JPS6358437B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is capable of compensating for dropouts in a reproduced video signal from, for example, a VTR, and also correcting the continuity of the carrier phase of a chroma signal during variable speed reproduction.

That is, for example, in order to compensate for dropout of a reproduced video signal from a VTR, the conventional method is as shown in FIG.

In the figure, 1 is an input terminal to which a reproduced video signal from a VTR is supplied, and the signal from this input terminal 1 is supplied to a 3.58 MHz band elimination filter 2 and a band pass filter 3, and the luminance signal Sy and chroma signal are The signal Sc is separated. These separated luminance signal Sy and chroma signal Sc are supplied to delay circuits 4 and 5 for one horizontal period, respectively. In the luminance signal Sy system, the signal from the delay circuit 4 and the signal from the filter 2 are selected by the selection switch 6. In the chroma signal Sc system, the phase of the signal from the delay circuit 5 is inverted by the inverter 7, and the signal from the inverter 7 and the signal from the filter 3 are selected by the selection switch 8. Signals from these switches 6 and 8 are mixed in a mixing circuit 9. The signal from the mixing circuit 9 and the signal from the input terminal 1 are selected by a selection switch 10 and taken out to an output terminal 11.

Therefore, when a dropout occurs in this circuit, the switch 10 is switched to the adder circuit 9 side, and one or both of the luminance signal system and chroma signal system switches 6 and 8 are switched to the delay circuits 4 and 5 side. Then, one or both of the luminance signal Sy and the chroma signal Sc is interpolated with a signal from one horizontal period earlier. Note that since the phase of the carrier wave of the chroma signal Sc is inverted every horizontal period, an inverter 7 is provided on the output side of the delay circuit 5 to perform phase correction.

Furthermore, when performing variable speed playback such as slow playback or double speed playback in the above-mentioned VTR, the same field may be played repeatedly or fields may be played back intermittently. In this case, the phase of the chroma signal is corrected so that the phase of the carrier wave of the chroma signal becomes continuous.

That is, in FIG. 2, the signal interpolated by the dropout compensation circuit described above is input to the input terminal 12.
supplied to A delay circuit 1 for one horizontal period in which the signal from this input terminal 12 constitutes a comb filter.
3 and the subtraction circuit 14, and this delay circuit 1
3 is supplied to a subtraction circuit 14, and the signal from this subtraction circuit 14 is supplied to a 3.58 MHz bandpass filter 15 to extract only the chroma signal Sc. This chroma signal Sc is supplied to the phase correction circuit 16, where phase correction processing such as phase inversion is performed so that the phase of the carrier wave is continuous. Further, the signal from the input terminal 12 is supplied to the subtraction circuit 18 through a delay circuit 17 corresponding to the time delay of the filter 15, and the chroma signal from the filter 15 is supplied to the subtraction circuit 18.
Sc is supplied to the subtraction circuit 18, the chroma signal Sc in the video signal is removed, and only the luminance signal Sy is extracted. This luminance signal Sy is supplied to a delay circuit 19 corresponding to the time delay of the correction circuit 16. Then, the chroma signal Sc from the correction circuit 16 and the luminance signal Sy from the delay circuit 19 are mixed in the mixing circuit 20, and the signal from the mixing circuit 20 and the signal from the input terminal 12 are selected by the selection switch 21. It is taken out to the output terminal 22.

Therefore, in this circuit, even during variable speed reproduction, a signal with continuous carrier phases of the chroma signal Sc is extracted, and good reproduction is always performed.

In these circuits, the separation of the luminance signal Sy and chroma signal Sc in the dropout compensation circuit (FIG. 1) does not necessarily have to be accurate, and a normal band-removal filter 2 and band-pass filter 3 are sufficient. On the other hand, in order to separate the luminance signal Sy and the chroma signal Sc in the chroma signal phase correction circuit (FIG. 2), it is necessary to accurately extract only the chroma signal Sc, and a comb filter is used. Furthermore, in the dropout compensation circuit,
It is undesirable to use a filter that includes a delay element, such as a comb filter, to include a delay element in the circuit.

For this reason, conventionally, the above-mentioned two circuits were connected in series. However, in such a configuration, each circuit repeats the luminance signal.
Separating the Sy and chroma signals Sc caused severe signal deterioration, and the large number of circuit elements required many inconveniences, such as an increase in price and an increase in the size of the device.

In view of these points, the present invention aims to integrate the above-mentioned two circuits and obtain a signal with good characteristics with a simple configuration. An embodiment of the present invention will be described below with reference to the drawings. In the drawings, parts corresponding to those in FIGS. 1 and 2 described above are designated by the same reference numerals.

In FIG. 3, the signal from the delay circuit 5 and the signal from the switch 8 are supplied to the subtraction circuit 14,
The signal from this subtraction circuit 14 is transmitted to the phase correction circuit 16.
supplied to Further, a signal from the switch 6 is supplied to a delay circuit 19. Furthermore, the signal from the input terminal 1 and the signal from the mixing circuit 20 are supplied to a selection switch 21.

Therefore, in this circuit, when the switch 8 is normally switched to the filter 3 side, the delay circuit 5 and the subtraction circuit 14 form a comb filter. The chroma signal Sc is separated accurately by this comb filter and the bandpass filter 3.
In other words, the delay circuit 5 and filter 3 replace the delay circuit 13 and filter 15, and the chroma signal
Separation of Sc is performed.

When a dropout occurs in the chroma signal Sc, the switch 8 is switched to the inverter 7 side, and a signal delayed by one horizontal period is taken out from the subtraction circuit 14 and supplied to the phase correction circuit 16. The other operations are the same as in FIGS. 1 and 2.

In this way, dropout compensation and phase correction of the chroma signal are performed.According to the present invention, the luminance signal Sy and the chroma signal Sc can be separated only once, and the chroma signal Sc during normal operation can be separated.
A signal separated by a comb filter is supplied to the phase correction circuit 16, and since the comb filter is removed during dropout compensation, a good signal can always be taken out.

Furthermore, since the delay circuit 13, bandpass filter 15, etc. are replaced by the delay circuit 5, bandpass filter 3, etc., the configuration becomes extremely simple. Furthermore, since the number of circuit elements is reduced, the price can be lowered and the device can be made smaller.

Note that since the chroma signal Sc during dropout compensation is separated only by the bandpass filter 3, the characteristics of the filter 3 must be made somewhat stricter than those of the conventional filter. However, since the dropout compensation period is only one horizontal period, there is no problem even if the separation of the chroma signal Sc during this period is somewhat inferior.

[Brief explanation of the drawing]

1 and 2 are system diagrams of a conventional device, and FIG. 3 is a system diagram of an example of the present invention. 1 is an input terminal, 2 is a band rejection filter, 3 is a band pass filter, 4 and 5 are delay circuits for one horizontal period, 6, 8, and 21 are switches, 7 is an inverter,
14 is a subtraction circuit, 16 is a phase correction signal for a chroma signal, 19 is a delay circuit, 20 is a mixing circuit, and 22 is an output terminal.

Claims (1)

[Claims] 1. The video signal is supplied to a band elimination filter and a band pass filter to separate the luminance signal and chroma signal, and the separated luminance signal and chroma signal are each supplied to a delay circuit of one horizontal period, and the luminance signal system is is provided with a first switch for selecting the signal after the delay of one horizontal period and the original signal, and the chroma signal system has a signal obtained by inverting the phase of the signal after the delay of one horizontal period and the original signal. and a subtraction circuit for extracting a difference signal between the signal from the second switch and the signal delayed by one horizontal period, and the signal from the subtraction circuit is adjusted to a predetermined phase. A video signal processing circuit which, after processing, mixes it with the signal from the first switch and extracts it.