Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H7/00—Instruments in which the tones are synthesised from a data store, e.g. computer organs
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
  • H04S3/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/155—Musical effects
  • G10H2210/265—Acoustic effect simulation, i.e. volume, spatial, resonance or reverberation effects added to a musical sound, usually by appropriate filtering or delays
  • G10H2210/295—Spatial effects, musical uses of multiple audio channels, e.g. stereo
  • G10H2210/301—Soundscape or sound field simulation, reproduction or control for musical purposes, e.g. surround or 3D sound; Granular synthesis
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
  • H04R2499/10—General applications
  • H04R2499/11—Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's

Definitions

• the present invention relates to audio processing and, more particularly, to three-dimensional spatialization of synthetic sound sources.
• non-parametric methods are known. No particular parameter is used a priori to modify samples previously stored in memory.
• the best-known representative of these methods is classical wave table synthesis.
• Parametric synthesis methods which rely on the use of a model that makes it possible to manipulate a small number of parameters, compared to the number of signal samples produced in the sense of the non-parametric methods.
• Parametric synthesis techniques typically rely on additive, subtractive, source / filter or non-linear models.
• Some techniques are based on the consideration of HRTFs ("Head Related Transfer Function") transfer functions representing the disturbance of acoustic waves by the morphology of an individual, these HRTFs functions being specific to this individual.
• HRTFs Head Related Transfer Function
• the sound reproduction is carried out in a way adapted to the HRTFs of the listener, typically on two remote speakers (“transauraf") or from the two earpieces of a headset (“binaural")
• Other techniques for example Vamphonic "or the” multichannel "(5.1 to 10.1 or more) provide rather a restitution on more than two speakers.
• some HRTFs techniques use the separation of the frequency and position variables of the HRTFs, thus giving a set of p basic filters (corresponding to the first p eigenvalues of the covariance matrix of the HRTFs whose variables statistics are the frequencies), these filters being weighted by spatial functions (obtained by projection of the HRTFs on basic filters).
• the spatial functions can then be interpolated, as described in US-5,500,900.
• Spatialization of many sound sources can be achieved through a multichannel implementation applied to the signal of each of the sound sources.
• the gains of the spatialization channels are applied directly to the sound samples of the signal, often described in the time domain (but possibly also in the frequency domain). These samples sound are processed by a spatial isation algorithm (with gain applications that depend on the desired position), irrespective of the origin of these samples.
• the proposed spatialization could apply to both natural and synthetic sounds.
• each sound source must be synthesized independently (with a temporal or frequency signal), in order to then be able to apply independent spatialization gains.
• N sound sources it is therefore necessary to perform N synthesis calculations.
• the application of the gains to sound samples, whether they come from the time or frequency domain, requires at least as many multiplications as there are samples.
• Q gains M being the number of intermediate channels (surround channels for example) and N being the number of sources.
• this technique requires a high calculation cost in the case of the spatialization of many sound sources.
• the so-called “virtual loudspeakers” method makes it possible to encode the signals to be spatialized by applying them in particular gains, the decoding being done by convolution of the signals encoded by pre-calculated filters (Jérians Daniel, "Representation of acoustic fields, application to the transmission and reproduction of complex sound scenes in a multimedia context", PhD Thesis, 2000).
• an exemplary embodiment which is referred to in this document WO-05/069272 and in which the sources are synthesized by associating amplitudes at frequencies constituting a "sound tone" (for example a fundamental frequency and its harmonics ), plans to group synthesized signals by identical frequencies, with a view to subsequent spatialization operating on the frequencies.
• a "sound tone” for example a fundamental frequency and its harmonics
• FIG. 1 This exemplary embodiment is illustrated in FIG. 1.
• S N respective amplitudes a 0 1 , ai 1 , ..., a p 1 , ..., a /, ..., a 0 N , a- ⁇ ..., a p N , where, in the general notation al, j is a source index between 1 and N and i is a frequency index between 0 and p.
• amplitudes of a set ao j , a- ⁇ j , ..., a p j to be assigned to the same source j can be zero if the corresponding frequencies are not represented in the sound signal of this source j .
• the amplitudes ai 1 , ..., ai N relative to each frequency fi are grouped ("mixed") to be applied, frequency by frequency, to the SPAT spatialization block for encoding operating on the frequencies (in binaural for example, in anticipating interaural delay to be applied to each source).
• the signals of the channels Ci,..., C k , originating from the spatialization block SPAT, are then intended to be transmitted through one or more networks, or else stored, or other, for the purpose of a subsequent restitution (preceded by where appropriate, a suitable spatialization decoding). This technique, although very promising, still deserves some optimizations.
• the present invention improves the situation.
• a method for jointly synthesizing and spatialising a plurality of sound sources in associated positions of the space comprising: a) a step of assigning to each source at least one parameter representative of a amplitude, b) a spatialization step implementing an encoding in a plurality of channels, in which each amplitude parameter is duplicated to multiply by a spatialization gain, each spatialization gain being determined, on the one hand, for an encoding channel and, secondly, for a source to be spatialised, c) a step of grouping the parameters multiplied by the gains, in respective channels, by applying a sum of said multiplied parameters to all the sources for each channel and d) a parametric synthesis step applied to each of the channels.
• the present invention proposes for this purpose to first apply a spatialization encoding, then a "pseudo-synthesis", the term “pseudo” aiming at the fact that the synthesis applies in particular to the encoded parameters, derived from spatialization and not to usual synthetic sound signals.
• a feature that the invention proposes is the spatial encoding of some synthesis parameters, rather than performing a spatial encoding of the signals corresponding directly to the sources.
• This spatial encoding applies more particularly to synthesis parameters which are representative of an amplitude and it advantageously consists in applying to these few synthesis parameters spatialization gains which are calculated as a function of respective desired positions of the sources. It will thus be understood that the parameters multiplied by the gains in step b) and grouped in step c) are not really sound signals, as in the general prior art described above.
• the present invention uses a mutual parametric synthesis where one of the parameters has the dimension of an amplitude. Unlike techniques of the prior art, it thus takes advantage of the advantages of such a synthesis to perform the spatialization.
• the combination of synthesis parameter sets obtained for each of the sources advantageously makes it possible to globally control the encoded blocks of mutual parametric synthesis.
• the present invention then makes it possible to spatialize simultaneously and independently of numerous synthesized sound sources from a parametric synthesis model, the spatialization gains being applied to the synthesis parameters rather than to the samples of the time or frequency domain. This embodiment thus ensures a substantial saving of the computing power required because it implies a low calculation cost.
• the technique in the sense of the invention requires fewer calculations than the usual techniques in the sense of the prior art. For example, at the surround order 1 and in two dimensions (ie three intermediate channels), the invention already allows a calculation gain for only four sources to spatialize.
• the present invention also makes it possible to reduce the number of gains to be applied. Indeed, the gains are applied to the synthesis parameters and not to the sound samples. Updating parameters such as the volume is generally less frequent than the sampling frequency of a signal, a calculation economy is thus achieved. For example, for a frequency of updating parameters (such as the volume in particular) of 200 Hz, a substantial saving in multiplication is achieved for a sampling frequency of the signal of 44100 Hz
• the fields of application of the present invention may concern both the musical field (including polyphonic ringtones of mobiles), the field of multimedia (including video game sound systems), the field of virtual reality (rendering of sound scenes). , simulators (synthesis of engine noise), or others.
• FIG. 2 illustrates the general processing of spatialization and synthesis provided for in a method according to the invention
• FIG. 3 illustrates a processing of the spatialized and synthesized signals for spatial decoding with a view to restitution
• FIG. 4 illustrates a particular embodiment in which several amplitude parameters are assigned to each source, each parameter being associated with a frequency component
• FIG. 5 illustrates the steps of a method in the sense of the invention, and may correspond to a flowchart of a computer program for the implementation of the invention.
• At least one parameter Pi is assigned to a source Si from among a plurality of sources Si, ..., S N to be synthesized and spatialized (i being between 1 and N ).
• Each parameter pi is duplicated in as many spatialization channels provided in the spatialization block SPAT.
• M encoding channels are provided for the spatialization
• each parameter pi is duplicated M to apply respective spatialization gains g ⁇ ..., where M (i being, as a reminder, an index of source Si).
• M i being, as a reminder, an index of source Si
• new parameters p TM (i varying from 1 to N and m varying from 1 to M) are calculated by multiplying the parameters pi by the encoding gains g TM, obtained from the position of each of the sources.
• the parameters Pi m are combined (by summation in the example described) to provide the parameters p g m which feed M mutual parametric synthesis blocks.
• These M blocks constitute the synthesis module SYNTH, which delivers M time or frequency signals ss m (m varying from 1 to M), obtained by synthesis from of the parameters p g m .
• These signals ss m can then feed a conventional block of spatial decoding, as will be seen below with reference to FIG.
• the synthesis used is an additive synthesis with application of an inverse Fourier transform (IFFT).
• IFFT inverse Fourier transform
• a set of N sources is characterized by a plurality of parameters pi, k representing the amplitude in the frequency domain of the kth frequency component for the ith source Sj.
• the time signal Si (n) that would correspond to this source If, if it were synthesized independently of the other sources, would be given by:
• the parameter Pi, k represents the amplitude of a given frequency component k for a given source Si.
• G gains are predetermined for a desired position for the source Si and according to the selected spatialization encoding.
• Y m is a spherical harmonic of order m
• ⁇ i and ⁇ i are respectively the azimuth and the desired site for the Si source.
• the parameters p m i, k are then combined frequency by frequency, so as to obtain a single global parameter:
• the value of k 1 is less than ki because common frequencies can characterize several sources at once. In one embodiment, it may be provided to associate the same global set of frequencies to all sources, even if certain amplitude parameters for certain source frequencies are zero.
• the synthesis step consists of using these parameters p m g , k (m varying from 1 to M) to synthesize each of the M frequency spectra ss m ( ⁇ ) from the SYNTH synthesis module. It may be provided for this purpose to apply the technique described in FR-2,679,689, iteratively adding spectral envelopes corresponding to the Fourier transform of a time window (for example Hanning), these spectral envelopes being previously sampled , tabulated, centered at frequencies fk and then weighted by p m g , k , which is written as:
• K amplitude parameters p iik are assigned to each source Sj.
• the index i, of source is between 1 and N.
• the index k, of frequency is between 1 and K.
• K parameters are duplicated, M times, to be multiplied each by one gain Spatialization g TM.
• the index m, of spatialization encoding channel is between 1 and M.
• the processing then continues by multiplying the global parameter of each subchannel p m g , k associated with a frequency fk by a spectral envelope envk ( ⁇ ) centered at this frequency fk, and this, for all the K subchannels ( k between 1 and K), and globally, for all M channels (m being between 1 and M). Then the sub-channels K are summed in each channel m, according to the following relation:
• ss m ( ⁇ ") env k ⁇ ), for m ranging from 1 to M channels in total.
• the signals ss, m m (/ ⁇ ) encoded for their spatialization and synthesized in the sense of the invention are then obtained. They are expressed in the frequency domain.
• SS m (n) IFFT (ss m ( ⁇ )).
• successive frames can be achieved by a conventional technique of addition / overlap.
• SS m (n) can then be supplied to a spatialization decoding block.
• the processing performed by the spatial decoding DECOD block of FIG. 3 can be of the type:
• the adaptation filters from the surround format to the binaural format can be applied directly in the frequency domain, thus avoiding convolution in the time domain and a corresponding calculation cost.
• the spectra are then summed by ear before performing the inverse Fourier transform and the addition / recovery operation, ie:
• the present invention also relates to a computer program product, whether it is stored in a memory of a central unit or a terminal, or on a removable support adapted to cooperate with a reader of this central unit.
• This program comprises in particular instructions for the implementation of the method described above and a flowchart can be illustrated by way of example in Figure 5, summarizing the steps of such a method.
• Step a) is aimed at assigning the parameters representative of an amplitude to each source Sj.
• a parameter pi, k is assigned by frequency component f k as described above.
• Step b) aims at the duplication of these parameters and their multiplication by the gains g TM of the encoding channels.
• Step c) relates to the grouping of the products obtained in step b), with in particular the calculation of their sum on all Si sources.
• Step d) targets the parametric synthesis with multiplication by a spectral envelope env k as described above, followed by a grouping of the subchannels by applying, in each channel, a sum over all the frequency components (d index k ranging from 1 to K).
• Step e) aims at decoding the spatialization of the signals ss m originating from the respective channels, synthesized, spatialised and represented in the frequency domain, for a reproduction on two loudspeakers, for example in binaural format.
• the present invention also provides a device for generating synthetic and spatialized sounds, comprising in particular a processor, and in particular a working memory adapted to store instructions of the computer program product defined above.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• General Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Stereophonic System (AREA)
• Golf Clubs (AREA)
• Circuit For Audible Band Transducer (AREA)
• Telephone Set Structure (AREA)
• Telephone Function (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=37400911

Family Applications (1)

Country Status (8)

Families Citing this family (4)

Family Cites Families (12)

• 2007
  • 2007-03-01 WO PCT/FR2007/050868 patent/WO2007104877A1/fr active Application Filing
  • 2007-03-01 US US12/225,097 patent/US8059824B2/en active Active
  • 2007-03-01 DE DE602007002993T patent/DE602007002993D1/de active Active
  • 2007-03-01 JP JP2008558857A patent/JP5051782B2/ja active Active
  • 2007-03-01 ES ES07731685T patent/ES2335246T3/es active Active
  • 2007-03-01 PL PL07731685T patent/PL1994526T3/pl unknown
  • 2007-03-01 AT AT07731685T patent/ATE447224T1/de not_active IP Right Cessation
  • 2007-03-01 EP EP07731685A patent/EP1994526B1/de active Active

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events