KR940005206B1 - Speed changing reproducing method and apparatus of digital vtr - Google Patents

Abstract

The method for improving the data reproduction rate during picture search and compensating the error easily comprises the steps of: a) dividing the frame image data into a number of macro blocks; b) dividing the macro block into the a number of blocks; c) applying the inner error correction code to the divided block; and d) applying the outer error correction code to the block applied with inner one.

Description

Method and apparatus for facilitating variable speed regeneration of digital britial

1 is a general configuration diagram of a recorder in digital british.

FIG. 2 shows a data structure to which an error correction code is added in FIG.

3 is a cross section showing the format of data recorded on a tape.

4A-4C show the ENVELOPE waveform of the pickup signal and the size of the block to be recorded in variable speed reproduction.

5A-5B show one embodiment of a recording method according to the present invention.

FIG. 6 is a diagram showing a format for recording the macroblocks shown in FIGS. 5A and 5B on a tape.

7 is a view showing an embodiment of a device suitable for the reproducing method according to the present invention.

* Explanation of symbols for main parts of the drawings

1: First input terminal (Y) 2: Second input terminal (R-Y)

3: third input terminal (B-Y) 4: block forming machine

5 DCT converter 6 adaptive quantizer

7 variable length encoder 8 error code encoder

9: channel encoder 10: recording head

11, 21: tape 22: playhead

23 amplifier 24 equalizer

25: decoder 26: internal code decoder

27: selector switch 28: external code decoder

29: Error correction 30: Frame memory

31: Data extension part 32: Digital / analog converter

33: luminance / chromatic signal synthesizing section 34: control input terminal (PS)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital VTIAL, and more particularly, to a method and apparatus for increasing data reproduction rate and facilitating error correction during picture search.

Digital VT modulates and records the image information into a digital signal, and thus exhibits superior performance in signal-to-noise ratio (S / N), resolution, and editing compared to conventional analog VTals.

This digital VTal has evolved with the development of data compression, high density recording and error correction techniques in normal reproduction. On the other hand, even in variable speed playback, one of VT's essential functions, data is not continuously reproduced because the head transverses a plurality of tracks, and the video is composed of different feed information and has a higher error rate than normal playback. There is such a problem.

An object of the present invention is to provide a data recording method which overcomes the above problems and improves the ratio of valid data reproduced at variable speed reproduction.

Another object of the present invention is to provide a data recording method which is easy to correct errors in variable speed reproduction.

It is still another object of the present invention to provide a digital VTI which easily performs error correction during variable speed reproduction.

The data recording method of the present invention for achieving the above object divides the frame image data into a plurality of blocks, and adds an internal error correction code and an external error correction code to the data recording method. The method comprising: dividing the frame image data into macroblocks having a smaller size; Dividing the macroblock into a plurality of blocks; Adding an internal error correction code to the divided blocks; And adding an external error correcting code to the block to which the internal error correcting code is added.

A reproduction method of the present invention which achieves the above another object is a digital VTI data reproduction method for reproducing image data from data recorded by adding an internal error correction code and an external error correction code, wherein during normal playback, the internal error correction is performed. In addition to error correction by code, error correction by external code is performed, and only error correction by external error correction code is performed at variable speed reproduction.

The digital VT of the present invention which achieves another object described above has a digital VTD having an internal code decoder for performing error correction by an internal error correction code and an internal code decoder for performing error correction by an external error correction code. The input terminal of the inner code decoder is connected to one input terminal, the output terminal of the inner code decode is connected to the other input terminal, and the output terminal is connected to the input terminal of the outer code decoder, and has a control terminal for switching and controlling the two input terminals. It is characterized by including in the switching device. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a general configuration diagram of a recorder in digital VTI.

In FIG. 1, 1 is a first input terminal for introducing a luminance Y signal, 2 is a second input terminal for introducing a color difference signal RY, and 3 is a third input for introducing another color difference signal BY. Input terminal.

Normally, the ratio of the sampling frequency of the luminance signal and the color difference signal is 4: 1: 1 (Y: R-Y: B-Y). The input video signal (Y, RY, BY) is converted into a plurality of blocks each of which is composed of 64 sample values (8 LINE X 8 SAMPLE) in a block forming machine of 4, and DCT (Discrete Cosine Transform) in a DCT converter of 5 A discrete cosine transform (hereinafter referred to as DCT) is encoded in the adaptive encoding of six.

The visual characteristics of human beings are more sensitive to low frequency than high frequency, and the coding rate for high frequency components is lower than the coding rate for low frequency components through time-frequency transformation such as DCT transformation. The coded video signal is compressed more than in a variable length encoder using a Hoffman coding technique of 7, and an error correction code is applied in an error code encoder of 8. These signals are controlled by the channel encoder of 8 to control the color difference signals between tracks and recorded on the tape of 9.

FIG. 2 shows a data structure to which an error correction code is added in FIG. Error correction is very important for systems using data compression, such as digital VTial. The reason is that the ripple effect of loss of information of 1 bit is very large.

In general, a REED-SOLOMON codeword (INNER CORD) is added to data compressed in each unit block. Next, a REED-SOLOMON codeword (OUTER CODE) is added to each vertical column in a block of frame units.

In reproducing, error detection and correction first detects and corrects an inner code by an outer code, and then detects and corrects an error of data compressed by an inner code.

By such an error detection and correction method, a burst error occurring in a plurality of blocks in the horizontal direction, such as b, is corrected by an internal code and random errors occurring in a unit block are as shown in FIG. Also for (Burst error), each unit block in the burst error region is treated with a random error in the vertical direction, thereby making it possible to detect and correct errors.

3 is a diagram showing the format of data recorded on a tape. In FIG. 3, the data recorded on the tape includes an SYNC portion for identifying the synchronization required for signal reproduction, an ID portion for indicating a block address, a PLL portion, a DATA portion, and an internal code for error detection and correction (P. PARITY). It consists of.

4A-4C show the ENVELOPE waveform of the pickup signal and the size of the block to be recorded in variable speed reproduction. In FIG. 4A, the portion of the pickup signal having a low amplitude of ENVELOPE cannot reproduce data due to deterioration of the signal-to-noise ratio S / N, so that a reproducible area of a certain level or more exists.

As shown in FIG. 3B, when the data block to be recorded is large, block 1 cannot reproduce data because there is no SYNC portion, and block 2 reproduces only about one half of the data block, making signal recovery difficult. On the other hand, when the data block to be recorded is small, up to block 6 to block 11 can be reproduced.

When the data block to be recorded as shown in FIG. 3C is small, it is advantageous in variable speed reproduction as compared with the case where the data block to be recorded as in FIG. 3B is large. On the other hand, it is disadvantageous for error correction.

5A-5C show an embodiment of a recording method according to the present invention. In FIG. 5A, it can be seen that a block corresponding to one frame is divided into a plurality of smaller blocks (called macro blocks).

In FIG. 5B, each macro block is composed of a plurality of unit blocks having an inner code and an outer code block (Q. PARITY) corresponding to the unit block in the vertical direction.

With this recording method, the internal error is corrected by the internal code of the tandem error occurring in the unit block as shown in c of FIG. 5B in each macro block, and the burst error occurring in a plurality of blocks in the horizontal direction such as d In addition, error detection and correction are possible by treating each unit block in the burst error region with a random random error in the vertical direction.

FIG. 6 is a diagram showing a format for recording the macroblocks shown in FIGS. 5A and 5B on a tape.

7 is a view showing an embodiment of a device suitable for the reproducing method according to the present invention. In Fig. 7, 21 is a tape on which digital data is recorded, 22 is a playhead, 23 is an amplification for changing the level of the pickup signal, 24 is an equalizer for emphasizing the high frequency portion of the pickup signal, and 25 is a differential method. It is a decoder that uses. 26 is an internal code decoder, 27 is a changeover switch, 28 is an external code decoder, and 29 is an error detection and correction unit.

30 is a frame storage unit, 31 is a data expansion unit, 32 is a digital / analog converter, and 33 is a luminance and chroma signal recovery unit. In particular, the switching switch 27 is provided with a control terminal, and a signal indicating the variable speed mode is applied to the control terminal through the control input terminal of 34.

In the operation of FIG. 7, the switching switch 27 is connected to the PB side by the variable speed mode signal applied to the control input terminal 34 in normal reproduction. Therefore, both the inner code decoder 26 and the outer code decoder 28 operate to perform error detection and correction for the lambdon error c and the burst error d in FIG. 5B.

On the other hand, in variable speed reproduction, the switching switch 27 is connected to the PS side by the variable speed mode signal applied to the control input terminal of 34. Therefore, the inner code decoder 26 does not operate, but operates only the outer code decoder 28, and does not perform error detection and correction for the random error c of FIG. 5B, but only error detection and correction for the burst era d.

As described above, by applying the present invention, the ratio of the effective data reproduced at variable speed reproduction can be improved, and error correction can be easily performed, and the image quality reproduced at variable speed reproduction can be greatly improved.

Claims (4)

A digital VT data recording method for dividing frame image data into a plurality of blocks and adding an internal error correction code and an external error correction code to the blocks, the macroblock having the smaller size of the frame image data. Dividing into; Dividing the macroblock into a plurality of blocks; Adding an internal error correction code to the divided blocks; And adding an external error correction code to the block to which the internal error correction code is assigned. In the digital VT data reproducing method of reproducing video data from data recorded by adding an internal error correction code and an external error correction code, during normal playback, error correction by an external code as well as error correction by an internal error correction code is performed. And only error correction by an external error correction code during variable-speed playback. A digital VT having an internal code decoder that performs error correction by an internal error correction code and an internal code decoder that performs error correction by an external error correction code, wherein the internal code decoder input is connected to one input terminal and the internal code decoder is connected. And a switching means having an output terminal connected to the input terminal of the code decoder to the other input terminal and having an output terminal connected to the input terminal of the external code decoder means and having a control terminal for switching and controlling the two input terminals. Device. 4. The apparatus of claim 3, wherein a signal indicating a variable speed mode is applied to the control terminal.