Abstract:
An automatic AV synchronization adjusting method and apparatus to automatically adjust a synchronization error between a video signal and an audio signal generated in an AV system. The method includes: generating video and audio test signals; measuring an audio delay amount from when the audio test signal is generated to when the audio is output form a speaker; measuring an video delay amount from when the video test signal is generated to when the video is displayed on a display device; determining a final audio delay amount by subtracting the audio delay amount from the video delay amount; and adjusting a delay of an audio signal generated by an AV source device based on the determined audio delay amount.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2004-106544, filed on Dec. 15, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present general inventive concept relates to an audio/video (AV) playback system, and more particularly, to an automatic AV synchronization adjusting method and apparatus to automatically adjust a synchronization error between a video signal and an audio signal generated in an AV system.  
         [0004]     2. Description of the Related Art  
         [0005]     An AV system generally reproduces audio and video signals by connecting independent devices, such as a TV and an audio system, to each other. In these AV systems, a video signal reproduced by a display device and an audio signal reproduced by speakers may not be synchronized due to differences between processing times and/or signal paths.  
         [0006]      FIG. 1  is a block diagram of a conventional AV system.  
         [0007]     An AV source device  110  reads an AV signal from a disc or tape as a DVD player or a VTR and outputs the read signal to external devices. Here, the AV signal is in a synchronized state.  
         [0008]     A video display device  120  visually displays a video signal input from the AV source device  110  through a display panel such as a TV set or a monitor.  
         [0009]     An audio processing device  130  which includes a delay unit  132 , an amplifier  134 , and various signal processors (not shown), delays an audio signal generated by the AV source device  110  for a predetermined amount of time, and outputs the delayed audio signal to a speaker  140  after predetermined signal processing.  
         [0010]     In the AV system illustrated in  FIG. 1 , the video signal is directly output to the video display device  120 , whereas the audio signal is output to the speaker after passing through the delay unit  132 , the amplifier  134 , and the various signal processors. Here, a synchronization error occurs between the video displayed on the video display device  120  and the sound output from the speaker  140 . For example, the video signal is delayed for around 3 to 4 frames (51 to 68 ms) from when the video is reproduced by the AV source device  110  to when the video is displayed on the video display device  120 , whereas the audio signal is delayed for 3 to 4 samples (63 to 84 μs) when the audio is reproduced by the AV source device  110  to when the sound is output from the speaker  140 . As a result, in the AV system illustrated in  FIG. 1 , the video signal is generally delayed for at least 50 ms longer than the audio signal.  
         [0011]     Thus, for a conventional AV system, a user is required to determine a delay between audio and video during listening to the video from the video display device  120  and hearing the sound from the speaker  140  and to compensate for the delayed time in the audio processing device  130 . The amount of time delay in the video display device  120  is commonly greater than in the audio processing device  130 . To compensate for this, the user delays the audio signal for a predetermined time by manually adjusting a delay value of the delay unit  132  included in the audio processing device  130 .  
         [0012]     However, in a conventional AV synchronization adjusting method, since a user should determine whether audio and video are synchronized and how a delay of an audio signal differs from a delay of a video signal, inconvenience to the user is caused. Moreover, a user who is unfamiliar with use of electronic devices the AV system in a state in which an AV synchronization error is not compensated or asks a service center about the AV synchronization error.  
       SUMMARY OF THE INVENTION  
       [0013]     The present Your Ref. No.: SH-23510-US provides an automatic AV synchronization adjusting method and apparatus to automatically adjust a synchronization error between a video signal and an audio signal generated in an AV system.  
         [0014]     The present Your Ref. No.: SH-23510-US also provides an AV system to which the automatic AV synchronization adjusting method and apparatus is applied.  
         [0015]     Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.  
         [0016]     The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing an AV synchronization adjusting method in an AV system, the method including: generating video and audio test signals; measuring an audio delay amount from when the audio test signal is generated to when the audio is output from a speaker; measuring an video delay amount from when the video test signal is generated to when the video is displayed on a display device; determining a final audio delay amount by subtracting the audio delay amount from the video delay amount; and adjusting a delay of an audio signal generated by an AV source device based on the determined audio delay amount.  
         [0017]     The foregoing and/or other aspects and advantages of the present general inventive concept are also achieved by providing an AV system including: a signal source device to reproduce an AV signal from a predetermined recording medium; a display device having a video detector in front of a screen; a microphone; a speaker; an AV receiver to generate an audio test signal and a video test signal, to measure delay amounts of audio and video signals by detecting the audio test signal and the video test signal input via the microphone after passing through the speaker and a video-to-audio converter, respectively, and to delay an audio signal generated by the signal source device based on a final audio delay amount obtained by subtracting the audio delay amount from the video delay amount. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0019]      FIG. 1  is a block diagram of a conventional AV system;  
         [0020]      FIG. 2  is a block diagram of an AV system according to an embodiment of the present general inventive concept;  
         [0021]      FIGS. 3A and 3B  are an exterior view and a detailed diagram of a video-to-audio converter of  FIG. 2 ; and  
         [0022]      FIGS. 4A through 4C  are waveform diagrams illustrating detection of the amount of AV synchronization errors according to an embodiment of the present general inventive concept. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Hereinafter, embodiments of the present invention will now be described with reference to the accompanying drawings.  
         [0024]     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.  
         [0025]      FIG. 2  is a block diagram of an AV system according to an embodiment of the present invention.  
         [0026]     Referring to  FIG. 2 , the AV system includes an AV source device  210 , a display device  230 , an AV processing device  220 , a microphone  240 , and a speaker  250 .  
         [0027]     The AV source device  210  includes a DVD player or VTR, reads AV data from a recording medium such as a disc or tape, and outputs the read AV data to the AV processing device  220 .  
         [0028]     The display device  230  receives a video signal output from the AV processing device  220  and visually displays the video on a display panel such as a TV set or monitor. To measure a delay amount of the video signal, a video-to-audio converter  232  is attached in front of the screen of the display device  230  and converts the video to an audio signal. The video-to-audio converter  232  converts brightness information of a picture to an electrical signal and generates sound by generating a predetermined frequency signal from when a signal level greater than a threshold value is sensed.  
         [0029]     The speaker  250  reproduces sound from an audio signal which is amplified by the AV processing device  220 .  
         [0030]     The microphone  240  senses the sound output from the speaker  250  and the sound output from a speaker of the video-to-audio converter  232 .  
         [0031]     The AV processing device  220  delays and amplifies the audio signal input from the AV source device  210  and outputs the delayed and amplified audio signal to the speaker  250 . Also, the AV processing device  220  outputs the video signal input from the AV source device  210  to the display device  230 . In addition, the AV processing device  220  determines a delay amount of an audio signal input from the AV source device  210  using the audio signal generated by the video-to-audio converter  232  attached to the display device  230 . A detailed operation of the AV processing device  220  will now be described.  
         [0032]     A controller  223  determines an initial audio delay amount by selecting a video test signal and an audio test signal by switching second contact points of first and second switches SW 1  and SW 2  to third contact points, respectively.  
         [0033]     A video test signal generator  221  generates the video test signal, such as a black/white image, in response to a video test driving signal from the controller  223 . Here, the video test signal is converted to a predetermined frequency signal (discriminated from an audio test signal) by the video-to-audio converter  232  attached to the display device  230 .  
         [0034]     An audio test signal generator  222  generates an audio test signal having a frequency f1(HZ) in response to an audio test driving signal from the controller  223 . Here, the audio test signal is output to the speaker  250  after passing through an audio delay unit  227  and an amplifier  228 .  
         [0035]     The video test signal and the audio test signal may be generated either simultaneously or separately.  
         [0036]     An audio detector  226  detects an audio signal input from the microphone  240 . For example, the audio detector  226  includes a band pass filter having a frequency f1(HZ).  
         [0037]     A video detector  224  detects the predetermined frequency signal corresponding to a video-to-audio-converted signal input from the microphone  240 . For example, the video detector  224  may include a band pass filter having a frequency 2×f1(HZ) in order to discriminate the video test signal from the audio test signal.  
         [0038]     The controller  223  measures an audio delay amount between the audio test signal detected by the audio detector  226  and the audio test signal generated by the audio test signal generator  222  and measures a video delay amount between the predetermined frequency signal detected by the video detector  224  and the video test signal generated by the video test signal generator  221 . The controller  223  determines a final audio delay amount by subtracting the measured audio delay amount from the measured video delay amount.  
         [0039]     The audio delay unit  227  delays the audio signal generated by the AV source device  210  for a predetermined amount of time based on the final audio delay amount determined by the controller  223 .  
         [0040]     After measurement of the audio delay amount is completed, the controller  223  selects the audio signal and video signal generated by the AV source device  210  by switching the second contact points of the first and second switches SW 1  and SW 2  to first contact points, respectively.  
         [0041]      FIGS. 3A and 3B  are an exterior view and a detailed diagram of the video-to-audio converter  232  of  FIG. 2 .  
         [0042]     Referring to  FIG. 3A , the video-to-audio converter  232  includes a photoreceiver  310 , a main body  320 , and a speaker  330  and is attached in front of the screen of the display device  230 .  
         [0043]     Referring to  FIG. 3B , the photoreceiver  310  detects light eradiated from the screen of the display device  230  and converts the light to an electrical signal.  
         [0044]     A level detector  320 - 1  detects a signal level greater than a threshold from the electrical signal generated by the photoreceiver  310 .  
         [0045]     A tone signal generator  320 - 2  generates a tone signal of a predetermined frequency (ai.e., a frequency of 2×f1(Hz)) for a predetermined period from when the signal level greater than the threshold is detected by the level detector  320 - 1 .  
         [0046]     An amplifier  320 - 3  amplifies the tone signal generated by the tone signal generator  320 - 2  up to a predetermined level.  
         [0047]     The speaker  330  reproduces sound from the tone signal amplified by the amplifier  320 - 3 .  
         [0048]      FIGS. 4A through 4C  are waveform diagrams illustrating detection of AV synchronization error amounts according to an embodiment of the present general inventive concept.  
         [0049]     Referring to  FIG. 4A , the controller  223  outputs audio and video test signals by driving the audio and video test signal generators  221  and  222 . For example, the audio test signal is a tone signal having a frequency f1(Hz), and the video test signal is a black and white image.  
         [0050]     Referring to  FIG. 4B , a signal having a frequency f1(Hz) is output from the speaker  250 , and a signal of having a frequency 2×f1(Hz) is output from the video-to-audio converter  232  attached to the display device  230 .  
         [0051]     Referring to  FIG. 4C , an audio test signal  410  having a frequency f1(Hz) and a video test signal  420  having a frequency 2×f1(Hz) are input to the microphone  240 . Here, finally output audio and video delay amounts can be measured based on the originally generated audio and video test signal.  
         [0052]     The audio detector  226  detects the audio test signal  410  using a band pass filter having a frequency f1(Hz), and the video detector  224  detects the video test signal  420  using a band pass filter having a frequency 2×f1(Hz). The controller  223  measures video and audio delay amounts using the video detector  224  and the audio detector  226  and determines an adjusted audio delay amount. That is, the adjusted audio delay amount is obtained by subtracting the measured audio delay amount from the measured video delay amount.  
         [0053]     The embodiments of the present general inventive concept can be written as computer programs and can be implemented in general-use digital computers that execute the programs using a computer readable recording medium. Examples of the computer readable recording medium include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.), optical recording media (e.g., CD-ROMs, DVDs, etc.), and storage media such as carrier waves (e.g., transmission through the internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.  
         [0054]     As described above, according to embodiments of the present general inventive concept, an AV synchronization error in an AV system can be automatically compensated by measuring audio and video delay amounts using a microphone used for sound field space compensation of an AV receiver or level compensation of a speaker. In addition, a picture signal from a display device can be wirelessly detected to measure a delay amount of a video signal.  
         [0055]     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.