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EP2899997A1 - Étalonnage d'un système acoustique - Google Patents

Étalonnage d'un système acoustique Download PDF

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Publication number
EP2899997A1
EP2899997A1 EP14305092.0A EP14305092A EP2899997A1 EP 2899997 A1 EP2899997 A1 EP 2899997A1 EP 14305092 A EP14305092 A EP 14305092A EP 2899997 A1 EP2899997 A1 EP 2899997A1
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EP
European Patent Office
Prior art keywords
loudspeaker
sound system
loudspeakers
watermarks
loudspeaker sound
Prior art date
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Application number
EP14305092.0A
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German (de)
English (en)
Inventor
Michael Arnold
Peter Georg Baum
Xiaoming Chen
Ulrich Gries
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Thomson Licensing SAS
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Thomson Licensing SAS
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Priority to EP14305092.0A priority Critical patent/EP2899997A1/fr
Publication of EP2899997A1 publication Critical patent/EP2899997A1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
    • H04S7/30—Control circuits for electronic adaptation of the sound field
    • H04S7/302—Electronic adaptation of stereophonic sound system to listener position or orientation
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
    • G10L19/018—Audio watermarking, i.e. embedding inaudible data in the audio signal

Definitions

  • the invention relates to a method, an apparatus and a system for efficiently calibrating a multi loudspeaker sound system like e.g. a 5.1 or 3D audio or so-called home cinema or even a home 22.2 multichannel sound system with UHDTV.
  • a multi loudspeaker sound system like e.g. a 5.1 or 3D audio or so-called home cinema or even a home 22.2 multichannel sound system with UHDTV.
  • a method, an apparatus and a system for efficient calibrating a multi loudspeaker sound system with respect to a listening position are disclosed as determined in independent claims.
  • Advantageous embodiments of the invention are disclosed in respective dependent claims.
  • a method for calibrating a multi loudspeaker sound system to a listening position is disclosed, wherein watermarks distinct for each loudspeaker are transmitted in audio signals from loudspeakers of the multi loudspeaker sound system and are used for calibrating the multi loudspeaker sound system.
  • the watermarks are simultaneously transmitted in the audio signals from the loudspeakers, however, according to a further embodiment of the invention, the watermarks distinct for each loudspeaker are transmitted in a serial order with a predetermined shift for calculating a relative propagation delay of sound originating from each loudspeaker of the multi loudspeaker sound system.
  • the watermarks distinct for each loudspeaker are watermark signatures specific for each one loudspeaker by a pattern embedded in each one channel of the multi loudspeaker sound system for identifying the loudspeaker playing back the respective channel.
  • a symbol pattern in a pattern individual for each loudspeaker by individual mark symbols at the same position in the symbol pattern, or a mark symbol at an individual position in the symbol pattern for each one of the loudspeakers of the multi loudspeaker sound system, or a combination of both is used for identifying the loudspeaker playing back a specific channel of the multi loudspeaker sound system.
  • Watermarks are pseudo randomly generated noise signals, which are e.g. generated with different seed values for each one of the loudspeakers of the multi loudspeaker sound system, or are signatures or symbol patterns designed to maximize orthogonality between signatures or symbol patterns specific for each loudspeaker of the multi loudspeaker sound system.
  • the watermarks are synchronously embedded in the audio signals of each channel, or are embedded with a predetermined time difference to each other for calculating a relative propagation delay with regard to a specific user location being the desired listening position.
  • a first step it is furthermore advantageous in a first step to select one of the loudspeakers as a reference loudspeaker, which is arranged in a known or easy to determine distance to the listening position, or which according to further embodiments reproduces or is related to a standard sound pressure level at the listening position.
  • all channels of the multi loudspeaker sound system reproduce e.g. simultaneously an audio signal with distinct watermarks for each one of the loudspeakers for calculating a relative propagation delay of the sound originating from each one of the loudspeakers of the multi loudspeaker sound system with regard to the reference loudspeaker.
  • watermarks distinct for each loudspeaker in audio signals from the loudspeakers of the multi loudspeaker sound system are received via a microphone in a receiving device for detecting the watermarks by correlating with reference patterns individual watermarks in a correlator for identifying the loudspeakers with regard to the reproduced channel, and for measuring a relative propagation delay of the sound originating from the loudspeakers of the multi loudspeaker sound system.
  • the measured relative propagation delay is used for adjusting the sound pressure level of the loudspeakers with respect to relative distance differences between each loudspeaker and the listening position.
  • the microphone of the receiving device should be arranged nearly congruent or held congruent with the listening position. Therefore, listening position and position of the microphone and position of the receiving device shall be understood in the description as the same location.
  • the equation describes the situation of a spherical sound source in a free field propagation which is an approximation of the real situation in a room including reflections. Nevertheless other laws describing the sound pressure level dependence on the propagation distance as e.g. by incorporating directivity aspects of the loudspeakers are also applicable. That means, the calculation of level differences is mapped to the problem of determining differences in distances to the reference loudspeaker. This is done by using watermarking to embed an additional signal into each loudspeaker signal.
  • Watermarks distinct for each loudspeaker of the multi loudspeaker sound system are also used for such a calibration by measuring a relative propagation delay of the sound originating from the loudspeakers. This is performend in the same way as mentioned above as each listening position deviating from a reference listening position is a new listening position for which the relative propagation delay of the sound originating from the loudspeakers is measured.
  • the apparatus is a receiving device receiving watermarks distinct for each loudspeaker transmitted in audio signals from the loudspeakers for identifying each one of the loudspeakers reproducing a channel of the multi loudspeaker sound system. Therefore, the receiving device is provided with a microphone receiving the watermarks distinct for each loudspeaker, a processor via an analog/digital converter connected with the microphone for at least temporarily recording the audio signals transmitted from the loudspeakers of the multi loudspeaker sound system, detecting the watermarks distinct for each one loudspeaker by correlating received watermarks with reference patterns and for determining a relative propagation delay of the audio signals originating from the loudspeakers, each reproducing a channel of the multi loudspeaker sound system, identified by the watermark in the reproduced audio signal.
  • the receiving device is part of a remote control for controlling the multi loudspeaker sound system, wherein a controller is configured upon request to alter the sound pressure level provided by the channels and corresponding loudspeakers of the multi loudspeaker sound system at the listening position and position of the microphone respectively corresponding to relative propagation delays of the audio signals originating from the loudspeakers.
  • the remote control is therefore provided with a calibration button for an automated calibration for one listening position or for an optimisation with regard to two listening positions.
  • the receiving device is a mobile device like a smart phone or tablet personal computer with a microphone, a so-called phablet, comprising a display supplied by the processor of the mobile device for visualising a calibration of the audio signals reproduced by the loudspeakers of the multi loudspeaker sound system.
  • the means for visualising the calibration is a software application configured to determine via a control element one of the loudspeakers of the multi loudspeaker sound system as a reference loudspeaker and is configured to determine a distance to the reference loudspeaker for calibrating the audio signals reproduced by the loudspeakers of the multi loudspeaker sound system.
  • control element to determine one of the loudspeakers of the multi loudspeaker sound system as a reference loudspeaker and the configuration to determine a distance to the reference loudspeaker are input fields and the configuration to display the calibration of the audio signals reproduced by the loudspeakers is a bar graph visualised on the display.
  • the bar graph visualises a sound pressure level or a propagation delay of the sound originating from loudspeakers of the multi loudspeaker sound system.
  • the receiving device provided with the display has in addition a transmitter for controling the sound pressure level received from each one of the loudspeakers at a listening position and according to a further embodiment without such transmitter the sound pressure level received from each one of the loudspeakers is manually adjusted by a user according to calibration results visualised on the display of the receiving device.
  • the system for efficiently calibrating a multi loudspeaker sound system comprises embedding in channels of the multi loudspeaker sound system watermarks individual for each loudspeaker which plays back the respective channel, for identifying the loudspeaker playing back the respective channel and measuring a relative propagation delay of the sound originating from the loudspeakers in a receiving device for adjusting sound pressure levels at a listening position with respect to relative distance differences between loudspeakers and listening position.
  • the multi loudspeaker sound system comprises embedder upon request embedding in channels of the multi loudspeaker sound system watermarks individual for each loudspeaker which plays back the respective channel.
  • a recording medium like an optical disc or a memory stick carrying a watermarked multi-channel audio file is used for calibrating the multi loudspeaker sound system by playing back the recording medium with the multi loudspeaker sound system. Therefore, a multichannel audio file is split into separate channels, watermarks individual for each channel are embedded in each channel and a multi-channel encoder combines the watermarked audio channels into a multi-channel audio file recorded on the recording medium.
  • Fig.1 shows as an example a schematic of a typical living room equipped with a multi loudspeaker sound system like e.g. a 5.1 or 3D audio or home-theater system comprising a main device MLSS of the multi loudspeaker sound system, a center-channel loudspeaker CS, a main left-channel loudspeaker ML, a main right-channel loudspeaker MR, a left surround channel loudspeaker LS and a right surround channel loudspeaker RS.
  • the disclosed calibrating system is also applicable and even more efficient for multi loudspeaker sound systems with much more channels and loudspeakers repectively as e.g.
  • the center-channel loudspeaker CS is arranged next to a television set TV and the four further loudspeakers ML, MR, LS, RS are arranged according to the side name as seen from a first or second listening position LP1 or LP2 as well as next to the walls of the room.
  • the multi loudspeaker sound system is used to reproduce sound or speech provided by the main device MLSS of the multi loudspeaker sound system or provided by the television set TV connected to the main device MLSS of the multi loudspeaker sound system.
  • the International Telecommunication Union standard for multichannel recording and playback is very specific when it comes to loudspeaker configuration and placement for playback of multichannel recordings as e.g. illustrated in Fig. 2 for a 5.1 channel sound system.
  • the 5.1 channel sound system has been specified in Recommendation ITU-R BS.775, which calls for five identical speakers placed in an arc around the centrally located listener LP.
  • the center-channel is therefore a duplicate of the front left and right channel so they are the surrounds in this model.
  • a method, an apparatus and a system for efficient calibrating a multi loudspeaker sound system wherein a watermark distinct and therefore individual for each channel of the multi loudspeaker sound system is embedded in an audio signal reproduced with a loudspeaker LS, ML, CS, MR and RS of the multi loudspeaker sound system and is used for calibrating the multi loudspeaker sound system with a receiving device at a listening position LP1 or LP2 shown in Fig. 1 .
  • the sound system calibration based on watermarking uses a reference loudspeaker level Lo at the listening position LP1 or LP2 such as e.g.
  • an index i O is assigned to reference values.
  • the equation describes the situation of a spherical sound source in a free field propagation which is an approximation of the real situation in a room including reflections. Nevertheless other laws describing the sound pressure level dependence on the propagation distance can be used which e.g. incorporate directivity aspects of the sound sources and loudspeakers repectively.
  • a method for calibrating a multi loudspeaker sound system wherein different watermarks in different channels identifying the loudspeakers of the multi loudspeaker sound system are used for calibrating the multi loudspeaker sound system by simultaneously reproducing all the channels with the multi loudspeaker sound system and recording the result with a microphone MIC at the listening position LP1 or LP2 in a receiving device.
  • the structure of the receiving device is illustrated in Fig. 13 .
  • the user records a superposition of all audio signals, in the following denoted by z at the listening position LP1 or LP2 with a recording device using the microphone MIC in the receiving device illustrated Fig. 13 .
  • the receiving device incorporates a watermark detector which generates symbol patterns equivalent to watermarks embedded in the audio signals according to the number M of loudspeakers.
  • ADC analog/digital converter
  • WF whitening the signal with a whitening filter WF
  • the superposition of all audio signals z is correlated with each symbol pattern by a correlator CR connected to the whitening filter WF.
  • ⁇ z a illustrated in Fig. 7 is above a pre-determined threshold to determine the number of samples M to be moved along the buffer BUF arranged in front of whitening filter WF shown in Fig. 13 . If the symbol is detected, the loudspeakers LS, ML, CS, MR and RS can be identified and the corresponding correlation lag ⁇ z , ai determined as e.g. shown in Fig. 7 for a correlation reference loudspeaker ⁇ z , ao and the one of the loudspeakers having determined as the first one ⁇ z,a1 as e.g. right surround channel loudspeaker RS.
  • Differences in the occurrence of correlation peaks between reference loudspeaker O as for example the center-channel loudspeaker CS and all other loudspeakers RS, LS, ML and MR determine the propagation difference in samples Smpl.
  • the sound pressure level Lo of the reference loudspeaker O such as e.g. the centre loudspeaker CS in Fig. 1 , all the remaining loudspeaker levels Li can be adjusted according to the level equation mentioned above.
  • a configuration of a receiving device like a mobile device with a microphone MIC is disclosed, which has to be placed at the listening position LP1 or LP2, and generates information about relative distance differences ⁇ dio between the loudspeakers LS, ML, CS, MR and RS and listening posion LP1 or LP2 for adjusting the sound pressure level of the loudspeakers LS, ML, CS, MR and RS with respect to listening posion LP1 or LP2.
  • the receiving device is provided with a microphone MIC via an analog/digital converter ADC connected with a buffer BUF for temporally storing the audio samples captured with the microphone MIC.
  • the buffer BUF is via a whitening filter WF connected to a correlator CR and the whitening filter WF supplies the correlator CR for detecting a base pattern respectively a mark symbol by a feedback loop checking the number N of base pattern as e.g. a base pattern at different locations or different patterns included in the watermark signal.
  • the whitening filter WF applies a window to the buffered digital audio signal and transforms blocks of audio samples into a frequency domain by applying a Discrete Fourier Transformation DFT, the magnitude of Fourier coefficients is set to 1 and the whitening filter WF transforms the blocks by applying an inverse Discrete Fourier Transformation IDFT back into the time domain and applies a window to provide overlap-add blocks for correlation.
  • the correlator CR correlates the filtered audio blocks with all mark symbols N of the different audio watermarks in a mark symbol loop MSL, and a connected pattern detector PL detects peaks and locations of symbols in patterns in the number M of used patterns and individual watermarks, respectively, for calculating corresponding time delays between arrivals of mark symbols and base patterns respectively.
  • the pattern detector PL provides a pattern which in a further feedback loop supplies the input of the buffer BUF with a number M of pattern blocks for relating a detected pattern to further received patterns, so that individual patterns provided by corresponding sound sources as e.g. loudspeakers LS, ML, CS, MR and RS will be assigned to a corresponding channel of the multi loudspeaker sound system. That means that the pattern detector PL provides individual patterns with a mark symbol which identifies the one of the loudspeakers LS, ML, CS, MR and RS which transmitted the pattern. Furthermore, an output unit OD is connected to the pattern detector PL, wherein a calculation of relative distance differences and sound pressure level is performd as mentioned above.
  • the receiving device is part of a remote control RC for controlling the multi loudspeaker sound system. Except the microphone MIC, the elements of the receiving device are realised in a controller of the remote control RC configured upon request to alter the sound pressure levels provided by the channels and corresponding loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system at the listening position LP1 or LP2.
  • the listening position LP1 or LP2 and position of the microphone MIC are assumed as the same position in this description.
  • Sound pressure levels are altered corresponding to a relative propagation delay of the audio signals originating from the loudspeakers LS, ML, CS, MR and RS.
  • the remote control RC is provided with a calibration botton for an automated calibration for one listening postion LP1, or for an optimisation with regard to two listening positions LP1 and L2, by taking into account the changes in distances with respect to different listening positions LP1 and LP2.
  • Such optimisation is performed by averaging propagation delays measured with respect to the different listening positions LP1 and LP2.
  • calibration parameter measured and calculated for one or more listening positions LP1, LP2 are stored and assigned to a user profile for a fast calibration of the multi loudspeaker sound system, so that a calibration has not to be repeated.
  • the receiving device is a mobile device MD like a smart phone or tablet personal computer with a microphone, a so-called phablet shown in Fig. 3 .
  • the mobile device MD shown in Fig.3 is provided with a display supplied by a processor of the mobile device MD for visualising the calibration of the audio signals reproduced by the loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system.
  • the means for visualising the calibration is a software application APPMD illustrated in Fig. 6 .
  • the software application APPMD is configured to determine via a control element one of the loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system as a reference loudspeaker O and furthermore configured to determine a distance to the reference loudspeaker O for calibrating the audio signals reproduced by the loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system.
  • control element to determine one of the loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system as a reference loudspeaker o and the configuration to determine a distance do to the reference loudspeaker O are input fields and the configuration to display the calibration of the audio signals reproduced by the loudspeakers LS, ML, CS, MR and RS is a bar graph Level visualised on the display of the mobile device MD.
  • the bar graph Level visualises a sound pressure level or a propagation delay of the sound originating from loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system after selecting one of the loudspekers LS, ML, CS, MR and RS.
  • the receiving device provided with the display has in addition a transmitter for controling the sound pressure level Li received from each one of the loudspeakers LS, ML, CS, MR and RS at a listening position LP1 or LP2 via the main device MLSS of the multi loudspeaker sound system.
  • the sound pressure level Li received from each one of the loudspeakers LS, ML, CS, MR and RS is manually adjusted by a user according to calibration results visualised on the display of the mobile device MD.
  • the control element to determine one of the loudspeakers LS, ML, CS, MR and RS of the multi loudspeaker sound system as a reference loudspeaker O and the configuration to display a calibration of the audio signals on the display of the receiving device are realized with radio button or check boxes which indicate a selected loudspeaker and a calibration of remaining loudspeakers of the multi loudspeaker sound system. That means that the receiving device comprises a correlator for correlating the watermarks distinct for each loudspeaker of the multi loudspeaker sound system to identify the loudspeakers each reproducing a channel of the multi loudspeaker sound system and means for evaluating the corresponding sound pressure level at the listening position LP1 or LP2.
  • the system for efficiently calibrating a multi loudspeaker sound system comprises embedding in channels of the multi loudspeaker sound system watermarks individual for each loudspeaker which plays back the respective channel.
  • the audio signal is mapped into a time-frequency representation before embedding a watermark. It is common practice in audio processing to apply a short-time Fourier transform to obtain a time-frequency representation of the signal so as to mimic the behaviour of the ear.
  • the short-time Fourier transform consists of segmenting an input signal x in blocks samples of a predetermined length using a sliding window with a hop-size of a predetermined number of samples, and applying the Discrete Fourier Transformation DFT to each block after multiplication by an analysis window WA.
  • This analysis phase results in a collection of DFT-transformed windowed blocks X ⁇ n which is fed to the subsequent watermark embedding process Embedding.
  • Embedding modified DFT-transformed blocks ⁇ n output by the audio processing application are used to reconstruct the audio signal during the so-called synthesis phase.
  • the frames are inverse-transformed and multiplied by a synthesis window w s that suppresses audible artifacts by fading out spectral discontinuities at frame boundaries.
  • the resulting frames are added together with the appropriate time offset as depicted in Fig. 10.
  • Fig. 10 illustrates the analysis-synthesis framework, wherein the audio signal is mapped into a time-frequency representation before embedding a watermark, at which point the signal is mapped back to the time domain.
  • the embedding process for embedding into the phase as illustrated in Fig. 11 and Fig. 12 essentially comprises extracting the phase ⁇ n of WOLA coefficients from incoming transformed blocks X ⁇ n and arranging them sequentially in a 1-D signal ⁇ , applying a quantization based embedding algorithm to obtain the watermarked phases ⁇ , and segmenting the resulting signal in blocks of samples ⁇ n to reconstruct the watermarked transformed blocks ⁇ n , which can be subsequently inverse-transformed back to the time domain.
  • ⁇ [i] ⁇ _(a_k) [i], a_k ⁇ A, i ⁇ B ⁇ N + [0, B-1], where ⁇ _(a_k) is a sequence of angles associated with the symbol a_k and derived from a reference signal r (a k), i is the index in the 1-D signal ⁇ , B is the number of samples in one block and N is the number of blocks for one symbol.
  • Frequencies below frequency tap ⁇ l are discarded due to their high audibility whereas frequencies above frequency tap ⁇ h are ignored because of their high variability.
  • ⁇ i ⁇ i + ⁇ i / ⁇ i min ⁇ i , ⁇ i , i ⁇ B ⁇ N + ⁇ 1 , ⁇ h
  • ⁇ [i] ⁇ _(a_k) [i]- ⁇ [i] is the forecast embedding distortion in case of perfect quantization.
  • Fig. 11 and Fig. 12 are a geometrical illustration of the embedding process.
  • the phase ⁇ [i] is moved towards the intended target value ⁇ a k [i] while guaranteeing that the embedding distortion ⁇ [i] never exceeds the threshold ⁇ [i] specified by the perceptual model.
  • the target angle is close enough to be reached, whereas in a limited regime, the embedding process is constrained by the perceptual margin.
  • the detector is presented with audio blocks z that contain a watermark, and that may have undergone a number of modifications.
  • a k is the whitened version of z(resp.r a k ) and I is the correlation lag measured in samples.
  • the whitening process in the whitening filter WT in Fig. 13 consists in mapping the signal to the WOLA domain, setting the magnitude of the WOLA coefficients to 1, and returning to the time domain.
  • the array ⁇ z,a_k is expected to be close to normal distributed with zero mean.
  • the symbol a_k is embedded, it should exhibit a strong peak for a given correlation lag l_k*, whose position depends on the alignment of the two signals.
  • the symbol pattern for each channel is designed to maximize orthogonality ⁇ (a_i,a_j) ⁇ 0 ⁇ i ⁇ j.
  • a flow chart in Fig. 8 which illustrates that the audio signal at first is segmented SEG in overlapping blocks of samples and a sliding window is applied - a so-called windowing WIN - to avoid interruptions and to equalise overlapping parts of the blocks of audio signals.
  • Discrete Fourier Transformation DFT is applied to each block, which results in a collection of DFT-transformed windowed blocks which are fed to the subsequent watermark embedding process comprising a modulation MOD with symbol patterns provided by a symbol pattern generator SPG.
  • Symbol pattern generator SPG is supplied by a noise generator NG providing different pseudo random noise signals according to a number of mark symbols N and a number M of symbol patterns and individual watermarks respectively.
  • Mark symbols N are pseudo random noise patterns generated with a specific seed
  • different symbol patterns and watermarks respectively are patterns generated with different mark symbols at the same or different position in a pattern
  • different symbol patterns are patterns generated with the same mark symbol at a different location in the pattern.
  • the audio signal is modulated with symbol patterns in the Fourier domain of the audio signal and afterwards by an inverse Discrete Fourier Transformation IDFT reconstructed during a so-called synthesis phase.
  • the blocks are inverse-transformed and multiplied by a synthesis window WIN that suppresses audible artefacts by fading out spectral discontinuities at frame or block boundaries.
  • the resulting blocks are added together OA with the appropriate time offset and mapped back to the time domain.
  • the main device MLSS of the multi loudspeaker sound system comprises embedders EB upon request embedding in channels of the multi loudspeaker sound system watermarks individual for each loudspeaker which plays back the respective channel.
  • Multichannel audio files are split into separate channels 1..M in the main device MLSS of the multi loudspeaker sound system and switches SW1, ... SWM are provided for upon request embedding an individual watermark in each channel.
  • each embedder EB is connected with a volume controller VA for calibrating the sound pressure level provided by the corresponding loudspeaker LS1 ...LSM at the listening position LP1 or LP2, or for a, with respect to two listening positions LP1 and LP2, optimized reproduction of sound or speech with the multi loudspeaker sound system.
  • the volume controller VA is in an automated manner controlled by a receiving device transmitting results of a measured relative propagation delay of the sound originating from the loudspeakers of the multi loudspeaker sound system to the main device MLSS of the multi loudspeaker sound system.
  • a recording medium DP like an optical disc or a memory stick carrying a watermarked multi-channel audio file is used for calibrating the multi loudspeaker sound system, by playing back the recording medium with the multi loudspeaker sound system.
  • a multi channel audio file is split into separate channels in an exemplary computer device and watermarks individual for each channel are embedded in each channel.
  • the exemplary computer device comprises a multi-channel encoder which combines the watermarked audio channels WMC 1 ...WMC M into a multi-channel audio file MCE for recording the watermarked multi-channel audio file WMF on the recording medium DP.
  • watermarks distinct for each loudspeaker are transmitted in audio signals from loudspeakers of the multi loudspeaker sound system and are used for calibrating the multi loudspeaker sound system.
  • reference patterns are generated by a reference pattern generator RPG in the audio watermark detector of the receiving device as illustrated in the flow diagram for detecting audio watermarks shown in Fig. 9 .
  • a random phase generator RP preferably controlled by a key SK is connected to reference pattern generator RPG for a correlation of all reference patterns as generated by the audio watermark embedders EB. That means that the correlator CR of the audio watermark detector of the receiving device correlates whitened audio signals with all reference patterns of the audio signals distributed to loudspeakers L1 to Ln to perform a symbol detection SD so that a detected symbol DS is provided for further processing.
  • the correlator CR exhibits a strong peak for a given correlation lag, whose position depends on the location of the symbol in the watermark and the time of arrival.
  • the detection procedure of the watermarking system therefore first isolates the position and the amplitude of the correlation result peak for each symbol, and then identifies which symbol exhibits the largest peak. If the peak is larger than some detection threshold in the pattern detector PL shown in Fig. 13 , the symbol is decoded, otherwise the audio watermark detector reports that there is no watermark and nothing will be further executed.
  • the watermark detection method illustrated by a flow diagram in Fig.
  • the connected whitening filter WF processes audio samples stored in the buffer BUF to segment and window the samples in blocks, performs a transformation of the blocks into a frequency domain, setting a magnitude equal to 1 and a transformation back into the time domain with overlap-add blocks to provide a collection of audio blocks for correlation. That means that the whitening process performed in the whitening filter WF consists in mapping the signal to the WOLA domain, setting the magnitude of the WOLA coefficients to 1, and returning to the time domain.
  • the audio watermark detector of the receiving device computes a cross-correlation score for all symbols so that a correlation lag is determined by the number of samples between the symbols to measure and to determine a delay in arrival.
  • the multi loudspeaker sound system is calibrated by adjusting the channels and loudspeaker levels according to a propagation delay with means of the multi loudspeaker sound system by checking a propagation delay of the audio signals originating from the loudspeakers. Adjusting sound pressure levels or a time delay with respect to differences in the audio signal received from loudspeakers of the multi loudspeaker sound system at a listening position LP1 or LP2 in comparision to a reference listening position is disclosed.
  • Watermarks distinct for each loudspeaker are detected by correlating sound recorded in the receiving device with known watermark sequences, and sound pressure levels and a time delay are calibrated with respect to relative distance differences between loudspeakers and the listening position LP1 or LP2.
  • the disclosed calibration is efficient due to a simultaneous determination of propagation delay respective distance differences between loudspeaker and microphone position.
  • the duration needed for a calibration of a multi loudspeaker sound system is independent on the number of loudspeakers used in the setup.
  • An automatic adaptation of playback sound pressure level with respect to the distance of the listening position LP1 or LP2 relative to the each loudspeaker is provided and according to an embodiment of the invention even the complete calibration procedure will be performed in an automated manner upon user request. Any sound can be used for calibrating and the inaudibility of the embedded watermarks is ensured by a psychoacoustic model.
  • the calibration is executable with a mobile device and makes the setup or so-called calibration convenient for the user.

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  • Engineering & Computer Science (AREA)
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  • Physics & Mathematics (AREA)
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EP14305092.0A 2014-01-22 2014-01-22 Étalonnage d'un système acoustique Withdrawn EP2899997A1 (fr)

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CN108432271B (zh) * 2015-10-08 2021-03-16 班安欧股份公司 扬声器系统中的主动式房间补偿
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CN110278521A (zh) * 2018-03-18 2019-09-24 阿尔派株式会社 声学特性测定装置以及方法
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CN109286888A (zh) * 2018-10-29 2019-01-29 中国传媒大学 一种音视频在线检测与虚拟声像生成方法及装置
CN110677801A (zh) * 2019-08-23 2020-01-10 华为技术有限公司 一种音箱控制方法、音箱以及音箱系统
WO2022120051A3 (fr) * 2020-12-03 2022-11-03 Dolby Laboratories Licensing Corporation Orchestration de signaux de modulation à spectre étalé à séquence directe acoustique pour l'estimation d'indicateurs de scène acoustique
US12273698B2 (en) 2020-12-03 2025-04-08 Dolby Laboratories Licensing Corporation Orchestration of acoustic direct sequence spread spectrum signals for estimation of acoustic scene metrics
US12470885B2 (en) 2020-12-03 2025-11-11 Dolby Laboratories Licensing Corporation Orchestration of acoustic direct sequence spread spectrum signals for estimation of acoustic scene metrics
CN116137152A (zh) * 2021-11-18 2023-05-19 宏碁股份有限公司 声音水印的识别方法及声音水印的识别装置
EP4440149A1 (fr) 2023-03-28 2024-10-02 Sonova AG Procédé et système de suppression du sifflement de larsen

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