JPH03184493A - Reproducing signal processing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reproduced signal processing circuit applied to a rotary head type VTR.

[Summary of the invention]

The present invention provides a reproduced signal processing circuit in which a TBC is provided for a reproduced luminance signal and a low frequency converted color signal, respectively. A second noise removal circuit is provided on the output side of the second TBC for color signals, and a second noise removal circuit is provided on the output side of the second TBC for color signals, and a second noise removal circuit is provided on the output side of the second TBC for color signals. By turning on/off the operation of the noise removal circuit, it is possible to prevent a timing shift between the detection signal and the color signal.

[Conventional technology]

A rotating head type VTR is known in which a pair of magnetic heads are attached to a tape guide drum that rotates at a frame frequency, and the magnetic heads alternately contact a magnetic tape that is wound obliquely around the circumferential surface of the guide drum. TBC (
It is also known to provide a time base compensator). FIG. 3 shows the configuration around the TBC in a conventional reproduction signal processing circuit.

The FM demodulated reproduced luminance signal is supplied to a noise removal and dropout compensation circuit 31. A dropout pulse DOP is supplied to this circuit 31 to compensate for the dropout period. Further, the circuit 31 performs contour correction of the luminance signal and noise removal using vertical correlation. The output signal of this noise removal and dropout compensation circuit 31 is T
It is supplied to BC32. The TBC 32 converts the reproduced luminance signal into a digital signal, writes the digital signal to the buffer memory with a write clock synchronized with the reproduction side,
The configuration is such that digital signals are read from the buffer memory using a stable read clock. The reproduced luminance signal is supplied to the TBC controller 33 in order to form a write clock synchronized with the reproduced luminance signal. Also,
A stable read clock is generated based on the output signal of crystal oscillator 34.

The low frequency conversion color signal in the reproduced signal is sent to the TBC 35.
be provided. A TBC controller 33 is provided in common for the TBCs 32 and 35. The output signal of the TBC 35 is supplied to a frequency conversion circuit 36. The output signal of the frequency conversion circuit 36 is supplied to a noise removal circuit 37.

The noise removal circuit 37 performs noise removal operations such as crosstalk removal.

[Problem to be solved by the invention]

A cyclic comb filter is provided in each of the noise removal and dropout compensation circuit 31 and the noise removal circuit 37, and vertical correlation can be used to perform noise removal. However, if this noise removal operation is performed even in the vertical non-correlation portion, color deterioration occurs in the vertical direction. Therefore, the presence or absence of vertical correlation is detected from the difference between the reproduced luminance signal through a 1H (H: water period) delay circuit and the non-delayed signal, and when the level of the difference signal is large, that is, there is no vertical correlation. in some cases,
It has been proposed to stop the color signal noise removal operation.

However, since the TBCs 32 and 35 are provided, even if the noise removal and dropout compensation circuit 31 detects the presence or absence of vertical correlation, the noise removal circuit 37
35, a problem arises in that the timing of the detection signal deviates from the time axis compensated color signal.

Therefore, it is an object of the present invention to provide a reproduced signal that prevents a timing shift between the detection signal and the color signal when turning on/off the noise removal operation of the color signal using the detection signal obtained from the luminance signal. The purpose of this invention is to provide a processing circuit.

[Means to solve the problem]

This invention comprises: an FM demodulation circuit (3) to which an FM modulated luminance signal in a reproduced signal is supplied; a first TBC (10) to which a reproduced luminance signal from the FM demodulation circuit (3) is supplied; and a reproduction signal. a second TBC to which a medium low-pass converted color signal is supplied;
(11), a frequency conversion circuit (20) provided on the output side of the second TBC (11), and a reproduced luminance signal from the first TBC (10) supplied,
A first noise removal circuit (15) that removes noise from the reproduced luminance signal, performs vertical correlation detection, and generates a detection signal corresponding to the presence or absence of vertical correlation; and a reproduced color signal from the frequency conversion circuit (20). is supplied,
It consists of a second noise removal circuit (21) that removes noise from the reproduced color signal and stops the noise removal operation when it is detected by the detection signal that there is no vertical correlation.

[Effect]

Vertical correlation is detected based on the luminance signal obtained at the output side of TBCIO, and a detection signal corresponding to the presence or absence of correlation is formed. Since this detection signal turns on/off the operation of the noise removal circuit 21 provided on the output side of TBCll, it is possible to prevent timing deviation between the detection signal and the color signal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, 1 is F separated from the reproduced signal.
This is an input terminal for an M-modulated luminance signal.

The limiter 2, the FM demodulation circuit 3, and the de-emphasis circuit 4 perform FM demodulation of the FM modulated luminance signal. The reproduction luminance signal from the de-emphasis circuit 4 is supplied to the mixer 5, and the pseudo vertical synchronization signal QVD is inserted in the mixer 5 only during variable speed reproduction.

A switching pulse Ps is supplied from a terminal 7 to the pseudo vertical synchronization signal generation circuit 6 . switching pulse Ps
is a pulse signal that is inverted for each field in synchronization with the rotational phase of the tape guide drum, that is, the magnetic head.

The switching pulse Ps is formed from the output signal of a magnetic rotation detector associated with the tape guide drum. The pseudo vertical synchronization signal generation circuit 6 generates a pseudo vertical synchronization signal QVD whose timing is delayed by a predetermined time from the rising edge and the falling edge of the switching pulse Ps. The pseudo vertical synchronization signal QVD is supplied to the mixer 5 via the gate circuit 8.

The gate circuit 8 is supplied with a control signal from a terminal 9 indicating that variable speed reproduction is in progress. Variable speed playback operations include slow playback, still playback, cue playback, review playback, and the like. Therefore, the pseudo vertical synchronization signal Q is supplied to the mixer 5 via the gate circuit 8 only during these variable speed playback operations.
VD is supplied.

The output signal of the mixer 5 is supplied to the TBCIO and TBC controller 12. TBCII regarding color signals is also provided. A low frequency conversion color signal is supplied to this TBCII from an input terminal 13. A write timing signal and a read timing signal are commonly supplied to the TBCIO and 11 from the TBC controller 12.

For example, TBCIO and 11 have an FI with a capacity of 5 lines.
An FO memory is provided for each. A luminance signal and a low frequency conversion color signal digitized at a sampling frequency of 4 fsc (fsc: color subcarrier frequency) are written into this memory. The write-side clock is generated by a PLL based on a horizontal synchronization signal separated from the reproduced luminance signal.

The read-side clock is formed based on the output signal of the crystal oscillator 14. Signals read from the TBCIO and 11 memories are converted into analog signals by the D/A converters, respectively.

The time-base compensated luminance signal from TBCIO is supplied to the noise removal and dropout compensation circuit 15. Dropout is detected from the level of the reproduced signal, and a dropout pulse with a pulse width corresponding to the dropout period is generated. For this dropout pulse, the same time axis compensation as for the luminance signal and the low-frequency conversion color signal is performed using, for example, TBCII for the color signal. The time-base compensated dropout pulse is supplied to a noise removal and dropout compensation circuit 15.

Regarding the luminance signal, noise is removed using a cyclic comb filter. Further, the noise removal and dropout compensation circuit 15 is provided with a correlation detector that generates a detection signal indicating the presence or absence of vertical correlation from the level of the difference signal between the IH (H: horizontal period) delayed signal and the non-delayed signal. ing. This detection signal is supplied to the noise removal circuit 21 (Jj) regarding the color signal. The reproduced luminance signal from the noise removal and dropout compensation circuit 15 is taken out to the output terminal 16 and is also supplied to the mixer 17. A composite color video signal is taken out at the output terminal 18.

Note that since noise removal for the luminance signal causes deterioration of vertical resolution, it is designed to work only when the tape speed during playback is slow.

The low frequency conversion color signal from Tl3C11 is sent to the frequency converter 20.
is supplied to In the frequency converter 20, the low frequency converted color signal is converted to the original carrier frequency fsc (in the NTSC system, fs
c = 3, 58 MHz) signal. The carrier color signal from frequency converter 20 is supplied to noise removal circuit 21 . The noise removal circuit 21 includes a crosstalk removal circuit, a noise removal circuit using a cyclic comb filter similar to that for the luminance signal, a contour compensation circuit, and the like.

The above-mentioned detection signal obtained from the reproduced luminance signal is supplied to the noise removal circuit 21 regarding the carrier color signal, and the vertical direction non-correlation section stops vertical noise removal.
Vertical color degradation is prevented. The reproduced color signal from the noise removal circuit 21 is taken out to the output terminal 19 and is also supplied to the mixer 17.

In one embodiment described above, de-emphasis circuit 4 produces a reproduced video signal as shown in FIG. 2A. Figure 2A
For simplicity, illustration of the horizontal synchronizing signal and equivalent pulses is omitted. Figure 2B shows the switching pulse P
Indicates s. The switching pulse Ps is a pulse that is inverted for each field, and its rising edge and falling edge are specified to have timings TI (for example, 7H) earlier than the vertical synchronizing signal VD of the reproduced video signal.

As shown in FIG. 2C, the pseudo vertical synchronization signal generation circuit 6 has an edge delayed by T2 (Tt>T2) from each of the rising edge and falling edge of the switching pulse Ps, and is slightly later than the vertical synchronization signal VD. A wide pseudo vertical synchronization signal QVD is generated. During variable speed playback, an ill-like vertical synchronization signal QVD is supplied to the mixer 5 through the gate circuit 8. Therefore, as shown in the second diagram, a reproduced luminance signal in which a pseudo vertical synchronizing signal QVD is inserted in place of the original vertical synchronizing signal VD is obtained from the mixer 5. During variable speed playback, the vertical synchronization of the monitor is stabilized by the pseudo vertical synchronization signal QVD.

〔Effect of the invention〕

In this invention, the presence or absence of vertical correlation is detected on the output side of the TBC, and based on this detection, the on/off of the color signal noise removal operation provided on the output side of the TBC is controlled. It is possible to prevent timing deviations from occurring between the two.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the pseudo vertical synchronization signal insertion operation of this embodiment, and FIG. 3 is a block diagram of a conventional configuration. . Description of main symbols in the drawings 1: Input terminal for FM modulated luminance signal, 5: 1 xer-1 6: Pseudo vertical synchronization signal generation circuit, 10.11: TBCl 13: Input terminal for low frequency conversion color signal.

Claims (1)

[Claims] An FM demodulation circuit to which an FM modulated luminance signal in a reproduced signal is supplied; and a first FM demodulation circuit to which the reproduced luminance signal from the FM demodulation circuit is supplied.
, and a second TBC to which the low-frequency converted color signal in the reproduced signal is supplied.
BC, a frequency conversion circuit provided on the output side of the second TBC, and a reproduced luminance signal from the first TBC, which removes noise from the reproduced luminance signal and performs vertical correlation detection. , a first noise removal circuit that generates a detection signal corresponding to the presence or absence of the vertical correlation, and a reproduced color signal from the frequency conversion circuit, which removes noise from the reproduced color signal and removes noise from the detection signal. A reproduced signal processing circuit comprising: a second noise removal circuit that stops a noise removal operation when it is detected that there is no vertical correlation.