Abstract:
A gain adjusting system for adjusting a gain of a sound signal in an audio system, includes a first detecting unit for capturing images of one or more faces of users and determining the number of faces and the size of the faces present in the images; a controller for receiving face data from the first detecting unit for comparing the sizes of faces in subsequently captured images with an initial face size and accordingly deciding and outputting a first decision signal; and a gain regulator coupled to the controller for adjusting the gain level of the sound signal according to the first decision signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a gain adjusting system, and more specifically, to an active gain adjusting system for a speaker or microphone which adjusts the gain according to an estimated distance between the users and the speaker or microphone. 
         [0003]    2. Description of the Prior Art 
         [0004]    Conventionally, speaker volume and microphone gain are passively controlled. That is, the volume of the speaker and the gain of the microphone are adjusted when users feel like they should be changed. Users need to utilize a remote control or push buttons on an audio device for adjusting the speaker volume. However, having to manually change the speaker volume is not a convenient or friendly man-machine interface. Similarly, it is not convenient to have to manually adjust microphone gain if the users change their distance from the microphone. 
       SUMMARY OF THE INVENTION 
       [0005]    It is therefore an objective of the claimed invention to provide gain adjusting systems and related methods in order to solve the above-mentioned problems. 
         [0006]    According to an embodiment of the present invention, a gain adjusting system for adjusting a gain of a sound signal in an audio system, includes a first detecting unit for capturing images of one or more faces of users and determining the number of faces and the size of the faces present in the images; a controller for receiving face data from the first detecting unit for comparing the sizes of faces in subsequently captured images with an initial face size and accordingly deciding and outputting a first decision signal; and a gain regulator coupled to the controller for adjusting the gain level of the sound signal according to the first decision signal. 
         [0007]    According to another embodiment of the present invention, a gain adjusting system for adjusting a gain of a sound signal in an audio system includes a first detecting unit coupled to the controller, the first detecting unit detecting a reflected signal reflected from a user and outputting the reflected signal; a controller for receiving the reflected signal from the first detecting unit and accordingly deciding and outputting a first decision signal; and a gain regulator coupled to the controller for adjusting the gain level of the sound signal according to the first decision signal. 
         [0008]    According to yet another embodiment of the present invention, a method of adjusting a gain of a sound signal in an audio system includes capturing images of one or more faces of users and determining the number of faces and the size of the faces present in the images; comparing the sizes of faces in subsequently captured images with an initial face size and accordingly deciding and outputting a first decision signal; and adjusting the gain level of the sound signal according to the first decision signal. 
         [0009]    According to still another embodiment of the present invention, a method of adjusting a gain of a sound signal in an audio system includes detecting a reflected signal reflected from a user; deciding and outputting a first decision signal according to the reflected signal; and adjusting the gain level of the sound signal according to the first decision signal. 
         [0010]    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  
         [0011]      FIG. 1  is a functional block diagram of a gain adjusting system according to the present invention. 
           [0012]      FIG. 2  is a flowchart summarizing a method of adjusting the gain according to the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0013]    Please refer to  FIG. 1 .  FIG. 1  is a functional block diagram of a gain adjusting system  10  according to the present invention. The gain adjusting system  10  receives two different kinds of input for determining how to adjust the gain output (volume) of a speaker  24  or the gain input of a microphone  26 . A face detecting unit  12  receives a face detecting signal FD(t) containing images of one or more faces of users near the object in use, whether it is the speaker  24  or the microphone  26 . The face detecting unit  12  analyzes the images and determines how many faces are captured and the image size of the captured faces. In general, the larger the face appears in the image, the closer the face is to the object in use, and vice versa. Face detection refers to determining 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. As will be explained below, the size of the faces detected by the face detecting unit  12  can be used to estimate an overall distance between the user(s) and the object in use. 
         [0014]    In addition, a beam sensor  16  receives a beam signal B(t). A beam transmitter  14  constantly emits electromagnetic beams, and the beam signal B(t) represents the beams that are reflected back to the beam sensor  16  when the beams are obstructed by an object. For example, the beam transmitter  14  and the beam sensor  16  can utilize infrared beams, ultrasonic beams, laser beams, microwave beams, or other similar types of electromagnetic beams. The beam sensor is used to roughly estimate the distance between a user and the object in use. After receiving the reflected signal B(t), the beam sensor  16  needs to analyze the signal strength. Consequently, a rough distance between the user and the object in use is estimated. 
         [0015]    The present invention makes use of both face detection and beam sensing to adaptively adjust the gain of the object in use. The face detecting unit  12  is set as the default mechanism to evaluate the gain. When certain conditions are met, the beam sensor  16  is instead the mechanism used to determine the gain. 
         [0016]    The face detecting unit  12  outputs the number of faces detected and the size of the detected faces to a quantizer  18 . In addition, the quantizer  18  also receives the beam signal strength output from the beam sensor  16 . The quantizer  18  quantizes the face data and/or the beam data and outputs the quantized data to a controller  20 . The quantizer  18  can be either a uniform quantizer or a non-uniform quantizer. 
         [0017]    The controller  20  utilizes the data from the face detecting unit  12  and/or the beam sensor  16  to determine how the gain should be adjusted, as will be explained below. The controller  20  uses this data to estimate the overall distance between the users and the object in use, and outputs a decision signal to a gain regulator  22 . The gain regulator  22  then adjusts the gain of the object in use according to the decision signal. 
         [0018]    A flowchart summarizing a method of adjusting the gain according to the present invention is illustrated in  FIG. 2 . Initially, the gain is set when the system powers on. At this time, an initial face size is also calculated of all the users when the system is powered on, and an initial beam strength is recorded. All of these initial parameters are stored in a memory  21  accessed by the controller  20 . 
         [0019]    In step  50 , the controller  20  receives data from the face detecting unit  12  and the beam sensor  16 . In step  52 , the controller  20  analyzes the face data provided by the face detecting unit  12  to determine if any faces have been captured. If so, the controller  20  determines if number of faces captured by the face detector is greater than a predetermined value. If yes, the controller uses the face data from the face detector and ignores the data from bean sensor. In this embodiment, the predetermined value is set to be one. That is, when more than one face has been captured, the data from the beam sensor  16  is ignored and the face data is instead used to determine the decision signal according to a calculated result which will be described below. 
         [0020]    In step  56  the controller  20  compares the current size of the faces with the initial face size calculated when the system is powered on. The face size data is used to generate a first ratio R 1  in step  57 , where RI is a ratio of the number of face sizes that are different from the initial face sizes to the total number of faces. R 1  represents that some of the users detected by the face detector have moved away or closer from the speaker/microphone since the time the system was powered on. If R 1  is less than a threshold value, the gain does not have to be adjusted. That means minor part of the users has been moved so the system will not be adjusted. On the other hand, if the number of face sizes that have changed is greater than a first threshold value, two ratios are calculated in step  58 . R 2  represents the ratio of the number of faces that are smaller than the initial face size to the total number of detected faces. A higher value of R 2  represents that more users have moved farther away from the speaker/microphone since it was powered on. Another ratio R 3  represents the ratio of the number of faces that are larger than the initial face size to the total number of detected faces. A higher value of R 3  represents that more users have moved closer to the speaker/microphone since it was powered on. R 2  and R 3  are initially equal to zero when the system is powered on since the initial face size is computed at this time and users have not had a chance to move closer to or farther from the object in use. 
         [0021]    In step  60 , both R 2  and R 3  are compared to respective second and third threshold values. If either R 2  is greater than the second threshold or if R 3  is greater than the third threshold value, the gain is adjusted in step  62 . If R 2  is greater than the second threshold, the gain should be increased since most of the users have moved farther from the object in use. On the other hand, if R 3  is greater than the third threshold, the gain should be decreased since most of the users have moved closer to the object in use. If neither R 2  nor R 3  are greater than their respective threshold values, the gain is maintained at its initial value in step  66 . 
         [0022]    Back to the decision signal output from the controller  20 , in the embodiment above, the decision signal is determined according to either R 2  or R 3  and the compared results with the threshold values. That is, if R 2  is greater than the second threshold, the decision signal will be indicative of increasing the gain; if R 3  is greater than the third threshold, the decision signal will be indicative of decreasing the gain. 
         [0023]    If during steps  52  and  54  it is determined that no faces were captured or that only one face was captured, step  64  is instead executed for comparing the strength of the beam signal to a beam threshold value to estimate an overall distance of the users from the speaker/microphone. If the strength of the beam signal has changed from the initial beam signal strength by more than the beam threshold value, then the gain is adjusted accordingly in step  62 . If the beam signal has become weaker than the initial bean signal, the gain is increased since this indicates that the user has moved farther away. On the other hand, if the beam signal has become stronger, the gain should be decreased since the user has moved closer to the object in use. If the beam signal strength is still close to the initial beam signal strength, then the gain is maintained at its initial value in step  66 . 
         [0024]    Decision signal in the embodiment above is determined according to the beam signals and the compared results with the threshold values. That is, if the beam signal is weaker than the initial bean signal, the decision signal is indicative of increasing the gain; if the beam is stronger, the decision signal is indicative of decreasing the gain. 
         [0025]    The threshold values mentioned above can be set by various ways. Users can set the thresholds to adjust their speaker volume or microphone gains based on personal preferences. Also, these thresholds can be set by computer based on average human hearing. 
         [0026]    In summary, the present invention gain adjusting system  10  and related adjusting method free the users from having to manually adjust the gain of the object in use. Instead, the controller  20  automatically adjusts the gain according to the distance that the users are from the object in use. Both face detection and beam signal strength measurements can be used to ensure that the distance between the users and the object in use is estimated accurately in different kinds of situations. 
         [0027]    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.