JPH0327693A - Time base compression signal reproducing device - Google Patents

Abstract

PURPOSE:To attain compensation with a standard delay element by detecting a dropout of a reproduced time base compression signal, superimposing a frequency at the outside of a video signal band to the part, expanding and decoding the time base detecting the frequency to compensate the dropout. CONSTITUTION:A 1st analog section 2 detects a dropout of a time base compression signal, demodulates the time base compression signal to apply synchronizing separation. A digital memory section 3 applies expansion and decoding of the time base of the demodulated time base compression signal and superimposes the frequency signal for dropout generation identification. An injection section 4 generates a sampling clock signal for the time base compression signal required by the memory section 3. A 2nd analog section 5 detects the frequency for dropout generation identification in a video signal whose time base is expanded and decoded to compensate the dropout. Thus, the dropout is compensated by using a standard delay element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a time-base compressed signal reproducing device that performs dropout compensation and reproduces and restores a time-sleeve compressed signal.

[Summary of the Invention] The present invention provides a time-domain compressed signal reproducing device that performs dropout compensation to reproduce and restore a time-domain compressed signal, which detects dropouts in a reproduced time-domain compressed signal,
A frequency signal outside the video signal band is superimposed on the dropout part, the time axis is expanded and restored, and then the frequency signal is detected and dropout correction using an IH-based delay element is performed in the baseband. By doing this, dropout compensation can be performed using standard components and circuits such as delay elements.

[Prior Art] Conventionally, video signal reproducing devices for VTRs (video table recorders) suffer from lack of reproduced signals (dropouts) caused by poor contact between the head and the tape.
A dropout convenience is used to compensate for this. Dropout detection is generally performed on the reproduced signal before demodulation.

When a dropout is detected, the dropout compensator compensates by inserting the completely reproduced IH (one horizontal scan line) previous signal into the dropout portion. Strictly speaking, the signal before IH in the above does not have the same signal waveform as the dropout portion, but since the line correlation is high in the video signal, sufficient compensation can be performed visually.

In this dropout compensator, an IH delay element is used to obtain a signal before IH.

[Problems to be Solved by the Invention] However, when applying the dropout compensator of the video signal reproducing device in the above-mentioned conventional technology to a video signal whose time axis is compressed (time axis compressed signal), Because the axis is compressed, the IH period in the time axis compressed signal is shorter than the IH period in the original video signal.If the delay time of the IH delay element is not shortened at the same compression rate, the IH period in the time axis compressed signal will be shorter when the signal is inserted. A misalignment will occur.

Therefore, if the compression ratio differs, the IH delay element will be different each time, and there is a problem that standardization is impossible. Expansion and restoration of the time axis can be performed by once digitizing the time axis compressed signal, storing it in a memory, and slowing down the reading speed. During such time axis expansion/restoration processing, it is also conceivable to read the address before IH when a dropout occurs and perform dropout compensation. However, in this case, problems such as adding memory and complicating address processing are expected.

The present invention was devised to solve the above-mentioned problems, and is a time-base compressor that enables components such as circuits and delay elements used for dropout compensation of time-base compressed signals to be standardized regardless of their compression ratio. The purpose of the present invention is to provide a signal reproducing device.

[Means for Solving the Problems] The configuration of the time-domain compressed signal reproducing device of the present invention for achieving the above object includes means for detecting dropouts in the reproduced time-domain compressed signals; control means for superimposing a frequency signal outside the band of the time-domain compressed signal on the time-domain compressed signal or the digitized signal of the time-domain compressed signal when detecting the time-domain compressed signal; The invention is characterized by comprising means for detecting the frequency signal in the restored signal expanded on the original time axis, and means for performing dropout compensation for the restored signal when the frequency signal is detected.

[Operation] The present invention detects signal dropout in a reproduced time-base compressed signal, and superimposes a frequency signal outside the signal band on the dropout portion to generate an identification signal indicating that dropout has occurred. do. By detecting this frequency signal after stretching and restoring the time axis, it is possible to identify the occurrence of dropouts in the baseband, and perform dropout compensation using standard delay elements. do it like this.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. This embodiment takes as an example a case where a video signal is reproduced in which a luminance signal arranged in time series and a chroma signal arranged sequentially by color difference lines are recorded in a time axis compression method on a magnetic tape or the like. The time-base compressed signal reproducing device of this embodiment includes a magnetic head 1 for reproducing a recorded signal from a magnetic tape (not shown), a dropout of the time-base compressed signal reproduced by the magnetic head 1, and a time-base compressed signal. A first analog section 2 demodulates and performs synchronization separation, etc., and expands and restores the time axis of the demodulated time axis compressed signal, and upon detecting dropout, superimposes a frequency signal for identifying dropout occurrence. an injection unit 4 that generates a sampling clock signal for the time-axis compressed signal required by the digital memory 3, and a frequency for identifying the occurrence of dropouts in the video signal whose time axis has been expanded and restored. and a second analog section 5 that detects the signal and performs dropout compensation.

In the first analog output 2, 21 is a head amplifier that amplifies the reproduced signal from the magnetic head 1, 22 is a dropout detection circuit that detects a dropout from the reproduced signal of the magnetic head 1, and 23 is the reproduced signal of the head amplifier 21. This is a demodulation circuit that demodulates the . Since the recorded signal on the magnetic tape is recorded with pre-emphasis in order to reduce triangular noise during FM demodulation, the reproduced signal after demodulation is de-emphasized through the de-emphasis circuit 24 to reduce the S/N of the Takagi signal component. Improve. De-emphasis circuit 24
If the band of the reproduced time sleeve compressed signal output from the circuit is, for example, around 7 MHz, it is sent to the clamp 26 through an 8 MHz low-pass filter, and this clamp circuit 26 converts the signal level to the A/D. It is clamped to fit the conversion level range of (analog/digital) conversion and sent to the digital memory section 3. In addition, the output from the de-emphasis circuit 24 is connected to a sync separator (synchronization separation circuit) 27 and an injection filter 4.
The horizontal synchronizing signal H and vertical synchronizing signal V separated by the sync separator 27 are sent to the injection section 4 and the digital memory section 3.

In the digital memory section 3, 3l inputs the time-base compressed signal from the above-mentioned clamp circuit 26 to the injection circuit 4.
32 is an A/D conversion circuit that converts into digital data using a sampling pulse 1536fo (a signal having a frequency 1536 times the fundamental frequency (15.75 KHz) fH of the horizontal synchronization signal) generated from a sampling clock signal from the A/D converter circuit; It is a first-in first-out memory (CF I FO) that selectively stores the luminance signal among the time-base compressed signals digitized by the D conversion circuit 3l in a first-in, first-out manner as a signal synchronized with the sampling pulse 1536fH. On the other hand, 33 is a first memory which selectively stores color difference line sequential chroma signals among the time axis compressed signals digitized by the A/D conversion circuit 3l in a first-in, first-out manner using a signal synchronized with the sampling pulse 1536f+i. In-first-out memory (PIFO). Here, the A/D conversion circuit 31 and F
A switch circuit 34 is interposed between the IFOs 32 and 33, and frequency signal data generated by the controller 35 is written into the FIFOs 32 and 33 in accordance with a switching command from the controller 35. The detection pulse of the dropout detection circuit 22 is input to the control unit 35, during which it issues a switching command to the switch circuit 34, and also outputs the A/D conversion data of the time axis compressed signal alternately for each sampling pulse, for example. Each Ftl? Input as '032, 33 data. As a result, an analog signal with a frequency signal of 1/2 of the sampling pulse is superimposed. etc. effect. This frequency signal naturally falls outside the video signal band. In this way, the data stored in the PIPO 32 and FIFO 33 are synchronized with the horizontal synchronization signal H and the vertical synchronization signal V, and are clocked in parallel with clock signals having expansion ratios corresponding to their respective compression ratios. Decompress/restore and read. The luminance signal data read from F I FO3 2 is D/A (digital/analog)
The conversion circuit 36 converts the signal 960ru synchronized with the reading clock signal into an analog signal, and converts it into an analog signal.
The line-sequential chroma signal read from 33 is converted into an analog signal by the D/A conversion circuit 37 using a signal 192fo synchronized with the read clock signal. The luminance signal and chroma signal converted into these analog signals are sent to the second analog section 5. A/D conversion in the above, D/A
Conversion and writing to FIFOs 32 and 33. The read timing is controlled by the data selection circuit 38, and the sampling pulse 1536f* necessary for this control is input from the injection section 4, and the clock signal 960fo is input from the internal oscillation circuit 39. Separation of the luminance signal data and chroma signal data to be written into the FIFOs 32 and 33 is performed by temporally switching the writing period based on the synchronization signals H and V from the sync separator 27. A clock signal for reading the chroma signal and a clock signal 192fH for the D/A conversion circuit 37 are obtained by dividing the frequency of the clock signal 960fH.

In the injection unit 4, 41 is a burst extraction circuit for extracting a pilot burst signal superimposed on the reproduced time-base compressed signal, and 42 is a burst extraction circuit 4.
An injection lock circuit 43 draws in the pilot burst signal extracted at 192f. i
This is an 8-multiplying circuit that obtains a sampling clock signal of 1536fH by multiplying the frequency signal by 8. The burst extraction circuit 41 temporally creates a gate signal in synchronization with the horizontal synchronization signal H from the sync separator 27, and extracts the pilot burst signal inserted into a predetermined portion of the time-base compressed signal. Both the injection lock circuit 42 and the 8-multiplier circuit 43 are phase comparators. Voltage controlled oscillator circuit (
VCO). It can be configured with a PLL (phase locked loop) circuit consisting of a frequency dividing circuit or the like.

In the second analog converter 5, the luminance signal input from the D/A conversion circuit 36 is passed through a 5 MHz low-pass filter (
LPF) 5 1 and 5 MH superimposed by the control unit 35
A chroma signal inputted to a band pass filter (BPF) 52 that detects a frequency signal for identifying the occurrence of dropout exceeding z and manually inputted from the D/A conversion circuit 37 is
1MHz, which passes only chroma signals within the MHz band
a low-pass filter (LPF) 61, and a band-pass filter (BPF) that detects a frequency signal for identifying dropout occurrence exceeding IMHz superimposed by the control unit 35.
62. The output of the low-pass filter 51 is input directly and through the IH delay circuit 53 to the switch circuit 54, and by switching, the output of the filter 5l is normally input to the luminance signal Y. When identifying the occurrence of dropout by detecting the frequency signal, the output of the IH delay circuit 53 is used to insert the luminance signal before IH into the dropout portion to perform dropout compensation. The frequency signal detected by the bandpass filter 52 is waveform-shaped by a waveform shaping circuit 55, thereby obtaining a dropout pulse, which controls switching of the Uero switch circuit 54 to the IH delay circuit 53 side. The output of the filter 6l is input directly and through the 2H delay circuit 63 to the switch circuit 64, and by switching, the output of the filter 6l is normally sent to the subsequent stage as a chroma signal, and the bandpass filter 62 outputs a frequency signal for identifying the occurrence of dropout. At the time of detection, a 214M color difference signal is inserted into the dropout part using the output of the 2H delay circuit 63,
Perform dropout compensation. The reason why the 2II color difference signal is used in the above is that the chroma signal is sent out sequentially over the RY and BY color difference lines.

The frequency signal detected by the bandpass filter 62 is waveform-shaped by a waveform shaping circuit 65, thereby obtaining a dropout pulse, which is then sent to the 2H delay circuit 63 of the switch circuit 64.
Controls switching to the side.

The chroma signal output from the switch circuit 64 is branched into three, one directly, one through the lHn delay circuit 66, and the other one input to the switcher 68 through the 2H delay circuit 67. . The switcher 68 converts the directly input line-sequential color difference signal into R-Y or B.
-Y alternately, and the color difference signal that is not being sent out at that time is 1/2 of the sum of the color difference signal before IH of the IH delay circuit 66 and the color difference signal before 2H of the 28 delay circuit 67.
It is created from , interpolated, and distributed alternately to B-Y or RY.

The operation and effect of the embodiment configured as above will be described. FIG. 2 is an explanatory diagram of the operation and effects of this embodiment.

(a) shows the reproduced time axis compressed signal, in which the horizontal synchronizing signal 1-{ is followed by the pilot burst signal B, the luminance signal Y, and the chroma signal R-Y or B-Y sequentially on the color difference line. It is compressed and sent out in chronological order. For example, if a dropout occurs in a period T spanning the luminance signal and the chroma signal, the digitized time-axis compressed signal data is transferred to this dropout portion using the F'IF
l of the sampling pulse shown in (b) when writing to O
/2 frequency signal 1/2f. is superimposed as an identification signal. After the time axis of this frequency signal is expanded and restored, the frequency signal is detected separately by a bandpass filter for a luminance signal and a chroma signal, and (C). Dropout pulse DOPY (luminance signal side) and DOPC as shown in (d)
(chroma signal side). While the dropout pulses D O P Y and D O P c are being detected, the dropout portion of the luminance signal Y, which has been completely regenerated and restored before IH, is removed as shown in (e). In the chroma signal, as shown in (f), dropout compensation is performed by inserting the same type of color difference signal (for example, R-Y) that has been completely reproduced and restored 2H before in the dropout part. conduct. in this way,
If the dropout compensation of the time axis compressed signal is performed at the baseband, when obtaining the luminance signal before IH or the chroma signal before 2H, the conventionally used delay element based on IH can be used. It becomes possible to perform dropout compensation based on the data, and it becomes possible to standardize delay elements and circuits without being affected by the compression ratio of the time axis.

It goes without saying that the present invention is applicable not only to color-difference line sequential time-domain compressed signals but also to various time-domain compressed signals. Also, address manipulation is required, but F
Memory can be used instead of IFO. Furthermore, the frequency signal for identifying dropout occurrence is superimposed using A/D.
It may be performed at the analog signal stage before conversion. As described above, the present invention can be applied in various ways and can take various embodiments in accordance with its gist.

[Effects of the Invention] As is clear from the above explanation, according to the time-domain compressed signal reproducing device of the present invention, dropouts in a time-domain compressed signal can be detected at the baseband. An out-compensator can be used, and dropout compensation can be performed using standard circuits and components such as delay elements that are not affected by the compression rate of the time axis.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation and effect of this embodiment. l...Magnetic head, 2...First analog section, 3.
・・Digital memory section, 4.・Innoecnotan section,
5... Second analog section, 22... Dropout detection circuit, 34... Switch circuit, 35... Control section, 5
2... Band pass filter, 53... II {delay circuit, 54... Swissoji circuit, 62... Band pass filter, 62... 2 H delay circuit, 64... Switch circuit. -641

Claims (1)

[Claims] (1) means for detecting a dropout in a reproduced time-domain compressed signal; and when the dropout is detected, a frequency signal outside the band of the time-domain compressed signal is transmitted to the time-domain compressed signal or the time-domain compressed signal thereof; control means for superimposing the frequency signal on the digitized signal; means for detecting the frequency signal in the time axis compressed signal or a restored signal obtained by expanding the digitized signal to the original time axis; 1. A time-base compressed signal reproducing device comprising: means for compensating for dropout of a restored signal. A time axis compressed signal reproducing device characterized by: