JPH0442875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal reproducing apparatus for reproducing a video signal recorded on a magnetic tape in the form of a digital signal.

The video signal is converted into a digital signal and recorded helically on magnetic tape using a rotating magnetic head.
In a digital VTR that reproduces this, one feed section is divided into multiple blocks, each block is encoded (addition of an error correction code, etc.), and an address is assigned to each block. It is interleaved and recorded.

During reproduction, an error detection and correction circuit 1 detects an error for each data block as shown in the data processing system of FIG. If there is an uncorrectable error, the write control signal output from the error detection/correction circuit 1 prohibits memory writing, and the previously reproduced data is stored at the corresponding address in the memory 2.

In this way, the latest error-free playback data is successively written into the memory 2, and read out via the buffer memory to form a playback video signal.

In the case of slow reproduction, since the inclinations of the track and the head scanning trajectory are different from each other, reproduction scanning is performed spanning two or more fields (tracks). For this reason, 1 field memory 2 in Figure 1
Data spanning two or more fields will be mixed and written in the field. Therefore, when there is a lot of movement on a screen, there will be differences in the images in the vertically divided parts of one screen, resulting in a distorted screen when viewed continuously. This disturbance is particularly noticeable in low-speed playback, which is close to still playback, and in still playback, the screen becomes such that the difference between the top and bottom of the screen is clearly noticeable.

In view of the above-mentioned problems, the present invention makes it possible to form a slow or still playback screen using playback data obtained for each track even if the track is played back across a plurality of tracks.

The video signal reproducing apparatus of the present invention, as shown in the basic configuration in FIG. 2, reproduces a magnetic tape on which a video signal in which one field section is divided into a plurality of blocks and encoded in block units is helically recorded. and an error detection and correction circuit 1 for detecting and correcting errors in the reproduced video signal, and a plurality of one-field memories (3a to 3n) for storing output signals of the error detection circuit.
, a detection circuit 4 for detecting a signal indicating a field and a signal indicating a block of the video signal included in the output signal, and data connected to the plurality of one-field memories and supplied with the output signal of each one-field memory. It has a selector 5 and a data selector control circuit (control counter 7) that controls switching of the data selector and sequentially selects the plurality of one-field memories using a signal corresponding to the reproduction speed of the magnetic tape.

According to the signal indicating the field and the signal indicating the block detected by the detection circuit 4, one of the plurality of one-field memories (3a to 3n) and its block are selected, and the reproduced memory is selected. Write the corresponding field and block signals of the video signal.

Then, the control circuit selects the reproduction signals stored in the plurality of one-field memories (3a to 3n) in the order of field numbers at a cycle corresponding to the tape speed, reads them out from the data selector 5, and reproduces them. It is adapted to obtain a video signal.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a digital diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram of a reproduction data processing circuit of a VTR.
The digital video signal reproduced in FIG. 2 is applied to the error detection/correction circuit 1 in the same manner as in FIG. In this embodiment, block address data and field number data (for example, 0:00:00:00 seconds:00 field) are attached to each block.

The memory 3 includes a plurality of field memories 3a and 3b each having a storage capacity of one field.
...consists of 3n. During slow playback, playback is performed across multiple tracks as described above, so when writing playback data to the memory 3, the field number/block address detection circuit 4
Then, the field number and block address are detected for each block, and according to the detection result, the data is distributed to one field memory 3a, 3b, etc. whose field number corresponds to the playback data.
... is written to the corresponding block address.

Therefore, for example, in the case of slow playback at 1/2 speed, two adjacent tracks T can be scanned in one scan.
T ₁ , T ₂ , T ₂ , T ₃ , T ₃ , T ₄ ... (numbers are field numbers). For example, when scanning T ₁ and T ₂ , the playback data of the latter half of track T ₁ is stored in the memory. 3a, and the first half data of track _T2 is written to memory 3b. Further, in the scanning of T ₂ and T ₃ , the reproduction data of the latter half of track T ₂ is written to the memory 3b, and the data of the first half of track T ₃ is written to the memory 3c.

In this way, in the case of 1/2 slow playback,
Storage into one one-field memory is completed by two scans, and reproduced video data from the same track is written into each one-field memory. Each memory 3a, 3b, . . . 3n is used in a circular manner, and the last memory 3n is followed by the nearest memory 3a.

The contents of each one field memory 3a to 3n are selected and read out in the order of field numbers by a data selector 5, and are derived as a reproduction signal through a one field buffer memory 6. The data selector 5 is switched according to the tape speed.
For example, a control (CTL) pulse recorded on the side edge of the tape and used as a reference signal for the tracking servo is used as a signal representing the tape speed (or track position), and is used as a signal to control the up/down counter 7. A switching control signal for the data selector 5 is obtained by counting the data.

In the case of 1/2 slow playback, the period of the CTL pulse is twice that of standard playback, so the control counter 7 increases by one count every two track scans, and the count output is used by the data selector 5. can be switched. Therefore, each time storage in one one-field memory is completed by two track scans, the readout of the memories 3a, 3b, . . . , 3n is sequentially switched.

As a result, a 1/2 speed slow playback screen is obtained. In each of the memories 3a, 3b...3n,
Since data of the same track having the same field number is stored, the playback screen will not be disturbed even if playback scanning is performed across two tracks. In the case of 1/2 slow playback, the contents of each field memory 3a, 3b, . . . , 3n are repeatedly read out twice. If necessary, the error correction circuit 8
You can correct the error with . Note that during reverse slow playback, the control counter 7 becomes a down counter.

Next, FIG. 3 is a partial plan view of the tape showing the relationship between the track T on the magnetic tape 10 and the head scanning locus in the case of 1/2 slow playback. This track pattern was recorded using a rotating two-head type VTR with alternate tracks at different azimuths. Track as shown in part A of Figure 3.
The same rotary head scans S ₁ and S ₂ with respect to T ₂ , and one complete field of video data can be extracted from one track in two scans. Note that the scanning locus of the other reverse azimuth head is not shown in FIG. Part B of Figure 3 is
This is a case where all parts of one track T ₆ are scanned in three scans, but at least two scans (first and second scans S ₁₁ , S ₁₂ or second and third scans) One complete field of data can be obtained by scanning (S ₁₂ , S ₁₃ ).

FIG. 4 is a waveform diagram showing the state of contact of the head with respect to the track corresponding to part A in FIG. Can be read.

FIG. 5 is a partial plan view of a magnetic tape similar to FIG. 3 in the case of 1/4 slow playback. In this case, the azimuth head corresponding to track T ₁ is
Scan 4 times like S ₁ , S ₃ , S ₅ , S ₇ to track
The entire T ₁ is scanned. The reverse azimuth head is
Scan like S ₀ , S ₂ , S ₄ , S ₆ .

Figure 6 shows the case of -1/4 slow playback, and in this case too, track _T1 is scanned as _S1 , _S3 , _S5 , _S7 , and information for one complete field is extracted. Ru.

As described above, in the range from -1/2 to +1/2 times the speed, the same track is scanned multiple times, and good error-free data is written one after another into the corresponding one-field memories 3a to 3n.

If the speed is 1/2 times or more or -1/2 times or less, the entire area of one track may not be completely scanned, and the error rate increases. In this case, if an auxiliary head is provided as shown in FIG. 7 to cover the area that cannot be scanned, data for one complete field can be extracted. In Fig. 7A, even in the case of a two-head type, from the main heads 11A and 11B
Auxiliary heads 12A, 12B separated by 90° can be provided on the rotating disk 13. Figure 7B is 1
In the case of a head type, for the main head 12
An auxiliary head 12 can be provided at a position of 180°. The auxiliary head is provided at the same height as the main head, and the auxiliary head scans areas not scanned by the main head.

In the case of still playback, the tape is moved several tracks and then stopped. As a result, one track is scanned multiple times with the same head during the movement period, so it is possible to import one complete field's worth of data without errors from the same track, just as in the case of slow playback. A high-quality still screen can be obtained by repeatedly reading data for one field.

As described above, the present invention provides a plurality of storage areas each having a storage capacity of one field, and corresponds to the data of the field number and block address assigned to each block of the reproduced encoded video signal. The data is distributed to the storage areas of the field addresses to be stored in the corresponding addresses. Further, the plurality of storage areas are selected and read out in the order of field numbers at a cycle corresponding to the tape movement speed.

Therefore, according to the present invention, when the same track is scanned multiple times with slight shifts during slow playback, each piece of data from this track is written to the corresponding one field storage area, and errors are removed from one track. One complete field of data is obtained. For this reason, unlike the conventional case where one field's worth of data is constructed by mixing data read from multiple tracks, there are no discrepancies in each part of the playback screen, and no discrepancies occur at any playback speed. There is a one-to-one correspondence between the reproduction track and the reproduction field, and extremely high-quality variable-speed reproduction images can be obtained.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional digital VTR playback data processing circuit, Figure 2 is a block diagram of a digital VTR playback data processing circuit to which the present invention is applied, and Figure 3 is a track diagram during 1/2 slow playback. a partial plan view of a magnetic tape showing a head scanning trajectory;
Fig. 4 is a waveform diagram showing the contact state of the head with respect to the track during 1/2 playback, Fig. 5 is a partial plan view of the tape similar to Fig. 3 during 1/4 slow playback, and Fig. 6 is -1 A partial plan view of a tape similar to that shown in FIG. 3 during /2 reverse slow playback, and FIGS. 7A and 7B are schematic plan views showing modifications of the rotating magnetic head device used in the present invention, respectively. In the symbols used in the drawings, 3a to 3n...1 field memory, 4...field number/block address detection circuit, 5...data selector, 7...control counter, 10...magnetic tape, 11A, 11B...main head, 12A, 12B
...It is an auxiliary head.

Claims (1)

[Scope of Claims] 1. In a video signal reproducing device that reproduces a magnetic tape on which a video signal obtained by dividing one field section into a plurality of blocks and encoding each block is recorded helically, an error in the reproduced video signal is provided. an error detection and correction circuit that performs detection and correction; a plurality of one-field memories that store output signals of the error detection and correction circuit; and detection of signals indicating fields and blocks of the video signal included in the output signal. a data selector connected to the plurality of one-field memories and supplied with an output signal of each one-field memory; and a data selector that controls switching of the data selector by a signal corresponding to the playback speed of the magnetic tape. a data selector control circuit that sequentially selects the plurality of one-field memories; One field and its block are selected and the signals of the corresponding field and block of the reproduced video signal are written, and the control circuit stores the signals in the plurality of one field memories at a cycle corresponding to the tape speed. A video signal reproducing device characterized in that the reproduced signal is selected in the order of field numbers and read out from the data selector to obtain a reproduced video signal.