Abstract:
A surveillance system includes a plurality of microphones for generating audio signals in response to detecting sound, a video camera for generating a stream of video signals, and a driving unit for controlling the direction in which the video camera points. The surveillance system also includes a decision unit for determining a location from which the detected sound is coming from based on the differences in the audio signals generated by the plurality of microphones to control the driving unit to point the video camera in the direction of the location from which the detected sound is coming from.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a surveillance system, and more specifically, to a surveillance system capable of tracking objects and dynamically changing the resolution of stored video.  
         [0003]     2. Description of the Prior Art  
         [0004]     Conventionally, surveillance systems used for home security usually capture images in a fixed region. The surveillance systems cannot quickly respond when someone enters the house. Moreover, fixed recording resolution is used in traditional surveillance systems. This leaves users with a tradeoff involving the choice between longer recording time or higher resolution recordings. Capturing images with high resolution is necessary when an intruder enters the house. However, more storage space is needed to store high resolution images. Furthermore, in normal situations when there is no intruder present, it is not efficient to capture images with higher resolution.  
       SUMMARY OF THE INVENTION  
       [0005]     It is therefore an objective of the claimed invention to provide a home surveillance system and related surveillance method in order to solve the above-mentioned problems.  
         [0006]     According to an embodiment of the claimed invention, a surveillance system includes a plurality of microphones for generating audio signals in response to detecting sound, a video camera for generating a stream of video signals, and a driving unit for controlling the direction in which the video camera points. The surveillance system further comprises a decision unit for determining a location from which the detected sound is coming from based on the differences in the audio signals generated by the plurality of microphones to control the driving unit to point the video camera in the direction of the location from which the detected sound is coming from.  
         [0007]     According to another embodiment of the present invention, a method of performing video and audio surveillance includes generating audio signals with a plurality of microphones, generating a stream of video signals with a video camera, determining a location from which the detected sound is coming from based on the differences in the audio signals generated by the plurality of microphones, and driving the video camera to point in the direction of the location from which the detected sound is coming from.  
         [0008]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a functional block diagram of a surveillance system according to the present invention.  
         [0010]      FIG. 2  is a flowchart illustrating the present invention surveillance method. 
     
    
     DETAILED DESCRIPTION  
       [0011]     Please refer to  FIG. 1 .  FIG. 1  is a functional block diagram of a surveillance system  10  according to the present invention. The surveillance system  10  can be used for home security or in other environments such as in an office setting. The surveillance system  10  receives input from a video camera  12  and microphone arrays  14 . The microphone arrays  14  contain multiple microphones placed at different locations. Using sound propagation principles, the individual microphone signals can be filtered and combined to enhance sound originating from a particular direction or location. The location of the principal sounds sources can also be determined dynamically by investigating the correlation between different microphone channels.  
         [0012]     Audio signals received from the microphone arrays  14  and a stream of video signals generated by the video camera  12  are sent to a decision unit  16 . The decision unit  16  uses the sound information provided by the microphone arrays  14  to determine the location that the sound is coming from, and instructs a driving unit  18  to point the video camera  12  to point in the direction of the sound.  
         [0013]     The decision unit  16  contains a database  164  containing facial images corresponding to a list of approved users, such as the residents of the house that the surveillance system  10  is installed in. The database  164  works in conjunction with a face recognition and tracking unit  162  in order to determine the presence and the location of a face in an image by distinguishing the face from all other patterns in the scene. Most approaches exploit the temporal correlation between successive frames in order to refine the localization of the target. The purpose of face tracking is used to follow one or more faces through a video sequence. Face recognition also allows the tracked face to be compared with the faces that have been registered in the database  164  to ensure that people entering the area under surveillance are approved users.  
         [0014]     A storage unit  20  is used to record the audio signals generated by the microphone arrays  14  and the stream of video signals generated by the video camera  12 . The recording quality is an important factor for face recognition. Images with higher quality allow for higher recognition accuracy. For example, it is beneficial to increase the recording resolution or color quality when the surveillance system  10  is in an emergency state or when an intruder is detected. However, recording at higher resolution or at higher color quality increases the amount of storage space that is needed. Therefore, in one embodiment of the invention, we can apply a lower resolution or lower color quality when the surveillance system  10  is in a normal state, i.e., not in an emergency state, to save storage space.  
         [0015]     As will be explained below, when the decision unit  16  determines that an object that is not registered with the database  164  as an approved user has entered, the decision unit  16  triggers an alarm unit  22  to generate an alarm. The alarm unit  22  can generate the alarm in a variety of ways, such as an audible alarm, a visual alarm, or by notifying the relevant authorities.  
         [0016]     In this embodiment, two operation modes, normal mode and guarding mode, are implemented in the surveillance system  10 . Initially, the surveillance system  10  starts in a normal mode, which stores video images on the storage unit  20  using a second image format. Meanwhile, the microphone arrays  14  are working to detect sound. When sound is detected, the decision unit  16  uses the signals provided by the microphone arrays  14  to estimate the location of the sound source. The decision unit  16  then instructs the driving unit  18  to point the video camera  12  at the estimated position. Since sound has already been detected, the surveillance system  10  switches from normal mode to guarding mode for attempting to detect if any intruder has caused the sound. In order to facilitate face recognition, the storage unit  20  stores video images with a first image format while in guarding mode. The first image format is different from the second image format in various ways. For example, as described in the previous paragraph, the image resolution and/or the color quality of the first image format applied in the guarding mode is higher than those of the second image format applied in the normal mode. The decision unit  16  then utilizes the face recognition and tracking unit  162  to track the face of the object that has entered the surveillance area in order to try and recognize the face. If the tracked face is not one that is registered in the database  164 , this means that an intruder has entered, and the decision unit  16  triggers the alarm unit  22  to generate the alarm.  
         [0017]     On the other hand, if the captured image is an approved user listed in the database  164 , the surveillance system  10  will stop surveillance by stopping the camera recording and sound detection. The approved user may reactivate the surveillance system  10  when he or she leaves.  
         [0018]     The operating method of the surveillance system  10  is summarized in the flowchart contained in  FIG. 2 . Steps contained in the flowchart will be explained below.  
         [0019]     Step  50 : The surveillance system  10  is activated in normal mode, and stores video in the storage unit  20  using low resolution or low color quality.  
         [0020]     Step  52 : Determine if the microphone arrays  14  have detected any sound. If so, go to step  54 . If not, go to step  58 .  
         [0021]     Step  54 : Estimate the location of the detected sound.  
         [0022]     Step  56 : The decision unit  16  instructs the driving unit  18  to point the video camera  12  at the estimated location.  
         [0023]     Step  58 : Determine if an intruder is present. The intruder can be detected through sounds picked up by the microphone arrays  14  or through images recorded by the video camera  12 . If an intruder is present, go to step  60 . If not, go back to step  52 .  
         [0024]     Step  60 : The surveillance system  10  switches to guarding mode, and stores video in the storage unit  20  using high resolution or high color quality. The face recognition and tracking unit  162  performs face recognition using the increased video resolution.  
         [0025]     Step  62 : Compare the detected face with the facial images stored in the database  164  to determine if the intruder is an approved user. If the user is an approved user, go to step  66 . Otherwise, go to step  64 .  
         [0026]     Step  64 : The decision unit  16  triggers the alarm unit  22  to start the alarm.  
         [0027]     Step  66 : Stop the surveillance system  10  since an approved user has entered the surveillance area.  
         [0028]     Step  68 : Determine if the user has reactivated the surveillance system  10 . If so, go back to step  50 . Otherwise, go back to step  66 .  
         [0029]     In summary, a smart surveillance system is proposed that can actively track the location of the user using sound location estimation and face tracking. Moreover, the stored recording resolution can be actively changed depending on whether there is an intruder present or not. In addition, facial recognition can be used to automatically shut down the surveillance system if an approved user is present or to trigger the alarm if an unauthorized intruder is present.  
         [0030]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.