JPH0554760B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to video recording and playback devices, and more particularly to methods and apparatus for adjusting such devices to reduce degradation of video signals recorded and played back on magnetic recording media.

Video recording and playback devices are often used in communication channels where television or other video signals are recorded and played back on magnetic recording media. Each sequence of recording and playback of a video signal results in the production of a copy (ie, a copy of a copy) of what is missing from the original video signal received by the communication channel. In practice, some degradation of the video signal occurs during the recording and playback process due to imperfections in the recording and playback equipment. This degradation manifests itself in the reproduced video signal as signal level, amplitude, frequency and/or phase errors. The degree of degradation generally depends on factors such as the characteristics of the equipment used to record and playback the video signal as well as the characteristics of the equipment used to transmit the video signal. Moreover, the degree of degradation increases significantly as the number of recording and playback sequences that a video sequence undergoes increases. The degradation is cumulative in that the degradation resulting from each recording/playback sequence by an imperfect or misadjusted video recording and playback device is additively combined with the degradation resulting from all previous and subsequent sequences by this device. It is. Even a small number of recording/playback sequences of analog video signals by this device, such as those occurring during electronic editing processes, result in significant degradation of the final generation of the resulting video signal.

Conventional analog equipment for recording and reproducing video information signals on magnetic tape (herein referred to as
It is known that in VTR devices (referred to as VTR devices), multiple degradations of the resulting video signal can be partially alleviated by precise adjustment of the VTR device's controllers that define various characteristics of the video signal. For example, the characteristics of a color television signal recorded and played back by a VTR device include system gain and phase, black signal level, system differential gain, system differential phase, and system frequency and transient VTR equipment parameters such as target response. In practice, the precise adjustment of the controls that affect these parameters is made during the manufacture of the VCR equipment;
Control mechanisms are provided on the device to allow the user of the device to readjust some of these parameters. However, such adjustments and readjustments can be difficult and time consuming, especially since misadjustments do not become apparent until the video signal has been recorded and played back several times. Additionally, adjusting the VTR device for one parameter typically affects the proper settings of the controller for other parameters. This results in several
Several trials and error adjustments to each of the VTR device's controls are typically required before the VTR device is properly adjusted for the desired quality recording and playback of the video signal.

Video recording and playback equipment used to provide color television signals for teleproduction and broadcasting stations typically includes a time base corrector (TBC), a synchronizer, and other video signal processing equipment. It includes accessory equipment which serves to ensure that the television signal provided for such purposes is stable, complies with signal standards and is free of significant noise. For example, TBCs and synchronizers accept video signals from unstable or unsynchronized sources and provide adjustable delays such that the video signals presented to their output remain perfectly stable with respect to a set time reference. It is in the nature of a time delay device. Such devices typically apply the signal to an adjustable time delay device to change the delay according to the time difference between the received video signal and a stable time reference, such that the video signal is connected to this stable time reference. It serves to eliminate time differences in the received video signals by making them output by the device in synchronization with the video signals.

The TBC and synchronizers currently used for teleproduction and broadcasting purposes are of digital design. It includes memory in the form of an array of digital data storage elements that act as an adjustable time delay device. As long as the television signal is commonly in analog form, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), digital signal processing circuits, and analog video signal processing circuits convert storage elements into analog video signal sources. and is provided to interface with a device for receiving a stabilized analog video signal. The size of the array of data storage elements is selected to provide sufficient storage capacity to cause the video signal to be delayed for a period of time that provides for cancellation of the maximum timing difference that occurs in the video signal with respect to timing differences.
Most of the respective horizontal blanking intervals and vertical synchronization intervals contained in the received television signal are stored in memory, typically for the new blanking and television signals to be inserted into the video signal after being recovered from memory. It is practical to avoid this. Therefore, the capacity of the memory is usually somewhat smaller than would be required to store all of the intervals of the video signal corresponding to the maximum time delay interval to be provided by the memory.

A synchronizer works to synchronize video signals from different asynchronous sources. Most commonly, they are adapted to accept video signals provided by a remote source and delay them so that they are presented in synchronization with the timing reference of the local source. Some synchronizers are designed to provide a single television field or a pair of interlaced television fields for synchronous combination with a video signal provided by a local source. Field and frame synchronizers are examples of these. Other synchronizers can synchronize the continuous stream of video signals to a local video device timing reference. Such devices typically include
It includes an array of data storage elements of sufficient capacity to store data from at least one, and often two, television fields. In a synchronizer having such a capacity to store data from two television fields, the received video data is alternately routed for storage to different parts of the array of data storage elements on a field-by-field basis. . Similarly, data is recovered alternately from different array sections on a field-to-field basis, and when data is avoided from one of these array sections, the received video data is stored in the other different array sections. .

The TBC serves, for example, to eliminate timing instabilities or errors that normally occur in video signals recorded from, and played back from, a temporal recording medium. Generally, both continuously varying timing errors and step timing errors occur in such signals. In some cases, these errors are of limited range and a small storage capacity memory can provide the necessary delay to eliminate these errors.
However, rotating head helical scan VTR devices of current design are capable of reproducing video signals at different speeds and feed directions of the magnetic tape to create stop, slow, fast and reversing motion effects.
This changes the relative transducer to tape speed and creates a constant frequency error that is more dependent on tape feed speed and direction. Additionally, the playback of television fields stored on tape is intermittently skipped or repeated, which introduces instantaneous discontinuities or step changes in the signal timing of multiple horizontal lines and the playback relative to that of the timing reference. introduces a change in the field sequence of the video signal. Significant timing errors exist as a result of such devices providing a TBC with a large memory capacity sufficient to store data from at least one television field. Additionally, certain TBCs with large storage capacities are configured to perform functions similar to those of synchronizers, and in doing so generally operate in the manner described above.

TBC devices used especially for teleproduction and broadcast station purposes often perform other functions besides the normal time base corrector. The most common of these other functions are dropout compensation, system phasing control, image enhancement, high speed tape shuttle image compositing, and boost timing of the output video signal. Broadly speaking, the performance of each of these features affects the video signal, and therefore adjustment of these features can increase the optimal video signal quality obtained.

It is also known to use TBCs and synchronizers in connection with systems in which video information is stored on video discs as well as in systems where video information is stored on magnetic tape. A video disk system using one converter head per disk recording surface with a TBC and synchronizer is regulated by storing video information in digital memory and then recirculating the stored information through the system on a non-real-time basis. I was being forced to do it. In other words, in such a video disc system, the information recovered or reproduced from the video disc device is recycled after a temporal interruption and used for adjusting the TBC and synchronizer. Such systems have been limited to non-real-time recirculation of video information due to the configuration of one transducer head per magnetic recording surface.

As further background to the invention, it is useful to describe a typical television signal for teleproduction and broadcast station purposes. Such television signals are a composite of several different signal components, namely a video information signal component and several synchronization signal components. A typical television signal is formed from horizontally distributed lines of video information separated by a time interval of horizontal line-related synchronization signals defining the beginning of each line. The horizontal lines are also organized into a raster of vertically distributed lines defining fields of lines separated by vertical field-related synchronization signals. The fields are organized into frames, each consisting of two spatially interlaced fields of horizontal lines, each field line having a different raster position on the sign. Various synchronization signals included in the television signal serve to synchronize the processing of the television signal and the operation of these processes and other devices using the television signal. In color television signals organized according to some standard, such as the NTSC standard, the synchronization signal includes vertical and horizontal blanking intervals, each consisting of a composite of several synchronization signals. The vertical blanking interval includes a vertical blanking level that extends between starting and ending transition edges that define the duration of the vertical blanking interval. This blanking level includes a number of horizontal blanking interval pulses, a number of equalization pulses, a series of pulse intervals defining vertical sync pulses, and a colored burst of sinusoidal chrominance subcarrier signal ( Typically 9-11 cycles) are applied during about 1/2 after the vertical interval. Each horizontal blanking interval during the entire field of lines after the vertical blanking interval and between successive vertical blanking intervals includes a horizontal blanking level extending between the start and end signal transition edges. These edges define the duration of the horizontal blanking interval. A horizontal sync pulse followed by a color burst is applied to each horizontal blanking level. One horizontal sync pulse and one color burst are applied to each horizontal line of the television signal and serve to synchronize horizontal scanning and color generation. Vertical synchronization pulses are applied to each field of the television signal to keep the vertical scan synchronized.
The series of vertical sync pulses prevents horizontal scan synchronization defects. Equalization pulses are provided to ensure proper scanning motion synchronization with the required spatial interlacing of the two fields that make up one television frame. The horizontal and vertical blanking levels are ramped to blank the display during horizontal and vertical retrace, and the associated transition edges provide a smooth signal transition between the video information signal and the blanking period.

NTSC color television signals are organized into frames of 525 horizontal lines occurring at a frame rate of 30 Hertz. Each frame contains two fields, each consisting of 262.5 horizontal lines, so the field speed is 60 Hertz. Horizontal line speed is approximately 15750 Hz,
The color subcarrier frequency is approximately 3.58 MHz.

For NTSC standard color television signals,
The frequency of the color subcarrier components is such that each horizontal line actually contains 227-1/2 cycles of a continuous color subcarrier waveform.
As a result, there is a half-cycle phase difference between the chrominance components in adjacent horizontal lines. Because of the line-to-line phase alternation of the relationship between the color subcarrier and horizontal sync components, the horizontal lines can easily be interchanged with each other without careful consideration to maintain phase coherence with respect to the chrominance components of the color video signal. do not have. Such considerations must also be taken when using one field of a video signal in place of another.

According to the general format in which video signal information is provided for broadcasting purposes under the NTSC standard, a television signal can be said to be a composite of a video information signal and some synchronization signals. More specifically, a television signal is formed from lines of video information separated by time periods of horizontal and vertical synchronization signals. In connection with a raster display, the synchronization signal organizes the video information into a number of horizontal lines that are evenly distributed vertically to define the field. More specifically, the horizontal sync pulse defines the start of each field at the top of the raster, and the horizontal sync pulse defines the start of each horizontal line of the raster. The odd lines of the interlaced raster define one field and the even lines define the other field. Therefore, each frame can be said to consist of odd and even fields of interlaced horizontal lines. In color television signals, the synchronization signal also includes a color subcarrier signal.
Such a subcarrier burst signal is provided for each horizontal scan line and serves as a phase reference for the color generation or hue of that line.

It is known in the prior art to provide repeated cycling of signal fields of video information to provide still images. however,
When a single field of NTSC color video information is continuously repeated, the phase of the chrominance component of the continuously repeated field does not follow the required line-to-line color filter reference phase sequence. This results in signal interference unless preventive measurements are taken. Typically, this proactive measurement involves separating the chrominance and luminance signal components from the composite video signal, shifting the phase of the chrominance signal by 180°, and recombining the chrominance and luminance signals.
However, such differential processing of chrominance and luminance signals is not completely satisfactory because it causes a degradation in video signal resolution. Furthermore, such processing is not performed when a continuous color video signal passes through the video signal path formed by this device.
Therefore, equipment adjustments made in conjunction with the use of video signals containing such processed chrominance components are likely to be inaccurate due to the presence of impairments introduced into the video signal by this chrominance signal processing. .

In connection with the above description, it will be apparent that the task of identifying and correcting factors causing signal degradation in systems involving several occurrences of a video signal is complex. Furthermore, current methods and schemes for generating this work have not always been completely satisfactory, especially in systems associated with VCR equipment. Therefore, adjusting the video signal processing elements of the VTR equipment, associated TBCs, and other operationally related equipment that affect the characteristics of the video signal as it passes through, so that the video signal is not degraded as it passes through such elements. There is a fundamental need for improved and convenient methods and means for doing so. It is an object of the present invention to meet this need, particularly for video recording and playback devices of the analog type used in conjunction with time base correction devices using digital signal processing techniques.

The method and apparatus of the present invention makes such adjustments rapid, accurate, and convenient by sequentially recording and reproducing periods of the color video signal that are passed through a selected delay between each successive playback and subsequent recording. enable what is done. This delay maintains a synchronous relationship between the chrominance component of the video signal and the independently generated stable color subcarrier reference timing signal, but in which the periods of the color video signal are repeated and continuous without any interruption in time. The data is recorded and played back a selected number of times. One embodiment of the method of the present invention includes providing a video test signal to a VTR device, regenerating the video test signal through selected delays corresponding to even horizontal line periods to the input of the VTR device, and cycling, operating the VTR device to record these recirculated signals, repeating the storage, playback recirculation and recording steps for a number of selected cycles; Based on changes in signal characteristics detected by comparing various occurrences
Including adjusting the beed control of the VCR device.

A system according to the invention includes, in one embodiment, a VTR device of analog type having a time shift correction circuit including a memory of sufficient capacity to provide a selected delay of a selected period of a cover video signal. . Means are coupled to the memory for receiving a selected period of the video signal after this delay and recirculating it for tape related recording and playback in a VTR device. Control means for causing selected periods of the video signal to be recorded, played back and recirculated a selected number of times.
Combined with VCR equipment. for receiving a recirculated video signal and selectively adjusting a controller of a VTR device based on changes in the recirculated signal detected by comparing different occurrences of the recirculated signal; Means are provided. The delay provided by the memory maintains a synchronous relationship between the chrominance component of the video signal and the independently generated stable color subcarrier reference timing signal so that the periods of the color video signal are repetitive and continuous without interruption in time. Selected to be recorded and played back a selected number of consecutive times.

These and other objects of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.

FIG. 1 is a diagram of a tape guide drum assembly for a rotating head helical scanning videotape recording and reproducing apparatus.

FIG. 2 is a diagram of a portion of a videotape having information magnetically recorded by, for example, the assembly of FIG.

FIG. 3 is a functional block diagram of a videotape recording and reproducing apparatus according to the present invention.

FIG. 4 is a functional block diagram of a videotape recording and reproducing apparatus incorporated in a system according to the present invention.

FIG. 1 is a diagram for understanding the environment of the present invention. This generally shows a cylindrical tape guide drum assembly 11, such as that used in VCR equipment, which extracts video information from a magnetic tape as the tape is fed into a helical path around the drum. Uses a rotating head for recording and playback. More specifically, drum assembly 11 includes an upper drum 13 rotatable about a central axis 17 and a fixed lower drum 15 axially aligned with the upper drum. A first guide member 21 is mounted to guide the magnetic tape 19 towards the fixed lower drum 15 and a second guide member 23 is mounted to guide the tape out of the upper rotating drum 13. has been done. at least 2
Two electromagnetic conversion heads 27 and 29 are connected to the rotating drum 1.
3 at positions spaced apart in the circumferential direction. For purposes of the present description, conversion head 27 is understood to be operative to record video information on tape 19, and conversion head 29 is understood to be operative to reproduce information signals from the tape. sea bream. A VTR configured to record and play video information according to the Type C tape format standard typically includes such a conversion head, and such head is configured to record and play back information simultaneously. can be made to operate normally.

In the operation of the drum assembly 11 shown in FIG.
The tape 19 is introduced towards the drum 15 from the lower right side by a guide 21, is forced to run around the drum in a helical path indicated by the arrow 19A, and is guided out of the upper rotating drum 13 by a guide member 23. be made into To record and reproduce video signal information on tape 19 with conversion heads 27 and 29, rotating drum 13 is rotated in the direction indicated by arrow 13A in synchronization with the advance of tape 19.

By using drum guide assembly 11 as described above, a track 31 of video information such as that shown in FIG. 2 can be magnetically recorded on tape 19 by transducer head 27.
More particularly, the information tracks 31 are separate and parallel and are sufficiently small with respect to the longitudinal centerline of the tape 19 such that the length of each track 31 considerably exceeds the width of the tape 19. Positioned at an angle. The information recorded along track 31 typically includes composite television information including synchronization information and video information used in controlling the operation of the television signal processor during playback of the information recorded from tape 19. It's a signal. However, upon playback, the distortions and other instabilities described above are introduced into the played video signal.

FIG. 3 shows a generally analog VTR device 106 and a TBC connected to correct time deviation errors in the video signal at the output of the VTR device.
1 shows a video system consisting of a device 107; Although the TBC device is normally mounted on a stand-alone chassis, the VTR device and the TBC device are shown as functionally integrated in the scheme of FIG.
TBC device 107 is to be understood as including a conventional analog-to-digital conversion circuit at its input and a conventional digital-to-analog conversion circuit at its output. In a preferred embodiment, TBC device 107 includes memory of sufficient capacity to digitally store at least one field of the video information portion of the composite television signal. As will be explained in more detail below, the memory of TBC 107 is stored for a period corresponding to a period of video information that is repeatedly recorded and played in connection with tape 19.
It can serve to delay the video information played by the VTR. This delay provided by the memory is associated with the simultaneous recording and playback operations performed by conversion heads 27 and 29 and is selected to obtain the desired number of occurrences of the composite video information period. It allows repeated recording and playback of periods of composite video information consecutively without interruption (i.e., in real time).

The system of FIG. 3 further includes the VTR device 106 and
It includes one or more controllers 108 for selectively adjusting elements that significantly affect the signal processing circuitry within TBC device 107. For example, controller 108 may include a variable capacitor and resistor to control the bandwidth of a filter in the signal processing circuit. Additionally, controller 108 typically provides adjustment of parameters such as system gain and phase, black level, system differential gain, system differential phase, and system frequency and transient response. Additionally, controller 108 allows adjustment of the delay time period provided by TBC 107. digital tbc
In , such adjustment is accomplished by controlling a memory address generator operatively associated with the memory of the TBC. Under control of the memory address generator, the delay time period provided by the TBC may be adjusted in increments corresponding to a selected multiple of the time period of one horizontal line of the composite video signal. In flexible digital TBCs configured for use with VTRs used for teleproduction and broadcast purposes, these TBCs are part of one cycle of the color subcarrier signal component contained in a composite color video signal;
For example, the delay can be controlled to be adjusted in increments corresponding to 1/2. The manner in which such adjustments are made to the delay provided by TBC 107 in accordance with the present invention is described in more detail below.

The system of FIG. 3 further includes a video signal generator 113 connected to a video switch 123 via line 115. Video signal generator 11
3 can be, for example, a video camera, another VTR device or a computer programmed to provide video information. Preferably,
Signal generator 113 includes means for providing standard video test signals, such as color bar test patterns. A signal generator provides an instruction signal to a counter 131, which is shown as integral with video switch 123 in the illustrated embodiment. In practice, this indication signal is derived from the horizontal sync pulses present in the video test signal. Counter 131 is a known device that sequentially counts instruction signals and provides an output to operate video switch 123 when a preselected count is reached.

As shown in the scheme of FIG. 3, video switch 123 has two operating positions. In the first position, switch 123 connects video signal generator 113 to VTR device 106 via line 125.
Connect to. In the second position, video switch 123 connects line 125 to line 133 at the output of TBC device 107 to control the VTR.
Provides recirculation of the video signal through device 107.
Return routing may be provided via a direct cable as shown by line 133 or via a known routing switch.

Furthermore, in the method shown in Fig. 3, the signal monitor 1
39 is connected to receive an output signal from the TBC device 107. The purpose of monitor 139 is to detect changes in parameters of video signal information caused by error conditioning of the system through which the video signal passes as the signal is repeatedly recorded and played back to and from the tape associated with VTR 108. It is to be. Monitor 139 may be, for example, an oscilloscope or a voltage comparator that indicates changes in the level of the signal caused by incorrect adjustment of the system gain.

The operation of the overall scheme of FIG. 3 will now be described. Assume initially that video switch 123 is in the first position and video signal generator 113 provides pulses to counter 131 and a selected time period of video test signal to VTR device 106. When the video test signal is received, the VTR device 1
06 record this signal and reproduce each almost simultaneously. This places the VTR device 106 in an edit mode and provides recording and playback transducers such as transducer heads 27 and 29 of the drum guide assembly 11 of FIG. 1 to respectively record and playback video test signals along tape 19. This is achieved by controlling the equipment. In practice, such reproduction of a video test signal is approximately 1/2
This occurs over a field time period of 3. This time period will allow the system to set up some of the signal delay. The delay balance is
It is provided by the normal signal propagation delay through the selected memory delay device of TBC 107. After a selected period of time after the video test signal is first transmitted to VTR device 106, counter 131 differentially differentially switches switch 123 to its second position in response to a pulse from signal generator 113. In this second position, the switch 123
7 to the input of the VTR device 106. Switch 123 remains in the second position for a period of time consistent with the desired number of cycles or occurrences of this cycled video test signal.

The scheme of FIG. 3 also operates such that after the video test signal information is played back, this signal information is transmitted to the TBC device 107 for digitization and storage in the device's memory. Typical signal propagation delays across the system as well as the recording conversion head 2 of FIG.
After a memory delay period equal to the desired total delay which is less than the combined delay resulting from the circumferential separation of the regenerative converter head 29, the stored information is read back from the memory and converted into an analog form. and recirculated to the input of VTR device 106. Upon receiving this recirculated test signal information, the VTR device 106 starts recording and playing again, and transmits the signal information to the TBC device 107 again.The TBC device 107 once again digitizes and stores the transmitted signal. death,
Recall and recirculate the signal information after a selected delay. The steps associated with recycling, recording, reproducing, and storing video signal information may be repeated for any desired number of cycles or replays. Preferably, at each cycle, i.e. after a preselected number of cycles, the video signal from the TBC device 107 is transmitted to the monitor 139, and the characteristics of the test signal information caused by repeated recirculation are transmitted to the video signal from the TBC device 107. Changes are displayed.

In practice, the scheme of Figure 3 may operate in two stages. In the first stage, the video test signal is
TBC without recording and playback by VTR device 106
Routed directly to device 107. This test signal is then stored in digital form in the memory of the TBC device and then after a selected delay time.
It is called up and recirculated via the TBC device 107. The steps of storing and recycling the video test signal are repeated for a selected number of cycles. For this reason, changes in the signal value can be detected by comparing different occurrences of the signal, and for the TBC device 107 to regenerate signal degradation after several occurrences of recirculation. controller (the control line that carries the control signal from this controller is shown at 108 in the figure)
), the adjustment can be determined and made. In practice, such adjustments typically include adjustments to analog-to-digital and digital-to-analog conversion circuits. After such adjustments to TBC device 107 are made, a second step is performed.

In the second stage of the formula's operation in Figure 3,
Video test signal information is VTR device 106 and TBC
routed through both devices 107;
It is then recycled as described above. This second
During the step , adjustments are made to the VTR device 106 by the controller 108 based on changes detected by comparing various occurrences of recycled test signal information. Typically, these adjustments are made to minimize signal degradation after several occurrences of recirculation. Such adjustments are usually made by the VCR equipment manufacturer before shipping the product, but
These adjustments can be made by the user according to the same technique. In practice, user adjustments are usually
This is done to fine tune the system parameters that determine the VTR's system gain and phase, system frequency and transient response, system differential phase, and black, white, and chrominance signal levels.

As can be seen, the above-described scheme makes it relatively easy to detect changes in the characteristics of a recirculating video signal since the changes in signal characteristics are typically multiplied with each recirculation occurrence. For example, if the signal characteristics are distorted by 0.1% with each recirculation, after 20 recirculations the signal characteristics will have changed by about 2%. Of course, such relatively large changes or distortions may affect the VTR device 106.
and smaller changes that occur after a single pass of the signal information of the TBC device 107 are more easily detected and corrected.

In a preferred embodiment of the invention, periods of video information corresponding to an even number of consecutive horizontal lines taken from the composite video signal are recirculated a selected number of times. To facilitate the conditioning procedure for NTSC type television signals, this time period is selected to be either 262 or 264 horizontal lines in duration. By selecting such a time period, the phase of the chrominance component contained in the recirculated composite video signal is matched to the phase of the color subcarrier reference throughout the duration of recirculation. The operation of VTRs, TBCs and other television signal processing equipment is synchronized to this color subcarrier standard. Furthermore, this phase matching is maintained without the need to separate the prominence component from the composite video signal after each reproduction of the signal, thus
There is no need to process the separated chrominance components to adjust their phase relative to the phase of the color subcarrier reference before the video signal is recirculated and recorded. This processing of chrominance components is
This would be necessary if a time period of video information corresponding to one television field (262-1/2 horizontal lines in an NTSC television signal) or an odd number of horizontal lines were selected for recirculation. Probably. As mentioned above, such processing would be necessary because each such processing degrades the video signal and for some recirculation of the video signal, continued such processing would degrade the video signal. must be avoided because it would double the Further, conditioning the VTR 106 and TBC 107 using such degraded signals is typically not a product of normal scanning of the VTR and TBC as this degradation is not intended to be corrected by the conditioning procedure of the present invention. It becomes an error.

In one preferred embodiment of the invention, the composite
Time periods of video information corresponding to 262 consecutive horizontal lines taken from an NTSC video signal are selected for recirculation a selected number of times. For such time periods of video information, the delay period or period between successive recordings of video signal information is one field period in time (i.e., 262−1/2
line period). As will be described in more detail below, the TBC's output signal processor continuously converts video information from the TBC memory by inserting the necessary synchronization components at times determined by the applicable television signal standards. Organizes continuous lines of received video information into fields that are properly interlaced. As mentioned above, approximately one-third of this delay is of a mechanical nature due to the spacing of the read head 29 from the record head 27 of the drum guide assembly of FIG. The remaining delay is due to signal propagation delays in TBC device 107 and other circuits in the recirculation path.

As can be seen from the foregoing, the scheme of FIG. 3 can be operated in a mode that causes VTR 106 to record recirculated video information during signal recirculation. The result of this recording is a videotape with several occurrences of the recycled field, each occurrence being recorded separately on the videotape. These occurrences can be evaluated individually by repeatedly playing back a single recorded track from the videotape so as to obtain successively selected occurrences of the video test signal. Desired adjustments can be made manually to the VTR 106 and TBC 107 based on evaluation of the information that is continuously played back from the tape.

FIG. 4 shows a scheme for automatically adjusting VTR device 306. In this embodiment, VTR device 306 is an integral TBC device of the type described above having a memory of sufficient capacity to store a time period of video information corresponding to the amount of delay required to be provided by the TBC. must be understood to include. The present invention includes a memory capable of storing a video information portion of a composite video signal of at least one television field.
TBC has sufficient capacity for this purpose.
In the system of FIG. 4, lines 351a and 35
1b supports the recirculated signal from VTR device 306 to sample/hold circuit 155. The sample/hold circuit 155 includes first and second switches 359 and 361, respectively, connected for control by a digital logic circuit 365. Additionally, sample/hold circuit 355 and logic circuit 365 constitute means for automatically adjusting the level and parameters of the video signal played by VTR device 306.

Details of the digital logic circuit 365 and sample/hold circuit 355 of FIG. 4 are described below, although these circuits are shown by way of example and by way of example only, and other circuits may accomplish substantially the same function. It should be understood that it can be given for Therefore, in FIG. 4, the first AND gate 367 of the logic circuit 365 connects the first switch 359 of the sample/hold circuit 355
Similarly, the logic circuit 3
65 AND gate 371 is connected to control a second switch 361 of sample/hold circuit 355. These AND gates 367
and 371 receive a video drive signal on line 375 indicating the occurrence of input of video test signal information. This video drive signal can be generated, for example, from a known signal generator. In addition to the video drive signal, first AND gate 367 receives, via line 377, a signal representative of the occurrence of a selected recirculation cycle of video test signal information of VTR device 306. Similarly, the second AND gate 371 receives a signal on line 381 indicating the occurrence of the selected recirculation after the test signal information. In practice, the signal on line 377 preferably indicates a first generation of test signal information, and the signal on line 381 indicates a preselected subsequent generation of test signal information.

The requirements of sample/hold circuit 355 of FIG. 4 are described next. In that circuit, a first switch 359 is connected to a capacitor 383 in parallel with a first input of a differential amplifier 387. Similarly,
The second switch 361 is the second switch of the differential amplifier 387.
is connected to a capacitor 389 in parallel with the input of .
Capacitors 383 and 389 and differential amplifier 3
87 is a known one. When connected as shown in FIG. 4, the output signal from differential amplifier 387 is indicative of the difference in voltage across capacitors 383 and 389. The output of the differential amplifier 387 is sent to the VTR device 3.
06 on line 391.

Before proceeding to describe the operation of the overall system of FIG. 4, the operation of digital logic circuit 365 in conjunction with sample/hold circuit 355 will be described. First, it is reiterated that digital logic circuit 365 and sample/hold circuit 355 are described by way of example only and other equivalent circuits are provided. In the operation of the digital logic circuit 365,
AND gate 367 connects lines 375 and 3
If both of its inputs to 77 are logic 1, it will give a logic 1 output. Similarly, AND gate 37
1 provides a logic 1 output if its inputs on lines 375 and 381 are both logic 1s. In practice, the input on line 377 is preferably predetermined such that both lines 375 and 377 support an extended logic 1 signal during the initial recirculation period of video signal information, thus In this situation, the output of AND gate 367 will be a logic 1 only on the first recirculation. Similarly, in practice, the input on line 381 is
Both 5 and 381 are predetermined to indicate a logic 1 only on the selected nth signal recirculation, thus only after the nth recirculation occurrence.
The output of AND gate 371 becomes a logic one. As can be seen, the sample/hold circuit 355
The occurrence of a logic 1 on line 369 causes switch 359
and similarly the occurrence of a logic 1 on line 373 operates to close switch 361.

The operation of the overall control scheme of FIG. 4 will now be described. Initially, VTR device 306 is placed in standard editing mode and the tape is played. In this, one field of video test signal information is recorded on one track extending along the tape, and the VTR device 306 plays back the recorded field of video test signal information for a desired number of recirculation cycles. Allows the signal to be recirculated. In other words, the scheme initially begins regenerating (i.e., playback) the field of video test signal recorded at transducer head 29, and upon separation of transducer heads 27 and 29 of drum assembly 11 of FIG. from the original field of the video test signal using the conversion head 27 after a time period of less than one television field period, ie after a time period of about two-thirds of the television field period, by an amount determined accordingly. is controlled to begin rerecording a field of video signal containing a selected even number of horizontal lines (262 in the preferred embodiment) on an adjacent track. Thereafter, continue recording and playing back the selected even horizontal lines. As discussed above, this continuous, simultaneous recording and playback of the video signal test lasts for a selected number of occurrences of the video test signal. At the beginning of signal circulation in the manner of FIG. 4, one pulse is provided on line 375, the duration of which is sufficient to include the selected number of recirculation cycles. For example, the pulse on line 375 lasts for 20 recirculation cycles. Coinciding with the start of the first recirculation cycle,
Line 377 is pulsed. With a pulse on two lines 375 and 377, AND gate 367 provides a logic 1 output signal, which maintains switch 359 in sample/hold circuit 355 closed. With switch 359 closed, the video output signal from VTR 306 is developed across capacitor 383 and provides a voltage change representing the voltage level of the originally recycled video signal information. Line 381 is pulsed after this recirculation process has progressed to the nth recirculation occurrence. This pulse causes AND gate 371 to provide a logic 1 output on line 373, thereby causing switch 361 of sample/hold circuit 355 to close. With switch 361 closed, capacitor 389 is charged to a voltage representing the voltage level of the nth occurrence of the recycled video signal. Therefore, two capacitors 38
With 3 and 389 varied as described above, differential amplifier 387 provides an output signal equal to the difference in voltage at its inputs. In the case where the voltage across capacitors 383 and 389 is proportional to the system gain, for example, the output of differential amplifier 387 will be the result of the video system gain produced over a series of n recirculations in VTR unit 306. represents the difference. Alternatively, capacitor 383 may be charged with a different reference voltage than the voltage representing the first recirculation of video test signal information. In such a case, the output of differential amplifier 387 represents the difference between the characteristics of the nth recirculating signal and the selected reference voltage.

Sample/hold circuit 355 may be operated to evaluate long-term averages of signal parameters or to evaluate signal parameters at specific times during the video test signal. If, for example, a long-term average evaluation over the entire period of the video test signal is important, the respective switches 359 and 361
is operated to remain closed for the entire playback time period of the video test signal at the particular occurrence that is sampled by sample/hold circuit 355. Such operation is accomplished, for example, by applying logic 1 pulses on lines 377 and 381 at appropriate times with a duration corresponding to the entire playback time period of the selected occurrence of the video test signal. However, if evaluation of a signal parameter at a particular time during a video test signal is desired, the duration and normal time of the logic 1 pulse is determined by the desired duration that switches 359 and 361 are to be evaluated. and selected to be closed upon playback of the selected occurrence of the video test signal at a desired time. As will be appreciated, the sample duration and times of the two occurrences of the video test signal are selected according to the nature of the signal parameter evaluation desired.

The output of the differential amplifier 387 of FIG. 4 may be used to automatically adjust a controller, such as a system gain controller, of the VTR device 306 or associated time base correction device. In practice, the output signal from amplifier 387 typically provides negative feedback to minimize changes in the video signal as a result of the multiple occurrences of recording and reproducing the signal by VTR device 306.

It is clear from this point that the comparison of video signal information values from different recirculation occurrences must be provided from the same video field. For example, if two interlaced video fields F1 and F2 forming a single raster frame of video information are passed through VTR device 306 during each recirculation cycle, then one signal characteristic It is preferred to compare values from a first occurrence of field F1 with values of the same signal characteristic from a later occurrence of field F1 but not field F2.

To facilitate comparing recirculated video signal information recirculated vs. recirculated, the recirculated video signal information is Preferably a selected delay period. For this reason, the preferred delay period is equal to an even number of horizontal line periods approximately equal to the duration of one video field. Furthermore, in order to obtain a meaningful comparison between recirculated reproductions of the video test signal, especially in the case of color video signals, the recirculation must be performed in order to achieve proper phase synchronization with the color subcarrier reference signal. There must be an appropriate delay after each occurrence.

For the purpose of illustrating the necessary delay periods for synchronization and stability of the chrominance components with respect to the color subcarrier standard, it is assumed that one field of color video information according to the NTSC standard is equal to the duration of one television field in a recirculating signal path. Consider the case where the signal must be recirculated via the scheme of Figures 2 or 3 with a delay period of . With this delay, the chrominance components of each horizontal line of video signal information recovered from TBC memory have the same phase relationship with respect to the horizontal sync pulse that defines the beginning of the line as the original or first occurrence of the video signal information. It will have. As mentioned above, the NTSC color video signal has chrominance components that have a phase that alternates line-to-line by 180° with respect to the occurrence of the horizontal sync pulse. The chrominance components of the continuously displayed horizontal lines in a given raster section alternate topologically by 180°. Thus, a sequence of four consecutive television fields occurs between displays at a given raster position of a horizontal line with chrominance components of the same phase. The resulting recirculation of video signal information over a delay of one television field period introduces undesirable phase discontinuities in the chrominance components with respect to the color subcarrier reference. Such discontinuities are provided according to the present invention.
Interfere with proper adjustment of VTR and TBC.

Eliminating the negative effects of such phase discontinuity,
The phase engine in the recirculation path is made equal to an even number of horizontal lines so that the correct chrominance phase is provided when the video test signal is recirculated. this is,
The chrominance phase of the line recovered from the TBC memory is made to match the required phase defined by the phase of the color subcarrier reference. As mentioned above, this is accomplished in the preferred embodiment of the invention by providing a delay from the TBC memory such that a total delay corresponding to a time period of 262 lines is provided in the recirculation path. As a result of this delay period, which is less than the delay of one complete field under the NTSC standard,
The time period of one horizontal line of the original video test signal is discarded by the operation of the TBC memory and is not recirculated. As a result, the remaining horizontal lines of the field of the video test signal that are recovered from the TBC memory are shifted in time by a time period corresponding to the abandoned lines. Although this remaining horizontal line is thus displaced in time, the video test signal is the horizontal and vertical reference signal with which the operations of the VTR, TBC, and operationally related equipment are normally synchronized and controlled. provided by TBC in a horizontally and vertically synchronized relationship. This synchronization of the remaining horizontal lines of the video test signal corresponds to one television field period in synchronizing the horizontal lines of the video signal with respect to the stable horizontal reference timing signal and with respect to the stable vertical synchronization reference timing signal. This is the result of the inherent TBC operation in providing multiple horizontal lines synchronously. The above-mentioned time deviations of the horizontal line recovered from the TBC memory associated with maintaining stability of the horizontal and vertical signal timing are recirculating video test signals that move gradually in the vertical direction through the display provided by the monitor. becomes. This movement occurs at a rate of one horizontal line per television field period. Chrominance of recirculating video test signal,
Such movement is achieved in accordance with the present invention by the VTR, so that the horizontal and vertical timing is maintained synchronously with respect to a corresponding stable reference timing signal.
Does not interfere with the ability to adjust the TBC and operationally associated equipment.

The manner in which the TBC operates to maintain the recirculating video test signal synchronously with respect to a stable reference timing signal will be better understood from the following description of the operation of a typical digital TBC device.
A common digital TBC includes a memory configured to store digital portions representing taken samples of the analog signal received thereby. The memory is operatively associated with a memory address generator that controls the times and locations at which digital portions are stored and retrieved from memory. Memory address generators are usually organized into two parts, one
One part controls the storage of digital minutes of memory and
The other part controls the recovery of digital parts from memory. Typically, the operation of a memory address generator that controls memory storage is controlled by timing signals provided by color burst, horizontal sync, and vertical sync components contained in and extracted from the received video signal. Thus, the received video signal is stored in the TBC memory at a time determined by the timing of the received video signal itself.
However, in recovering stored video signals from memory, memory address generators are commonly used to synchronize and control the operation of VTRs, TBCs and other operationally related devices. It is controlled by a stable timing reference signal provided from a stable color subcarrier, horizontal sync and vertical sync reference signals. A memory address generator provides storage and recovery memory address signals such that recovery of the video signal at a particular storage location typically results in a period following that storage corresponding to one-half of the maximum delay that can be provided by the memory. This is why it is placed in TBC. This normal period between storage and recovery at a particular storage location occurs when the received video signal is properly timed with respect to a stable reference signal.

Any deviation from the proper timing relationship is reflected as a corresponding difference from the proper timing relationship between the timing signal provided from the received video signal and the stable timing reference signal. This difference results in a change in the interval between times at which a storage location within the TBC memory is selected by the memory address generator for storage of a particular video signal segment and for subsequent playback. Such a change in the interval between storage and recovery of video signal minutes results in a change in the delay of the transmission of the video signal through the TBC, which compensates for differences in the timing of the received video signals. For example, if a video signal is received by the TBC faster than the appropriate time determined by a stable timing reference signal, the memory location in the TBC memory will be moved faster by the memory address generator for storage. is accessed. Because the time of recovery of a video signal minute from the storage is made constant by a stable timing reference signal, faster storage of a video signal minute results in a longer period of video signal minute storage into the TBC memory. . The longer time period of storage in memory differs from the normal time period of such storage by the same amount as the faster suitable reception time of reception of the video signal. Therefore,
The longer storage interval in memory compensates for variations in time of reception of the video signal. As is clear,
The TBC also functions in a comparable manner to shorten the storage time interval into memory to compensate for reception of the video signal later than the proper time defined by the stable timing reference signal.

Most digital TBCs are configured to store a digital portion of the time period of a composite video signal defined by a continuous horizontal line blanking interval, often with short periods of line identification data for each or multiple horizontal Give the line spacing. The color burst, blanking, horizontal sync and vertical sync (along with the pre- and post-equalization periods) signal periods contained in the received composite video signal are inserted into the video signal recovered from the TBC memory so that a new corresponding signal is inserted into the video signal recovered from the TBC memory. abandoned. These new synchronization signals are inserted into the recovered video signal by an output signal processing device operatively associated with the TBC. Such devices serve to insert a new synchronization signal into the video signal, so that the sequence of horizontal lines recovered from TBC memory is separated by the appropriate number of horizontal line intervals (for NTSC television signals, 262 -1/2 line spacing), and the various new synchronization signals are positioned in the video signal at appropriate times. Such a signal processing device detects successive horizontal lines recovered from the TBC memory without regard to the particular raster line position at which the particular recovered horizontal line appeared in the composite video signal received by the TBC. It works to insert a synchronization signal according to the number of . For this reason, the digital minutes of stored line intervals can be recovered in any order, and any stored intervals can be recovered from memory and combined video The signal can be organized into field intervals.

This property of the digital TBC is such that in the method and apparatus of the present invention, one period of the original video test signal corresponding to an even horizontal line spacing is synchronized with the color subcarrier, horizontal sync and vertical sync related timing reference signals. It is preferably used to enable repetitive recording and playback. More specifically,
As discussed above in connection with the embodiment of the invention illustrated in FIGS. 1-4, a video test signal, such as that reproduced by conversion head 29 and received at the input of TBC 107, can be used for one television set. It is delayed from the time recorded by the circumferentially spaced conversion heads 27 by approximately one third of the signal period.
This delay in the reproduction of the video signal is viewed by the TBC as a timing difference with respect to the proper timing relationship between the video signal and the timing reference signal received by the TBC. In response to this timing difference, the TBC as described above, storage and playback of the stored digital portion of the video signal introduces a compensating delay between the storage and recovery times. In accordance with the present invention, a controller 108 (FIG. 3) associated with the memory address generator of TBC 107 is configured to set the cycle of memory location addresses generated for recovery of stored video signal digital portions. Adjusted, the recovery of the stored video signal digital portion is an even number, preferably 262
is varied to introduce a compensating delay that provides an overall delay for the video test signal through the recirculation path corresponding to the horizontal line spacing of the book. In this manner, the phase of the chrominance component of the recirculated composite video signal is maintained in synchronization with that of the color subcarrier timing reference signal. Such adjustments are made by adjusting one of the original video test signals.
This is accomplished by discarding two horizontal line spacings. As mentioned above, this results in a gradual vertical movement of the video test signal on the display. However, the chrominance, horizontal and vertical timing of the recirculated video test signal
VTR, TBC and any other operatively associated video signal path to be maintained synchronized with respect to a corresponding stable reference signal by the cooperative dynamic action of the TBC memory and operatively associated output signal processor. No interference with the adjustment of the equipment will occur.

As will be appreciated, such a relinquishment of one horizontal line interval in the manner described above reduces the information vertically by one line per each recirculation in the display of the remaining recirculated fields of the video test signal. This causes a shift in the displayed image information. Therefore,
If the test signal information is a color bar test pattern, this pattern is
Only the line appears by rolling upwards. However, vertical synchronization stability is maintained by the operation of the output signal processing device in conjunction with the TBC. As mentioned above, such a device adds vertical synchronization signal intervals and associated pre- and post-equalization to a sequence of horizontal line intervals of a video signal that is recovered from TBC memory at appropriate times with respect to a stable timing reference signal. Operates to insert synchronization signal intervals. Therefore, vertical movement is an artifact that typically does not substantially affect the detection of changes in signal values or adjustments to video signal parameters. In return, adjustments to video signal parameters can be easily made as long as the recirculating video signal information is properly timed with respect to the horizontal sync and color subcarrier sync signals when recirculating. In practice, if such synchronization can be maintained satisfactorily during recirculation in a VTR without passing through an operationally associated timebase corrector,
The time base corrector becomes unnecessary and can be replaced by a constant delay of appropriate length.

As will be apparent in this connection, another aspect of providing a satisfactory delay period (i.e., a period with an even number of delay lines) is to The first step is to adjust the memory address generator to introduce an overall delay. The recovery of the stored video signal digital minutes is accomplished by setting the cycle of memory location addresses generated for the recovery of the stored video signal digital minutes until the Delayed by line time period. This additional delay causes the phase of the chrominance component of the recirculating composite video signal to remain synchronous with the phase of the color subcarrier timing reference signal. However, it comes at the cost of introducing a gradual movement of the video test signal in a downward vertical direction when displayed on a monitor. For embodiments configured to provide a recirculating signal path delay corresponding to 262 horizontal line spacing, the recirculating video information included in the test signal is appropriate for the horizontal sync and color subcarrier sync signals. the video test signal is a color subcarrier,
Synchronized with horizontal and vertical synchronization reference signals.
The vertical transition motion of the video test signal on the display typically does not interfere with the comparison of signal values on a source-to-occurrence basis.

Embodiments of the invention are similarly designed for PAL, SECAM and other television signal standards.
It may be configured to regulate BTRs, TBCs and other operationally related devices. However, television signals organized according to such other television signal standards may have different signal levels, frequencies, phases, timing, and other well-known characteristics than television signals organized according to NTSC standards. have characteristics. Synchronizing the recirculating video signal to a chrominance, horizontal and vertical synchronization reference timing signal, such as configuring embodiments of the present invention to adjust apparatus designed to other television signal standards. It is necessary to provide a delay in the video signal recirculation path with a time period selected according to criteria that maintains the video signal recirculation path. This required delay time period is readily determined from the characteristics of the television signal standards for which VTRs, TBCs and other operationally related equipment are designed, and therefore need not be described in detail.

For teleproduction and broadcast station purposes
Electronic editing control systems commonly associated with VTRs can be operated to enable successive generation of any selected sequence of multiple re-occurrences of the video signal. Each sequence then consists of a re-occurrence of a different video signal. This is for example the third and fourth
It takes advantage of the use of existing editing control schemes to carry out the steps of the recirculation technique carried out by the apparatus shown in the figures and the use of simple techniques for carrying out the apparatus adjustment method of the present invention. Has advantages.

In embodiments of the present invention that use electronic editing control and equipment adjustment methods to implement the video signal recirculation step, the time period of the intermittent color video test signal is initially extended to the length of the tape. It is recorded by a VTR along the way. this is,
This can be accomplished, for example, by using the signal generator 113 of FIG. For this purpose, switch 123 is permanently positioned by coupling line 115 to input line 125 to VTR 106 for the duration necessary to record a continuous color video test signal time period. During this recording of the test signal, other typical control signals, namely a control track signal and a time code signal, are also recorded along the tape in synchronization with the video signal. The time code identifies each frame of the video signal formed by two interlaced television fields by unique address signals in hours, minutes, seconds, and frames. For NTSC color television signals, the time code is in the form of the time and control code standards adopted by SMPTE. The time period of continuous video test signals recorded on tape can be of any length required. Typically, the length of this period is selected to provide multiple sequences of a selected number, typically 20, of reoccurrences consecutively and without interruption in time, such that each of the video test signals This allows sufficient time to make adjustments to the device according to the invention without unnecessary interruptions.

After a selected length of a continuous color video test signal has been recorded to tape, a list of time code signals is selected that identifies a sequence of unique edit entry and edit exit frames of the recorded video test signal. The input to the editing control scheme is via an operator control provided for the purpose. Each selected edit entry code specifies the particular frame at which the recirculation field is to be recorded first after its first playback from tape, and each selected edit exit code specifies the particular frame at which the recirculation field is to be recorded for the first time after its first playback from tape. specifies the particular frame to be finally recorded. Each pair of editing entry and exit codes thus determines the recirculation of a selected number of video test signals, and thus the regeneration of each of the plurality of sequences.

Current electronic editing control schemes are controllable to select either of two interlaced fields of a frame, identified by a time code signal, to begin or end editing. According to the present invention, the editing control method is
The apparatus is operative to record a continuous sequence of recirculated video signals at positions along the tape separated by tape lengths corresponding to those required to record one field.
The helical-operated VTR described above has a sequence of edit entry and exit time codes selected to record one field on each track along the tape, and an edit control scheme that uses the edit exit code of one sequence and the edit exit code of a subsequent sequence. The edit entry code is controlled to interrupt the recording operation of the VTR for a period of time required by the VTR to advance the tape a distance separating adjacent recording tracks on the tape.

Following input of the sequences of edit entry and exit time code signals, the edit control scheme is placed into an insert edit mode of operation. In this mode, the edit control scheme is operative to replace a time period of previously recorded information with a new record of information that is phase or time coherent with the remaining previously recorded information. Control related VTRs. Upon entering this mode, the editing control scheme first controls the VTR to synchronize the tape advance to the desired normal recording/playback speed and to synchronize the tape advance relative to the recording transducer head at which a new recording is to be started. position. During this time period, the playback conversion head (29 in FIG. 1) described above is operated to play back the previously recorded video test signal. The recording transducer head (first 27) in the figure is disabled by the editing control method during this period. When the identified track reaches the location of the rotary conversion head, the recorded time code signal identifying the track is played back by the VTR's time code conversion head and communicated to the editing control system. In response to receiving this regenerated time code signal, the editing control scheme causes the recording transducer head to detect the last of the video test signals to be reproduced by the reproducing transducer head before the identified track reaches the position of the rotating transducer head. Record the recirculating video test signal obtained from the field. The record transducer head performs editing control until the track on the tape identified by the edit exit time code signal paired with the associated edit entry time code signal that initiated the insert edit operation reaches the location of the rotary record transducer head. It stays activated by the method. During this time period, the recirculating video test signal is transferred to the VTR 106 in the recirculating path 133 (see FIG. 3), as described above.
It is repeatedly recorded, played back and recirculated via the signal path defined by TBC 107 and any other operatively associated devices. This results in multiple generation of video test signals on output line 135 corresponding to time periods defined by the paired edit entry and exit time codes.

When the track defined by the edit exit time code reaches the position of the rotary conversion head, the corresponding time code signal recorded on the tape is
is reproduced by a time code conversion head. The time code signal is provided to the edit control system which responsively disables the recording transducer head thereby terminating the recording of the recirculating video test signal.

As mentioned above, the next edit entry time code in the selected column of edit time codes identifies the track recorded on the tape and the preceding recirculating video test signal along two track positions from this track. The last recirculation of the sequence is recorded.
Therefore, the recording transducer head remains disabled for the time that one recorded track is scanned by the recording transducer head. As can be seen, this corresponds to the time period of one television field. However, during this period of time, the playback conversion head plays back the video test signal recorded on this track and displays it on the monitor 139, for example.
(FIG. 3) operates to provide to the operatively associated TBC and any operatively associated equipment.

When the track defined by the next selected edit entry time code reaches the position of the rotary converter head, the corresponding time code signal is played back by the time code converter head of the VTR. As mentioned above, this edit control scheme reactivates the record transducer head in response to the reproduced edit entry time code signal. As a result, the converter head records a recirculating video test signal obtained from the last field of the video test signal played by the reproducing converter head before the identified track reaches the location of the rotating converter head. activated. As is clear from the above, this last field is determined by the edit exit time code of the immediately preceding recording sequence of the recirculating video test signal and of the next sequence of the recirculating video test signal to be recorded. A field of the previously recorded original video test signal is located on the track separating the tracks identified by the edit entry time code. The recirculating video test signal is repeatedly recorded and played back during the next time period ending with the playback of the time code signal from the tape corresponding to the next edited exit time code in the selected time code column. and a VTR coupled to a rotating recording and playback conversion head.
and recirculation through signal paths defined by operatively associated devices. During the previous sequence of video test signal recirculation this
As occurring at the output of the VTR, the number of repeated occurrences of the video test signal is in the time period defined by the second pair of edit entry and exit time codes included in the selected row of edit time codes. handle.

The edit control scheme continues through controller 108 (the third
The VTR continues to be controlled in the manner described above in response to the selected sequence of edit codes received from the operator via the inputs contained in FIG. As can be seen, this provides the output of the VTR with several sequences of respective multiple occurrences of the video test signal consecutively and non-interruptively. Furthermore, by appropriate selection of the editing exit and entry time codes defining the respective sequences and the delay time periods provided by the TBC memory, the recirculating video signal is maintained in synchronization with the chrominance, horizontal and vertical timing reference signals. be done. This creates pairs of editing exit and entrance time codes separated by an amount corresponding to a multiple of the number of fields defining a color frame (which is 4 in a color television signal organized according to the NTSC standard). TBC to select and give the entire video signal delay of the video signal recirculation path corresponding to 262 horizontal line spacing
This is conveniently achieved by operating memory. However, it should be understood that the length of all sequences of recorded recirculating video test signals need not be the same. Accordingly, the time period separating the edit entry and exit time codes that define each sequence may vary from sequence to sequence. However, maintaining uniform sequence lengths facilitates precise adjustment of the video signal processing equipment.

It will be clear from the foregoing description of one embodiment of a method for implementing the invention by use of current editing control schemes designed for use with teleproduction and broadcast type VTRs that this method Such an embodiment is similar to that implemented by the third illustrated device. In this regard,
The video switch 123 of such a device performs the equivalent function performed by the editing control scheme in activating and disabling the recording transducer head 127 directed by the drum assembly 11 of FIG. . When switch 123 is in the position coupling line 115 to input line 125 to VTR 106, it connects VTR 106 to recirculation path 133.
Disconnect from. The same result is obtained when the editing control scheme disables the recording transducer head.
This is to terminate the recirculation and recording of the video test signal as well. By switching switch 123 to couple input line 125 to VTR 106 to recirculation path 133, the recirculating video test signal is caused to be repeatedly recorded on tape by VTR 106. This also occurs when the edit control scheme activates the recording transducer head.

The method and apparatus of the present invention as described above for providing repetitive recording and playback of periods of composite video information continuously without interruption, i.e. in real time, to obtain a desired number of occurrences of the period of composite video signal. Embodiments of the present invention provide a recirculating recycler that is iteratively recirculated for such recording and playback to maintain a synchronous relationship between the chrominance component of the recirculated video signal period and the color subcarrier reference timing signal. depends on delaying each period by an amount corresponding to an even number of horizontal line periods. However, such a synchronization relationship lengthens each horizontal line included in the recirculated period of video information by an amount corresponding to 1/2 or an odd multiple of cycles of the color subcarrier signal component of the video signal. can be generated and maintained by shortening or shortening. In the embodiment shown in FIGS. 3 and 4, this means that each of the video test signals stored in time is varied in relation to the horizontal reference timing signal by the aforementioned fraction of the color subcarrier signal cycle. This is accomplished by adjusting the controller 108 associated with the TBC's memory address generator to restore the horizontal line period of . As a result of such adjustment, the recirculated video signal gradually shifts horizontally when displayed on a monitor. However, the recirculated video signal remains synchronized with the chrominance, horizontal and vertical reference timing signals for the duration of the recirculation. This movement occurs at the field rate of the video test signal (60 Hz for NTSC television signals) and corresponds to the number of odd multiples of 1/2 cycles of the color subcarrier signal to which each horizontal line time interval is adjusted. It is.

Regardless of the manner in which this delay is achieved by the TBC memory to the recirculation path,
VCR and any other operationally related equipment
The adjustment is made by comparing two or more occurrences of the selected video signal period obtained by recording and playing back the selected time period by the VTR. By comparing two or more such occurrences, changes in the characteristics of the video signal can be accurately determined.
This is because such changes can only result from operations performed on the video signal by the device during passage of the signal through the device between the occurrences being compared.

Although the invention has been described with particular reference to the illustrated embodiments and various modifications have been described, such disclosure is not to be construed as limiting. Of course, various other modifications and other embodiments will become apparent to those skilled in the art after reading this disclosure. For example, although these embodiments have been described in detail in connection with a color television signal organized according to the NTSC standard, the video signal conditioning techniques of the present invention may be applied to television signals organized according to other standards. It is also applicable to signals. It is therefore intended that the appended claims cover all various other embodiments that fall within the spirit and scope of the invention.

Claims (1)

Claims: 1. A video image quality improvement method for adjusting video signal values to improve the video image quality provided in an analog format video recording and playback device, comprising: recording one video field period; reproducing, digitizing, and then storing the video signal included in the at least one video field period in a digital data storage memory associated with the video recording and playback device; recovering the stored video signal after a preselected delay period and recording the recovered video signal; a selected number of repetitions of the recording, playback, digitization, storage and recovery of the video signal; iteratively performing a corresponding number of generation of said video signal, the video signal value depending on changes detected between different generation of said video signal affecting said video image quality provided in said video recording and playback device; A method for improving video image quality, characterized in that it comprises the steps of: adjusting the video recording and reproducing device to change the video image quality. 2. In a video image quality improvement method for improving the video image quality provided in an analog format video recording and reproducing device: (a) a video signal containing test information in a memory connected to said video recording and reproducing device; (b) operating said video recording and playback device to retrieve said video signal from said memory, record and playback said recalled video signal, and then said played back video signal; (c) successively repeating step (b) above for a selected number of repetitions to produce a corresponding number of occurrences of the reproduced video signal, each occurrence of the reproduced video signal; (d) different occurrences of said video signal affecting said video image quality provided in said video recording and playback device; A method for improving video image quality, comprising the steps of: adjusting said video recording and reproducing device to change video signal values within said video recording and reproducing device in response to changes detected between said video recording and reproducing devices. 3. The video image quality improving method according to claim 2, wherein the repeatedly stored video signal includes approximately one field of video information. 4. In the method for improving video image quality as claimed in claim 2, the video signal is divided into a first 1. A method for improving video image quality, characterized in that the video image is recorded by a second video converting head and played back by a second video converting head. 5. The video image quality improvement method of claim 2, wherein the video signal is recorded by a first video conversion head such that the time between recording and playback is the selected delay. and reproduced by a second video conversion head. 6. A video image quality improvement method for adjusting video signal parameters of an analog type video recording and playback device comprising digital circuitry with operatively associated memory to provide a selected delay, comprising: (a) said video recording; and (b) operating said video recording and playback device to record said video signal and then play back said recorded video signal to transmit said video signal to said video signal. (c) recirculating the video signal from the memory to the video recording and reproducing device after a selected delay period and operating the video recording and reproducing device; and record the recirculated video signal,
(d) operating said video recording and reproducing device so that the time between successive recordings of the video signal is equal to an even number of horizontal lines of said video signal; (e) successively repeating steps (c) and (d) above for a selected number of repetitions, and transmitting the same to said memory; (e) repeating steps (c) and (d) above for a selected number of repetitions; (f) detecting a change in said video signal that affects said video image quality provided in said video recording and playback device after said corresponding number of occurrences; (g) said plurality of said controlling the video signal parameters of the video recording and playback device to improve the video image quality provided in the video and playback device according to the detected change in the played video signal caused by a recirculation cycle; A method for improving video image quality, comprising the following steps: 7. A method for improving video image quality as claimed in claim 6, including counting the number of recirculations of the video signal from the memory to the video recording and playback device, and counting the number of recirculations of the video signal from the memory to the video recording and playback device; 1. A method for improving video image quality, comprising operating a video switch to stop recirculating the video signal after reaching a certain number. 8. The video image quality improvement method of claim 6, wherein the video signal is processed by a first video conversion head such that the time between recording and playback is less than the selected delay period. 1. A method for improving video image quality, characterized in that the video image is recorded by a second video conversion head and played back by a second video conversion head. 9. A video image quality improvement method for adjusting video signal values to improve the video image quality provided in an analog format video recording and playback device, comprising: at least one of the video signals comprising video test signal information having a chrominance component; recording a video field period; reproducing and storing said video signal included in said at least one video field period; color subcarrier reference timing generated independently of a chrominance component of said video signal; recovering and re-recording said stored video signal after a predetermined delay period selected to maintain a synchronous relationship between the signals; and generating a selected number of said video signals. repeating said playback, storage, recovery and re-recording steps of said video signal between selected various occurrences of said video signal so as to improve said video image quality provided in said video recording and playback device; A method for improving video image quality, comprising the steps of: adjusting the video recording and playback device in response to the detected change. 10. A method for improving video image quality according to claim 9, characterized in that the delay period is selected to be equal to the duration of an odd multiple of 1/2 cycle of the color subcarrier timing signal. A video image quality improvement method. 11. A video image quality improvement method for adjusting analog circuitry of a video recording and playback device to improve the quality of a video image obtained from a video signal processed by the video recording and playback device, wherein said video signal is The processing of the video signal by the video recording and playback device is controlled in accordance with a reference timing signal, and the processing of the video signal by the video recording and playback device is controlled by the video information component that defines the content of the video image. said video image quality improvement method is adapted to affect said video information component contained in said signal, and said video image quality improvement method comprises: (b) operating said analog circuitry to process said selected video signal provided to said video recording and playback device; (c) said selected video signal is (d) recovering said selected video signal after being processed by analog circuitry; (d) recovering said selected video signal from a time before said selected video signal was provided to said video recording and playback device; (e) providing said recovered selected video signal to said video recording and playback device at a time delayed by a selected period of time so as to maintain a synchronized relationship between said signal and said reference timing signal; Repeating steps (b) to (d) consecutively a selected number of times, producing a corresponding number of successive said selected video signals without any temporal interruption between successive occurrences of said selected video signals. (f) forming a sequence of successive occurrences of said selected video signal affecting the quality of the video image obtained from the video signal processed and output by said video recording and reproducing device; (g) adjusting said analog circuitry in response to said detected change in said video information component to record and record said video information; A video image characterized by the step of: causing a change in the video information component in the analog circuit to improve the quality of the video image obtained from the video signal processed and output by the playback device. How to improve quality. 12. A method of improving video image quality as claimed in claim 11, characterized in that the selected period of the selected video signal corresponds to an even horizontal line period. 13. In the method for improving video image quality as set forth in claim 11, the video recording and reproducing device includes a video recording and reproducing portion and a time axis correction portion, and the video recording and reproducing portion and the time axis correction Each of the sections includes analog circuitry, and first steps (a) to (g) above are performed without the video recording and playback section until the desired adjustment of the analog circuitry of the time base correction section is obtained. Then, from step (a) above
(g) said video recording and playback device formed with said time base correction section operatively coupled to said video recording and playback section until the desired adjustment of analog circuitry of said video recording and playback section is obtained; A method for improving video image quality, characterized in that the method is performed by: 14. The video image quality improving method according to claim 13, wherein the selected period of the selected video signal is an even horizontal line period. 15. The video image quality improving method as claimed in claim 14, wherein the even numbered horizontal line period is equal to one video field period. 16. A video image quality improvement device for use with an analog-format video recording device, comprising: (a) an analog-to-digital conversion circuit and a digital delay circuit coupled to the analog-to-digital conversion circuit and comprising an information storage memory having a selectable delay; (b) selectively connecting the output of said video recording device to its input and continuously and continuously transmitting a delayed video signal containing test information from said digital delay circuit; coupling means operative to repeatedly recirculate and after each recirculation cycle to replace the stored video signal in said memory of said digital delay circuit with a new occurrence of said video signal; ) means for controlling the number of said recirculation cycles to cause a selected number of occurrences of said video signal; and is connected to said video recording device and adjusts the video signal value in response to a detected change from one occurrence of said video signal to another occurrence. A device for improving video image quality, comprising: comparing means having an output and generating an output proportional to the difference between the compared video signal values. 17. The video image quality improving device according to claim 16, wherein the coupling means includes a video switch. 18. The video image quality improving device according to claim 16, wherein the coupling means is a route determining switch device. 19. A video image quality improvement device as claimed in claim 16, coupled to said video recording device and adapted to record a video signal in response to a detected change from one occurrence of said video signal to another occurrence. An apparatus for improving video image quality, further comprising adjusting means for adjusting a signal value.