Abstract:
To improve the accuracy of the voice recognition system for an AV system, the present invention includes a reflected sound remover having a plurality of filters, the reflected sound remover being configured to receive an input sound signal including a reflected AV system audio, a user&#39;s voice, and a noise, and being configured to remove the reflected audio from the input sound according to user&#39;s voice information; a voice detector detecting the user&#39;s voice from a signal outputted from the reflected sound remover and obtaining the user&#39;s voice information based on the detected user&#39;s voice; and a voice recognition unit comparing the detected user&#39;s voice with voice patterns that belong to at least one model.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Application P2003-45765, filed on Jul. 7, 2003, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to perceiving a phonic input, and more particularly, to an apparatus and a method of perceiving a user&#39;s phonic input in AV system. 
     2. Discussion of the Related Art 
     In general, electronic home appliances such as TVs and audios are equipped with remote controllers that manipulate such home appliances. Yet, it has long been inconvenient that the remote controller must be near a user&#39;s reach. If the user loses the remote controller, the user has to manipulate the home appliances themselves. Furthermore, it is inconvenient for the disabled and the elder to even manipulate their home appliances by their remote controllers themselves. Due to this, the voice recognition system has been developed and applied to the many electronic home appliances. 
     The voice recognition system makes it possible that people communicate with machinery and computers by only people&#39;s phonic expressions. Even though the voice recognition system has been applied to many fields and brought much convenience to the people, it has not been successful in the AV (audio-visual) system. The fact that there are too many noises around as well as from the AV appliances and remote distance from the AV appliances to users makes the voice recognition system less reliable and accurate. Accordingly, there are many problems that need to be solved to implement the voice recognition system in the AV system. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an apparatus and a method of voice recognition system in AV system that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide an apparatus and a method of voice recognition system under a situation where reflected sound and noises are present 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a voice recognition system for an audio-visual (AV) system comprises a reflected sound remover having a plurality of filters, the reflected sound remover being configured to receive an input sound signal including a reflected AV system audio, a user&#39;s voice, and a noise, and being configured to remove the reflected audio from the input sound according to user&#39;s voice information; a voice detector detecting the user&#39;s voice from a signal outputted from the reflected sound remover and obtaining the user&#39;s voice information based on the detected user&#39;s voice; and a voice recognition unit comparing the detected user&#39;s voice with voice patterns that belong to at least one model. 
     The reflected sound remover includes a first filter bank dividing the original AV system audio into a first plurality of signals having different frequency ranges; a second filter bank dividing the input sound into a second plurality of signals having the different frequency ranges; a plurality of adaptive filters removing the reflected AV system audio from the second plurality of signals using the first plurality of signals; and a third filter bank combining the signals outputted from the plurality of adaptive filters. 
     The reflected sound remover further includes at least one of a blocking frequency, a transmitting frequency, and a reflected sound removing rate of the filters, according to the detected property information of the user&#39;s voice. The voice recognition unit compares the first probability and the second probability with reference values, and recognizes the user&#39;s voice depending on an outcome of the comparing the first and the second probabilities with reference values. 
     The voice recognition unit calculates a plurality of probabilities that the user&#39;s voice matches the predetermined voice patterns in the first model, and selects a highest probability from the plurality of probabilities as the first probability. In addition, the voice recognition unit calculates a plurality of probabilities that the user&#39;s voice matches the voice patterns in the second model, and selects a highest probability from the plurality of probabilities as the second probability. The first model includes voice patterns which correspond to predetermined words and the second model accumulates voice patterns which do not correspond to the predetermined words. 
     In another aspect of the present invention, A method for recognizing a voice for an audio-visual (AV) system includes receiving an input signal including a reflected AV system audio, a user&#39;s voice, and a noise; removing the reflected AV system audio from the input signal according to user&#39;s voice information by passing the input signal through a plurality of filters; detecting the user&#39;s voice from the first signal and obtaining the user&#39;s voice information based on the detected user&#39;s voice; and comparing the detected user&#39;s voice with voice patterns that belong to at least one model. 
     The step of controlling the plurality of filters includes fixing parameters of the plurality of filters during an interval from a starting point to an ending point of the user&#39;s voice. The parameters include at least one of a blocking frequency, a transmitting frequency, and a reflected sound removing rate of the plurality of filters. 
     The step of comparing the detected user&#39;s voice with voice patterns from at least one model includes calculating a first probability that the user&#39;s voice matches the voice patterns in a first model, and calculating a second probability that the user&#39;s voice matches the voice patterns in a second model. It also includes determining the ratio of the first probability and the second probability and comparing the determined ratio with reference values, and recognizing the user&#39;s voice depending on the ratio of the first probability and the second probability. 
     In another aspect of the present invention, a voice recognition system for an audio-visual (AV) system includes a voice detector detecting a user&#39;s voice from a received sound; and a voice recognition unit calculating a first probability that the user&#39;s voice matches one of voice patterns in a first model and a second probability that the user&#39;s voice matches one of voice patterns in a second model, and recognizing the user&#39;s voice according to a ratio of the first probability and the second probability. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; 
         FIG. 1  is an example of a TV including a voice recognition system in accordance with the present invention; 
         FIG. 2  is a block diagram illustrating the voice recognition system in AV system in accordance with the present invention; 
         FIG. 3  is a detailed diagram illustrating a reflected sound remover in accordance with the present invention; 
         FIG. 4  is a flowchart illustrating the voice recognition system in the AV system in accordance with the present invention; and 
         FIG. 5  is an example illustrating a user&#39;s decoded audio signal by the voice recognition system in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  illustrates an example of an audio-visual (AV) system including a voice recognition system according to the present invention. Referring to  FIG. 1 , the TV  10  includes the voice recognition device  20 , which receives reflected sound, noises and a user&#39;s voice. The reflected sound is TV  10  sound that is reflected by walls or remote objects. The best mode to place the voice recognition device  20  is on the front side of the TV  10 . 
       FIG. 2  is a block diagram illustrating the voice recognition system  20  in AV system according to the present invention. Referring to  FIG. 2 , the TV  10  includes a microphone (not shown in  FIG. 2 ), which receives the TV reflected sound, the noises, and the user&#39;s voice and converts them into frequency signals. The voice recognition system  20  includes a reflected sound remover  21 , which receives the frequency signals from the microphone and outputs only vocal signals corresponding to the user&#39;s voice. It is relatively easy for a minute noise to be recognized whereas it is very difficult for the reflected sound to be recognized. Therefore, as shown in  FIG. 3 , the present invention includes a first, a second and a third infinite-impulse response filter banks (IIR filter bank)  211 ,  212 ,  213  respectively in order to efficiently separate and remove said reflected sound. 
     The first filter bank  211  includes an M number of channel filters (H 0 , H 1 , H 2 , . . . H M-1 ) to divide audio signals decoded from broadcast signals into different frequency ranges (sub bands). The second filter bank  212  also includes an M number of the channel filters (H 0 , H 1 , H 2 , . . . H M-1 ) to divide the audio signals converted from the TV reflected sound, the noises, and the user&#39;s voice into the different frequency ranges (sub bands). Each channel of the H 0 , H 1 , H 2 , . . . H M-1  passes the signals according to the frequency ranges. 
     The reflected sound remover  21  further includes an adaptive filter unit  215  containing filters (W 0 , W 1 , W 2 , . . . W M-1 ), which receives the divided signals from the first filter bank  211  and the second filter bank  212 . Each of the W 0 , W 1 , W 2 , . . . W M-1  receives respectively the signals at the same frequency range from the first filter bank  211  and the second filter bank  212 . For example, the filter W 0  receives the signal from the channel filter (H 0 ) of the first filter bank  211  and the signal from the channel filter (H 0 ) of the second filter bank  212 . The adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) compare the two outputted signals from the first filter bank  211  and the second filter bank  212  and determine if the frequencies and amplitudes of the two signals are identical or similar. The adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) detect the signal from the second filter band  212  to be nearly identical to the signal from the first filter bank  211 . If the signal from the second filter bank  212  is nearly identical to the signal from the first filter bank  211 , the signals are considered to be the TV reflected sound signals. Then the adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) removed the signal from the signals from the first filter bank  212 . As a result, the adaptive filter unit  215  outputs the divided signals except for the reflected TV sound signals. The third filter bank  213  receives and combines the divided signals from the adaptive filter unit  215 . The combined signals include the user&#39;s voice and may include the noises and the residual reflected sound signals. Therefore, the present invention may include a noise remover (not illustrated), which filters the signals from the third filter bank  213  based on a threshold value. 
     The voice recognition system  20  further includes a voice detector  22 , which receives the signals from the reflected sound remover  21  and detects the user&#39;s voice from the received signals. The voice detector  22  obtains a user&#39;s voice information based on the user&#39;s voice. For example, to determine an interval of the user&#39;s voice, the voice detector  22  detects a beginning and an end of the voice and detects the frequency range, amplitude, and a wave shape of the user&#39;s voice. Now, the voice detector  22  sends the user&#39;s voice information to the reflected sound remover  21  and a voice recognition unit  23 . 
     The voice recognition system  20  also includes a memory  24 , which stores voice patterns, probability models having statistical data of the voice patterns. When the user&#39;s voice is detected in the voice detector  22 , the voice recognition unit  23  compares the user&#39;s voice with the stored voice patterns in the memory  24 . It then determines a probability (similarity level) of each stored voice matching the user&#39;s voice. Based on the probability, it determines if the user&#39;s voice is a certain voice pattern that corresponds to the stored voice in the memory  24  and what voice pattern it is. A controller  11  in the TV  10  manipulates the TV  10  as the user&#39;s voice desires. 
       FIG. 4  is a flowchart illustrating a voice recognition system in AV system. When the user says a user&#39;s voice such as “volume down”, the user&#39;s voice is received by the microphone and transmitted to the reflected sound remover  21 . However, the reflected TV sound and the noises are transmitted to the reflected sound remover  21  along with the user&#39;s voice. 
     The transmitted user&#39;s voice, TV reflected sound, and noises are divided into the different frequency ranges and the divided reflected TV sound is removed by the adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) and the noises is removed by the noise remover (S 30 ). The reflected sound remover ( 21 ) removes the reflected TV sound by using the IIR filter banks  211 ,  212 ,  213  according to sub bands filtering method. 
     The voice detector  22  receives all the signals but the removed reflected sound and the noises from the reflected sound remover  21 . As show in  FIG. 5 , the sinusoidal waves of the signals are analyzed into frames in order to detect the user&#39;s voice (S 31 ). The voice detector  22  also figures the starting and ending points of the signals and determines the frequency range and the amplitudes, and so on. The voice detector  22  compares energy (i.e. amplitude) of the user&#39;s voice with a predetermined reference value. For example, a point, where the energy of the signal inputted to the voice detector  22  is greater than a first threshold value, is the starting point, and another point, where the energy of the signal inputted to the voice detector  22  is greater than a second threshold value, is the ending point. 
     When the starting point of the user&#39;s voice is determined, the adaptive filter unit  215  stops adapting. But it restarts adapting when the ending point of the user&#39;s voice is determined. Adjusting is immediately predicting a route of the TV sound when reflected, altering filtering parameters such as blocking frequencies or passing frequencies of the adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) according to the reflected sound route being changed. An example of the reflected sound route is change according to the user&#39;s moving. 
     However, the filtering parameters of the adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) should be fixed when the reflected sound remover  21  receives both the reflected sound and the user&#39;s voice together because it is difficult to know the precise filtering parameters. The filtering parameters of the adaptive filters (W 0 , W 1 , W 2 , . . . W M-1 ) can be changed according to the reflected sound route only when the reflected sound itself is received. 
     The voice recognition unit  23  determines a first probability of the user&#39;s voice matching at least one of the stored voice patterns corresponding to predetermined words. It also determines a second probability of not matching one of voice patterns corresponding to words which are not predetermined (S 32 ). To determine the first probability, the user&#39;s voice is first compared with each of the voice patterns stored in a first model such as “change channel”, “volume up”, and “volume down”. The probabilities (i.e. similarities) of the stored voice patterns matching the user&#39;s voice are calculated. The first model is specifically a hidden markov model (HMM) which includes the voice patterns corresponding to the predetermined words. The voice recognition unit  23  determines considers the highest probability among the calculated probabilities as the first probability. To determine the second probability, the voice recognition unit  23  uses a second model, particularly a filler model accumulating the voice patterns corresponding to the words which are not predetermined. The user&#39;s voice is compared with each of the voice patterns stored in the second model and the probabilities of the stored voice patterns in the second model matching the user&#39;s voice are calculated. The voice recognition unit  23  considers the highest probability among the calculated probabilities as the second probability. It then determines the ratio of the first and the second probabilities (the former/the latter) and compares the ratio with a first reference value and a second reference value (S 33 , S 35 ). As a note, the first reference value is used for malfunction percent of 0.5% and the second reference value is used for malfunction percent of 5%. The first and the second reference values are obtained from the experiments. 
     If the ratio of the first and the second probabilities is greater than or equal to the first reference value, the voice recognition unit  23  recognizes the transmitted user&#39;s voice. For example, the voice recognition unit  23  assures the voice pattern that corresponds to the first probability from the first model and sends an instruction corresponding to the voice pattern to the controller  11 . The controller  11  now manipulates the TV  10  based on the user&#39;s voice pattern. 
     If the ratio of the first and the second probabilities is less than the first reference value and greater than the second reference value, the voice recognition unit  23  does not automatically recognize the transmitted user&#39;s voice but displays a word that best corresponds to the user&#39;s voice. For example, the voice recognition unit  23  requests the controller  11  that it assures the voice pattern that corresponds to the first probability from the first model (S 36 ). The controller  11  then displays the assured voice pattern (i.e. volume down) and waits to receive the user&#39;s confirmation. If the user says, “yes”, “OK”, or “select” as a confirmation (S 37 ), the controller  11  volumes down the TV  10  (S 38 ). If the user refuses the confirmation by saying “No” or “cancel”, the controller  11  deletes the display voice pattern, “volume down” on the TV  10 . 
     If the ratio of the first and the second probabilities is less than the second reference value, the voice recognition unit  23  does neither attempt to recognize the user&#39;s voice nor sends any signal to the controller  11  (S 39 ). Therefore, the controller  11  does not respond to the user&#39;s voice. 
     The present invention makes it possible that the voice recognition system functions precisely even with the reflected sound and the noises because it detects the user&#39;s voice based on the ratio of the two probabilities of the user&#39;s voice being matched and not matched one of the stored voice patterns. The present invention is also applicable to not only the electronic home appliances but also translating devices, handsets, toys, and the like. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.