IMPROVEMENTS IN, OR RELATING TO, VISUAL SPEECH SYNTHESIS

Abstract: The invention provides a method and apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, in which the acoustic speech signal is analyzed to identify its constituent elemental speech units, and an image of moving human facial features is generated and displayed on a display screen. The facial feature movements are substantially synchronized, in real time, to the constituent elemental speech units. In particular, a series of facial movement patterns for the constituent elemental units of acoustic speech signals, which are indicative of movement, in three-dimensions, of a number of points around the mouth of a speaker, are generated and stored, and, in response to the identification of each of the constituent elemental units of the acoustic speech signal delivered by the speaker, a respective stored movement pattern is retrieved for displaying on the display screen. The facial features around the mouth preferably include the region around the lips, cheeks and nose, and the number of points around the mouth may amount to at least ten points.

Description: IMPROVEMENTS IN, OR RELATING TO, VISUAL SPEECH SYNTHESIS The invention relates to visual speech synthesis and, in particular, to a method and apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal In essence speech production is based on the basic mechanisms of phonation which is related to the vibration of the vocal cords, and vocal articulation which is related to the time-varying geometry of the vocal tract responsible for the phonemic structure of speech When a person causes his/her diaphragm to be forced upwards, air is expelled from the lungs and flows into the trachea, glottis (the gap between the two vocal cords) and larynx before reaching the upper part of the vocal tube, called the vocal tract which is formed by the pharynx, nasal and oral concavities The penodical closure of the glottis interrupts the air flow, generating a variation of the air pressure whose frequency can be raised to the acoustic range The harmonic components of this acoustic wave, which are multiples of the fundamental (i e pitch) frequency, are then modified as long as the air flows through the vocal tract The nature of the modification is dependent on the geometry of the vocal tract The shape of the vocal tract can, in fact, be varied by moving the jaw, tongue lips and velum (palate) This mechanism enables the vocal tract to implement a time-varying system, having the capability to filter the incoming acoustic wave, reshaping its spectrum and modifying the produced sound Speech is the concatenation of elementary units, called phones, generally classified as - vowels, when they correspond to a stable configuration of the vocal tract, or alternatively, as consonants when they correspond to transient articulatory movements Each phone can then be characterized by means of a few attributes (i e open/closed, front/back, oral/nasal and rounded/unrounded), which qualify the articulation manner (i e fricative, like /f/, /s/, plosive, like /b/, /p/, nasal, like /n/ /m/, ) and articulation place (i e labial, dental alveolar, palatal, glottal) Some phones, like vowels and a subset of consonants, are accompanied by vocal cord vibration and are called "voiced" phones, while other phones, like plosive consonants, are totally independent of vocal cord vibration and are called "unvoiced" phones With voiced phones, the speech spectrum is shaped, as previously described, in accordance with the geometry of the vocal tract, with characteristic energy concentrations around three main peaks called "formants", located at increasing frequencies, FI, F2 and F3 An observer skilled in lip reading is able to estimate the likely locations of formant peaks by computing the transfer function from the configuration of the visible articulators This computation is performed through an estimation of four basic parameters, namely (i) the length of the vocal tract, L, (n) the distance, d, between the glottis and the place of maximum constriction, (in) the radius, r, of the constriction, and (iv} the ratio between the area, A, of the constπction and the length, L, of the vocal tract While the length, L, of the vocal tract can, a priori, be estimated, taking into account the sex and age of the speaker, the other parameters can be inferred (roughly) from the visible configuration If the maximum constriction is located in correspondence of the mouth, thus involving lips, tongue and teeth, as is the case for labial and dental phones, the estimation is usually reliable In contrast, when the maximum constriction is non-visible, such as in velar phones (/k/, /g/), the estimation is usually very poor Lip reading represents the highest synthesis of human expertise in converting visual inputs into words and then into meanings It consists of a personal database of knowledge and skills constructed and refined by training, having the capability to associate virtual sounds to specific mouth shapes, generally called "viseme", and thereby infer the underlying acoustic message The lip reader's attention is basically focused on the mouth, including all its components, i e lips, teeth and tongue, but significant help, in a lip reader's comprehension, also comes from the entire facial expression of the speaker In lip reading, a significant amount of processing is performed by the lip reader, himself, who is skilled in post-filteπng the converted message, to recover from errors and from communication lags It is possible, through linguistic and semantic reasoning, to exploit message redundancy and obtain an understanding from the context of the message This kind of knowledge-based interpretation is performed by the lip reader in Audio-visual speech perception and lip reading rely on two perceptual systems, working in cooperation, so that, in the case of hearing impairments, the visual modality can efficiently integrate, or even substitute for, the auditory modality It has been demonstrated experimentally that exploitation of visual information, associated with the movements of a speaker's lips, improves the comprehension of speech, with these expeπments, the Signal-to-Noise Ratio (SNR) is incremented up to 15 dB and auditory failure is, in most of cases, transformed into near-perfect visual comprehension The visual analysis of the speaker's face provides different levels of information to the observer, improving the discrimination of signal from noise The opening/closing of the lips is, in fact, strongly correlated to the power of the speech signal and provides useful indications concerning the manner in which the speech stream is segmented Whilst vowels can be recognized rather easily, both through heanng and vision, consonants are conversely very sensitive to noise and visual analysis often represents the only way for successful comprehension The acoustic cues, associated with consonants, are usually characterized by low intensity, a very short duration, and fine speech patterning It has been shown (see B Dodd, R Campbell, "Hearing by eye the psychology of lipreadmg", Lawrence Erlbaum Ass Publ , particularly Figure B 1 Auditory confusion of consonant transitions, CV, in white noise with decreasing Signal to Noise Ratio expressed in dB, and Figure B 2 Visual confusion of consonant transitions, CV in white noise among adult heanng impaired persons) in relation to auditory confusion, that cues of nasality and voicing are efficiently discriminated, through acoustic analysis, differently from place cues, which are easily distorted by noise (see Figure B 1 of Dodd et al) The opposite situation occurs in the visual domain (see Figure B 2 of Dodd et al), where place is recognized far more easily than voicing and nasality By decreasing the Signal to Noise Ratio, consonants, which are initially discriminated, are progressively confused and clustered When the 11 th cluster is formed (dashed line of Figure B 2 of Dodd et al), the resulting 9 groups of consonants can be considered as distinct visemes Place cues are, in fact, associated with mid-high frequencies, i e above 1 kHz, which are usually scarcely discriminated in most of the hearing disorders However, nasality and voicing reside in the lower part of the frequency spectrum Moreover, place cues are characteπzed by a short-time, fine spectral structure, requiring high frequency and temporal resolution, whereas voicing and nasality cues are mostly associated with unstructured power distribution over several tens of milliseconds In any case, observing the face of a speaker is evidently of great advantage to speech comprehension and almost necessary in the presence of noise, or hearing impairments, i e vision directs the auditor's attention, adds redundancy to the signal and provides evidence of those cues which would be irreversibly masked by noise It is known that, in normal verbal communication, analysis and comprehension of the vanous articulation movements relies on a bimodal perceptive mechanism for the continuous integration of coherent visual and acoustic stimuli In the case of impairments in the acoustic channel, due to distance, noisy environments, transport bamers (for example, a pane of glass) or pathologies the prevalent perceptive task is consequently performed through the visual modality In this case, only the movement and the expressions of the visual articulatory organs are exploited for comprehension, ι e the vertical and horizontal opening of the speakers lips, vertical jaw displacement, teeth visibility, tongue position and other minor indicators, such as, inflation of the speaker's cheeks and nose contractions It is known, from the results of experimental phonetics, that hearing impaired people behave differently from normal hearing people in lip reading In particular, visemes, such as, bilabial lb, p, m/, fricative /f, v/, and occlusive consonants IX, 61 are recognized by both hearing impaired people and people having normal hearing, whereas other visemes, such as, /k, g/, are recognized only by hearing impaired people The occurrence of correct recognition for each viseme is also different between normal and hearing impaired people For example, hearing impaired people are much more successfully than normal heanng people in recognizing nasal consonants /m, n/ These two specific differences in phoneme recognition is difficult to explain because velum, which is the primary articulator involved in phonemes, such as, /k, g/, or /m, n/, is not visible and its movements cannot be perceived in lip reading A possible explanation, stemming from recent results in experimental phonetics, relies on the exploitation of secondary articulation indicators commonly unnoticed by the normal observer It is an object of the present invention to provide a method and apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal It is another object of the present invention to provide a telecommunication system including an apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal, to facilitate an enhanced understanding of acoustic speech signals for users of the system who have impaired hearing and a lip reading skill According to a first aspect of the present invention, there is provided, a method for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including the steps of analyzing the acoustic speech signal to identify its constituent elemental speech units, generating and displaying, on a display screen, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, said method being characterised by the step of displaying, on the display screen a series of movement patterns for respective constituent elemental units of the acoustic speech signal, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of the speaker, and substantially synchronized, in real time, to a respective constituent elemental speech unit According to a second aspect of the present invention, there is provided, a method for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including the steps of analyzing the acoustic speech signal to identify its constituent elemental speech units, generating and displaying, on a display screen, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, said method being characterised by the steps of generating and storing a series of facial movement patterns for the constituent elemental units of acoustic speech signals for display on the display screen, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of a speaker for a respective constituent elemental speech unit The methods outlined in preceding paragraphs, may include the step of retneving, in response to the identification of each of the constituent elemental units of the acoustic speech signal delivered by the speaker, a respective stored movement pattern for display The facial features around the mouth may include the region around the lips, cheeks and nose, and the number of points around the mouth may amount to at least ten points In a preferred method of the present invention, generation of the series of facial movement patterns may include the steps of storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, analyzing acoustic speech signals to identify the related acoustic parameters that define said constituent elemental speech units, making three-dimensional measurements, at each of said number of points around the mouth of a speaker, for each of the identified acoustic parameters, companng, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions, at each of said number of points for a respective acoustic parameter, establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points, and storing the movement patterns for each of said acoustic parameters The transformation may be a linear function which describes a difference for a measurement point as a function of acoustic parameters Also, the acoustic parameters may be statistically estimated from known data using multiple linear regression techniques The constituent elemental units resulting from analysis of said acoustic speech sιgnal(s) may be in the form of a series of phones representative of vowels and consonants In accordance with the method of the present invention the acoustic parameters may be estimated every 20 milliseconds (50 Hz) According to a third aspect of the present invention, there is provided, a method for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal, in which the acoustic speech signal is analyzed to identify its constituent elemental units of speech, in which the speaker's facial movements, associated with each of said constituent elemental speech units, are measured, said analysis and facial measurements being synchronized, in time, and used to synthesize the visual representations of the speaker's facial movements, and in which the synthesized visual representations are displayed, for viewing by a person to whom the acoustic speech signal is addressed, contemporaneously with receipt, by that person, of the respective constituent elemental speech units, characterised in that said method includes the steps of storing a visual representation of human facial features, including at least the mouth together with information indicative of a normal position of a number of points around the mouth, analyzing the acoustic speech signal to identify the related acoustic parameters that define said constituent elemental speech units during the acoustic speech signal analysis, making three-dimensional measurements at each of said number of points around the mouth of the speaker, for each of the identified acoustic parameters, comparing, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions at each of said number of points for a respective acoustic parameter, establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters, said movement pattern being a transformation from said acoustic parameters to the differences, in three- dimensions, between the measured and normal positions of each of said number of points transmitting the resulting movement patterns, to a recipient, at the same time as, and in synchronism with, the respective constituent elemental speech units, and displaying the movement patterns of the mouth on said display unit in synchronism with receipt, by the recipient, of respective constituent elemental units of the acoustic speech signal According to a fourth aspect of the present invention, there is provided, apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including a display unit for displaying said visual representations, means for analyzing the acoustic speech signal to identify its constituent elemental speech units, generation means for generating and displaying, on said display unit, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, characterised in that said apparatus is adapted to displaying, on the display screen, a series of movement patterns for respective constituent elemental units of the acoustic speech signal, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of the speaker and substantially synchronized, in real time, to a respective constituent elemental speech unit According to a fifth aspect of the present invention, there is provided, apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including a display unit for displaying said visual representations, means for analyzing the acoustic speech signal to identify its constituent elemental speech units generation means for generating and displaying, on said display unit, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, characterised in that said generation means include means for generating a series of facial movement patterns for the constituent elemental units of acoustic speech signals for display on the screen, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of a speaker for a respective constituent elemental speech unit, and in that said apparatus includes storage means for storing said series of facial movement patterns The apparatus of the present invention may include retrieval means, responsive to the identification of each of the constituent elemental units of the acoustic speech signal delivered by the speaker, to retrieve a respective stored movement pattern for display on said display unit With the apparatus of the present invention, the facial features around the mouth may include the region around the lips, cheeks and nose, and the number of points around the mouth may amount to at least ten points The generation means may include storage means for storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, analyzing means for analyzing acoustic speech signals to identify the related acoustic parameters that define said constituent elemental speech units, measurement means for making three-dimensional measurements, at each of said number of points around the mouth of a speaker, for each of the identified acoustic parameters, comparison means for comparing for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions, at each of said number of points for a respective acoustic parameter, and transformation means for establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points The transformations established by the transformation means may be a linear function which describes a difference for a measured point as a function of acoustic parameters, and the analyzing means may be adapted to statistically estimate the acoustic parameters from known data using multiple linear regression techniques The constituent elemental speech units resulting from analysis of the acoustic speech sιgnal(s) may be in the form of a series of phones representative of vowels and consonants, and the acoustic parameters may be estimated every 20 milliseconds (50 Hz) According to a sixth aspect of the present invention, there is provided, apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal including a display unit for displaying the visual representations, analyzing means for analyzing the acoustic speech signal to identify its constituent elemental units of speech, measurement means for measuring the speaker's facial movements, associated with each of said constituent elemental speech units, said facial measurements and speech signal analysis being synchronized, in time, means for synthesizing the visual representations of the speaker's facial movements, said synthesized visual representations being displayed, on said display unit, for viewing by a person to whom the acoustic speech signal is addressed, contemporaneously with receipt, by that person, of the respective constituent elemental speech units, characteπsed in that said apparatus includes storage means for storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, analyzing means for analyzing the acoustic speech signal to identify the related acoustic parameters that define said constituent elemental speech units measurement means for making, during the acoustic speech signal analysis, three-dimensional measurements, at each of said number of points around the mouth of the speaker, for each of the identified acoustic parameters, comparison means for comparing, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions, at each of said number of points for a respective acoustic parameter, transformation means for establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters, said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points, and transmitting means for transmitting the resulting movement patterns, to a recipient, at the same time as, and in synchronism with, the respective constituent elemental speech units, and in that said apparatus is adapted to display movement patterns of the mouth on said display unit in synchronism with receipt, by the recipient, of respective constituent elemental units of the acoustic speech signal According to a seventh aspect of the present invention, there is provided, apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, in accordance with the method as outlined in preceding paragraphs According to an eighth aspect of the present invention, there is provided, a telecommunication system including a plurality a telephone handsets and switching means adapted to interconnect any two, or more, of said telephone handsets, characterised in that said system includes apparatus, as outlined in preceding paragraphs, for providing an enhanced understanding of acoustic speech signals for users of said telephone handsets who have impaired hearing and a lip reading skill Each of said telephone handsets may be adapted to be connected to, or be integral with, said apparatus, the display unit of the apparatus is adapted to display facial movement patterns in synchronism with receipt of respective constituent elemental units of an acoustic speech signal received by a respective telephone handset, and the facial movement display enables a handset user to comprehend a substantial part of the content of said acoustic speech signal through lid reading of the facial movements The foregoing and other features according to the present invention will be better understood from the following description of specific embodiments of the invention In accordance with the method and apparatus of the present invention, a lip readable visual synthetic output is provided through the automatic analysis of continuous speech, close attention being paid to the definition of suitable indicators, having the capability to descπbe the visually relevant articulation places, such as, labial, dental and alveolar, with the least possible residual of ambiguity It will be seen from subsequent description that the methodology of the present invention provides real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal, around the mouth of the speaker, i e the analysis-synthesis facial region is the region around the lips, including the cheeks and nose Thus, with the method and apparatus of the present invention, facial movements, emanating from an acoustic speech signal, are controlled at a number of points around the mouth, and advanced calculations are made of speech-facial movement transformations, i e. transformations from acoustic speech parameters to facial movement parameters Known methods and apparatus for the provision of real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, normally involve analysis of the acoustic speech signal to identify its constituent elemental units, and the generation and display, on a display screen, of an image of moving human facial features The displayed facial feature movements are substantially synchronized, in real time, to the constituent elemental speech units In accordance with the method and apparatus of the present invention, a series of facial movement patterns for the constituent elemental units of acoustic speech signals are generated and stored These facial movement patterns are indicative of movement, in three-dimensions, of a number of points, for example, at least ten points, around the mouth of a speaker The facial features around the speaker's mouth, for which the movement patterns are generated and stored, preferably include the region around the lips, cheeks and nose The generation of the series of facial movement patterns is preferably effected, in accordance with the present invention, by firstly storing a visual representation of human facial features including at least the mouth, in its normal state, together with information indicative of a normal position of a number of points, for example, at least ten points, around the mouth which, as previously stated, preferably includes the region around the lips, cheeks and nose The next stage of the movement pattern generation process is to undertake an analysis of acoustic speech signals to identify the related acoustic parameters that define the constituent elemental speech units and to make three-dimensional measurements, at each of the number of points around the mouth of a speaker, for each of the identified acoustic parameters The acoustic parameters may, for example, be estimated statistically from known data using multiple linear regression techniques As previously stated, speech is the concatenation of elementary units, called phones, generally classified as vowels, when they correspond to a stable configuration of the vocal tract, or alternatively, as consonants, when they correspond to transient articulatory movements Each phone can, as previously stated, be characterized by means of a few attπbutes (i e open/closed, front/back, oral/nasal and rounded/unrounded), which qualify the articulation manner (i e fricative, like IV, Is/, plosive, like /b/, /p/, nasal, like /n/, /m/, ) and articulation place (i e labial, dental alveolar, palatal, glottal) Some phones, like vowels and a subset of consonants, are accompanied by vocal cord vibration and are called "voiced" phones, while other phones, like plosive consonants, are totally independent of vocal cord vibration and are called "unvoiced" phones When voiced phones, the speech spectrum is shaped, as previously descπbed, in accordance with the geometry of the vocal tract, with characteristic energy concentrations around three main peaks called "formants", located at increasing frequencies, FI, F2 and F3 Furthermore, an observer skilled in lip reading is, as previously stated able to estimate the likely locations of fonmant peaks by computing the transfer function from the configuration of the visible articulators Thus, in accordance with the present invention, the constituent elemental speech units resulting from analysis of the acoustic speech signals may be in the form of a series of phones representative of vowels and consonants At the next stage of the movement pattern generation process, three-dimensional measurements are made at each of the number of points around the mouth of the speaker for each of the identified acoustic parameters The measured and normal positions for each of the number of points around the mouth are then compared for each of the acoustic parameters in order to determine a positional difference, in three- dimensions, at each of the number of points for a respective acoustic parameter A movement pattern is then established for the number of points around the mouth for each of the acoustic parameters The resulting movement patterns are each a transformation from the acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of the number of points around the mouth The transformation may, for example, be a linear function which describes a difference for a measurement point as a function of acoustic parameters The facial movement patterns for each of the acoustic parameters are then stored for subsequent use in the synthesis and display of facial movements associated with an acoustic speech signal Thus, in response to the identification of each of the constituent elemental units of the acoustic speech signal, delivered by the speaker, a respective stored facial movement pattern is retrieved and displayed, on a display screen, for viewing by a recipient of the speech signal The acoustic parameters that define the constituent elemental speech units may, for example, be estimated every 20 milliseconds (50 Hz) The display screen will, therefore, provide a real-time visual representation of the speaker's facial features substantially synchronized, in real-time, with the constituent elemental units of the acoustic speech signal This display will enable a person having impaired hearing and a lip reading capability, to obtain an enhanced understanding of the acoustic speech signal Whilst the method and apparatus of the present invention could be used in a number of application, which will be directly evident to persons skilled in the art, a particular application for the present invention is in a telecommunication system having subscribers with impaired hearing and a lip reading capability Thus, in a telecommunication system including a plurality a telephone handsets and switching means adapted to interconnect any two, or more, of the telephone handsets, the present invention enables users of the telephone handsets, who have impaired heanng and a lip reading skill, to obtain an enhanced understanding of acoustic speech signals through viewing the displayed real-time visual representations of a speaker's facial movements whilst listening to the acoustic speech signal In other words, the display unit of the apparatus would be adapted to display facial movement patterns in synchronism with receipt of respective constituent elemental units of an acoustic speech signal received by a respective telephone handset, and the facial movement display would enable a handset user to comprehend a substantial part of the content of the acoustic speech signal through lid reading of the facial movements With such a telecommunication system, each telephone handset could, for example, be adapted to be connected to, or be integral with, the apparatus of the present invention Whilst a video telephone system would enable a hearing impaired subscriber having a lip reading capability, to obtain an enhanced understanding of an acoustic speech signal, a conventional telephone system, incorporating the apparatus of the present invention or operating in accordance with the method of the present invention is more cost effective and uses considerably less bandwidth than a video telephone system However, the method and apparatus of the present invention could be adapted for use in a telecommunication system by using real-time visual images of the speaker's facial movements instead of the stored representations The bandwidth requirements of such a telecommunication system would be greater that a conventional telephone system but less than a conventional video telephone system In order to realize such an arrangement, the method of the present invention for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal, includes the steps of storing a visual representation of human facial features, including at least the mouth, in a normal state, together with information indicative of a normal position of a number of points, for example, ten points, around the mouth, and analyzing the acoustic speech signal to identify the related acoustic parameters that define the constituent elemental speech units During acoustic speech signal analysis, three-dimensional measurements would be made, at each of the number of points around the mouth of the speaker, for each of the identified acoustic parameters These measurements may, for example be made every 20 milliseconds (50 Hz) The next step of the method involves comparing, for each of the identified acoustic parameters, the measured and normal positions for each of the number of points around the mouth to determine a positional difference, in three-dimensions, at each of the number of points for a respective acoustic parameter, in order to establish a movement pattern for the number of points around the mouth for each of said acoustic parameters As before, the movement pattern is a transformation from the acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of the number of points around the mouth The resulting movement patterns are transmitted at the same time as, and in synchronism with, the respective constituent elemental speech units The movement patterns are then displayed on a display unit in synchronism with receipt, by a listener, of the respective constituent elemental units of the acoustic speech signal

Claims: CLAIMS 1 A method for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including the steps of analyzing the acoustic speech signal to identify its constituent elemental speech units, generating and displaying, on a display screen, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, said method being characterised by the step of displaying, on the display screen, a series of movement patterns for respective constituent elemental units of the acoustic speech signal, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of the speaker, and substantially synchronized, in real time, to a respective constituent elemental speech unit 2 A method for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including the steps of analyzing the acoustic speech signal to identify its constituent elemental speech units, generating and displaying, on a display screen, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, said method being characteπsed by the steps of generating and storing a series of facial movement patterns for the constituent elemental units of acoustic speech signals for display on the display screen, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of a speaker for a respective constituent elemental speech unit 3 A method as claimed in claim 1 or claim 2, characteπsed by the step of retrieving, in response to the identification of each of the constituent elemental units of the acoustic speech signal delivered by the speaker, a respective stored movement pattern for display 4 A method as claimed in any preceding claim, characterised in that said facial features around the mouth include the region around the lips, cheeks and nose 5 A method as claimed in any preceding claim, characterised in that said number of points around the mouth amount to at least ten points 6 A method as claimed in claim 2, or any of claims 3 to 5, when appended to claim 2, characterised in that the generation of said series of facial movement patterns includes the steps of storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, analyzing acoustic speech signals to identify the related acoustic parameters that define said constituent elemental speech units, making three-dimensional measurements, at each of said number of points around the mouth of a speaker, for each of the identified acoustic parameters, comparing, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions, at each of said number of points for a respective acoustic parameter, - establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters, said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points, and storing the movement patterns for each of said acoustic parameters 7 A method as claimed in claim 6 characterised in that the transformation is a linear function which describes a difference for a measurement point as a function of acoustic parameters 8 A method as claimed in claim 6, or claim 7, characterised in that said acoustic parameters are statistically estimated from known data using multiple linear regression techniques 9 A method as claimed in any preceding claim, characteπsed in that the constituent elemental units resulting from analysis of said acoustic speech sιgnal(s) are in the form of a series of phones representative of vowels and consonants 10 A method as claimed in any preceding claim, characterised by the step of estimating said acoustic parameters every 20 milliseconds (50 Hz) 11 A method for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal, in which the acoustic speech signal is analyzed to identify its constituent elemental units of speech, in which the speaker's facial movements, associated with each of said constituent elemental speech units, are measured, said analysis and facial measurements being synchronized, in time, and used to synthesize the visual representations of the speaker's facial movements, and in which the synthesized visual representations are displayed, for viewing by a person to whom the acoustic speech signal is addressed, contemporaneously with receipt, by that person, of the respective constituent elemental speech units, characterised in that said method includes the steps of storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, - analyzing the acoustic speech signal to identify the related acoustic parameters that define said constituent elemental speech units, during the acoustic speech signal analysis, making three-dimensional measurements at each of said number of points around the mouth of the speaker, for each of the identified acoustic parameters, - comparing, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions, at each of said number of points for a respective acoustic parameter establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters, said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points, transmitting the resulting movement patterns, to a recipient, at the same time as, and in synchronism with, the respective constituent elemental speech units, and displaying the movement patterns of the mouth on said display unit in synchronism with receipt, by the recipient, of respective constituent elemental units of the acoustic speech signal 12 Apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including a display unit for displaying said visual representations, - means for analyzing the acoustic speech signal to identify its constituent elemental speech units, generation means for generating and displaying, on said display unit, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, characterised in that said apparatus is adapted to displaying, on the display screen, a series of movement patterns for respective constituent elemental units of the acoustic speech signal, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of the speaker, and substantially synchronized, in real time, to a respective constituent elemental speech unit 13 Apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, including a display unit for displaying said visual representations, means for analyzing the acoustic speech signal to identify its constituent elemental speech units, generation means for generating and displaying, on said display unit, an image of moving human facial features, said facial feature movements being substantially synchronized, in real time, to said constituent elemental speech units, characterised in that said generation means include means for generating a series of facial movement pattems for the constituent elemental units of acoustic speech signals for display on the screen, each of said movement patterns being indicative of movement, in three-dimensions, of a number of points around the mouth of a speaker for a respective constituent elemental speech unit, and in that said apparatus includes storage means for storing said series of facial movement pattems 14 Apparatus as claimed in claim 12, or claim 13, characterised in that said apparatus includes retrieval means, responsive to the identification of each of the constituent elemental units of the acoustic speech signal delivered by the speaker, to retrieve a respective stored movement pattern for display on said display unit 15 Apparatus as claimed in any of claims 12 to 14, characterised in that said facial features around the mouth including the region around the lips, cheeks and nose 16 Apparatus as claimed in any of claims 12 to 15, characteπsed in that said number of points around the mouth amount to at least ten points 17 Apparatus as claimed in any of claim 13, or any of claims 14 to 16 when appended to claim 13, characterised in that said generation means include storage means for storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, analyzing means for analyzing acoustic speech signals to identify the related acoustic parameters that define said constituent elemental speech units, measurement means for making three-dimensional measurements, at each of said number of points around the mouth of a speaker, for each of the identified acoustic parameters, compaπsoπ means for comparing, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions at each of said number of points for a respective acoustic parameter, and transformation means for establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters, said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points 18 Apparatus as claimed in claim 17, characterised in that each of said transformations established by said transformation means is a linear function which describes a difference for a measured point as a function of acoustic parameters 19 Apparatus as claimed in claim 17, or claim 18, characterised in that said analyzing means are adapted to statistically estimate said acoustic parameters from known data using multiple linear regression techniques 20 Apparatus as claimed in any of claims 12 to 19, characteπsed in that the constituent elemental units resulting from analysis of said acoustic speech sιgnal(s) are in the form of a series of phones representative of vowels and consonants 21 Apparatus as claimed in any of claims 12 to 20, characteπsed in that said acoustic parameters are estimated every 20 milliseconds (50 Hz) 22 Apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal including a display unit for displaying the visual representations, analyzing means for analyzing the acoustic speech signal to identify its constituent elemental units of speech, measurement means for measuπng the speaker's facial movements, associated with each of said constituent elemental speech units, said facial measurements and speech signal analysis being synchronized, in time, means for synthesizing the visual representations of the speaker's facial movements, said synthesized visual representations being displayed, on said display unit, for viewing by a person to whom the acoustic speech signal is addressed, contemporaneously with receipt, by that person of the respective constituent elemental speech units characterised in that said apparatus includes storage means for storing a visual representation of human facial features, including at least the mouth, together with information indicative of a normal position of a number of points around the mouth, analyzing means for analyzing the acoustic speech signal to identify the related acoustic parameters that define said constituent elemental speech units, measurement means for making, during the acoustic speech signal analysis, three-dimensional measurements, at each of said number of points around the mouth of the speaker, for each of the identified acoustic parameters, comparison means for comparing, for each of said acoustic parameters, the measured and normal positions for each of said number of points around the mouth to determine a positional difference, in three-dimensions, at each of said number of points for a respective acoustic parameter, transformation means for establishing a movement pattern for said number of points around the mouth for each of said acoustic parameters, said movement pattern being a transformation from said acoustic parameters to the differences, in three-dimensions, between the measured and normal positions of each of said number of points and transmitting means for transmitting the resulting movement patterns, to a recipient, at the same time as, and in synchronism with, the respective constituent elemental speech units, and in that said apparatus is adapted to display movement patterns of the mouth on said display unit in synchronism with receipt, by the recipient, of respective constituent elemental units of the acoustic speech signal 23 Apparatus for providing real-time visual representations of a speaker's facial movements, associated with an acoustic speech signal delivered by the speaker, in accordance with the method as claimed in any of claims 1 to 11 24 A telecommunication system including a plurality a telephone handsets and switching means adapted to interconnect any two, or more of said telephone handsets, characteπsed in that said system includes apparatus, as claimed in any of claims 12 to 23, for providing an enhanced understanding of acoustic speech signals for users of said telephone handsets who have impaired hearing and a lip reading skill 25 A telecommunication system as claimed in claim 24, characterised in that each of said telephone handsets is adapted to be connected to, or be integral with, said apparatus, in that the display unit of said apparatus is adapted to display facial movement patterns in synchronism with receipt of respective constituent elemental units of an acoustic speech signal received by a respective telephone handset, and in that said facial movement display enables a handset user to comprehend a substantial part of the content of said acoustic speech signal through lid reading of the facial movements

Inventors: LJUNGQVIST MATS, LJUNGQVIST, MATS
Applicants: LJUNGQVIST MATS, TELIA AB, LJUNGQVIST, MATS
Application year: 1998
Main classification: G10L21
IPC codes: G06K9, G10L13, G10L15, G10L21, H04M3