Abstract:
A frame conversion device for switching between a plurality of image signals that are not synchronous and outputting each image signal continuously and synchronously. In addition, a desired signal is extracted from the continuous image signals and then output in parallel with the continuous image signals. The frame conversion device utilizes a frame conversion unit for recording an image signal optionally selected from a plurality of input image signals. A frame unit is utilized for reproducing a recorded signal outputted from the frame conversion unit independent of the operation of the frame conversion unit. The frame conversion unit includes an identification signal assigning part which assigns an identification signal to a non-image region of an image signal selected from a plurality of input signals. Frame-converting storage parts store the selected image signal. A signal output part selectively reads the image signal stored in each frame-converting storage device. The frame unit includes an identification signal detecting part that detects the identification signal included in the image signal produced in the frame conversion unit. A reproduction controlling part extracts a frame timing of the image signal assigned a predetermined identification signal. A recording storage part, at the extracted frame timing, stores an image signal corresponding to the predetermined identification signal and continuously outputs the image signal.

Description:
This patent application is a continuation-in-part of U.S. patent application Ser. No. 09/159,992 filed Sep. 24, 1998, now Pat 6,172,710. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a frame converting device having a function to continuously output a plurality of image signals in a synchronized state while switching the image signals from a plurality of asynchronous inputs, and a function to extract a desired one of the continuous image signals from such plural inputs and outputs the extracted signal, and particularly, to improvement of a monitoring function when reproducing a recorded signal. 
     A known image switcher switches image signals from a plurality of cameras and the like and outputs the signals as one image signal. In switching such image signals, the input image signals from the cameras are often asynchronous with each other, but the disturbance of synchronous signals in the output image signals is inconvenient. In such case, all the input image signals are synchronized in advance by using a camera having a TBC (Time Base Corrector) function. Otherwise, asynchronous-synchronous conversion must be performed for each input by using a frame-converting device having a frame memory. 
     First problem: a camera having the TBC function is expensive, and therefore it is difficult to use the camera in a low-price route. Further, in the frame-converting device, the number of frame memories is the same as that of input image signals. While an image signal is stored into one of the frame memories, reading from another frame memory is performed. 
     Second problem: this type of device selects a either one of a first operation to switch the image signals from the plurality of cameras to outputs them as one image signal and to perform monitor display or VCR recording, or a second operation to extract a desired image signal from image signals from the plurality of cameras, switched to form one signal, and reproduced on a VCR or the like, and to perform display based on the extracted signal on the monitor. 
     In such frame-converting device, the number of frame memories must be the same as that of input image signals. This increases the price of the device. Further, the monitor display, and the VCR recording operation and cannot be performed in parallel to the VCR reproduction operation. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to solve or at least mitigate the above-described problems, and has its object to realize a frame converting device which performs a first operation to continuously output a plurality of image signals in a synchronized state while switching the respective asynchronous image signals, by using fewer frame memories than the number of input image signals, in parallel to a second operation to extract a desired image signal from image signals switched to form one signal and to output the extracted signal. 
     Accordingly, a first aspect of the present invention provides a frame conversion device as recited in claim  1 . Advantageous embodiments are defined in the dependent claims. 
     This frame converting device time-divisionally stores and reads a plurality of image signals by means of less frame-conversion storage means than input image signals while switching the signal input means and the signal output means. Thus the device continuously outputs the image signals in a synchronized state while switching a plurality of asynchronous image signals with less frame memories than input signals. 
     Further, the device detects the identification signals included in the image signals in frame units, extracts frame timing of an image signal with a predetermined identification signal from the image signals in frame units, stores the image signal of the frame timing, and continuously outputs the image signal. Thus, the device extracts a desired image signal from image signals switched to form one signal, and outputs the extracted image signal. 
     As the device has the recording frame-converting unit and the reproduction frame unit, the device can perform these two operations in parallel. 
     As to claim  3 , the frame converting device can record the image signal from the recording frame-converting unit by the VCR, and when the recorded image is reproduced by the VCR, extract a desired image signal from image signals switched to form one signal by the reproduction frame unit. 
     As to claim  4 , when a desired image signal is extracted from image, switched to form one signal and outputted the frame-converting device can extract the desired image signal based on input from the operation means. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a block diagram of a first embodiment of a frame conversion device according to the invention; 
     FIG. 2 is a block diagram of a second embodiment of a frame conversion device according to the invention; and 
     FIG. 3 is a time chart that shows an operation statement of a frame conversion device as shown in FIG.  2 . 
    
    
     The following reference signs are used in the drawings: 
       1 : CPU  11 ,  21 : switch (signal input means)  13 ,  23 : A/D converter 
       14 ,  24 : identification signal assigning part  15 ,  25 : switch 
       16 ,  26 : frame memory (storage means)  17 ,  27 : D/A converter 
       31 ,  32 : switch (signal output means)  40 : frame unit for reproducing 
       41 : A/D converter  42 : ID detecting part  43 : operating part 
       44 : reproduction controlling part  45 : frame memory  46 : D/A converter 
       47 : on-screen display part. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, embodiments of the present invention will be described with reference to attached drawings. 
     FIG. 1 is a block diagram showing the construction of a frame-converting device according to respective embodiments of the present invention. In FIG. 1, the device comprises a recording frame-converting unit having two routes, i.e., a first route (route A)  10  and a second route (route B)  20 , each route having four inputs, and a reproduction frame unit  40 . That is, the frame converting device of the present invention comprises the recording frame-converting unit and the reproduction frame unit  40  which operate independently of each other. 
     In FIG. 1, reference numeral  1  denotes a CPU as control means for controlling respective elements of the device. The CPU  1  especially controls switching respective switches and controls writing/reading storage means. 
     Numeral  11  denotes a switch as signal input means for switching inputs of four image signals CAM 1  to CAM 4  (television cameras  1  to  4 ). Numeral  13  denotes an A/D converter that converts an image signal passed through the switch  11  into a digital image signal. 
     Numeral  14  denotes an identification signal supply unit which supplies an identification signal (ID 1  to ID 4 ) to a non-image area (vertical retrace period or the like) of the digital image signal so as to identify from which camera the signal comes. Note that the identification signal supply unit  14  includes identification signal generators (ID_ 1  generator to ID_ 4  generator) for generating the respective identification signals and a switch  15 . 
     Numeral  16  denotes a frame memory as storage means for storing a plurality of switched digital image signals respectively in frame units. Note that the frame memory  16  preferably is having independently operative input port and output port switches a memory. 
     Numeral  17  denotes a D/A converter that D/A converts the digital image signal read from the frame memory  16  into an analog image signal. Note that the switch  11  to the D/A converter  17  constructs the first route (route A). 
     Numeral  21  denotes a switch as signal input means for switching input of four image signals CAM 5  to CAM 8  (cameras  5  to  8 ). Numeral  23  denotes an A/D converter that converts the image signal passed through the switch  21  into a digital image signal. 
     Numeral  24  denotes an identification signal supply unit which supplies an identification signal (ID 5  to ID 8 ) to a non-image area (vertical retrace period or the like) of the digital image signal so as to identify from which camera the signal comes. Note that the identification signal supply unit  24  includes identification signal generators (ID_ 5  generator to ID_ 8  generator) for generating the respective identification signals and a switch  25 . 
     Numeral  26  denotes a frame memory as storage means for storing a plurality of switched digital image signals respectively in frame units. Note that the frame memory  26  preferably is having independently operative input port and output port such as a memory. 
     Numeral  27  denotes a D/A converter that D/A converts the digital image signal read from the frame memory  26  into an analog image signal. Note that the switch  21  to the D/A converter  27  constructs the second route (route B). 
     Further, numeral  31  denotes a monitor output switch as signal output means for alternately reading an image signals stored in the respective frame memories  16  and  26  by alternately switching the route A and the route B and outputting them. 
     Further, numeral  32  denotes a VCR output switch for outputting image signals for recording in an external VCR, as signal output means for alternately reading image signals stored in the respective frame memories  16  and  26  by alternately selecting the route A and the route B outputting them. 
     Numeral  41  denotes an A/D converter which A/D converts the image signal, that has been sent from the recording frame-converting unit then recorded by the VCR, and reproduced by the VCR. Numeral  42  denotes an ID detector that detects the identification signal included in the A/D converted digital image signal. Numeral  43  denotes an operation unit for operation of selection to extract a desired image signal. 
     Numeral  44  denotes a reproduction controller which read/write controls the frame memory  45  based on the detected identification signal and the operation of selection, and controls a channel display on an on-screen display in accordance with the detected identification signal. The frame memory  45  is used for storing a desired image signal to reproduce under the control of the reproduction controller  44 . 
     Numeral  46  denotes a D/A converter that D/A converts the digital image signal read from the frame memory  45  into an analog image signal. Numeral  47  denotes an on-screen display unit (OSD) which superimpose-outputs a channel display in accordance with the identification signal on the analog image signal, under the control of the reproduction controller  44 . Note that the on-screen display unit  47  comprises a character generator, a superimpose circuit and the like. 
     The frame converting device having the above construction can continuously output synchronized image signals by storing respective asynchronous image of eight inputs in the recording frame-converting unit into two frame memories. Further, in parallel to this operation, the device detects the identification signals included in the image signals in frame units, extract frame timing of an image signal with a predetermined identification signal from the image signals in frame units, and the image signal of the frame timing and continuously outputs them. Thus, the device can extract a desired image signal from image signals switched to form one signal and outputs them. 
     Hereinafter, the operation will be described with reference to a timing chart. Note that for the sake of simplification of explanation, description will be made by using a frame converting device shown in FIG. 2 for two inputs, two routes and one output (four input and one output) in each route, as the recording frame-converting unit. In FIG. 2, the elements identical to those in FIG. 1 have the same reference numerals, and overlapped explanation will be omitted. 
     First, the CPU  1  generates a reference synchronizing signal for operating the respective elements of the device. In this case, the reference synchronizing signal may be a synchronizing signal independent of CAM 1  to CAM 4  or may be a synchronizing signal synchronized with any of CAM 1  to CAM 4 . Herein after as an example, a synchronizing signal of the signal CAM 1  is used as the reference synchronizing signal (FIG.  3 ( a )). 
     Then the CPU  1  supplies a select A signal to the switch  11  for switching the input in the route A. The select A signal is used to alternately select the image signal from the CAM 1  and the image signal from the CAM 2 , in two-frame units. 
     Similarly, the CPU  1  supplies a select B signal to the switch  21  for switching the input in the route B. the select B signal is used to alternately select the image signal from the CAM 3  and the image signal from the CAM 4 , in two-frame units. Further, the select B signal is one-frame phase shifted from the select A signal. 
     In this case, as the select A signal and the select B signal are switched in two-frame units, the asynchronous and inconstant timing image signal for one frame is included in any one of two frame periods. 
     First, when the switch  11  is on the CAM 1  side in accordance with the select A signal (FIG.  3 ( b )), the image signal of the CAM 1  is passed through the switch  11  and converted by the A/D converter  13  into a digital image signal at a timing within the two-frame periods. In parallel to this operation, the identification signal ID_ 1  from the switch  15 , have been switched in accordance with the select A signal, is supplied within the retrace period of the digital image signal. The signal is stored into the frame memory  16  (CAM 1  in FIG.  3 ( c )). 
     Further, when the switch  11  is switched to the CAM 2  side in accordance with the select A signal, the image signal to the CAM 2  is passed through the switch  11  and converted by the A/D converter  13  into a digital image signal at a timing within the two-frame periods. In parallel to this operation, the identification signal ID_ 2  from the switch  15 , have been switched in accordance with the select A signal, is supplied within the retrace period of the digital image signal. The signal is stored into the frame memory  16  (CAM 2  in FIG.  3 ( c )). 
     Further, when the switch  11  is switched to the CAM 3  side in accordance with the select B signal (FIG.  3 ( d )), the image signal of the CAM 3  is passed through the switch  21  and converted by the A/D converter  23  into a digital image signal at a timing within the two-frame periods. In parallel to this operation, the identification signal ID_ 3  from the switch  25 , have been switched in accordance with the select B signal, is supplied within the retrace period of the digital image signal. The signal is stored into the frame memory  26  (CAM 3  in FIG.  3 ( e )). 
     Further, when the switch  21  is switched to the CAM 4  side in accordance with the select B signal, the image signal of the CAM  4  is passed through the switch  21  and converted by the A/D converter  23  into a digital image signal at a timing within the two-frame periods. Then, in parallel to this operation, the identification signal ID_ 4  from the switch  25 , switched in accordance with the select B signal, is supplied which the retrace period of the digital image signal. The signal is stored into the frame memory  26  (CAM 4  in FIG.  3 ( c )). 
     Further, reading from the frame memory  16  is performed at a timing of the last one frame within the respective two frame periods of the select A signal, based on the synchronizing signal (FIG.  3 ( a )). That is, when the select A signal is the CAM 1  in the last one frame period of the CAM 1 , the digital image signal of the CAM 1  is read from the frame memory  16  (CAM 1  in FIG.  3 ( f )). Further, when the select A signal in the last one frame period of the CAM 2 , the digital image signal of the CAM 2  is read from the frame memory  16  (CAM 2  in FIG. ( f )). Note that the read digital image signal is converted by the D/A converter  17  into an analog image signal. 
     Similarly, reading from the frame memory  26  is performed at a timing of the last one frame within the respective two frame periods of the select B signal, based on the synchronizing signal (FIG.  3 ( a )). That is, when the select B signal is in the last one frame period of the CAM 3 , the digital image signal of the CAM 3  is read from the frame memory  26  (CAM 3  in FIG.  3 ( g )). Further, when the select B signal is in the last one frame period of the CAM 4 , the digital image signal of the CAM 4  is read from the frame memory  26  (CAM 4  in FIG. ( g )). Note that the read digital image signal is converted by the D/A converter  27  into an analog image signal. 
     Then, the switch  31  is controlled to be switched for each one frame in synchronization with the synchronizing signal (FIG.  3 ( a )). As shown in FIG.  3 ( h ), as the monitor output, an image signal in a synchronized state for each one frame, as CAM 1  CAM 2  CAM 3  CAM 4  . . . is outputted. 
     Further, the switch  32  is controlled to be switched for each one frame in synchronization with the synchronizing signal (FIG.  3 ( a )). As shown in FIG.  3 ( h ), as the VCR output, an image signal in a synchronized state for each one frame, as CAM 1  CAM 2  CAM 3  CAM 4  . . . is outputted. The monitor display is performed on an external display or the like by using the image signal. 
     In this manner, the frame converting can device continuously outputs sequentially switched image signals in a synchronized state by storing four asynchronous output image signals into two frame memories. The recording is made by the external VCR based on the image signal. At this time, the recording of the external VCR is continuously made. 
     Then, as the respective image signals are provided with the identification signal, it is possible to superpose a camera number or the like on a displayed image, for example, by utilizing the identification signals without recording character information indicative of the camera number or the like on a recording medium for the VCR, on the display device side which receives the monitor output or the VCR device side which receives the VCR output. Note that this construction can prevent miss of image information on the recording medium in comparison with a case of recording character information. 
     Further, in the VCR device, it is possible to extract only an image of a desired camera from a signal recorded on a tape. That is, is reproduced the image tape where the signal from the recording frame-converting unit is recorded, and the reproduced image signal is supplied to a VCR input (the input side of the A/D converter  41 ). FIG.  3 ( i ) shows the image signal reproduced in this case. Note that input of the image signal into the A/D converter  41  is made independently of the operation of the recording frame-converting unit. 
     Then, assuming that selection has been made at the operation unit  43  to select a channel  1  (CAM 1 ), the reproduction controller  44  refers to the result of detection by the ID detector  42 . Then the reproduction controller  44  performs read/write control on the frame memory  45 , such that if the identification signal of the signal CAM 1  has been detected, the signal is written into the frame memory  45 , on the other hand, if the identification signal of other signal than the CAM 1 , the selected signal is read from the frame memory  45  (FIG.  3 ( j )). 
     Then, the digital image signal read from the frame memory  45  is D/A converted and outputted as an analog image signal. Further, on the on-screen display unit  47 , display indicating that the image is based on the signal of the CAM 1  (channel display) is superimposed at a predetermined position in the image. In such manner, the image signal of the CAM 1  selected from the operation unit  43  is extracted, and continuously outputted to a PB monitor output. Note that as the PB monitor output is obtained independently of the operation of the recording frame-converting unit, the VCR recording can be performed in parallel to the VCR reproduction. 
     Note that the description has been made as an example where four inputs of image signals are switched, however, even in case of eight inputs of image signals as shown in FIG. 1, image signals, sequentially switched in a synchronized state, can be outputted. Further, even if the number of CAM inputs is greater, the operation can be made without any problem. 
     Further, in the example, the CAM input image signals are in an asynchronous state, however, even if synchronous image signals are inputted, the operation can be made without any problem. Further, the asynchronous image signals from cameras have been used as the CAM 1  to CAM 4 , however, devices which generate various image signals can be employed as well as the television cameras. 
     Further, in the above description, the CAM 1  is extracted in the reproduction frame unit  40 , however, the image signal may be switched for another CAM image signal at arbitrary timing. Further, it may be arranged such that, if any operation has not been performed since the power was turned on, display is performed based on a predetermined image signal or an image signal with the least number. 
     Further, display may be performed by switching the signals as CAM 1  CAM 2  CAM 3  CAM 4  CAM 1  . . . in predetermined second (a predetermined number of frames) units. That is, if the image signal from the VCR in FIG.  3 ( i ) is used, the image signal is switched for each one frame and the display cannot be visible. However, if display is switched every several seconds, the situation of respective CAM inputs can be obtained. 
     As described in detail above, the frame converting device described in this specification time-divisionally stores and reads a plurality of image signals with respect to a plurality of storage means fewer than the input image signals while switching the signal input means and the signal output means at predetermined timing. Thus, the device continuously outputs the image signals in a synchronized state while switching the asynchronous image signals. 
     Further, the frame converting device detects identification signals included in the image signals in frame units, extract frame timing of an image signal with a predetermined identification signal from the image signals in frame units, and stores and continuously outputs the image signal of the frame timing. Thus, the device extracts and outputs a desired image signal from image signals switched to form one signal. 
     Further, as the frame converting device of the present invention comprises a recording frame-converting unit and a reproduction frame unit, the two conversion processing operations can be realized, independently, and further in parallel in accordance with necessity, by one frame converting device, without preparing a frame converting device for recording and a frame converting device for reproduction. 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of other elements or steps than those listed in a claim. The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware.