JPH05219479A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide a magnetic recording and reproducing device which digital- records a video signal by which a reproduced screen on which picture data at an another time is overlapped can not be outputted at the time of a high speed reproduction, and the reproduced screen without many errors can be outputted. CONSTITUTION:A tape feed speed is controlled by periodically switching the tape feed speed faster than a normal reproducing speed, and the tape feed speed slower than the normal reproducing speed by a tape feed speed control means 13. The reproduced screen is prepared based on data reproduced without any tracking from a magnetic tape in the period of the tape feed speed slower than the normal reproducing speed, and switched in each period when the tape feed speed is changed by a high speed reproducing processing means 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for digitally recording image data such as TV signals.

[0002]

2. Description of the Related Art In recent years, a magnetic recording / reproducing apparatus for digitally recording a TV signal such as a D1-VTR has attracted attention. In this magnetic recording / reproducing apparatus, the tape feeding speed during high speed reproduction is faster than the normal reproduction speed. It is kept at an arbitrary constant speed. At this time, the reproducing head crosses a plurality of tracks on the tape, and the image data in the same field cannot be completely reproduced from the tape. Conventionally, during such high-speed reproduction, a correction process is performed in which missing data is estimated and created from the reproduction data in pixel units.

In the structure of such a conventional magnetic recording / reproducing apparatus, image data is compressed by high-efficiency encoding, and data having a rate smaller than the original image data rate is digitally recorded on the tape and then reproduced at high speed. There is.

As a method of compressing image data by high efficiency encoding, there is a method of dividing the image data into blocks each consisting of a plurality of adjacent pixels and encoding each block. For example, the size of one block is 8 pixels × 8 lines. When data compressed by such high efficiency coding is recorded and normally reproduced, the reproduced data is reproduced in block units. If there is an error in the reproduced data and missing data occurs, the data is missing in block units. During normal playback, this missing data is corrected by replacing it with the data of the same block on the screen one field before or one frame before,
It is possible to reproduce almost the original image.

[0005]

However, during high speed reproduction, a large number of blocks of missing data occur in the screen at the same time. When correcting these missing data, it is difficult to reproduce the original image by inferring it from the data of the blocks reproduced in the screen at the same time. Further, it is conceivable to replace the data of the same block on the screen reproduced one frame or more before with the missing data, but in this case, the images of a plurality of fields become mosaic images, which is visually unsightly. there were.

As a method for solving this, a method of controlling the tape feeding speed during high-speed reproduction to intermittently normally reproduce screen data at the same time is considered. This method requires tracking so that the reproducing head scans the tracks on the tape without crossing the tracks. However, the response time of this tracking is long. Therefore, there is a drawback that the cycle of switching the screen of the reproduced image is long. Further, in order to shorten the response time of the speed control, there is a drawback that the speed control mechanism has a complicated structure such as dynamic tracking and the apparatus becomes complicated.

The present invention solves the above problems. The speed control mechanism has a simple structure, the cycle of switching the screen of the reproduced image is short, and the screen of the reproduced image is the original image at the same time. It is an object of the present invention to provide a magnetic recording / reproducing device capable of outputting a high-speed reproduced image.

[0008]

In order to achieve the above object, the present invention controls the tape feeding speed by periodically switching between a tape feeding speed higher than the normal reproducing speed and a tape feeding speed lower than the normal reproducing speed. Magnetic recording so as to have a tape feed speed control means and a high speed reproduction processing means for creating a high speed reproduction image based on data reproduced without tracking from the magnetic tape during a tape transfer speed slower than the normal reproduction speed. This constitutes a playback device.

[0009]

The present invention has the above-mentioned configuration, and + n (n> 1)
During double speed high speed reproduction or -n times high speed reproduction, the tape feeding speed control means controls the tape feeding speed to make the average tape feeding speed + n times or -n times the normal speed. The period T in which the speed changes is kept substantially constant.
An acceleration period T ₁ , a high speed period T ₂ , a deceleration period T ₃ , and a low speed period T ₄ are present in this one cycle T. Tracking is not performed in this low speed period T ₄ . The tape feeding speed in the low speed period T ₄ is + m (0 ≦ m <1) times or −m times the normal reproduction speed so that the reproducing head can completely reproduce the data in each track on the tape. To speed. The low-speed period T ₄ is a period in which the reproduction data in each low-speed period includes at least one field of image information.

The high-speed reproduction processing means creates image data of at least one field from the data reproduced from the tape in the low-speed period T _4, and uses this created image data as a high-speed reproduced image to create image data in the next low-speed period. It outputs until it is done.

Therefore, the tape feed speed control mechanism has a simple structure, and the cycle of switching the screen of the reproduced image is T, and the high speed reproduced image can be output so that the screen of the reproduced image becomes the original image at the same time. It is possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. (FIG. 1) is a block diagram showing a reproducing unit of a magnetic recording / reproducing apparatus according to an embodiment of the present invention, and (FIG. 2) is a tape feeding speed at the time of high-speed reproduction of the magnetic recording / reproducing apparatus according to the embodiment of the present invention. FIG. 3 is a block diagram showing a recording section of the magnetic recording / reproducing apparatus in one embodiment of the present invention.

First, the recording operation of the embodiment will be described. In the recording section of the magnetic recording / reproducing apparatus shown in FIG. 3, a video signal is input to the input terminal 1. The video signal is converted into digital image data by the A / D converter 2. The image data is subjected to processing such as rearranging the data in an order suitable for high efficiency encoding in the input circuit 3 and applied to the high efficiency encoding circuit 4. In the high efficiency encoding circuit 4,
For example, encoding is performed for each block composed of data of 64 pixels of 8 pixels × 4 lines × 2 fields, and the image data is converted into compressed data. The compression cycle in consideration of rearrangement of image data, so-called shuffling, etc. is one frame. The error correction code is added to the compressed data in the error correction coding circuit 5, divided into two channels, and applied to the modulation circuits 6 and 7. In the modulation circuits 6 and 7, the data is modulated, and SYNC and ID are further added to form the data of the SYNC block. SYNC
The data in the block is parallel / serial converted in the recording order, and then the magnetic head 1 is passed through recording amplifiers 8 and 9.
It is applied to 0 and 11 and recorded on the magnetic tape 12. The relationship between this recorded data and the original video signal is
The data of 10 tracks corresponds to the image data of one frame of the TV signal.

Next, the normal reproducing operation of the embodiment will be described.
In the reproducing section of the magnetic recording / reproducing apparatus shown in FIG. 1, the speed control circuit 13 applies a control signal 15 to the capstan motor 14 so that the magnetic tape 12 runs at the normal reproducing speed. Further, the FG signal 16 is applied from the capstan motor 14 to the speed control circuit 13. The signals reproduced from the magnetic tape 12 by the reproducing heads 17 and 18 are demodulated by the reproducing amplifiers 19 and 20 into demodulation circuits 21 and 22.
Applied to. The demodulation circuit performs SYNC detection and ID detection processing, further demodulates the data, and applies the data to the correction circuit 27 for each SYNC block data. In the correction circuit 27, error correction processing is performed for each SYNC block, and the error-corrected data, ID, and error flag are applied to the correction circuit 28. The modification circuit 28 has a memory for storing data corresponding to one frame of image data. If the error flag information is "no error", the SYN
The C block data is stored in the memory address corresponding to the ID information content. At this time, if the content of the error flag information is "error present", the SYNC block data is not stored in the memory. As a result, the block data in which the error has occurred has been subjected to a modification process so that it is replaced with the data one frame before. The compressed data output from the retouching circuit 28 is converted into each pixel data of the original image data by the decoding circuit 29, the order of the data is rearranged by the output circuit 30, and the original image data is converted. This image data is output as the original video signal from the output terminal 33 via the D / A converter 31.

Next, the positive side high speed reproduction operation of the embodiment will be described. In the reproducing section of the magnetic recording / reproducing apparatus shown in FIG. 1, the speed control circuit 13 applies a control signal 15 to the capstan motor 14 so that the magnetic tape 12 runs at the tape feeding speed shown in FIG. To do. That is, the period during which the tape feed speed changes is T which is substantially constant. In this period, there are an acceleration period T ₁ , a high speed period T ₂ , a deceleration period T ₃ , and a low speed period T ₄ . The magnitude of the speed in the high-speed period is approximately V _F , the magnitude of the speed in the low-speed period is V _S , and if the magnitude of the normal reproduction speed is V _N , V _F > V _N > V There is a relationship of _S , and the average tape feed speed is a value calculated from these, which is + n times the normal playback speed. V
_S is about 1/3 of the normal playback speed. This T ₄
During this period, the reproducing head scans the tape without tracking. T ₄ is set to about 200 msec so that the data on the tape scanned during this period includes print data corresponding to one frame of image data. The signal reproduced from the magnetic tape 12 by the reproducing heads 17 and 18 for the entire period of T is transmitted through the reproducing amplifiers 19 and 20 to the demodulation circuit 21 which is the input unit of the high speed reproduction processing means 32.
And 22 are applied.

During the period of T ₄ , a low speed period signal 25 indicating a low speed period is applied from the speed control circuit 13 to the demodulation circuits 21 and 22, the correction circuit 27 and the correction circuit 28. The low-speed period signal 25 causes the demodulation circuit to perform SYNC during the period T _4.
Detection, ID detection processing, data demodulation, S
Data is applied to the correction circuit 27 for each YNC block data. In the correction circuit 27, error correction processing is performed for each SYNC block, and the error-corrected data and ID are applied to the correction circuit 28. SYNC block data is I
It is stored in the address of the memory corresponding to the D information content.
At this time, even if the error flag information content is "error present", the SYNC block data is stored in the memory.
The ID is inspected to detect that all the data corresponding to one frame of the image data has been stored in the memory. The SYNC block data after this detection time is not stored in the memory even during the period of T ₄ .

After one frame of data is stored in the modifying circuit 28, the modifying circuit 28 outputs one frame of data to the decoding circuit 29. A valid data period signal 26 indicating that the data is valid is applied from the modifying circuit 28 to the output circuit 30 while the data of one frame is being output. The output circuit 30 stores the data of one frame applied from the decoding circuit 29 in the replacement memory if the data. The output circuit 30 continuously outputs the data of one field among the image data of one frame after rearranging the data in order for the period T.

These operations are repeated every cycle T. Therefore, the screen of the reproduced image during high-speed reproduction is switched at the cycle T. For example, T ₁ = 100 msec, T ₂ = 200 mse
c, T ₃ = 100 msec, T ₄ = 200 msec, V _F
= If the normal reproduction speed is 20 times, the high speed reproduction reproduction speed n is n = 10 times, and the screen switching period T is T = 6.
It will be 00 msec. As described above, the high-speed reproduction image on the positive side can be obtained. Also, the negative side high speed reproduction can be realized in almost the same manner.

The above operation is one embodiment of the present invention, and various modifications can be considered in each block other than the operation described above.

For example, as another embodiment of the present invention, it is conceivable to arbitrarily set the high speed reproduction speed n, and
It is also conceivable that the output circuit outputs one frame of data stored in the memory during the period T for each frame of the output image. Further, it is conceivable that the output circuit divides the period T into two and sequentially outputs the data of two fields stored in the memory in each period.

As another embodiment of the present invention, it is conceivable that the correction circuit clears the data stored in the memory and reproduced during the previous low speed period between T _{1 and} T ₃ . In this case, the quality of the reproduced image is improved. Also, the period of T ₄ is one frame period, that is, about 100
It may be set to msec. In this case, the reproduced image has a screen in which two adjacent frames of data are mixed, but the screen switching cycle T can be shortened.

As another embodiment of the present invention, if a reverse azimuth head for special reproduction is added to the reproducing head at the time of high speed reproduction and the data is reproduced by twice as much as the normal reproducing head, the time required to fetch the necessary image data is obtained. Becomes shorter, T ₄ can be made smaller, and the screen switching period T can be made smaller.

As another embodiment of the present invention, the high-efficiency coding method may compress image data in one field cycle. In this case, T ₄ can be halved as compared with the case of one frame period. Further, in the case of compressing in two frame cycles, the same operation as above can be realized by doubling T ₄ as compared with the case of one frame cycle. That is, in the high-efficiency coding method, when compressing image data in k (k ≧ 2) frame cycles, T ₄ is multiplied by k as compared with the case of one frame cycle, and the same operation as described above is performed. Can be realized.

According to the magnetic recording / reproducing apparatus of the above embodiment, the tape feeding speed is switched to reproduce the data at the tape feeding speed lower than the normal reproducing speed, and the tape feeding speed is the same as the high speed reproducing on average. By doing so, it is possible to obtain a high-speed reproduced image in which the image data at the same time is switched at a constant cycle with a simple structure of the tape feed speed control mechanism.

[0025]

As is apparent from the above description, the present invention can improve image quality during high-speed reproduction in a magnetic recording / reproducing apparatus for digitally recording a video signal such as a TV signal. That is, there is an effect that a high-speed reproduction image in which image data at different times overlap does not occur and an output image can be displayed on a screen with few errors. Further, even in the case of recording and reproducing by performing high efficiency encoding such that the encoding period extends over a plurality of frames, there is an effect that the image quality during high speed reproduction can be secured. Further, a magnetic recording / reproducing device that embodies such an operation can be realized by a simple circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a reproducing unit of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change in tape feeding speed during high-speed reproduction on the positive side of the magnetic recording / recording / reproducing apparatus in one embodiment of the present invention.

FIG. 3 is a block diagram showing a recording unit of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 Input Terminal 12 Magnetic Tape 13 Speed Control Circuit (Tape Feed Speed Control Means) 25 Low Speed Period Signal 26 Effective Data Period Signal 32 High Speed Reproduction Processing Means 33 Output Terminal

Claims (1)

[Claims] 1. A tape feed speed control means for controlling the tape feed speed by periodically switching between a tape feed speed faster than the normal play speed and a tape feed speed slower than the normal play speed, and a tape feed speed slower than the normal play speed. A magnetic recording / reproducing apparatus having a high-speed reproducing processing means for producing a high-speed reproduced image based on data reproduced without tracking from the magnetic tape during the period.