JPS6153890A - Time base error correcting device - Google Patents

Abstract

PURPOSE:To provide a time base error correcting device with a simple circuit by combining a color signal processing circuit having the specified function and a digital correcting circuit to remove fluctuation of a time base. CONSTITUTION:The color signal separated in a Y/C separating circuit 1 is supplied to the color signal processing circuits ICCA and ICCB. Both the ICCA and ICCB have a relationship of interleave to a luminance signal, and forms two carrier chrominance signals in which the phase of a color signal is reverse processed. These two carrier chrominance signals are selected in the specified order in a switch 11, supplied to a Y/C adding circuit 19, and added to the luminance signal. An output of the Y/C adding circuit 19 is supplied to the digital correcting circuit 3 to remove a jitter ingredient. With only one digital correcting circuit, the time base error correcting device with a simple circuit can be provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a time axis error correction device for removing time axis fluctuation components from a reproduced video signal, and in particular for variable speed reproduction of a PAL video signal. The present invention relates to a time axis error correction device useful when

[Conventional technology]

At broadcasting stations, the jitter components that occur during playback are usually removed from reproduced video signals with time axis fluctuations using a time axis error correction device (hereinafter referred to as TBC), and the signals are output in synchronization with standard television signals. is being carried out.

However, when one of the color signals (B-Y) is inverted line by line, as in PAL composite television signals, and the signal is reproduced at a variable speed, the color signal does not match the specified value. Since the output is not necessarily in order, it is necessary to invert the phase of the reproduced color signal every few fields.

Figure 4 shows the conventional NTSC that can be applied during such variable speed playback.
This figure shows a block diagram of the TBC in the system, where 1 is a Y/C filter that includes a low-pass filter 1a that separates the input reproduced video signal from Y/C, and a band-pass filter 1b.
C separation circuit; 2 is a synchronous burst signal separation circuit; 3 is a digital correction circuit for removing time axis fluctuation; as is well known, the A/D converter 3a and main memory 3B
, D/A converter 3c, write clock generator 3d
, a control circuit 3e that controls clock signals for writing and reading data, a read clock generator 3f, and the like.

Reference numeral 4 denotes a frequency dividing circuit for frequency dividing a clock signal having a jitter component, and a frequency dividing circuit 4 for locking the conversion frequency generating circuit 5 for converting the color signal component obtained from the Y/C separation circuit 1 into a low frequency range. forming a signal. The conversion frequency generation circuit 5 includes a burst gate circuit 5a, a phase comparator 5b, a voltage controlled oscillator 5c, a frequency converter 5d, and a bandpass filter 5e.
It is composed of

In this case, the signal obtained from the frequency dividing circuit 4 contains a jitter component, and the voltage controlled oscillator 5c locked with this signal also contains a jitter component.

Incidentally, the color signal component obtained from the bandpass filter 1b has jitter components removed by, for example, an Arc circuit on the playback device side, and is then sent to the frequency converter 6.
is mixed with the output of the conversion frequency generation circuit 5 and converted to a low frequency by the low-pass filter circuit 7 (for example,
(4.43M in the case of PAL) (z+688KHz), a low-range color signal component containing a jitter component similar to the luminance signal is obtained.

Then, similar to the luminance signal, this low-frequency color signal component is
/D converter 8a, memory 8b, D/A converter 8c
The color signal is input to a digital correction circuit 8 that removes the jitter component of the color signal, and the jitter component is removed.

9.10 is the first and second frequency conversion that converts the color signal converted to the low frequency band again to the high frequency band (4.43 MHz) and forms two carrier color signals in which the phase of the color signal is reversed. The circuit is shown, voltage controlled oscillators 9a, 10a,
Frequency converter 9b.

10b, bandpass filter 9c*10c, burst gate circuit 9d, TOd, phase comparator 9e.

10e. And phase comparator 9
e is supplied with a synchronous color subcarrier signal extracted from a standard video signal by a separation circuit 12, and the other phase comparator 10e is supplied with a signal whose phase has been adjusted in a phase shift circuit 13. . In addition, 11 is the said 1st. A switch circuit for selectively taking out the carrier color signal output from the second frequency conversion circuit 9 and 10 is shown, and this switch circuit 11 is controlled by the color signal inversion control signal C·■ output during variable speed reproduction. There is.

14 is a burst signal addition circuit; 15 is an addition circuit that adds a carrier color signal that has been inverted by the switch circuit 11 to the luminance signal from which jitter components have been removed; 16 is a circuit that adds a synchronization signal; and 17 is a synchronization circuit. A signal separation circuit is shown.

Since this time axis error correction device (TBC) is configured as described above, the color signal component separated from the reproduced video signal is once converted into a low-frequency color signal in the frequency converter 6, and then converted into a luminance signal. After the same jitter is added, the jitter component is removed in the digital correction circuit 8, and the signal is converted into a high-frequency color signal again. During conversion, two carrier color signals with reversed phases are formed, and these are selectively taken out by the switch circuit 11 so that the order of the color signals output during variable speed reproduction is in a predetermined order. , it is possible to obtain a screen without hue shift even during variable speed playback.

However, in this device, two digital correction circuits (3), (
8) is required, which increases the price and requires circuits for frequency conversion on the input side and the output side, respectively, making the configuration complicated.

FIG. 5 shows a block diagram of a time axis variation error correction device (TBC) showing another conventional example (for example, Japanese Patent Application Laid-Open No. 153518/1983) which has been adopted to solve the above-mentioned problems. The same parts as in FIG. 4 are given the same reference numerals.

In the case of this device, the reproduced composite video signal is separated into a color signal component and a luminance signal component in the Y/C separation circuit 1, and the separated color signal component (carrier color signal) is first interleaved with the luminance signal. Convert to the color signal in

In other words, the color signal component from which the jitter component has been removed by the A20 circuit on the playback device side is converted into a low frequency color signal by the first frequency converter 6a, passed through the bandpass filter 7a, and then passed through the second frequency converter 6a. The frequency converter 6b converts the frequency back to the original high frequency, and the bypass filter 7b
It is added to the luminance signal in the Y/C adder circuit 19 via the Y/C adder circuit 19.

At this time, the first. The conversion frequencies (f+, , f2) applied to the second frequency converters 5a, 6b are used to convert synchronized burst signals of luminance signals having jitter components into separation circuits 2. Since the signal is extracted from the frequency dividing circuit 4 and inputted to the conversion frequency generating circuit 5, the carrier color signal contains the same jitter component as the luminance signal due to this double hetero gain circuit.

Then, the Y/C adder 19 adds the interleaved luminance signal and carrier chrominance signal, and inputs the signal to the digital correction circuit 3 to remove the jitter component of the video signal in order to remove time axis fluctuations. Further, in order to apply the above-described phase inversion to the carrier color signal, a second Y/C separation circuit 2 is provided.
0 to low pass filter 20 & band pass filter 20
b, and supplies the carrier color signal extracted from the bandpass filter 20b to the color signal inversion circuit 21.

As shown in Figure 6, the PAL system chroma signal CPAL is converted to a point P-P' on the R-Y axis every horizontal period, so the inversion of the color signal forms the R-Y signal. What is necessary is to invert the V signal forming the B-Y signal with respect to the U signal forming the B-Y signal.

Therefore, in this TBC, the carrier color signal is inputted to a decoder 21a that demodulates the V signal and a decoder 21b that demodulates the U signal, and both are passed through low-pass filters 22a and 22b to an encoder 23a for the V signal and an encoder 23 for the U signal.
Enter b.

Then, the V signal is inverted modulated by the signal output from the color subcarrier generator 26. At this time, the phase of the ■ signal is inverted in a predetermined order by the color signal inversion processing signal CIIH. Then, in the UV signal addition circuit 27, a carrier color signal subjected to inversion processing is formed.

In addition, 24 is a decoder error detection circuit, 25 is a demodulation carrier generator, and the color subcarrier generator 26 is the separation circuit 1.
2 are also synchronized with the extracted standard color subcarrier.

The carrier color signal outputted from the UV signal addition circuit 27 and subjected to inversion processing is passed through a bandpass filter 28 to the Y/C
It is added to the luminance signal in an adder circuit 15, and a synchronization signal and a burst signal are added in a synchronization signal addition circuit 16 and output.

18 is a delay circuit whose processing time is approximately equal to the color signal processing time, and 29 is a delay circuit which is approximately equal to the inversion processing time.

In this conventional device, a carrier chrominance signal that is in an interleaved relationship with the luminance signal is first formed by a double hetero gain circuit on the input side, and both the luminance signal and chrominance signal components restored to the interleaved relationship are changed over time. Since it is input to the digital correction circuit 3 that removes the
Although there is an advantage that there is only one digital correction circuit (3) including memory, there is a problem that the video signal deteriorates significantly because it is necessary to perform Y/C separation twice.

Furthermore, since decoder and encoder means are required for color signal inversion processing, the circuit configuration remains complicated.

[Problem that the invention seeks to solve]

The present invention was made to solve these conventional problems, and is useful for removing time axis fluctuation components from a signal when a PAL television signal is recorded and reproduced using a low-frequency conversion type. The present invention provides a time axis error correction device that can simultaneously perform color signal inversion processing and interleave relationship restoration.

[Means for solving problems]

FIG. 1 shows a block diagram of the main parts of a time base error correction device (TBC) according to the present invention, and parts having the same functions as those in the prior art are designated by the same reference numerals.

I CCA and I CCB surrounded by dashed-dotted lines in this figure
denotes first and second color signal processing blocks, each of which includes a first frequency converter 30, 40 and a low-pass filter 31.
．． 41, second frequency converter 32 42, band pass filter 33, 43, burst gate circuit 34, 44, phase comparator 35, 45, voltage controlled oscillator 36, 46, frequency dividing circuit 37 47, frequency converter 38, 48, and band pass filters 39, 49.

Note that 50 is a phase shifter, which is not necessary in terms of structure.

The time axis error correction device of the present invention forms two carrier color signals which are in an interleaved relationship with the luminance signal and have the phase of the brown signal reversed by the color signal processing blocks ICCA and ICCB, and switch circuit 11
The selected signals are selected in a predetermined order by , and inputted into the digital correction circuit 3 which adds them to the luminance signal again and removes jitter components.

[Effect]

The operation of the color signal processing block I CCA will be explained below.

The composite (non-interleaved) PAL video signal input to the input terminal T is passed through the low-pass filter 1a.
The signal is separated into a luminance signal and a color signal by a bandpass filter 1b.

The frequency fsc of the separated carrier color signal is mixed with the output frequency fa of the voltage controlled oscillator 36 in the first frequency converter 30, and passed through the low-pass filter 31 to fa-f.
The sc component is extracted. This signal is generated by frequency-dividing (1/
4) The resulting signal is mixed in the frequency converter 38 to obtain a band pass filter, and the mixed frequency obtained by mixing in the second frequency converter 32 is extracted from the low-pass filter 31.

The signal is compared with the frequency f sc ' of the color subcarrier in a phase comparator 35 to control the frequency of the voltage controlled oscillator 36 such that f sc '.

Therefore, a carrier color signal containing a jitter component is output from the bandpass filter 33, and a carrier color signal containing a jitter component is output.
The interleaving relationship with the 1Ill degree signal is restored.

Similarly, in the color signal processing circuit I CCB at t52, since the color subcarrier f sc ' having a jitter component is input to the phase comparator 45 and frequency converter 48 via the phase shifter 50, voltage control is performed. If the oscillation frequency of the oscillator 46 is fb, it is controlled as follows, and the bypass filter 43 outputs di-
A carrier color signal having a color component is output.

However, in the second color signal processing block ICCB, the bandpass filter 49 outputs the output frequency of the number converter 42 as follows. Then, the oscillation frequency fb of the voltage controlled oscillator 46 is controlled so as to satisfy the following equation.

Therefore, as shown below, the carrier color signal output from the first color signal processing block ICCA and the carrier color signal output from the second color signal processing block ICCB have their V-axes reversed. It has become a thing.

That is, in the above-mentioned FIG. 6, the chroma signal CPAL of the PAL system is CPAL:Usin ωs t±VCO5(1)S
t (ωs = f sc).

(Si indicates that the V-axis is inverted for each line.) This signal is, CPAL= Cs1n (ωst±φ) . . . old and old, group, ■.

When the color signal of the 0th equation is frequency-converted using the oscillation frequencies fa, fb, (ωa, ωb) of the voltage controlled oscillator 36°46, the first frequency converter 30 obtains Ca = Cs.
1n (ωst±φ) X5inωat(ωa=2πf
a) -cos ((ωs-ωa)t±φ)] is obtained, and when only the low-frequency signal is extracted by the low-pass filter 31, the following is obtained.

On the other hand, in the second color signal processing block I CCB, similarly, from the first frequency converter 40, Cb = C5in
(ωst±φ) X5in Cb tfeast(ω
S-ωb)t±φ)] is obtained, and when only the low range is extracted by the low-pass filter 41, the following is obtained.

The 0th equation is converted to +ωa) by the second frequency converter 32.
tφ)] Therefore, when only the component of ωS' is extracted in the bandpass filter 33, the following equation is obtained, and a carrier color signal containing the frequency component of ωS', that is, the jitter component is output.

On the other hand, when the signal of the 0th equation is applied to the second frequency converter, +ωb) is converted to φ)] +sin (ωS ′乎φ)] When only the ωS ′ component is extracted by the bandpass filter 43, l is obtained.

C=-Cs+n (ωs ′ is φ) ・・・・・・
・・・・・・■.

As shown in I-L, 1st. Second color signal processing block IC
Comparing the carrier color signals of the 0th expression and the 0th expression extracted from CA and ICCB, it is found that the term φ indicating the phase is inverted with respect to the 0th expression and the 0th expression, and jitter It can be seen that an inverted version of the brown signal is obtained, including the component (ωs').

Therefore, the first. Second color signal processing block ICCA
, the carrier color signal output from the ICCB is selectively taken out by the switch circuit 11 and supplied to the Y/C addition circuit 19, which adds the color signal having the desired phase in any field to the luminance signal. can do.

The composite video signal thus formed is input to a digital correction circuit 3 that removes time axis fluctuations to remove jitter components, and then a synchronization signal and a burst signal are added to the composite video signal to create a standard video signal. It will be possible to output it as .

〔Example〕

FIG. 2 is a block diagram of a color signal processing circuit showing another embodiment of the present invention, in which the color signal processing blocks ICCA of FIG.
This is a simplified version of ICCB.

That is, the first frequency converter 30, the low pass filter 31 . The circuit is simplified by sharing the burst gate circuit 34, phase comparator 35, voltage controlled oscillator 36, frequency dividing circuit 37, frequency converter 38, etc. with the second color signal processing block ICCB.

In this embodiment, as shown in the figure, a low-pass filter 1b
A color signal component component sc that does not include a jitter component is extracted from the output frequency pass filter 31 of the voltage controlled oscillator 36 in the first frequency converter 30 .

The frequency mixer 38 uses a color subcarrier f sc '' with a jitter component extracted from the luminance signal and a frequency dividing circuit, and the bandpass filter 49 uses a lower band wave frequency converter 32.4.
2.

Therefore, carrier color signals containing jitter components fsc'' and fsc'' are respectively formed from the bandpass filters 33 and 43.

As mentioned above, this signal maintains an interleave relationship with the luminance signal, and is the inverted version of the V-axis of the brown signal. Therefore, if this signal is taken out alternately for each frame by the switch circuit 11, the colors are changed in a predetermined order. An inverted signal is obtained, and as described above, an image signal without hue shift can be obtained during variable speed reproduction.

FIG. 3 shows a further simplified version of the color signal processing circuit shown in FIG. 2, with the second frequency converter 42 and bandpass filter 43 omitted.

Therefore, the inversion operation of one color signal is performed by the bandpass filter 39.
．． 49 is selected by the switch circuit 11 and inputted to the second frequency converter 32.

Since the relationship of conversion frequencies in this circuit is the same as that in FIG. 2, detailed explanation thereof will be omitted.

In the above embodiments, the output frequencies of the voltage controlled oscillators 36 and 46 were fa and fb in the case of FIG. 1, but can be seen as follows.

Also, in this circuit, if the frequency dividing circuit 37.47 is ÷n, , and the same wave number as in FIGS. 2 and 3 will be obtained.

Note that n is not particularly limited as long as it is an integer.

〔Effect of the invention〕

As explained above, in the time axis error correction device of the present invention, in order to remove time axis fluctuations during recording and reproduction of PAL television signals, etc., the chrominance signal is interleaved with the luminance signal by the chrominance signal processing circuit. Two carrier color signals whose phases have been inverted are formed, selectively extracted in a predetermined order, added to the luminance signal again, and jitter components removed. Therefore, unlike the conventional method, there is no need to use a digital correction circuit that performs color signal jitter processing, and the circuit can be significantly simplified, and the Y/C
Since separation is performed only once, there is little signal deterioration. Further, since less processing is required for the chroma signal, there is an advantage that the chroma signal does not deteriorate and adversely affect the image.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing a time axis error correction device of the present invention, Fig. 2 is a block diagram showing an embodiment of the time axis error correction device of the invention, and Fig. 3 is a block diagram showing an embodiment of the time axis error correction device of the invention. is a block diagram showing another embodiment of the time axis error correction device of the present invention, FIG. 4 is a block diagram showing a conventional time axis error correction device, and FIG. 5 is a block diagram showing another conventional time axis error correction device. FIG. 6 is a block diagram showing the inversion of the chroma signal (RY), (B-Y)
It is a coordinate diagram. In the figure, 1 is a Y/C separation circuit, 2 is a synchronous burst signal separation circuit, 3 is a digital correction circuit, 4 is a frequency division circuit, 5 is a conversion frequency generation circuit, 6 is a frequency converter, 7 is a low-pass circuit, 8 is a digital correction circuit, 9 is a first frequency converter, 1
0 is a second frequency converter, 11 is a switch circuit, 12 is a separation circuit, 13 is a phase shift circuit, 14 is a burst signal addition circuit, 15 is an addition circuit, 16 is a synchronization signal addition circuit,
17 is a synchronization signal separation circuit, 18 is a delay circuit, and 19 is a Y/
C addition circuit, 20 is a Y/C separation circuit, 21 is a color signal inversion circuit, 22 is a low-pass filter, 23 is an encoder, 2
4 is a decoder error detection circuit, 25 is a demodulation carrier generator, 26 is a color subcarrier generator, 27 is a UV signal addition circuit, 28 is a bandpass filter, 29 is a delay circuit, 30
is a first frequency converter, 31 is a low-pass filter, 32
is a second frequency converter, 33 is a bandpass filter, 3
4 is a burst gate circuit, 35 is a phase comparator, 36 is a voltage controlled oscillator, 37 is a frequency divider circuit, 38 is a frequency converter,
39 is a band pass filter, 4o is a first frequency converter, 41 is a low pass filter, 42 is a second frequency converter, 43 is a band pass filter, 44 is a burst gate circuit, 45 is a phase comparator, 46 is a voltage A controlled oscillator, 47 a frequency dividing circuit, 48 a frequency converter, 49 a band pass filter, and 50 a phase shifter. Procedural amendments stamped) January 9, 1985

Claims (1)

[Claims] In an apparatus for reproducing a PAL television signal in which a chrominance signal has been converted to the lower frequency side of a luminance signal and removing a jitter component included in the chrominance signal and removing time axis fluctuations of the reproduced PAL television signal. , a Y/C separation circuit that separates a luminance signal and a chrominance signal from the reproduced PAL television signal, and a conversion signal formed based on a synchronization signal included in the separated luminance signal to convert the chrominance signal into A color signal processing circuit is provided which converts the frequency and forms a color signal restored in an interleaved relationship with the luminance signal, and which controls the PAL television signal so that the color sequentiality of the PAL television signal is maintained during the frequency conversion. 1. A time-base error correction device, characterized in that said color signal whose color characteristics are maintained is added to said luminance signal again, and then inputted to a digital correction circuit that removes time-base fluctuations.