19 / 111 7 / 40 Computer program. The computer program product comprises a non-transient storage medium including the program code to be executed through the processing circuit of a decoder device configured to operate on a communication network, where the execution of the program code causes the decoder device to perform operations according to the first aspect.

[0014] According to a fifth aspect, a method is provided for generating a hidden audio subframe for an audio signal in a decoding device. The method comprises generating frequency spectra based on subframes wherein consecutive subframes of the audio signal have the property that an applied window format of the first subframe of the consecutive subframes is a mirrored version or a time-inverted version of a second subframe of the consecutive subframes. A signal spectrum corresponding to a second subframe of the first two consecutive subframes is stored. The method additionally includes receiving a bad frame indicator for a second consecutive subframe.The method further includes obtaining the signal spectrum, detecting peaks in the signal spectrum on a fractional frequency scale, estimating the phase of each peak, and deriving a time-inverted phase adjustment to apply to the stored spectrum peaks for the first subframe of the two consecutive second subframes based on the estimated phase. The method further includes applying the time-inverted phase adjustment to the signal spectrum peaks to form time-inverted phase-adjusted peaks. The method further includes applying a time inversion to the occultation audio subframe, combining the time-inverted phase-adjusted peaks with a noise spectrum from the signal spectrum to form a combined spectrum for the first subframe of the two consecutive second subframes, and generating an occultation audio subframe. Petition 870260054451, dated 05 / 06 / 2026, page 20 / 111 8 / 40 synthesized based on the combined spectrum.

[0015] According to a sixth aspect, a decoder device is provided that is configured to generate a hidden audio subframe from an audio signal. The decoder device comprises a processing circuit and a memory operatively coupled to the processing circuit, wherein the memory includes instructions which, when executed by the processing circuit, cause the decoder device to perform operations according to the first or fifth aspect.

[0016] According to a seventh aspect, a decoder device is provided. The decoder device is configured to generate a hidden audio subframe from an audio signal, wherein the decoder device is adapted to perform the method according to the fifth aspect.

[0017] According to an eighth aspect, a computer program is provided. The computer program comprises program code to be executed through the processing circuit of a decoder device configured to operate on a communication network, wherein the execution of the program code causes the decoder device to perform operations according to the fifth aspect.

[0018] According to a ninth aspect, a computer program product is provided. The computer program product comprises a non-transient storage medium including program code to be executed through the processing circuit of a decoder device configured to operate on a communication network, wherein the execution of the program code causes the decoder device to perform operations according to the fifth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The attached drawings, which are included to provide a better understanding of the description and are incorporated and constitute a part Petition 870260054451, dated 05 / 06 / 2026, page 21 / 111 9 / 40 of this application illustrate certain non-limiting possibilities. In the drawings: Figure 1 is a block diagram illustrating a pair of encoders and decoders where encoding is done in the DFT domain; Figure 2 is a block diagram illustrating a pair of encoders and decoders where the decoder applies a DFT transform to facilitate frequency domain processing; Figure 3 is an illustration of two subframe windows of a decoder, where the window applied in the second subframe is a time-inverted or mirrored version of the window applied in the first subframe; Figure 4 is a block diagram illustrating an encoder and decoder system including a PLC method that performs phase estimation and applies ECU synthesis in inverted time using an inverted-time phase calculator according to some embodiments; Figure 5 is a flowchart illustrating the operations of a decoder device that performs time-reversed ECU synthesis, according to several modes; Figure 6 is an illustration of a time-inverted window on a sinusoidal waveform, according to some modalities; Figure 7 illustrates how an inverted time window affects the DFT coefficients in the complex plane, according to some modalities; Figure 8 is an illustration of Φ* versus frequency f according to some modalities; Figure 9 is a block diagram illustrating a decoder device according to some modes; Figure 10 is a flowchart that illustrates the operations of a decoder device according to some modes; Petition 870260054451, dated 05 / 06 / 2026, p. 22 / 111 10 / 40 Figure 11 is a flowchart that illustrates the operations of a decoder device according to some modes; DETAILED DESCRIPTION

[0020] Aspects of the present description will now be described in more detail hereafter in this document with reference to the accompanying drawings, in which examples of embodiments are shown. Embodiments can, however, be embodied in many different ways and should not be interpreted as limited to the embodiments set forth in this document. On the contrary, these embodiments are provided so that this description may be thorough and complete, and will fully convey the scope of actual embodiments to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. The components of one embodiment may be tacitly assumed to be present / used in another embodiment.

[0021] The following description presents various modalities of the subject matter described. These modalities are presented as didactic examples and should not be interpreted as limiting the scope of the subject matter described. For example, certain details of the modalities described may be modified, omitted, or expanded without departing from the scope of the subject matter described.

[0022] Figure 9 is a block diagram illustrating elements of a 900 decoder device, which may be part of a mobile terminal, a mobile communication terminal, a wireless communication device, a wireless communication terminal, user equipment, UE, a user equipment node / terminal / device, etc., configured to provide wireless communication according to the modalities. As shown, the 900 decoder may include a 906 network interface circuit (also referred to as a network interface) configured to provide communications with other devices / entities / functions / etc. The 900 decoder may also include a 902 processor circuit (also called a Petition 870260054451, dated 05 / 06 / 2026, page 23 / 111 11 / 40 processor) operatively coupled to the network interface circuit 906, and a memory circuit 904 (also called memory) operatively coupled to the processor circuit. The memory circuit 904 may include computer-readable program code which, when executed by the processor circuit 902, causes the processor circuit to perform operations in accordance with the modes described in this document.

[0023] According to other embodiments, the processor circuit 902 can be defined to include memory, so that a separate memory circuit is not required. As discussed in this document, the operations of the decoder 900 can be performed by the processor 902 and / or network interface 906. For example, the processor 902 can control the network interface 906 to transmit communications to multichannel audio players and / or to receive communications through the network interface 906 from one or more other network nodes / entities / servers, such as encoder nodes, repository servers, etc. Furthermore, modules can be stored in memory 904, and these modules can provide instructions so that when the instructions of a module are executed by the processor 902, the processor 902 performs the respective operations.

[0024] In the following description, subframe notation should be used to describe the modalities. In this document, a subframe denotes a part of a larger frame where the larger frame is composed of a set of subframes. The modalities described can also be used with frame notation. In other words, subframes can form groups of frames that have the same window format described in this document, and subframes do not need to be part of a larger frame.

[0025] Consider a decoder of an encoder-decoder pair in which the decoding method generates frequency spectra on a subframe basis. Consecutive subframes may have the Petition 870260054451, dated 05 / 06 / 2026, p. 24 / 111 12 / 40 property that the applied window format are time-inverted or mirrored versions of each other, as illustrated in Figure 3, where subframe 2 is a time-inverted or mirrored version of subframe 1. The decoder obtains the spectra of the reconstructed subframes ^it™'^), k) for cac|aqUadrom. In one embodiment, the subframe spectra can be obtained from a reconstructed synthesis of the time domain x(m,n) in which some index and sample. The dashed boxes in Figure 2 indicate that frequency domain processing can be done before or after the memory and PLC modules. The spectra can be obtained by multiplying x(™'n) with the subframe windowing functions and applying the DFT transform according to: jV-1 jV-1 x(m, n + ^fepi2) w2(n) en where N denotes the length of the subframe window a^cbpiz and is the distance in samples between the starting point of the first and second subframes. The subframe windowing functions wiín) and wz(n) are mirrored or time-inverted versions of each other. In this document, the subframe spectra are obtained from a time-domain synthesis of the decoder, similar to the system outlined in Figure 2. It should be noted that the modalities are equally applicable to a system in which the decoder directly reconstructs the subframe spectra, as outlined in Figure 1. For each correctly received and decoded audio frame™, the spectrum corresponding to the second frame is stored in memory.

[0026] For frames received correctly, the device Petition 870260054451, dated 05 / 06 / 2026, page 25 / 111 The 13 / 40 900 decoder can proceed with pre-forming the frequency domain processing steps, performing the inverse DFT transform and reconstructing the output audio using an overlay-addition strategy. Missing or corrupted frames can be identified by the transport layer that handles the connection and are signaled to the decoder as a “bad frame” via a Bad Frame Indicator (BFI), which may be in the form of a flag. When the 900 decoder detects a defective frame via a Bad Frame Indicator (BFI), the PLC algorithm is activated. The PLC follows the ECU phase principle [4]. The stored spectrum is fed into a peak detection algorithm that detects peaks on a fractional frequency scale. A set of peaks F = { / j}, í = 1,2,... / VpenJts can be detected which are represented by their estimated fractional frequency ft and where is the number of peaks detected. Similar to the sinusoidal code conversion paradigm, the spectral peaks are modeled with sinusoids with a certain amplitude, frequency, and phase. The fractional frequency can be expressed as a fractional number of DFT bins, so that, for example, the Nyquist frequency is found at f=+L. Each peak can be associated with a number of frequency bins that represent the peak. These are found by rounding the fractional frequency to the nearest integer and including neighboring bins, for example, the N™>«r peaks on each side: = [fi 1 tCj — { / íj — / Ví!enir, ·, ·, Íí; + / Ví!0nr} where H represents the rounding operation and Gí is the group of bins representing the frequency peak Λ the number Nnear is a tuning constant that can be determined when designing the system. A larger Nnear provides greater precision in each peak representation, but also introduces a greater distance between the peaks that can be Petition 870260054451, dated 05 / 06 / 2026, page 26 / 111 14 / 40 modeled. A suitable value for Nnear can be 1 or 2. The peaks of the occultation spectrum can be formed using these groups of bins, where a phase adjustment has been applied to each group. The phase adjustment is responsible for the phase shift in the underlying sinusoid, assuming that the frequency remains the same between the last correctly received and decoded frame and the occultation frame. The phase adjustment is based on the fractional frequency and the number of samples between the analysis frame of the previous frame and where the current frame would begin. As illustrated in Figure 3, this number of samples is w*-ep2i between the beginning of the second subframe of the last received frame and the beginning of the first subframe of the first ECU frame, and Nw between the first subframe of the last received frame and the first subframe of the first ECU frame. Note that Nw also provides the distance between the second subframe of the last received frame and the second subframe of the first ECU frame.

[0027] Figure 4 illustrates an encoder and decoder system in which a PLC block 109 performs a phase estimate using a phase estimator 112 and applies the ECU synthesis in reverse time using a reverse time phase calculator 113 according to the embodiments described below.

[0028] Figure 5 is a flowchart illustrating the steps of the time-reversed ECU synthesis, described below. For hiding the first subframe, the ECU synthesis can be done in reverse time to obtain the desired window format. The phase adjustment, or phase correction, or phase progression (these terms are used interchangeably throughout the description), for the first subframe to pico1 can be written as Mi = -2φ, - + W5fepZ1+ where Nu>st denotes the number of frames lost. Petition 870260054451, dated 05 / 06 / 2026, page 27 / 111 15 / 40 consecutive and Φ denotes the sinusoidal phase in frequency^. The term (Ntost - W / uii) manipulates the phase progression for rupture errors, where the step is incremented with the length of the complete frame^. For the first lost frame, = L. For frequencies centered on the frequency bins of the spectrum, XRneín(fe), the phase ^ is readily available simply by extracting the angle: in quekí=t / il.

[0029] In general, the frequency f is a fractional number and the phase needs to be estimated in operation 501. One estimation method is to use linear interpolation of the phase spectrum. Φί = - L / J) (ΓZ1) - ^„eí„([ / ÉJ))+ where We ^ represents the operators for rounding down and up, respectively. However, this estimation method was considered unstable. This estimation method additionally requires two-phase extractions, which requires the computationally complex arctan function if the spectrum is represented with complex numbers in the standard n+bi form. Another phase estimate that was considered reliable with relatively low computational complexity is Φί = ^X,ne,n{ki')-ffrac^c+^ ffrac =fi~ki where Âr^est is the rounding error and Φ€& is a tuning constant that depends on the window format to which it is applied. For the window format of this modality, a suitable value was found ^=°·33. For another window format, it was found = 0.48.pmgeneral, it is expected that a suitable value can be found Petition 870260054451, dated 05 / 06 / 2026, page 28 / 111 16 / 40 in the range 0·1'0·7!.

[0030] In operation 502, a time-inverted phase adjustmentA^: is derived as explained above.

[0031] The peaks of the occultation spectrum can be formed by applying phase adjustment to the stored spectrum in operation 503. xECU(m,k-) = (xmem{k')e^yrkGGi

[0032] The asterisk denotes the conjugate complex, which gives a time inversion of the operating signal 504. This results in a time inversion of the first subframe of the ECU. It should be noted that it may also be possible to perform the inversion in the time domain after the inverse DFT. However, if ^^(i-íO) represents only a part of the complete spectrum, this requires that the remaining spectrum be pre-treated, for example, by a time inversion before the DFT analysis.

[0033] The remaining dexEcu(™'k\) bins that are not occupied by picoGt bins can be referred to as the noise spectrum or the noise component of the spectrum. They can be filled using the stored spectrum coefficients with a random phase applied: X£Ctr(m,k) = k € GÉm which denotes a random phase value. The remaining bins can also be filled with spectral coefficients that retain a desired property of the signal, for example, the correlation with a second channel in a multichannel decoder system. In 505 operation the peak spectrum where G G*, is combined with the noise spectrum xEcu(™'k\ where € Gt form a combined spectrum.

[0034] In modes where noise is generated in the time domain and is windowed and transformed, a time inversion of the noise to match the windowing of the peak components and the combination with Petition 870260054451, dated 05 / 06 / 2026, page 29 / 111 17 / 40 The peak spectrum must be performed before applying the time inversion described above.

[0035] For the generation of the second subframe, which is synthesized in normal time (not reversed), regular phase adjustment can be used.

[0036] The ECU synthesis for the second subframe can be formed similarly to the first subframe, but omitting the complex conjugate over the peak coefficients. = Xmem{k}e^rkEGtXECV{w,k) =^me;n(íí)eJ·^^, ke GÉ

[0037] Once the combined occultation spectrum has been generated in operation 505, the combined occultation spectrum can be fed into the following processing steps in operation 506, including inverse DFT and an added overlay operation that results in an output audio signal.

[0038] The output audio signal can be transmitted to one or more loudspeakers, such as speakers for playback. The loudspeakers can be part of the decoding device, be a separate device, or be part of another device. Derivation of the Phase Correction Formula for Time-Inverted ECU Synthesis

[0039] Assume that the initial phase of the sinusoidal component is *A>e and that the frequency of the sinusoidal component is Λ. The desired phase of the sinusoidal component after advancing the samples is then Φι = Φΰ+ 2nfNsfgp / N

[0040] For a time-inverted continuation of the sinusoidal waveform, the phase needs to be mirrored on the real geometric axis, applying the complex conjugate or simply taking the negative phase -^!. As this angle Petition 870260054451, dated 05 / 06 / 2026, page 30 / 111 Phase 18 / 40 now represents the endpoint of the ECU synthesis structure; the phase needs to be wound back by the length of the analysis frame to reach the desired initial phase^z. φ2

[0041] To obtain a phase correction Δ^, the initial phase needs to be subtracted, that is, Φο f Δφ=Φζ &Φ=Φζ ~ Φο

[0042] The substitution Φ2 gives Δφ = -2φ0- 2nf(N3tgp+ N- 1) / A /

[0043] To add progression for consecutive frame losses (explosion loss), a factor corresponding to the number of samples between the starting points of the complete frames can be added, = _ÉJ-AÇuh. This provides the final phase correction. Δφ = -2φ0- 2nf(N + V,f0p- 1 +

[0044] The desired time reversal can be achieved in the DFT domain using a complex conjugate along with a circular shift of one sample. This circular shift can be implemented with a 2n;íí / Nda phase correction which can be included in the final phase correction. Δφ = -2φ0- 2nf(N + V,f0p- 1 + - l) / V / u„) / / V + 2nk / N

[0045] For coefficients representing a single peak, the frequency bin of the circular displacement can be approximated with the fractional frequency f, and the phase correction can be simplified to Δφ = —2φ0- 2nf(N + N5fBp- 1 + - l)A / / uii) / / V + 2nf / N = —2φ0- 2xf(_N + Nstep+ {Nlost- l) / V / uii) / A /

[0046] The windows can be designed so that N = in this case, the expression can be further simplified to Petition 870260054451, dated 05 / 06 / 2026, p. 31 / 111 19 / 40 Δφ = -2φ0- 2nf(Nsfep+ Nlt>stΝ) / Ν An alternative modality of the ECU's reversed-time synthesis.

[0047] In another mode, phase correction is done in two stages. The phase is advanced in a first step, ignoring the window mismatch. Δψ = 2^ + (^-1)ΛΙ / Βίί) X ecu,= ke

[0048] In a second step, the time inversion of the windowing can be achieved by reversing the phase back-^™, applying the conjugate complex and restoring the phase with k~)e~^m, k EGf£L ß / X ' - <zl

[0049] The motivation for this operation can be found by studying the effect of a time-inverted window on a sinusoidal wave, as illustrated in Figure 6. In Figure 6, the upper graph shows the window applied in the first direction, and the lower graph shows the window applied in the reverse direction. The three coefficients representing the sinusoidal wave are illustrated in Figure 7, which shows how a time-inverted window affects the DFT coefficients in the complex plane. The three DFT coefficients that approximate the sinusoidal wave in the upper graph of Figure 6 are marked with circles, while the corresponding coefficients in the lower graph of Figure 6 are marked with stars. The diamond denotes the position of the original phase of the sinusoidal wave, and the dashed line shows an observed mirror plane through which the coefficients of the time-inverted window are projected. The time-inverted window gives a mirroring of the coefficients in a mirroring plane with an angle Φ™. Φηι Φθ T Φ{τηε Petition 870260054451, dated 05 / 06 / 2026, p. 32 / 111 20 / 40

[0050] Through experimentation, it was discovered that ^f^ could be expressed as Φ / rac ^ffrac ffrac = fi~ki = [ / J where H denotes the rounding operation. It was also discovered that Φε, expressed as a positive angle, can be approximated by a linear relationship with In Figure 8, the angle Φ<- is expressed as a function of the frequency f. Studying the sawtooth shape of Figure 8, it was found that a good approximation of Φ* Φε where Φε is a constant. In one embodiment, ^c can be defined for Φε=°·33, which results in a close approximation. Since Φο is not explicitly known, an alternative approximation of Φ™ can be written as Φπι = 0k,· + Φε

[0051] where Φ^< is the phase of the maximum peak coefficient found in the frequency bin rounded after the first phase adjustment step, Φΐίί=

[0052] The operation of aligning the mirrored plane with the real geometric axis, applying the complex conjugate and reversing the phase can be understood as adjusting the phase of the shaped sinusoid to a phase-neutral position relative to the complex conjugate (° or ^), thus reversing only the time shape of the signal. The two-step approach is more computationally complex than the described method. Petition 870260054451, dated 05 / 06 / 2026, page 33 / 111 21 / 40 previously. However, observations can also lead to an approximation of Φο. It can be seen in Figure 7 that ^o can be expressed as Φθ=Φ^ 4 Φε ~ Φ / rac=~ ffrac^C + which is the phase approximation used above.

[0053] The operations of the decoder device 900 (implemented using the block diagram structure of Figure 9) will now be discussed with reference to the flow diagram of Figure 10 according to some embodiments. For example, modules can be stored in memory 904 of Figure 9, and these modules can provide instructions so that when the instructions of a module are executed by the respective processing circuit of the decoder device 902, the processing circuit 902 executes the respective operations of the flow diagram.

[0054] In operation 1000, processing circuit 902 generates frequency spectra based on subframes where consecutive subframes of the audio signal have the property that an applied window format of the first subframe of the consecutive subframes is a mirrored version or a time-inverted version of a second subframe of the consecutive subframes. For example, generating the frequency spectra of each subframe of the first two consecutive subframes involves determining: Zj2?rkn· x (m, n) (n) enn=0 Nl ΣΪZπΙιη x(m,n + ^fepi2)w2(n)e * where ^ denotes the length of a subframe window, the subframe windowing function ^lí^ is a subframe windowing function for the first subframe ^ifr^^ of consecutive subframes and ewz(n) is a subframe windowing function for the second subframe Petition 870260054451, dated 05 / 06 / 2026, p. 34 / 111 22 / 40 ^2(m, / Odos subquadros consequências, eN�^βριζ qumnúmero de amostras entre um primeiro subquadro dos dois primeiros subquadros consequências e o segundo subquadro dos dois primeiros subquadros consoantes.

[0055] In operation 1002, processing circuit 902 determines whether a bad frame indicator (BFI) has been received. The bad frame indicator provides an indication that an audio frame has been lost or corrupted.

[0056] In operation 1004, the processing circuit 902 stores, for each correctly decoded audio frame, the spectrum corresponding to the second subframe in memory. For example, for a correctly decoded frame m, the spectrum corresponding to the second subframe ^(^ is stored in memory, as := for correctly received frames, the decoder device 900 can proceed with the pre-formation of the frequency domain processing steps, performing the inverse DFT transform and reconstructing the output audio using an overlay strategy, as described above and illustrated in Figure 4. Note that the overlay-added principle is the same for both subframes and frames. Creating a frame requires applying overlay-added to the subframes, while the final output frame is the result of an overlay-added operation between frames.

[0057] When processing circuit 902 detects a bad frame via a bad frame indicator (BFI) in operation 1002, operations 1006 to 1030 of the PLC are performed.

[0058] In operation 1006, processing circuit 902 obtains the signal spectrum corresponding to the second subframe of a first two consecutive subframes previously decoded and processed correctly. For example, processing circuit 902 can obtain the signal spectrum from memory 904 of the decoding device. Petition 870260054451, dated 05 / 06 / 2026, page 35 / 111 23 / 40

[0059] In operation 1008, processing circuit 902 detects peaks in the signal spectrum of a previously received audio frame from the audio signal on a fractional frequency scale, the previously received audio frame before receiving the bad frame indicator.

[0060] In operation 1010, processing circuit 902 determines whether the hiding frame is for the first subframe of two consecutive subframes.

[0061] If the occultation frame is for the first subframe, in operation 1012, the processing circuit 902 estimates the phase of each of the peaks. In one mode, calculating a phase estimate for the time-inverted phase peaks corrected according to: ffrac =fi~ki where Φίέ is an estimated phase frequency, is a spectrum angle, ^Mem is a frequency bin, ffncé is a rounding error, Φεέ is an adjustment constant, and [£1. The adjustment constant ^c can be a value in a range between 0.1 and 0.7.

[0062] In operation 1014, processing circuit 902 derives a time-inverted phase correction to be applied to the signal spectrum peaks based on the estimated phase.

[0063] In operation 1016, processing circuit 902 applies time-inverted phase correction to signal spectrum peaks to form time-inverted phase-corrected peaks.

[0064] In operation 1018, processing circuit 902 applies a time inversion to the occultation audio subframe. In one embodiment, the time inversion can be applied by applying a complex conjugate to the occultation audio subframe.

[0065] In operation 1020, processing circuit 902 combines time-corrected phase-inverted peaks with a spectrum of Petition 870260054451, dated 05 / 06 / 2026, page 36 / 111 24 / 40 signal spectrum noise to form a combined spectrum of the audio subframe concealment.

[0066] Returning to Figure 11, in one embodiment, 1016 and 1018 can be executed by processing circuit 902 by associating each peak with several operating peak frequency bins 1100. The associated processing circuit 902 can apply time-inverted phase correction, applying time-inverted phase correction to each of the operating frequency bins 1102. In operation 1104, the remaining bins are filled using signal spectrum coefficients with a random phase applied.

[0067] Returning to Figure 10, in operation 1022, processing circuit 902 generates a synthesized audio concealment subframe based on the combined spectrum.

[0068] If the occultation frame is not for the first subframe as determined in operation 1010, processing circuit 902 derives in operation 1024 a non-time-inverted phase correction to apply to the signal spectrum peaks for a second occultation subframe of at least two consecutive occultation subframes.

[0069] In operation 1026, processing circuit 902 applies non-time-inverted phase correction to the peaks of the signal spectrum so that the second subframe forms non-time-inverted phase-corrected peaks.

[0070] In operation 1028, processing circuit 902 combines the time-corrected non-inverted phase peaks with a noise spectrum from the signal spectrum to form a combined spectrum for the second occultation subframe.

[0071] In operation 1030, processing circuit 902 generates a second synthesized occultation audio subframe based on the combined spectrum. Petition 870260054451, dated 05 / 06 / 2026, page 37 / 111 25 / 40

[0072] Returning to Figure 11, in one embodiment, 1026 and 1028 can be executed by the processing circuit 902 by associating each peak with several operating peak frequency bins 1100. The associated processing circuit 902 can apply non-time-inverted phase correction by applying non-time-inverted phase correction to each of the operating frequency bins 1102. In operation 1104, the remaining bins are filled using signal spectrum coefficients with a random phase applied.

[0073] Several operations in the flowchart of Figure 10 may be optional with respect to some decoder device modalities and related methods. With respect to the methods of example 1 (set out below), for example, the operations of blocks 1004 and 1022-1030 of Figure 10 may be optional. With respect to the methods of example 19 (set out below), for example, the operations of blocks 1010 and 1022-1030 of Figure 10 may be optional.

[0074] Example modalities are discussed below.

[0075] 1. Method for generating a subframe audio concealment of an audio signal in a decoding device, the method comprises: generating (1000) frequency spectra on a subframe basis wherein consecutive subframes of the audio signal have a property that an applied window format of the first subframe of the consecutive subframes is a mirrored version or a time-inverted version of a second subframe of the consecutive subframes; receive (1002) a bad picture indicator; detect (1008) peaks in a signal spectrum of a previously received audio frame from the audio signal on a fractional frequency scale, the previously received audio frame received before receiving the bad frame indicator; Petition 870260054451, dated 05 / 06 / 2026, page 38 / 111 26 / 40 estimate (1012) a phase of each of the peaks; derive (1014) a time-inverted phase correction to apply to the signal spectrum peaks based on the estimated phase; apply (1016) time-inverted phase correction to signal spectrum peaks to form time-inverted phase-corrected peaks; apply (1018) a time inversion to the audio subframe of concealment; combine (1020) the time-inverted phase-corrected peaks with a noise spectrum from the signal spectrum to form a combined spectrum for the occultation audio subframe; and generate (1022) a synthesized occultation audio subframe based on the combined spectrum.

[0076] 2. The method of Modality 1, in which a synthesized audio concealment frame comprises at least two consecutive concealment subframes and in which deriving time-inverted phase correction, applying time-inverted phase correction, applying time inversion, and combining time-inverted phase-corrected peaks are performed for a first concealment subframe of at least two consecutive concealment subframes, the method further comprises: derive (1024) a non-time-inverted phase correction to apply to the signal spectrum peaks for a second occultation subframe of at least two consecutive occultation subframes; apply (1026) non-time-inverted phase correction to the signal spectrum peaks for the second subframe to form non-time-inverted phase-corrected peaks; combine (1028) the non-time-inverted phase-corrected peaks with a noise spectrum of the signal spectrum to form a combined spectrum for the second occultation subframe; and generate (1030) a second occultation audio subframe Petition 870260054451, dated 05 / 06 / 2026, page 39 / 111 27 / 40 synthesized based on the combined spectrum.

[0077] 3. The method of any of the embodiments 1-2, wherein the audio concealment subframe comprises an audio concealment subframe for one of a lost audio frame and one corrupted audio frame.

[0078] 4. The method of any of the modes 1-3, in which the bad frame indicator gives an indication that an audio frame has been lost or corrupted.

[0079] 5. The method of any of the Modalities 1-4, additionally comprises obtaining the signal spectrum of the previously received audio signal frame from a decoder memory.

[0080] 6. The method of any of the Modalities 1-5, in which the application of time inversion comprises the application of a complex conjugate to the concealment audio subframe.

[0081] 7. The method of any of the Modalities 1-6 additionally comprises: associate (1100) each peak of the various peaks with various peak frequency bins representing the peak.

[0082] 8. The Mode 7 method in which for each peak of the various peaks, one of the time-inverted phase correction and the non-time-inverted phase correction is applied (1102) to the peak.

[0083] 9. The method of any of the Modalities 8 additionally comprises: Fill in the remaining (1104) bins of the signal spectrum using stored signal spectrum coefficients with a random phase applied.

[0084] 10. The method of any of the Modalities 1-9, wherein estimating the phase of each of the peaks comprises: Calculate a phase estimate for the time-inverted phase-corrected peaks according to: Petition 870260054451, dated 05 / 06 / 2026, p. 40 / 111 28 / 40 Φί ~ ffrae^C + ffrae=fi-^i where Φίέ is an estimated phase at frequency / i,'^”11'”'^) is an angle of the spectrumJ™»>in a frequency bin^ / r^c is a rounding error, Φεέ is a tuning constant and MW.

[0085] 11. The Modality 10 method in which 0ct has a value in an interval between 0.1 and 0.7.

[0086] 12. The Mode 10 method in which the phase estimate for non-time-inverted phase-corrected peaks is calculated according to: where Δφί denotes a phase correction of a sinusoid at frequency / *, ^ denotes a number of samples between two frames, ^iosr denotes a number of consecutive lost frames, and ^ denotes the length of a subframe window.

[0087] 13. The method of any of the Modalities 1-12 additionally comprises applying a random phase to the noise spectrum of the signal spectrum.

[0088] 14. The Mode 13 method in which random phase application to noise spectrum comprises applying random phase to the noise spectrum before combining non-time-inverted phase-corrected peaks with the noise spectrum.

[0089] 15. A decoder device (900) configured to generate a subframe audio concealment of a received audio signal, wherein a decoding method of the decoding device generates frequency spectra on a subframe basis in which consecutive subframes have a property that an applied window format is a mirrored version or a time-inverted version of each other, the decoder device comprises: Petition 870260054451, dated 05 / 06 / 2026, page 41 / 111 29 / 40 processing circuitry (902); and memory (904) coupled to the processing circuit, wherein the memory includes instructions which, when executed by the processing circuit, cause the decoder device to perform operations according to any of the modes 1-14.

[0090] 16. A decoder device (900) configured to generate a subframe audio concealment of a received audio signal, wherein a decoding method of the decoding device generates frequency spectra on a subframe basis wherein consecutive subframes have a property that an applied window format is either a mirrored version or a time-inverted version of each other, wherein the decoder device is adapted to operate in accordance with either of Modes 1-14.

[0091] 17. A computer program comprising program code to be executed by a set of processing circuits (902) of a decoder device (900) configured to operate on a communication network, wherein the execution of the program code causes the decoder device (900) to perform operations according to any of the modes 1-14.

[0092] 18. A computer program product comprising a non-transient storage medium including program code to be executed by a set of processing circuits (902) of a decoder device (900) configured to operate on a communication network, wherein the execution of the program code causes the decoder device (900) to perform operations in accordance with any of the Embodiments 1-14.

[0093] 19. A method for generating a concealment audio subframe for an audio signal in a decoding device, the method comprises: Petition 870260054451, dated 05 / 06 / 2026, page 42 / 111 30 / 40

[0094] generate (1000) frequency spectra on a subframe basis wherein consecutive subframes of the audio signal have a property that an applied window format of the first subframe of the consecutive subframes is a mirrored version or a time-inverted version of a second subframe of the consecutive subframes; store (1004) a signal spectrum corresponding to a second subframe of two consecutive first subframes; receive a bad frame indicator (1002) for two consecutive second subframes; obtain (1006) the signal spectrum; detect (1008) peaks in the signal spectrum on a fractional frequency scale; estimate (1012) a phase of each of the peaks; derive (1014) a time-inverted phase correction to apply to the stored spectrum peaks for a first subframe of the second two consecutive subframes based on the estimated phase; apply (1016) time-inverted phase correction to signal spectrum peaks to form time-inverted phase-corrected peaks; apply (1018) a time inversion to the audio subframe of concealment; combine (1020) the time-inverted phase-corrected peaks with a noise spectrum of the signal spectrum to form a combined spectrum for the first subframe of the second two consecutive subframes; and generate (1022) a synthesized occultation audio subframe based on the combined spectrum.

[0095] 20. The Mode 19 method, in which the synthesized audio concealment frame comprises at least two consecutive concealment subframes and in which deriving the time-inverted phase correction, apply the Petition 870260054451, dated 05 / 06 / 2026, page 43 / 111 31 / 40 time-inverted phase correction and combining the time-inverted phase-corrected peaks are performed for a first occultation subframe of at least two consecutive occultation subframes; the method further comprises: derive (1024) a non-time-inverted phase correction to apply to signal spectrum peaks for a second subframe of the second two consecutive subframes; apply (1026) non-time-inverted phase correction to the signal spectrum peaks for the second subframe of the second two consecutive subframes to form non-time-inverted phase-corrected peaks; combine (1028) the non-time-inverted audio subframe with a noise spectrum from the signal spectrum to form a second combined spectrum for the second subframe of the second two consecutive subframes; and generate (1030) a second synthesized audio subframe based on the second combined spectrum.

[0096] 21. The method of any of the embodiments 19-20, wherein the audio concealment subframe comprises an audio concealment subframe for one of a lost audio frame and one corrupted audio frame.

[0097] 22. The method of any of the modalities 19-21, in which the bad frame indicator gives an indication that an audio frame has been lost or corrupted.

[0098] 23. The method of any of the Modalities 19-22 additionally comprises obtaining the signal spectrum from a decoder memory.

[0099] 24. The method of any of the Modalities 19-23, in which the application of time inversion comprises the application of a Petition 870260054451, dated 05 / 06 / 2026, p. 44 / 111 32 / 40 combined complex to the audio subframe of concealment.

[00100] 25. The method of any of the modalities 18-24, additionally comprising:

[00101] associate each peak with multiple peak frequency bins that represent the peak.

[00102] 26. The Modality 25 method which additionally comprises, for each peak of the various peaks, the application of a time-inverted phase correction and a non-time-inverted phase correction to the peak.

[00103] 27. The method of any of the Modalities 26 additionally comprising:

[00104] Fill the remaining bins of the signal spectrum using stored spectrum coefficients with a random phase applied.

[00105] 28. The method of any of the Modalities 19-27, in which estimating the phase comprises: Calculate a phase estimate for the time-inverted phase-corrected peaks according to: Φί = - ffraetác + ffrae=fi-^i where Φίέ is an estimated phase at frequency ft, an angle of the spectrum Ãn™ at frequency Ã, 4^cé is a rounding error, Φεέ is a tuning constant and MW.

[00106] 29. The Modality 28 method in which 0ct has a value in an interval between 0.1 and 0.7.

[00107] 30. The Modality 28 method which additionally comprises the calculation of a phase estimate for the non-time-inverted phase-corrected peaks according to: where A^ denotes a phase correction of a sinusoid in Petition 870260054451, dated 05 / 06 / 2026, p. 45 / 111 33 / 40 frequency / ί, ^ denotes a number of frame samples between two frames, ^i^r denotes a number of consecutive missed frames, and ^ denotes a length of a subframe window.

[00108] 31. The method of any of the Modalities 19-30, in which generating the frequency spectra for each subframe of the first two consecutive subframes comprises determining: Zj2?rkn. x (m, n) uq (n) en=ü jV-1 ΣΪΖπKη x(m,n + Nsteplz)wz(n)e JV n=ü where ^ denotes a length of a subframe window, the subframe windowing function ^lí^ is a subframe windowing function ^i^^ for the first subframe of consecutive subframes and wz(n) is a subframe windowing function for the second subframe of consecutive subframes and a number of samples between a first subframe of the first two consecutive auxiliary subframes and the second auxiliary subframe of the first two consecutive auxiliary subframes.

[00109] 32. The method of any of the embodiments 19-31, which additionally comprises applying a random phase to the noise spectrum of the signal spectrum.

[00110] 33. The Mode 32 method in which random phase application to noise spectrum comprises applying random phase to the noise spectrum before combining non-time-inverted phase-corrected peaks with the noise spectrum.

[00111] 34. A decoder device (900) configured to generate a subframe audio hideout of a received audio signal, wherein a decoding method of the decoding device generates frequency spectra on a subframe basis wherein consecutive subframes have a property that an applied window format is a version Petition 870260054451, dated 05 / 06 / 2026, page 46 / 111 34 / 40 mirrored or a time-inverted version of each other, the decoder device comprises: processing circuitry (902); and memory (904) coupled to the processing circuitry, wherein the memory includes instructions which, when executed by the processing circuitry, cause the decoder device to perform operations according to any of the modes 19-33.

[00112] 35. A decoding device (900) configured to generate a concealed audio subframe of a received audio signal, wherein a decoding method of the decoding device (900) generates frequency spectra on a subframe basis wherein consecutive subframes have a window format property applied that is either a mirrored version or a time-inverted version of each other, wherein the decoding device is adapted to operate in accordance with either of the Modes 19-33.

[00113] 36. A computer program comprising a program code to be executed by a set of processing circuits (902) of a decoder device (900) configured to operate on a communication network, wherein the execution of the program code causes the decoder device (900) to perform operations according to any of the modes 19-33.

[00114] 37. Computer program product comprising a non-transient storage medium including program code to be executed by a set of processing circuits (902) of a decoder device (900) configured to operate on a communication network, wherein the execution of the program code causes the decoder device (900) to perform operations in accordance with any of the Embodiments 19-33. Petition 870260054451, dated 05 / 06 / 2026, page 47 / 111 35 / 40

[00115] Explanations are provided below for various abbreviations / acronyms used in this description. Abbreviation Explanation DFT Discrete Fourier Transform IDFT Inverse Discrete Fourier Transform LP Linear Prediction PLC Packet Loss Hiding ECU Error Hiding Unit FEC Frame Error Correction / Hiding

[00116] References are identified below.

[00117] [1] T. Vaillancourt, M. Jelinek, R. Salami, and R. Lefebvre, “Efficient Frame Erasure Concealment in Predictive Speech Codecs using Glottal Pulse Resynchronization,” 2007 IEEE International Conference on Acoustics, Speech and Signal Processing - ICASSP '07, Honolulu, HI, 2007, pp. IV-1113-IV-1116.

[00118] [2] J. Lecomte et al., “Packet-loss concealment technology advances in EVS,” 2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Brisbane, QLD, 2015, pp. 5708-5712.

[00119] [3] 3GPP TS 26.447, Codec for Enhanced Voice Services (EVS); Error Concealment of Lost Packets (Versão 12)

[00120] [4] S. Bruhn, E. Norvell, J. Svedberg e S. Sverrisson, “A novel sinusoidal approach to audio signal frame loss concealment and its application in the new evs codec standard,” 2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Brisbane, QLD, 2015, pp. 5142-5146.

[00121] Generally, all terms used in this document should be interpreted according to their common meaning in the relevant field of technique, unless a different meaning is clearly given and / or implied in the context in which it is used. All references to an element, apparatus, component, means, step, etc. should be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods described in Petition 870260054451, dated 05 / 06 / 2026, page 48 / 111 36 / 40 of this document do not need to be performed in the exact order described, unless a step is explicitly described as following or preceding another step and / or it is implied that one step must follow or precede another step. Any feature of any of the modalities described in this document may be applied to any other modality, where appropriate. Similarly, any advantage of any of the modalities may be applied to any other modalities and vice versa. Other objectives, features and advantages of the modalities involved will be evident from the description below.

[00122] In the above description of various embodiments, it should be understood that the terminology used in this document is intended to describe particular embodiments only and is not intended to be limiting. Unless defined otherwise, all terms (including technical and scientific terms) used in this document have the same meaning as commonly understood by someone skilled in the art to which this description pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of this descriptive report and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly defined in this document.

[00123] When an element is described as being “connected,” “coupled,” “responsive,” or variants thereof to another element, it may be directly connected, coupled, or responsive to the other element, or there may be intervening elements present. In contrast, when an element is described as being “directly connected,” “directly coupled,” “directly responsive,” or variants thereof to another element, there are no intervening elements present. Similar numbers refer to similar elements throughout the report. Additionally, “coupled,” Petition 870260054451, dated 05 / 06 / 2026, page 49 / 111 37 / 40 “connected”, “responsive”, or variants thereof as used herein may include docked, connected, or wireless responsive. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Well-known functions or constructions may not be described in detail for brevity and / or clarity. The term “and / or” includes any and all combinations of one or more of the associated listed items.

[00124] It will be understood that, although the terms first, second, third, etc. may be used in this document to describe various elements / operations, these elements / operations should not be limited by these terms. These terms are only used to distinguish one element / operation from another element / operation. Thus, a first element / operation in some embodiments may be called a second element / operation in other embodiments without departing from the teachings of this description. The same reference numerals or the same reference designators denote the same or similar elements throughout the descriptive report.

[00125] As used in this document, the terms “comprises”, “comprising”, “comprises”, “includes”, “including”, “includes”, “has”, “has”, “having” or their variants are open-ended, and include one or more stated features, integers, elements, steps, components or functions, but do not preclude the presence or addition of one or more other features, integers, elements, steps, components, functions or groups thereof. Furthermore, as used in this document, the common abbreviation “for example”, which derives from the Latin phrase “exempli gratia”, may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to limit such item. The common abbreviation “i.e.”, which derives from the Latin phrase “id est”, may be Petition 870260054451, dated 05 / 06 / 2026, page 50 / 111 38 / 40 is used to specify a particular item within a more general recitation.

[00126] The illustrative embodiments described in this document refer to block diagrams and / or flowchart illustrations of methods implemented by computer, apparatus (systems and / or devices) and / or computer program products. It should be understood that a block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, may be implemented by computer program instructions that are executed by one or more sets of computer circuits.These computer program instructions can be provided to a processor circuit of a general-purpose computer circuit, special-purpose computer circuit, and / or other programmable data processing circuit to produce a machine, such that the instructions, which execute through the computer processor and / or other programmable data processing apparatus, control and transform transistors, values ​​stored in memory locations, and other hardware components within such a set of circuits to implement the functions / acts specified in the block diagrams and / or block flowchart(s), and thus create means (functionality) and / or structure to implement the functions / acts specified in the block diagrams and / or block flowchart(s).

[00127] These computer program instructions may also be stored on a tangible computer-readable medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored on the computer-readable medium produce a manufactured article including instructions that implement the functions / acts specified in the block diagrams and / or flowchart block or blocks. Consequently, the embodiments of the present description may be Petition 870260054451, dated 05 / 06 / 2026, page 51 / 111 39 / 40 incorporated in hardware and / or software (including firmware, resident software, microcode, etc.) that runs on a processor, such as a digital signal processor, which may be collectively referred to as a “circuit set”, “a module”, or variants thereof.

[00128] It should also be noted that, in some alternative implementations, the functions / actions shown in the blocks may occur out of the order shown in the flowcharts. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on the functionality / actions involved. Furthermore, the functionality of a given block in the flowcharts and / or block diagrams may be separated into multiple blocks, and / or the functionality of two or more blocks in the flowcharts and / or block diagrams may be at least partially integrated. Finally, other blocks may be added / inserted between the blocks that are illustrated, and / or blocks / operations may be omitted without departing from the scope of the modalities.Furthermore, although some of the diagrams include arrows along communication paths to show a primary direction of communication, it should be understood that communication can occur in the opposite direction to the arrows shown.

[00129] Many variations and modifications may be made to the embodiments without departing substantially from the principles of the present description. All such variations and modifications shall be included in the present document within the scope of the present description. Consequently, the subject matter described above shall be considered illustrative and not restrictive, and the examples of embodiments are intended to cover all such modifications, enhancements, and other embodiments that fall within the spirit and scope of the present description. Thus, to the maximum extent permitted by law, the scope of the present description shall be determined by Petition 870260054451, dated 05 / 06 / 2026, page 52 / 111 40 / 40 is the broadest permissible interpretation of the present description, including the examples of modalities and their equivalents, and should not be restricted or limited by the detailed description above. Petition 870260054451, dated 05 / 06 / 2026, page 53 / 111

Claims

1 / 7 CLAIMS 1. Method for generating a concealment audio subframe of an audio signal in a decoding device, the method characterized in that it comprises: generating (1000) frequency spectra on a subframe basis wherein a first subframe window of consecutive subframes is a mirrored version or a time-inverted version of a second subframe window of consecutive subframes; detecting (1008) peaks of a signal spectrum of a previously received audio signal on a fractional frequency scale; estimating (1012) a phase of each of the peaks; deriving (1014) a phase adjustment for a time-inverted concealment audio subframe based on the estimated phase;apply (1016) phase adjustment to the signal spectrum peaks to form phase-adjusted peaks and to form a concealment audio subframe based on the phase-adjusted peaks, wherein applying phase adjustment includes applying (1018) a time inversion to the concealment audio subframe; and generating a synthesized concealment audio subframe based on the concealment audio subframe.

2. Method according to claim 1, characterized in that it further comprises: combining (1020) the tuned peaks with a noise spectrum of the signal spectrum to form a combined spectrum for the occultation audio subframe; and wherein the synthesized occultation audio subframe is further generated based on the combined spectrum.

3. Method according to claim 1, characterized in that a synthesized audio concealment frame comprises Petition 870260054451, dated 05 / 06 / 2026, p.54 / 111 2 / 7 less two consecutive obscuring subframes and in which deriving the phase adjustment, applying the phase adjustment, applying the time inversion and combining the phase-adjusted peaks are performed for a first obscuring subframe of at least two consecutive obscuring subframes, the method further comprises: deriving (1024) a phase adjustment to apply to the signal spectrum peaks for a second non-time-inverted obscuring subframe of at least two consecutive obscuring subframes; applying (1026) the phase adjustment to the signal spectrum peaks for the second non-time-inverted subframe to form non-time-inverted phase-adjusted peaks; combining (1028) the non-time-inverted phase-adjusted peaks with a noise spectrum of the signal spectrum to form a combined spectrum for the second obscuring subframe; and generate (1030) a second synthesized concealment audio subframe based on the combined spectrum.

4. Method according to claim 1, characterized in that it further comprises obtaining (1006) the signal spectrum of the audio signal previously received from a memory of the decoding device.

5. Method according to claim 1, characterized in that applying the time inversion comprises applying a complex conjugate to the phase-tuned peaks.

6. Method according to claim 1, characterized in that it further comprises associating (1100) each peak of the detected peaks with several peak frequency bins representing the peak.

7. Method according to claim 6, characterized in that for each peak frequency bin of the various peak frequency bins, one of the time-inverted phase adjustment and the non-time-inverted phase adjustment is applied (1102) to the peak frequency bin.

8. Method according to claim 7, characterized in that it further comprises: filling (1104) remaining bins of the signal spectrum using coefficients from the stored signal spectrum, wherein the spectral coefficients retain a desired property of the signal.

9. Method according to claim 8, characterized in that the desired property comprises correlation with a second channel in a multichannel decoder system.

10. Method according to claim 1, characterized in that estimating the phase of each of the peaks comprises: calculating a phase estimate for the time-inverted phase-adjusted peaks according to: Φί = - ffractàc + ffrac =fi~ki where Φί is an estimated phase at frequency ft, is an angle of the spectrum of a previously received audio signal in a frequency bin kt, ?frac is a rounding error, and Φσ is a tuning constant.

11. Method according to claim 10, characterized in that a phase adjustment for the time-inverted audio subframe peaks of the occultation is calculated according to: Δφ = -2φ0 - 2nf(NstepZ1 + Nlost w) / N where φ is the phase of a peak, ef is the frequency of a peak, Niost denotes the number of consecutive lost frames, N denotes the length of a subframe, and Nstep is a distance in samples between the starting point of an analysis subframe and the occultation subframe.

12. Decoder device (900) configured to generate a subframe audio concealment of an audio signal, characterized in that Petition 870260054451, dated 05 / 06 / 2026, page 56 / 111 4 / 7 the decoder device comprises: processing circuits; and memory operationally coupled to the processing circuits, wherein the memory includes instructions which, when executed by the processing circuits, cause the decoder device to perform operations comprising: generating frequency spectra on a subframe basis wherein a first subframe window of consecutive subframes is a mirrored version or a time-inverted version of a second subframe window of consecutive subframes; detecting peaks in a signal spectrum of a previously received audio signal on a fractional frequency scale; estimating the phase of each of the peaks;To derive a phase adjustment for a time-inverted audio subframe based on the estimated phase; to apply the phase adjustment to the signal spectrum peaks to form phase-adjusted peaks and to form an audio subframe based on the phase-adjusted peaks, where applying the phase adjustment includes applying a time inversion to the audio subframe; and to generate a synthesized audio subframe based on the audio subframe.

13. Decoding device according to claim 12, characterized in that it is further adapted to: combine the phase-tuned peaks with a noise spectrum of the signal spectrum to form a combined spectrum for the occultation audio subframe; and wherein the synthesized occultation audio subframe is further generated based on the combined spectrum. Petition 870260054451, dated 05 / 06 / 2026, p. 57 / 111 5 / 7 14. Decoding device according to claim 12, characterized in that a synthesized audio concealment frame comprises at least two consecutive concealment subframes and in which deriving phase adjustment, applying phase adjustment, applying time inversion and combining the phase-adjusted peaks are performed for a first concealment subframe of the at least two consecutive concealment subframes, wherein the decoding device is further adapted to: derive a phase adjustment to apply to the signal spectrum peaks for a second non-time-inverted concealment subframe of the at least two consecutive concealment subframes; apply the phase adjustment to the signal spectrum peaks for the second non-time-inverted subframe to form non-time-inverted phase-adjusted peaks;Combine the time-inverted, phase-adjusted peaks with a noise spectrum from the signal spectrum to form a combined spectrum for the second occultation subframe; and generate a second synthesized occultation audio subframe based on the combined spectrum.

15. Decoding device according to claim 12, characterized in that it is additionally adapted to obtain the signal spectrum of the audio signal previously received from a memory of the decoding device.

16. Decoding device according to claim 12, characterized in that it is adapted to apply time inversion by applying a complex conjugate to the adjusted phase peaks.

17. Decoding device according to claim 12, characterized in that it is further adapted to associate each peak of the detected peaks with several peak frequency bins that represent the peak.

18. Decoding device according to claim 17, characterized in that it is further adapted to apply one of the phase adjustment for a time-inverted occultation subframe and the phase adjustment for a non-time-inverted occultation subframe to each peak frequency bin of the various peak frequency bins.

19. Decoding device according to claim 18, characterized in that it is further adapted to: fill remaining bins of the signal spectrum using coefficients from the stored signal spectrum, the spectral coefficients retaining a desired property of the signal.

20. Decoding device according to claim 19, characterized in that the desired property comprises correlation with a second channel in a multichannel decoding system.

21. Decoding device according to claim 12, characterized in that it is adapted to estimate the phase of each of the peaks by calculating a phase estimate for the time-inverted phase-adjusted peaks according to: Φί = - ffractàc + ffrac =fi~ki where Φί is an estimated phase at frequency ft, is an angle of the spectrum of a previously received audio signal in a frequency bin kt, ?frac is a rounding error, and Φσ is a tuning constant.

22. Decoding device according to claim 21, characterized in that it is adapted to calculate a phase adjustment for the time-inverted audio subframe peaks of occultation, according to: Δφ = -2φ0 - 2nf(NstepZ1 + Nlost w) / N Petition 870260054451, dated 05 / 06 / 2026, page 59 / 111 7 / 7 where φ is the phase of a peak, ef is the frequency of a peak, Niost denotes the number of consecutive lost frames, N denotes the length of a subframe, and Nstep is a distance in samples between the initial point of an analysis subframe and the occultation subframe.

23. Computer-readable media, characterized in that it comprises computer-readable instructions which, when executed by a set of processing circuits (902) of a decoder device (900) configured to operate on a communication network, cause the decoder device (900) to perform operations comprising: generating (1000) frequency spectra on a subframe basis wherein a first subframe window of consecutive subframes is a mirrored version or a time-inverted version of a second subframe window of consecutive subframes; detecting (1008) peaks in a signal spectrum of a previously received audio signal on a fractional frequency scale; estimating (1012) a phase of each of the peaks; deriving (1014) a phase adjustment for a time-inverted audio subframe based on the estimated phase;apply (1016) phase adjustment to signal spectrum peaks to form phase-adjusted peaks and to form a concealment audio subframe based on the phase-adjusted peaks, wherein applying phase adjustment includes applying (1018) a time inversion to the concealment audio subframe; and generating a synthesized concealment audio subframe based on the concealment audio subframe. Petition 870260054451, dated 05 / 06 / 2026, pp. 60 / 111;

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