Abstract:
Method and apparatus for using video input to control speech recognition systems is disclosed. In one embodiment, gestures of a user of a speech recognition system are detected from a video input, and are used to turn a speech recognition unit on and off. In another embodiment, the position of a user is detected from a video input, and the position information supplied to a microphone array point of source filter to aid the filter in selecting the voice of a user that is moving about in the field of the camera supplying the video input.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to the field of computer technology. More particularly, the present invention relates to the use of computer technology for speech recognition. 
     BACKGROUND OF THE INVENTION 
     Speech recognition has the potential to provide a significant leap in the application of computing technology. One of the barriers in the adoption of speech recognition is its inability to distinguish the relevant spoken commands intended for the computer from the otherwise irrelevant speech common throughout the day, such as passing conversations, muttering, and background conversation. As a result, most speech recognition systems require the user to continuously indicate to the computer when to start or stop listening, so that the system does not interpret speech intended for other listeners. 
     Humans, however, are quite adept at determining what speech is directed at them, and use a number of techniques to guide them in this, such as: 
     1. Specific keywords (such as our names); 
     2. Body contact (such as a tap on the shoulder); 
     3. Proximity of the noise (relative volume); and 
     4. Visual clues (such as establishing eye contact, or pointing while one is moving their mouth). 
     In order to provide speech recognition systems with a human-like level of functionality, speech user interfaces have thus far focused on the first two techniques mentioned above. For instance, analogous to item  1  above, many speech recognition engines or units provide the ability to specify an “attention phrase” to wake up the computer and a “sleep” phrase to force an end to speech recognition. Most interface paradigms also provide a “toggle to talk” button, similar to a tap on the shoulder. These approaches alone, however, have limitations. Attention words are often missed, taking considerable time to eventually turn on or off speech recognition. Toggle to talk buttons require user proximity—undermining speech&#39;s inherent advantage of operating without having to be in physical contact with the speech recognition system. 
     Another problem with speech recognition systems is the inability of a speech recognition system to hone in on a specific audio source location. Recent microphone array research has, however, yielded the ability to hone in on a specific audio source location, thus providing the ability to filter extraneous, irrelevant sounds from the input audio stream. For example, using two microphones, one on each side of a speech recognition system (such as on the left and right side of the monitor of a PC-based system), background noise can be eliminated by using the microphone array to audially narrow into the words emanating from the user&#39;s mouth. The speech recognition algorithm can thus obtain a much cleaner audio source to use, increasing both its accuracy and its robustness in harsh (i.e., real world) audio environments. A problem with the microphone arrays, however, is that the user rarely sits still making it difficult to determine the source point to hone in on. This is especially so when speech recognition is performed in non-traditional PC uses (such as in a living room to control a television). Worse yet, if the speech recognition is performed via a hand held pad, the microphone itself is also moving. 
     As described below, the present invention provides a variety of embodiments that address the limitations of speech recognition systems noted above. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention provides a method and apparatus for controlling the operation of a speech recognition unit using a video image to detect gestures made by a user. In another embodiment, the invention provides a method and apparatus for filtering an audio input signal in a speech recognition system using a microphone array to isolate the source of the user&#39;s voice, where the location of the user is determined using a video image. In another embodiment, the above described embodiments are combined. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 illustrates in block diagram form an example embodiment of a computer system adapted for speech recognition according the present invention. 
     FIGS. 2 and 3 illustrate a first example embodiment of the invention wherein video input is used to aid in the control of a speech recognition unit. 
     FIGS. 4 and 5 illustrate another example embodiment of the invention in which video input is used to aid in obtaining a filtered audio input for a speech recognition unit. 
     FIG. 6 illustrates yet another example embodiment of the invention combining the embodiments of FIGS. 1-5. 
     FIG. 7 illustrates yet another example embodiment of the invention adapted for consumer/industrial products. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     Referring now to FIG. 1, there is illustrated in block diagram form a computer system of one embodiment of the present invention. The computer system comprises bus  100 , keyboard interface  101 , external memory  102 , mass storage device  103  and processor  104 . Bus  100  can be a single bus or a combination of multiple buses, and provides communication links between components in the computer system. Keyboard controller  101  can be a dedicated device or can reside in another device such as a bus controller or other controller. Keyboard controller  101  allows coupling of a keyboard to the computer system and transmits signals from a keyboard to the computer system. External memory  102  can comprise a dynamic random access memory (DRAM) device, a static random access memory (SRAM) device, or other memory devices. External memory  102  stores information from mass storage device  103  and processor  104  for use by processor  104 . Mass storage device  103  can be a hard disk drive, a floppy disk drive, a CD-ROM device, or a flash memory device. Mass storage device  104  provides information to external memory  102 . Processor  104  can be a microprocessor and is capable of decoding and executing a computer program such as an application program or operating system. An audio input device  105  is also provided, and includes a microphone  106 , and optionally a second microphone  106 ′ to receive sound in the environment of the system and convert it to a digital form that can be processed by the system, and in particular processor  104 . In addition, the computer system includes a video input device  107 , and includes a video camera  108  that is positioned to view a visual field proximate the computer system. Video input device outputs a digital video signal that can be processed by processor  104 , as described below. 
     Referring now to FIG. 2, there is illustrated a block diagram of an example embodiment  200  of a speech recognition system according to one embodiment of the invention. As illustrated in FIG. 2, a user  202  is positioned within the field of view of camera  108 , and within the range of microphone  106 . Audio input device  105  and video input device  107 , in turn, output digital information to a speech recognition unit  204  and a gesture recognition unit  206 . Gesture recognition unit  206  provides input to speech recognition unit  204 , which in turn provides input to a speech driven application  208 . 
     Referring now to FIG. 3, there is illustrated a flow diagram of the operation of gesture recognition unit  206 . Unit  206  receives one or more frames of a video image of a user  202 , obtained by cameral  108  ( 302 ). This image(s) is analyzed to determine if the user has made one or more gestures in a way that is intended to signify to the system that speech recognition should begin, or continue ( 304 ). As used herein, the term “gesture” shall mean any non-verbal movement, position or posture of a user, or the like. For example, unit  206  may be programmed or configured to recognize when a user  202  is looking directly at the camera  108 , and output a start/continue signal to the speech recognition unit  204  when this is true. This determination could be achieved, for example, using a face tracking algorithm to identify the user of interest in the field, and to detect when the user is looking at the camera. Suitable face tracking algorithms may provide for matching a user&#39;s face with a template of the user&#39;s face previously determined and stored, or detecting the outline of a user&#39;s head or features of the head and face by comparison to predetermined criteria or generic templates of the features of faces and heads. Detection of when a user is looking at the camera can also be accomplished, in one example embodiment, using a template matching procedure. This procedure can be used to determine when the user&#39;s eyes are directed straight at the camera  108 , or for example, when the user&#39;s head is facing straight at the camera. Alternatively, unit  206  can detect one or more specific body movements, such as a waving of the hand or the user pointing at the camera, to signify that speech recognition should start. In the case of this example embodiment, a full-body gesture recognition procedure is employed, and may analyze multiple video images for this purpose. Alternatively, two or more gestures may be required to activate the speech recognition system. For example, a user may be required to both point and look directly at the camera  108  in order to activate speech recognition. 
     Continuing to refer to FIG. 3, it is seen that if a gesture or sequence of gestures are detected to mean that speech recognition should start or continue, a start and/or continue signal is output ( 306 ) to the speech recognition unit  204 . Speech recognition unit  204  in turn is activated or continues to be activated. Similarly, if a gesture or combination of gestures are detected indicating that speech recognition should be stopped ( 308 ), unit  206  outputs a stop recognition signal ( 310 ) to unit  204 , which in turn deactivates speech recognition. It should be readily recognized that, in the case that speech recognition depends on the continuing presence of a certain gesture, such as looking directly into the camera  108 , the detection procedure would not require a separate detection of a stop gesture, and rather would only require ongoing recognition of the gesture that starts and continues speech recognition. Once this gesture ceased, unit  206  would cease from producing the start/continue signal, and the speech recognition unit  204  would stop recognition until such time as the start/continue signal was reactivated. Alternatively, embodiment  200  may also be adapted to recognize in addition the position of an instrument held by a user. 
     FIGS. 4 and 5 illustrate another embodiment  400  of the invention which provides a video-based face tracker unit  402  used to provide user-positioning information to microphone array processing unit  404 . Processing unit  404  in turns provides a filtered audio output signal to a speech recognition unit  406 . In operation, the input from the video camera  108  is processed by the two dimensional (2D) face tracker unit  402 , which determines and outputs (x, y) position information for the user  202  indicating the user&#39;s position in the space within the view of the camera  108 . Tracker unit  402  also produces an estimated z position based on the relative size of the head. This data, together with information on the known position of the camera  108  in relation to the microphone array formed by microphones  106  and  106 ′, is fed into the microphone array processing unit  402 , which for example uses a point of source filter. Processing unit  402  uses the information on the spatial position of the user to filter the incoming audio stream using microphone array point-of-source filtering, wherein the user&#39;s position is selected as the point-of-source to produce a stream of filtered audio carrying the user&#39;s voice. Thus, unit  402  can “find” the user&#39;s voice even if the user is moving. FIG. 5 illustrates, for one example, the positions that microphones  106  and  106 ′, and video camera  108 , may take, when the speech recognition system is deployed on a PC platform. Alternatively, tracker unit  402  may also track other aspects of a user&#39;s appearance, such as a reflective or light-emitting device the user may wear that would be easily identified in video processing. As an alternate embodiment, a second camera  108 ′ can be employed to provide stereoscopic vision (see dashed lines in the FIG.  4 ). This, in turn, can be used by an alternate three dimensional (3D) face tracker unit  402 ′, to provide a more accurate z position. 
     Referring now to FIG. 6, there is illustrated a system  600  which combines all or some of the features of embodiment  200  with embodiment  400 . System  600  is of the same design as embodiment  400 , but also includes the gesture recognition unit  206  for recognizing gestures to turn the speech recognition capability of speech recognition unit  204  on and off. Thus, system  600  has the capability to isolate the voice and body of a user in a crowded room, and to use gestures to turn speech recognition on and off. 
     Referring now to FIG. 7, there is illustrated a consumer or industrial product  700 , which has a control system  702  adapted to receive commands output from a speech recognition system embodiment  200 ,  400 , or  600 , as described above. Such a consumer or industrial product may be, for example and without limitation, a television, sound system, radio, kitchen appliance, automobile, or lighting system. 
     Although the invention has been described with respect to specific embodiments, it shall be understood that these embodiments are exemplary only, and that it is contemplated that the described methods and apparatus of the invention can be varied widely while still maintaining the advantages of the invention. Thus, the disclosure should not be taken as limiting in any way the scope of the invention. In addition, as used herein, the term “unit” shall refer to a digital device that may take the form of a hardwired circuit, software executing on a processor, or a combination of both. For example, units  204 ,  206 ,  401 ,  402 ,  404 , and application  208 , in one example embodiment and, not by limitation, may take the form of software executing in processor  104 , or all or some of the functionality of these components can be provided by hardware only. Furthermore, as used herein, the term machine readable medium shall include, but not be limited to, a storage disk, CD-ROM, RAM or ROM memory, or an electronic signal propagating between components in a system or network.