JP2568762B2 - Error rectifier for color video signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video signal error corrector in a digital VTR for recording and reproducing a color video signal.

[0002]

2. Description of the Related Art In a digital VTR, when an error exceeding the error correction capability occurs during reproduction, correction is performed. The error correction will be described below using a conventional example. FIG. 2 shows an example of a block configuration of a recording and reproducing circuit of the digital VTR.

First, the recording system will be described. Input terminal 13
The analog video signal input from the A / D converter 1
4 is sampled at a frequency (4Fsc) four times the subcarrier frequency (Fsc) and quantized to 8 bits. Then, the parity of the outer correction code is added by the outer ECC encoder 15, and is written to the next shuffling memory 16. At this time, the video data is written to the shuffling memory 16 at an address different from the order in which the video data was input in time series, and the reading is performed in a fixed order. In this way, by changing the order of the data and recording the data on the tape, when a burst error occurs during reproduction, the error is dispersed on the TV screen, so that error correction is facilitated. The write address of the shuffling memory 16 is determined by the synchronization signal separation circuit 17.
The sync signal separated from the input video signal is input to the field start pulse generator 18 and is generated based on the field start pulse generated here. Next, data is read from the shuffling memory 16 in units of blocks each consisting of a predetermined number of samples, and parity of an inner correction code is added in the inner ECC encoder 19 for each block. After that, the SYNC / ID adder 20 adds an ID indicating the field number and the block number generated by the SYNC for determining the start timing of the data block and the ID generator 21. And SYNC I
The output of the D adder 20 is a channel encoder 22, which modulates the modulated data into a data sequence convenient for the magnetic recording and reproducing system. Finally, the data is recorded on the magnetic tape 25 via the recording amplifier 23 and the recording head 24. Next, regarding a reproducing system, data reproduced through a reproducing head 26 and a reproducing amplifier 27 is returned to data before modulation in a channel decoder 28. And the inner E
The CC decoder 29 performs inner error correction by the inner correction parity added at the time of recording,
The data is written to the next deshuffling memory 30. This write address is generated based on the SYNC and ID detected by the SYNC / ID detector 31. The read address of the deshuffling memory 30 is based on the field start pulse generated by the synchronization signal separation circuit 33 and the field start pulse generator 34 from the reference signal input to the reference signal input terminal 32. At the same time, it is made just like when recording. In this way, the data read from the deshuffling memory 30 is returned to the data in the same order as the data sequence at the time of input. This data is subjected to outer error correction by the outer ECC decoder 35 based on the outer correction parity added at the time of recording and the error flag sent from the inner ECC decoder 29. Then, the error corrector 36 interpolates the errors that could not be corrected by the inner and outer correction circuits with normal samples around the error samples. Finally, the signal is converted back to an analog video signal by the D / A converter 37 and output from the output terminal 39.

[0004] When such shuffling is applied to recorded data, the reproducing head becomes one as in the high-speed search mode.
In the case where data is simultaneously reproduced from a plurality of tracks during one scan, a video signal of one field to be reproduced is synthesized from signals of a plurality of fields having different color frames. FIG. 3 shows this state. In FIG. 3, 40 is a magnetic tape, 41 is a trajectory of a head in a search mode, 1A, 1B, 1C,.
4A, 4B, and 4C are recording tracks.
An example is shown in which one field (1 V) is constituted by a track. By the way, in order to correctly reproduce the color in the reproduction in the search mode, it is necessary to separate the luminance signal component Y and the color signal component C and to perform processing such as inversion of the polarity of the color signal. However, since the shuffling is performed on a sample basis, it is impossible to separate the chrominance signal component and the luminance signal component from the composite signal as described above. Therefore, in order to solve this problem, the following contrivance has been made regarding the writing of data to the shuffling memory. That is, samples having the same subcarrier phase are always written to the same address of the shuffling memory in all the fields. This is illustrated in FIG. The subcarrier phase of the NTSC color video signal makes one cycle in four fields. When recording of each field is started from the ninth line in the first field, the eighth line in the second field, the ninth line in the third field, and the eighth line in the fourth field, the color frame A and the color frame B The phase of the subcarrier is inverted. Therefore, in order to align the subcarrier phases on the shuffling memory between the color frame A and the color frame B, the phase of the field start pulse of the color frame B is set to 2 with respect to the color frame A as shown in FIG. I'll shift only the sample. By doing so, the deshuffling memory 3 can be used during reproduction in the search mode.
Samples having the same subcarrier phase are written at the same address of 0, so that the luminance signal and the chrominance signal can be separated. That is, the above field start
The pulse and the subcarrier phase of the signal read from the deshuffling memory 30 always have a fixed relationship.

Next, the error retouching device 36 shown in FIG.
I will explain a little in detail. FIG. 5 shows a block diagram of the error retoucher 36. In the figure, 42 is a data input terminal, 43 is an error flag input terminal, 45 clock input terminal, 46 is a two-dimensional modifier, 47 is FIFO, and 48 is 1 /
A 910 frequency divider, 49 is a 1/262 frequency divider, 50 is a signal switch, and 51 is an output terminal. In FIG. 5, the two-dimensional retoucher 46 sets a sample with an error flag
Interpolation is performed by normal surrounding samples in the same field as the sample. Next, the error sample that could not be modified by the two-dimensional modifier 46 is replaced with the in-phase sample of the subcarrier one field before. That is, NT
In the case of the SC color video signal, the sample is replaced with the sample of 262 lines before. FIG. 6 illustrates this. That is, the frequency 4Fsc clock input to the clock input terminal 45 is frequency-divided by 1/910 by the frequency divider 48 to generate a line cycle signal, which is further frequency-divided by 1/262 by the frequency divider 49 to 262. A signal of a line cycle is generated, and the signal is input to a write start WST and a read start RST of the FIFO 47. In this way, the FIFO
The output of 47 is a signal delayed by 262 lines with respect to its input. When the error flag output from the two-dimensional corrector 46 is "0", the signal switch 50 falls to the side b, and when the error flag is "1", the signal switch 50 falls to the side a.
Thus, a sample that could not be two-dimensionally modified by the conventional modification method was always replaced by a sample before 262 lines.

[0006]

However, in a search mode in which a plurality of fields are mixed, or in a variable speed reproduction mode in which the same field is continuous or a field is skipped, a sample 262 lines before is a signal having the same subcarrier phase. Will not always be.
Therefore, the conventional method in which the sample is fixedly replaced with the sample 262 lines before has a problem that a retouching error occurs.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. Even during variable speed reproduction, a color video signal of a color video signal which can be replaced with a sample which is closest to the previous one field and has the same subcarrier phase can be replaced. It is intended to provide an error rectifier.

[0008]

According to the present invention, there is provided a color video signal error rectifier according to the present invention, comprising: a signal storage means capable of storing one or more fields of a signal ; Input of signal storage means
A signal for replacing the previous signal with the signal output from the signal storage means.
Signal replacement means and a reset signal every 262 horizontal scanning cycles.
A first reset signal generating means for generating a field of
Reset signal for each field at the same timing as the recording start point
A second reset signal generating means for generating a signal, and an output of the first reset signal generating means during normal reproduction, and an output of the second reset signal generating means during variable speed reproduction .
And a reset signal switching means for selecting an output, reset
Signal recording by the reset signal selected by the reset signal switching means.
Reset the write address and read address of the storage
Cut.

[0009]

According to the present invention, the output of the FIFO becomes the same with respect to the input and the subcarrier phase irrespective of the reproduction mode of the normal reproduction or the variable-speed reproduction according to the above-described configuration. Correction is possible.

[0010]

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

FIG. 1 is a block diagram showing the configuration of an error retoucher according to an embodiment of the present invention. In FIG. 1, 1 is a data input terminal, 2 is an error flag input terminal, 3 is a clock input terminal, 4 is a field start pulse input terminal,
5 is a reproduction mode input terminal, 6 is a two-dimensional corrector, and 7 is a FI.
FO, 8 is a 1/910 divider, 9 is a 1/262 divider,
10 and 11 are signal switches, and 12 is an output terminal. The description of the parts common to the conventional example is omitted. Signal switch 1
1 operates as follows. That is, in the normal reproduction mode, the camera falls down to the side a and performs the same operation as the conventional example. On the other hand, in the variable speed reproduction mode, the camera falls to the b side, and the WST and R
ST receives a field start pulse.
As described above, the field start pulse is always in phase with the subcarrier,
The output of O7 is equal with respect to its input and subcarrier phase. In addition, the sample to be replaced by the signal switch 10 is the sample whose spatial distance is closest to the error sample.

In the above embodiment, only the case of the NTSC system has been described, but it goes without saying that the present invention can be applied to a PAL system video signal in the same manner.

[0013]

The present invention as described above, according to the present invention includes a signal storage means capable of storing more than one field of signals, reproduction
According to the error information, the signal before input to the signal storage means is transmitted.
Signal replacement means for replacing the output signal of the signal storage means with a signal;
62 a first reset signal generating means for generating a reset signal each horizontal scanning period, the recording start point of the field data
2nd generation of reset signal for each field by imaging
And the output of the first reset signal generating means during normal reproduction, and the second output during variable speed reproduction.
And reset signal switching means for selecting the output of the reset signal generating means .
The reset signal causes the write address of the signal storage
By resetting the readout address and the readout address, it is possible to replace the error sample with a sample having the same subcarrier phase and the shortest spatial distance regardless of whether the reproduction mode is normal reproduction or variable-speed reproduction.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an error retouching device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a digital VTR in a conventional example.

FIG. 3 is a schematic diagram showing a head trajectory in a search mode of a conventional example.

FIG. 4 is a waveform diagram showing a relationship between a field start pulse and a subcarrier phase in a conventional example.

FIG. 5 is a block diagram showing a configuration of a conventional error rectifier.

FIG. 6 is a waveform chart for explaining a conventional modification method.

[Explanation of Signs] 1 Data input terminal 2 Error flag input terminal 3 Clock 4Fsc input terminal 4 Field start pulse input terminal 5 Reproduction mode input terminal 6 Two-dimensional corrector 7 FIFO 8,9 frequency divider 10,11 Signal switching 12 Data output terminal

Claims (1)

(57) [Claims] A composite color video signal is sub-keyed.
Sampling at four times the carrier frequency, and
Make the subcarrier phase of the field recording start point the same.
Error correction in digital VTR recording on tape
A signal storage means capable of storing a signal of one or more fields , and an input signal before input to the signal storage means in accordance with reproduction error information.
A signal arrangement for replacing a signal with a signal at the output of the signal storage means
Switching means; first reset signal generation means for generating a reset signal every 262 horizontal scanning cycles; and field resetting at the same timing as the recording start point of the field.
A second reset signal generating means for generating a reset signal each time, at the time of normal reproduction selects the output <br/> of the first reset signal generating means, at the time of variable speed reproduction said second reset signal generator
And a reset signal switching means for selecting the output of the unit, the reset signal selected by the reset signal switching means
Write address and read of the signal storage means
Error rectifier for color video signal to reset address .