JPH01213875A - System for detecting and correcting skew quantity - Google Patents

Abstract

PURPOSE:To easily detect and correct skew quantity by counting a time to regenerate a synchronizing signal or an identification signal from a recording medium and comparing the time with reference time. CONSTITUTION:A video to be recorded by video heads 3, 4-6 of a rotary drum 2 is taken out in order by a video head switching circuit 29 and conducted through ID signal detecting circuits 30 and 31 and a synchronizing signal detecting circuit 32 to a gate generating circuit 38. When a gate signal phi9 of the circuit 38 is 'H', a clock phi10 of a frequency divider 28 is counted by a programmable counter 40. A time length t2 between counted synchronizing signals S2 and Sm at the time of regenerating is fetched into a RAM 23 and a time length t1 between the computed signals S2 and Sm is integrated to a ROM 24. Then, a program is included to calculate a differential time DELTAt1=t1-t2. On the other hand, a CPU 22 executes the program of the ROM 24 and calculates the skew quantity error DELTAt1 and tension to obtain DELTAt1=0 is calculated from the program of the ROM 24. Then, tension setting 42 is executed and the skew quantity is detected and corrected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a digital videotape recorder (hereinafter referred to as
Regarding a device that records and reproduces a digital signal containing a small number of synchronization signals or ID signals that are repeated at a constant period, such as a digital VTR (abbreviated as a digital VTR), more specifically, the skew amount of a recording medium used in such a device. The present invention relates to detection and correction methods.

[Conventional technology]

The conventional method for detecting the amount of skew is disclosed in U.S. Pat.
As described in the full text of the publication No. 2881, by switching between the video head and the auxiliary video head, the time position of the horizontal synchronization signal reproduced by the auxiliary video head is measured, and this time position and the time of recording are used. By comparing the time positions of horizontal synchronization signals, the amount of skew is detected and corrected.

Here, the causes of skew will be described.

This occurs because the tension and contact of the tape with respect to the head changes between recording and reproduction. Also, when playing back a tape on a device different from the one used to record it,
This occurs because there is a slight difference in tension between recording and playback, and the effective length of the tape changes during playback, resulting in a change in the relative speed between the tape and the head. At this time, the horizontal synchronization signal, which is an analog synchronization signal, is originally a continuous signal that occurs at a constant time rate, but it does not occur at a constant rate and becomes discontinuous. Therefore, the amount of skew can be determined from the degree of discontinuity.

[Problem to be solved by the invention]

However, in a digital TR in which a television horizontal synchronization signal, which is an analog synchronization signal, is not recorded, there is a problem as to what reference should be used to detect the amount of skew.

An object of the present invention is to provide a skew amount detection and correction method that can detect and correct the skew amount without using an analog synchronization signal.

[Means to solve the problem]

To achieve the above object, the present invention provides an apparatus for recording on a recording medium or reproducing from a recording medium a digital signal that includes at least a synchronization signal or an ID signal that is repeated at a constant cycle. A measuring means for measuring the time required to reproduce an ID signal from the recording medium, and comparing the measured value by the measuring means with a known reference time required to reproduce the predetermined number of synchronization signals or ID signals. and a comparison means for detecting and correcting the skew amount of the recording medium based on the comparison result.

[Effect]

The skew amount detection and correction method according to the present invention operates based on a digital synchronization signal or an ID signal. As a result, if a digital synchronization signal or ID signal can be detected, a malfunction will occur regardless of whether the analog horizontal synchronization signal is recorded on a tape, segment recording method, non-segment recording method, or when the tape is wrapped around a drum depending on factors such as corners. This is a method that can easily detect and correct the amount of skew.

〔Example〕

The present invention will be explained below using examples. The recording format on the tape is SMPTE (Society
Ty of Motion Picture and
The following description is based on the D1 format of Television Engineers.

FIG. 2 is an explanatory diagram of a method in which the chi 11 is wound around the rotary head drum 2 over approximately 258 degrees, and video signal tracks are recorded and reproduced using four video heads 3°4.5.6. Note that 7 and 8 are guide posts, respectively.

FIG. 3 shows a track pattern of tape 1 recorded according to the method shown in FIG. In Fig. 3, 9 is a truck (indicated by the shaded area), and 20 trunks make up 1 truck.
Configure the frame. 10 is the starting point of the frame,
If the first track is recorded by head 3, the next track is recorded by heads 4, 5, 6 in that order, and 11 is the frame end point.

Figure 4 shows a detailed view of the truck. The track has two Vs
I DEO area, 5 EDIT GAP areas, 4
It consists of two AUDIO areas, and the numbers written with numbers and alphabets indicate ID numbers.

Further, for example, the VIDEC) eff area is composed of a 30-byte preamble, 160 sync blocks, and a 6-byte postamble.

FIG. 5 shows a detailed diagram of one sink block.

One sync block has a 2-byte synchronization signal 16.4
Byte ID signal 17.60 byte video signal 18.2
It consists of 0.6 byte error code 19°21.

That is, any ID number in the track formant shown in FIG. 4, for example, the ID of the VIDEO0 area.
By comparing the known recording time length of the section between number 03 and ■D number B8 in the VI DEO1 area and the time length of the same section during playback, the amount of skew (amount of tape expansion/contraction) can be determined.
can be detected. The same concept holds true when a synchronization signal is used instead of an ID signal.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, the microprocessor is a central processing unit (CP
U) 22, random access memory (RAM) 23,
It is composed of a read only memory (ROM) 24 and an address decoder 25, and is connected by a bus 26 including a data bus, an address bus, and a control bus.

The CPU 22 executes a program stored in the ROM 24 and processes data loaded into the RAM 23. The address decoder 25 is a circuit that generates control signals to each control circuit based on address bus data generated by the CPU 22. A clock is generated by an oscillator 27, and the clock whose frequency is divided by a frequency dividing circuit 28 is sent to the CPU 22.

Now, the video signals recorded and reproduced by the video heads 3, 4, and 5°6 of the rotating drum 2 are transferred to the video head switching circuit 2.
9, they are taken out in order.

The signal is then input to the ID signal detection circuits 30 and 31 and the synchronization signal detection circuit 32.

FIG. 7 is a time chart of various signals in FIG. 1 (and FIG. 8, which will be described later).

First, a method for detecting and correcting the skew amount based on the difference between the measured value of the time length over a plurality of arbitrary synchronization signals and its known reference value will be described.

Signal φ1 in FIG. 7 is a time chart for recording and reproducing the sync block shown in FIG.
S,,S,indicates the synchronization signal 16,! ,,If,1. ，
1. indicates the ID signal 17, and D,,D,,D,,,D,
is the video signal 18. Error code 19. Video signal 20. It consists of error code 21.

That is, the time length t2 required for reproduction of the synchronization signals S2 to S is measured, and the time length t2 required for reproduction of the synchronization signals S2 to S during recording is measured.
1 (known) 1+ and the error time Δ1. =1. -1. is calculated as the skew amount, and Δt
This method corrects the tape tension setting so that 1=0.

Please refer to FIGS. 1 and 7. In the ID signal detection circuit 30,
When the ID signal 11 is detected from the reproduced signal φ, a signal φ2 is generated on the data line 35. Similarly, the ID signal detection circuit 31 detects the ID signal 7 and generates the signal φ on the data line 36. This signal φ2. φ is input to the gate generation circuit 38'. Furthermore, the synchronization signal detection circuit 32 detects each synchronization signal and sends the signal φ4 to the data line 4.
Occurs in 3.

The gate signal φ9 from the gate generation circuit 38 is input to the programmable counter 40, and the counter 40 counts the clock φ1° frequency-divided by the frequency divider 28 only while the gate signal φ9 is at the "H" level. This counted value, ie, the time length t2 between the synchronization signal St and S1 during reproduction, is taken into the RAM 23. A pre-calculated time length t1 between synchronization signals S2 and S during recording is stored in the ROM 24, and this 1. and the playback time length t2, and the difference time Δ1. A program for calculating =1°-12 is included.

The CPU 22 executes the program in the ROM 24,
The skew amount error Δt is calculated. The CPU 22 calculates the tension sufficient to make this Δt+"O according to a predetermined program stored in the ROM 24, and sends this calculated value to the data bus 26. This calculated value of the tension is as follows.
Furthermore, it is converted into an analog value by the DA converter 41,
For example, it is supplied to the tension setting circuit 42 on the tape supply side to correct the skew amount.

Next, we will consider a method for detecting and correcting the amount of skew based on the ratio between the measured value of the time length over a plurality of synchronization signals and its known reference value.

This can be realized with a configuration similar to that described above.

However, the ROM 24 incorporates a pre-calculated time length (known reference value) 1+ between synchronization signals during recording, and compares it with the time length (measured value) tz between synchronization signals during playback to determine the skew amount error. Ratio Δ1. A program for calculating =tl/lz is included.

The CPU 22 uses the program in the ROM 24 to
This Δt2 is calculated, and the tension value is further calculated so that Δt2=1. The CPU 22 sends this calculated tension value to the data bus 26. Thereafter, the skew amount can be corrected in the same manner as before.

FIG. 6 shows the ID signal detection circuits 30 and 31 in FIG.
FIG. 2 is a circuit diagram showing a specific example.

Please refer to FIG. Multiple Exclusive Noah (EX
-NOR) is connected to the video head switching circuit 29, and the other input is connected to a circuit 34 that generates an ID pattern determined by the standard. EX-NO
The output of R is input to a multi-input NAND 37, and when patterns 33 and 34 match, 35 or 3
A negative polarity pulse is output at 6, and otherwise the level is "H".

Furthermore, the synchronization signal detection circuit 32 in FIG. 1 can be realized with the same configuration as the ID signal detection circuit shown in FIG.
4 should be set as the synchronization pattern. Signal φ4 in Figure 7
is line 4 when the synchronization is matched by the synchronization signal detection circuit 32.
Occurs on 3.

FIG. 8 is a circuit diagram showing a specific example of the gate generation circuit 38 in FIG. 1.

In FIG. 8, a signal φ7 is obtained by applying a signal φ4 to the set terminal of the flip-flop 46 and a signal φ2 to the reset terminal. Furthermore, inverter 48.0R53
, a signal φ is obtained by the latch 52 which receives the output (55) of the frequency dividing circuit 28 as a clock signal. Similarly, signal φ6 is obtained. Furthermore, by applying the signal φ8 to the set terminal of the flip-flop 54 and the signal φ6 to the reset terminal, a gate pulse of the signal φ9, which is at the "H" level during the period between the synchronizing signals S2 and S, is obtained.

〔Effect of the invention〕

According to the invention, there is no need to use an analog synchronization signal, for example a horizontal synchronization signal, but a digital synchronization signal or an ID
The advantage of using signals is that the skew amount can be easily detected and corrected in devices such as digital VTRs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 shows a tape wound around a rotating head drum over approximately 258 degrees, and video signal tracks recorded by four video heads.
Fig. 3 is an explanatory diagram showing the track pattern of a tape recorded according to the method shown in Fig. 2, Fig. 4 is a detailed diagram of the track, and Fig. 5 is a sync block recording and playback diagram. FIG. 6 is a circuit diagram showing a specific example of the ID signal detection circuit in FIG. 1, and FIG.
The figure is a time chart of various signals in FIG. 1, and FIG. 8 is a circuit diagram showing a specific example of the gate generation circuit 38 in FIG. 1. Explanation of symbols 1... Tape, 2... Rotating drum, 3.4, 5.6
...Image head, 7.8...Guide post, 9...
・Trunk, 10... Frame start point of the video track, 11... Frame end point of the video track, 1
6...Synchronization signal, 17...ID signal, 18.20.
...Video signal (data), 19.21...Error code, 22...CPU, 23...Random access memory, 24...Read only memory, 25...Address decoder, 26... bus, 27... oscillator,
28... Frequency divider, 29... Image head switching circuit, 30.31... Bowing signal detection circuit, 32... Synchronization signal detection circuit, 33° 35.36, 39.43... Data Line, 34...Pattern generation circuit, 37...Multi-input NAND, 38...Gate generation circuit, 40...
Programmable counter, 41...DA converter, 42
...Tension setting circuit, 44.45...Reel,
46, 47.54...Flip-flop, 48.51
...Inverter, 49°52...OR, 50, 53
... Lunch agent Patent attorney Akira Namiki Futsuki 1 Zutomi 2 Zuka 4 b Pomata Door〉Lar layer 5 Zuman 6 S'! A 7 Bunfu ε:

Claims (1)

[Claims] 1. In an apparatus for recording on a recording medium or reproducing from a recording medium a digital signal that includes at least a synchronization signal or ID signal that is repeated at a constant cycle, the apparatus comprises: measuring means for measuring the time required to reproduce from the recording medium;
Comparing means for comparing the known reference time required to reproduce the predetermined number of synchronization signals or ID signals with the measured value by the measuring means, and calculating the skew amount of the recording medium from the result of the comparison. A method for detecting the amount of skew. 2. In a device that records on a recording medium or reproduces from a recording medium a digital signal that includes at least a synchronization signal or an ID signal that is repeated at a constant period, the device reproduces a certain number of synchronization signals or ID signals from the recording medium. A measuring means for measuring the time t2 required for reproducing the predetermined number of synchronization signals or ID signals is compared with the measured value t2 by the measuring means to determine the skew amount error. Δt1 (=t1
A skew amount detection and correction method characterized by comprising a comparison means for determining and outputting the skew amount error Δt2), and a correction means for correcting the skew amount of the recording medium so that the skew amount error Δt1 becomes zero. . 3. In a device that records on a recording medium a digital signal that includes at least a synchronization signal or an ID signal that is repeated at a constant period, or reproduces from the recording medium, a certain number of synchronization signals or ID signals are reproduced from the recording medium. A measuring means for measuring the time t2 required for reproducing the predetermined number of synchronization signals or ID signals is compared with the measured value t2 by the measuring means to determine the skew amount error. Ratio Δt2 (=t
1/t2) and output, and a correction means for correcting the skew amount of the recording medium so that the skew amount error ratio Δt2 becomes zero. Correction method.