Abstract:
A method and apparatus of detecting a connection status of a digital video apparatus to a peripheral apparatus includes a digital video encoder configured to receive a digital video signal, and convert and output the digital video signal into an analog video signal, and a determination circuit configured to detect a voltage level of a horizontal synchronization signal of the analog video signal in a vertical blanking time determined by vertical synchronization signals, and determine whether the digital video apparatus is connected to a peripheral apparatus based on a detection result of the voltage of the horizontal synchronization signal of the analog video signal.

Description:
BACKGROUND  
       [0001]     1. Field  
         [0002]     This patent application relates to a digital video apparatus, and more particularly to a digital video apparatus which stably detects its status of connection to a peripheral apparatus.  
         [0003]     2. Description of Related Art  
         [0004]     A conventional digital video apparatus includes a digital video encoder and a digital to analog converter (DAC).  
         [0005]     The digital video encoder generates three digital television signals of a luminance signal Y, a chrominance signal C, and a composite signal YC from digital primary color signals of R (red), G (green), and B (blue), or digital signals of Y (luminance signal), Cb (blue color difference signal), and Cr (red color difference signal).  
         [0006]     The DAC converts the digital luminance signal Y, the digital chrominance signal C, and the digital composite signal YC to an analog luminance signal Y, an analog chrominance signal C, and an analog composite signal YC, and outputs these analog video signals.  
         [0007]     The digital video encoder converts a digital video signal taken by a digital video apparatus such as a digital camera to an analog video signal. The analog video signal is transmitted to and played on a peripheral apparatus such as a monitor television.  
         [0008]     The digital video apparatus and the peripheral apparatus such as a monitor television, which is detachable from the digital video apparatus, communicate signals such as a video signal with each other.  
         [0009]     The digital video apparatus including the digital video encoder detects a connection status of the peripheral apparatus such as a monitor television to the digital video apparatus. The above-mentioned digital video apparatus can save its power consumption by controlling outputs of the digital video encoder or the like based on the detected connection status. Power saving is a critical matter particularly for a battery-powered portable type digital video apparatus.  
         [0010]     An exemplary conventional detection circuit which detects a connection status of a peripheral apparatus such as a monitor television to the digital video apparatus is illustrated in  FIG. 1 .  
         [0011]     As illustrated in  FIG. 1 , the conventional detection circuit includes a resistor Rd, a resistor Re, a resistor Rt, a connector Tt, a comparator  1 , a resistor Rs, a power source Vs, a coupling capacitor Ct, and an amplifier At.  
         [0012]     In the conventional detection circuit, the comparator  1  compares a voltage at a connection point between the resistor Rd and the resistor Re (e.g, Re=2×Rd), and a voltage at a connection point between the resistor Rt and the connector Tt to detect a connection status at the connector Tt. The comparator  1  outputs a high level signal when the peripheral apparatus such as a monitor television is connected to the connector Tt.  
         [0013]     The conventional detection circuit of the digital video apparatus has a video signal output terminal, and determines whether the peripheral apparatus such as a monitor television is connected to the video signal output terminal of the digital video apparatus.  
         [0014]     Specifically, a resistor is provided to a terminal of the digital video apparatus, and pulled up to a power source. The resistor has an ohmic value which is significantly larger than that of a resistor provided to the monitor television and connected to a ground. For example, the resistor provided to the terminal of the digital video apparatus has about one mega ohms, and the resistor of the monitor television has 75 ohms.  
         [0015]     When the monitor television is connected to the terminal of the digital video apparatus, a voltage, determined by a voltage dividing ratio of the resistor of the monitor television having 75 ohms and the resistor at the terminal of the digital video apparatus having about one mega ohms, is generated at the terminal of the digital video apparatus.  
         [0016]     The conventional detection circuit detects a voltage change at the terminal of the digital video apparatus, and can detect a connection status of the peripheral apparatus such as a monitor television to the digital video apparatus.  
         [0017]     The above-mentioned configuration of the conventional detection circuit, which detects a voltage change determined by a voltage dividing ratio of resistors, can stably detect the connection status of the peripheral apparatus such as a monitor television to the digital video apparatus when the digital video apparatus does not output a video signal.  
         [0018]     However, when the digital video apparatus outputs a video signal, the above-mentioned configuration of the conventional detection circuit cannot stably detect the connection status of the peripheral apparatus such as a monitor television to the digital video apparatus due to a voltage level of the video signal.  
         [0019]     Furthermore, the above-mentioned configuration of the conventional detection circuit has a drawback that it needs external resistors, resulting in an increase of numbers of components.  
       SUMMARY  
       [0020]     This patent application describes a novel digital video apparatus. In one example, this novel digital video apparatus includes a digital video encoder, and a determination circuit. The digital video encoder receives a digital video signal, and converts and outputs the digital video signal into an analog video signal. The determination circuit detects a voltage level of a horizontal synchronization signal of the analog video signal in a vertical blanking time determined by vertical synchronization signals, and determines whether the digital video apparatus is connected to a peripheral apparatus based on a detection result of the voltage of the horizontal synchronization signal of the analog video signal.  
         [0021]     In the above-mentioned digital video apparatus, the determination circuit determines that the digital video apparatus is not connected to the peripheral apparatus if it is detected that the voltage of the horizontal synchronization signal of the analog video signal is zero.  
         [0022]     In the above-mentioned digital video apparatus, the determination circuit determines that the digital video apparatus is connected to the peripheral apparatus if it is detected that the voltage of the horizontal synchronization signal of the analog video signal is larger than a predetermined voltage.  
         [0023]     In the above-mentioned digital video apparatus, the predetermined voltage is within a range of from approximately 150 mV to approximately 250 mV.  
         [0024]     In the above-mentioned digital video apparatus, the digital video apparatus controls a power-on or power-off of the digital video encoder based on a detection result of the determination circuit.  
         [0025]     This patent application describes a novel method of detecting a connection status of a digital video apparatus to a peripheral apparatus. In one example, this novel method includes the steps of receiving, converting, detecting, and determining. The receiving step receives a digital video signal. The converting step converts the digital video signal into an analog video signal. The detecting step detects a voltage level of a horizontal synchronization signal of an analog video in a vertical blanking time determined by vertical synchronization signals. The determining step determines whether the digital video apparatus is connected to the peripheral apparatus based on a detection result of the voltage of the horizontal synchronization signal of the analog video signal.  
         [0026]     The above-mentioned determining step determines that the digital video apparatus is not connected to the peripheral apparatus if it is detected that the voltage of the horizontal synchronization signal of the analog video signal is zero.  
         [0027]     The above-mentioned determining step determines that the digital video apparatus is connected to the peripheral apparatus if it is detected that the voltage of the horizontal synchronization signal of the analog video signal is larger than a predetermined voltage.  
         [0028]     The above-mentioned predetermined voltage is within a range of from approximately 150 mV to approximately 250 mV.  
         [0029]     The above-mentioned digital video apparatus controls supply of power for the receiving and converting steps based on a detection result of the determination circuit.  
         [0030]     This patent application describes another novel digital video apparatus. In one example, this novel digital video apparatus includes an interface, a first signal generation circuit, a modulation circuit, a first adder circuit, a second adder circuit, a second signal generation circuit, a synchronization signal insertion circuit, a digital to analog converter, and a determination circuit. The interface receives and transmits a digital signal. The first signal generation circuit generates a luminance signal and a color difference signal. The modulation circuit modulates a color sub-carrier using the color difference signal. The first adder circuit inserts the color sub-carrier to a color burst position as a color burst signal and generates a digital chrominance signal. The second adder circuit adds the digital luminance signal and the digital chrominance signal to generate a digital composite signal. The second signal generation circuit generates a composite synchronization signal. The synchronization signal insertion circuit inserts the composite synchronization signal in the digital composite signal. The digital to analog converter receives a digital video signal from the synchronization signal insertion circuit and outputs an analog video signal. The determination circuit detects a voltage of a horizontal synchronization signal of the analog video signal in a vertical blanking time determined by vertical synchronization signals, and determines whether the digital video apparatus is connected to a peripheral apparatus based on a detection result of the voltage of the horizontal synchronization signal of the analog video signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     The features of the present application and many of the attendant advantages thereof can be more readily understood from the following detailed description with reference to the accompanying drawings, wherein:  
         [0032]      FIG. 1  is an exemplary circuit diagram of a conventional detection circuit configured to detect a connection status of a peripheral apparatus to a digital video apparatus;  
         [0033]      FIG. 2  is an exemplary block diagram of a digital video apparatus according to an exemplary embodiment of this patent application; and  
         [0034]      FIG. 3  is an exemplary waveform of a composite signal according to an exemplary embodiment of this patent application. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0035]     In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of the present patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.  
         [0036]     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG.  2  thereof, an exemplary block diagram of a digital video apparatus according to an exemplary embodiment of this patent application is described.  
         [0037]     The digital video apparatus includes an interface circuit  10 , a digital encoder portion  40 , and a determination circuit  50 .  
         [0038]     The digital encoder portion includes a first signal generation circuit  11 , a second signal generation circuit  12 , a modulation circuit  14 , a first adder circuit  15 , a second adder circuit  16 , a synchronization signal insertion circuit  17 , and a digital to analog converter (DAC)  18 .  
         [0039]     The determination circuit includes a comparator  20 , a flip-flop circuit  21 , a terminal resistor  22 , a coupling capacitor  23 , and a jack  30 .  
         [0040]     Digital primary color signals of R (red), G (green), and B (blue), and digital signals of Y (luminance signal), Cb (blue color difference signal), and Cr (red color difference signal) are input through the interface circuit  10 . These signals are transmitted to the first signal generation circuit  11  which generates a luminance signal and color difference signals.  
         [0041]     The first signal generation circuit  11  generates a digital luminance signal Y, a digital R-Y signal (i.e., V signal), and a digital B-Y signal (i.e., U signal) from the three digital primary color signals of R, G, and B, or digital signals of Y, Cb, and Cr, which are input to the digital video apparatus.  
         [0042]     The second signal generation circuit  12  generates a plurality of synchronization signals including horizontal and vertical synchronization signals, and generates a composite synchronization signal CSYNC based on the plurality of synchronization signals, using a master clock signal input from an external device (not shown). The synchronization signal insertion circuit  17  inserts the composite synchronization signal CSYNC in a composite signal (discussed below).  
         [0043]     The first signal generation circuit  11  outputs the BY signal (i.e., U signal) and the R-Y signal (i.e., V signal) to the modulation circuit  14 . The modulation circuit  14  modulates a color sub-carrier SC based on the B-Y signal (i.e., U signal) and the R-Y signal (i.e., V signal), and outputs a modulated signal. A frequency fSC for the color sub-carrier SC is about 3.58 MHz for NTSC (National Television System Committee), and about 4.43 MHz for PAL (Phase Alternating Line).  
         [0044]     The modulated signal output from the modulation circuit  14  is transmitted to the first adder circuit  15 . The first adder circuit  15  inserts the color sub-carrier SC in the modulated signal at a color burst position as a color burst signal and generates a digital chrominance signal C.  
         [0045]     The second adder circuit  16  adds the digital luminance signal Y and the digital chrominance signal C to generate a digital composite signal YC.  
         [0046]     The second signal generation circuit  12  outputs the composite synchronization signal CSYNC to the synchronization signal insertion circuit  17 .  
         [0047]     In the synchronization signal insertion circuit  17 , a synchronization signal is inserted in a signal such as the digital composite signal output from the second adder circuit  16 . After the insertion, the digital signal is converted to an analog signal by the DAC  18 , and is output as an analog video signal. The jack  30  receives the analog video signal through the terminal resistor  22  and the coupling capacitor  23 .  
         [0048]     The electrically driven DAC  18  is between the synchronization signal insertion circuit  17  and the coupling capacitor  23 , and outputs an analog video signal for monitoring.  
         [0049]     The video signal output from the DAC  18  is transmitted to a positive (+) terminal of the comparator  20  which is used as a determination circuit to detect a connection status of the peripheral apparatus such as monitor television to the jack  30 . A negative (−) terminal of the comparator  20  receives a determination voltage level of 200 mV, for example. The determination voltage level is switchable between 200 mV and 150 mV by a resistor, for example.  
         [0050]     The flip-flop circuit  21  receives an output from the comparator  20 , and registers the output from the comparator  20  according to a signal supplied through a clock-input terminal of the flip-flop circuit  21  during a vertical blanking time (i.e., vertical synchronization signal) which is illustrated in  FIG. 3 .  
         [0051]      FIG. 3  is an exemplary waveform of a composite signal according to an exemplary embodiment of this patent application. The composite signal includes horizontal synchronization signals, vertical synchronization signals, and luminance signals.  
         [0052]     A connection status of the peripheral apparatus such as a monitor television to the jack  30  is determined during low level periods of the horizontal synchronization signals in the vertical blanking time determined by the vertical synchronization signals. The vertical synchronization signals are transmitted from the second signal generation circuit  12 .  
         [0053]     The electrically driven DAC  18  outputs a composite signal including horizontal synchronization signals as illustrated in  FIG. 3 .  
         [0054]     When the peripheral apparatus such as a monitor television is not connected to the jack  30 , a low level of the horizontal synchronization signals in the vertical blanking time becomes 0 mV.  
         [0055]     Then the comparator  20  compares the low level of 0 mV with the determination voltage level of 200 mV, for example, and outputs a low level signal to the flip-flop circuit  21 .  
         [0056]     When the low level signal is transmitted to the flip-flop circuit  21  in the vertical blanking time, it is determined that the peripheral apparatus such as a monitor television is not connected to the jack  30 .  
         [0057]     When the flip-flop circuit  21  outputs a signal indicating that the peripheral apparatus such as a monitor television is not connected to the jack  30 , an external controller (not shown) having a CPU performs a sleep control to the first signal generation circuit  11 , the DAC  18 , the second signal generation circuit  12  or the like to save power consumption of the digital video apparatus.  
         [0058]     On the other hand, when the peripheral apparatus such as monitor television is connected to the jack  30 , a low level of the horizontal synchronization signal in the vertical blanking time becomes about 300 mV or more, for example.  
         [0059]     Then the comparator  20  compares the low level of 300 mV with the determination voltage level of 200 mV, for example, and outputs a high level signal to the flip-flop circuit  21 .  
         [0060]     When the high level signal is transmitted to the flip-flop circuit  21  in the vertical blanking time, it is determined that the peripheral apparatus such as a monitor television is connected to the jack  30 .  
         [0061]     The above-mentioned external controller (not shown) having a CPU does not perform a sleep control when the peripheral apparatus such as a monitor television is connected to the jack  30 , but normal operations of the digital video apparatus are performed.  
         [0062]     A determination timing of the above-mentioned connection status may be configured to be switchable between a field basis and a frame basis by storing setting conditions to a register or the like.  
         [0063]     As described above, when the connection status of the peripheral apparatus such as a monitor television is detected by an output from the comparator  20  in the vertical blanking time, a power on/off control of the digital video apparatus can be controlled by the digital video apparatus or an external controller (not shown) having a CPU, for example.  
         [0064]     To realize a power on/off control by the external controller (not shown), a digital video apparatus may be configured to transmit an interruption signal from the flip-flop circuit  21  to the external controller (not shown) when a connection status of the peripheral apparatus such as monitor television changes.  
         [0065]     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present patent specification may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substitutional for each other within the scope of this disclosure and appended claims.  
         [0066]     This application claims priority from Japanese patent application No. 2003-325471 filed on Sep. 18, 2003 in the Japan Patent Office, the entire contents of which are hereby incorporated by reference herein.