JPH0340678A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent picture quality deterioration such as line crawling or line flicker by quantizing only a video signal part not including a synchronizing signal at recording, recording the signal while two reference signals are inserted to a prescribed period of each channel and controlling the the gain of a correction circuit at the reproduction. CONSTITUTION:Only a video signal part except a synchronizing signal part of an input signal is quantized at recording and subject to time axis expansion and the result is split into two channels. A reference signal of a level V1 is added to the resulting signal. Moreover, a signal of a level V2 outputted from a reference signal generating circuit 2 is added by adders 30a, 30b. Video signal period detection circuits 15a, 16b detect the position of a reference signal at the reproduction and generate a signal whose DC voltage is -Vo for a period of the video signal. Thus, the DC voltage is lowered only for a period of the video signal and a level difference between channels in the reproducing signal is brought into a permissible limit or a detection limit or below. Thus, deterioration in the picture quality such as line crawling or line flicker is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a recording and reproducing apparatus that divides a video signal into m (m is an integer of 2 or more) channels and performs recording and reproducing.

BACKGROUND OF THE INVENTION In recent years, in recording and reproducing devices such as video tape recorders, in order to reduce the bandwidth required for recording and reproducing wideband signals, it has been considered to divide wideband signals into multiple channels for recording and reproducing. There is.

For example, the video signal Y1→Y2→Y as shown in FIG.
3→Y, →......, the first transmission channel receives the odd line video signal (Y1→Y3→...), and the second transmission channel receives the even line video signal (Y1→Y3→...). Y2→
Y, →...), and the time axis is expanded during recording (the first transmission channel has the second
The signal shown in FIG. 5C is supplied to the transmission channel . )
By performing time axis compression during playback, recording and playback of wideband signals can be realized using the same transmission path as before.

Here, we are considering a time-axis expanded luminance signal as the channel-divided signal, but it is also a time-division multiplexed signal in which the chrominance signal and luminance signal are time-axis multiplexed, or a time-division multiplexed signal in which the chrominance signal and the luminance signal are frequency-multiplexed. It is clear that the same thing can be said about composite signals.

Moreover, it is clear that the same thing can be said when the number of divided channels is three or more.

Problems to be Solved by the Invention However, with the above configuration, what happens when the video signal is recorded and played back? ! If the recording and reproducing circuits have different characteristics between channels due to transmission over several transmission channels (for example, DC
If there is a level difference, a DC level difference of ΔV will occur for each line as shown in the fifth diagram. ), the reproduced signal had the disadvantage of causing image quality deterioration such as line crawling and line flicker.

In view of the above-mentioned problems, the present invention provides a recording and reproducing apparatus that can actively correct the characteristic difference between channels and suppress the DC level difference and gain difference between channels to below the permissible limit or detection limit. be.

Means for Solving the Problems In order to solve the above problems, the recording and reproducing apparatus of the present invention quantizes only the video signal portion that does not include the synchronization signal during recording, and quantizes the video signal portion and the non-video signal portion at two levels. A reference signal having V1 and V2 is inserted and recorded in a predetermined period of each channel, and during playback, the gain and DC level are adjusted for each channel so that the level of the reproduced reference signal during the predetermined period becomes V1 and V2. a correction circuit that controls the correction circuit, an AD converter that feeds back quantized data to the correction circuit, and a clamp circuit that is connected between the correction circuit and the AD converter and adds a predetermined DC voltage for a video signal period. It is equipped with the following.

According to the present invention, with the above-described configuration, the gain of the correction circuit is controlled so that the level of a predetermined portion of the reference signal of the reproduced signal of each channel becomes a predetermined value, so that the characteristic difference between channels (
A signal with corrected DC level difference and gain difference) is obtained. Further, by adding a predetermined DC voltage only to the video signal period during reproduction, the decrease in the signal amplitude that can be input is suppressed without increasing the number of AD converters, and the deterioration of the SN ratio does not occur.

Embodiment A recording/reproducing apparatus according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a recording section of a recording/reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a video signal input terminal, 2 is an AD converter that converts only the video signal portion excluding the synchronization signal portion (the signal from Vat to Vah shown in FIG. 3(A)) into digital data; 3
is a channel division circuit that divides the output of the AD converter 2 into two channels and performs time axis expansion. 9 is a 54477 circuit that separates the horizontal synchronizing signal from the input video signal and sets the insertion period of the reference signal; 10a is the level V, (V
The first reference signal generation circuit 1.10b which inserts the reference signal of a l<V, <Va h) generates a level V2 (V2<Va l
) is the second reference signal generation circuit 2 which inserts the reference signals of
4b is an adder that adds the reference signal generated from the reference signal generation circuit 1 and the output signal of the channel division circuit 3. 5a, 5b are DA converters, 30a,
30b is an adder that adds a second reference signal to the output signals of the DA converters 5a and 5b. 6 is a recording signal processing circuit that converts the analog signal into a signal suitable for recording on tape; 7a and 7b are recording heads; 8
is magnetic tape.

With the above configuration, only the video signal portion can be quantized during recording, and as shown in FIG. 3(B), 2H
(H: Horizontal synchronization interval)
A reference signal with a level of 2 will be inserted.

Next, FIG. 2 is a diagram showing a reproduction section. In FIG. 2, lla and llb are reproduction heads, and 12 is a reproduction signal processing circuit having functions such as demodulation.

14a is an AD converter which inputs signals from Val to Vah in the same way as during recording, and 13a is an AD converter so that the level of the reproduction reference signal during a predetermined period becomes V1 and V2, respectively, according to the output signal of the AD converter 14a. This is a correction circuit that controls the gain and DC level of the reproduced signal. 15
16a is a video signal period detection circuit that detects a period corresponding to a video signal from a reproduced signal, and 16a is connected between the correction circuit and the AD converter, and is connected to a predetermined DC voltage according to the output of the video signal period detection circuit. This is an adder that adds . The other channel (13b, 14b, 15b.

The same applies to 16b). Furthermore, 18 is the above A
A channel synthesis circuit compresses the time axis of two channels of signals of the D converters 14a and 14b and synthesizes them into one channel; 19 is a DA converter; 20 is an output terminal.

The operation of the recording and reproducing apparatus configured as described above will be explained using FIGS. 1 to 4.

At the time of recording, only the video signal portion of the input signal excluding the synchronization signal portion is quantized, time-axis expanded, and divided into two channels. In this signal, as shown in Fig. 3 (B),
A reference signal of level ■1 is added to the period of Xl. It is assumed that the added level (1) is set to a level that the video signal can take. That is, Val<V, <Vah. In this state, DA conversion is performed, and the signal of level V2 output from the reference signal generation circuit 2 is sent to the adder 3.
Add at 0a30b. The level v2 to add is
In contrast to vl, it is assumed that the video signal is set to a level that cannot be reached. That is, V<Val. In this way, a signal shown in FIG. 3(B) which has been axially expanded and has a reference signal added thereto is obtained.

During reproduction, the two-channel reproduction signal output from the fine signal processing circuit 12 exceeds the maximum amplitude Vat to Vah that can be input to the AD converter, as shown in FIG. 4A. Further, the video signal period detection circuits 15a and 15b are
The position of the reference signal is detected and a signal is generated such that the DC voltage becomes -v0 only during the video signal period (FIG. 4B).The signal shown in FIG.
It is added to the reproduced signal shown in Figure A. That is, Fig. 4C
As shown in , the DC voltage decreases during the video signal period,
Both the reference signal and the video signal fall within the maximum amplitudes Val to Vah that can be input to the AD converter.

Further, in the correction circuit 13a13b, the levels of the reference signal during the period X1X2 are controlled to be V1 and V2, respectively.

As described above, according to this embodiment, during recording, a reference signal is inserted for a predetermined period, and during playback, a predetermined DC voltage is added for a video signal period, so that the reference signal and video signal have the maximum input li width of the AD converter. Go inside. Further, the level of the reference signal during a predetermined period is corrected to a predetermined value, and the gain and DC level of the reproduced signal are corrected. Therefore, it is possible to keep the level difference between each channel of the reproduced signal below the permissible or detectable limit, resulting in line crawling.

Image quality deterioration such as line flicker can be eliminated. Furthermore, it is now possible to input video signals up to the maximum input amplitude of the AD converter, and quantization allows ii!
ii. Quality deterioration can be suppressed.

In the first and second embodiments, the number of recording/reproducing channels is two, but it may be three or more.

Further, in the first and second embodiments, the reference signal is inserted every 2H, but it may be inserted every 2H or every IV (V: vertical synchronization interval).

Further, in the first and second embodiments, the levels of the reference signals are compared at two locations, but there may be three or more locations.

In addition, in the first and second embodiments, a luminance signal is considered as a video signal that is time-axis expanded during recording, but a time-division multiplexed signal in which a chrominance signal and a luminance signal are time-axis multiplexed, or a chrominance signal and a luminance signal The signal may be a decoded signal that is frequency multiplexed.

Effects of the Invention As described above, the present invention quantizes only the video signal portion that does not include a synchronizing signal during recording, and quantizes a reference signal having two levels V1 and 2 for the video signal portion and the non-video signal portion for each channel. a correction circuit that controls the gain and DC level so that the level of the reproduced reference signal during the predetermined period becomes V1 and V2 for each channel during playback; By comprising an AD converter that feeds back quantized data and a clamp circuit that is connected between the correction circuit and the AD converter and adds a predetermined DC voltage for the video signal period, the level difference between each channel can be reduced. It becomes possible to reduce the image quality to below the permissible limit or detection limit, and it is possible to eliminate image quality deterioration such as line crawling and line flicker.

Furthermore, it becomes possible to input a video signal up to the maximum input amplitude of the AD converter, and it is possible to suppress deterioration in image quality due to quantization.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are configuration diagrams showing one embodiment of the present invention,
Figure 3 is a waveform diagram of the video signal with the reference signal inserted and time axis expanded, Figure 4 is the waveform diagram of the reproduced reference signal, and Figure 5
The figure is a signal waveform diagram in conventional channel division recording. 3... Channel division circuit, 6... Recording signal processing circuit, 9... Timing generation circuit,
12... Reproduction signal processing circuit, 18...
Channel synthesis circuit.

Claims (1)

[Claims] A recording and reproducing device that divides a video signal into m (m is an integer of 2 or more) channels and records/reproduces the video signal, and when recording,
Only the video signal part that does not include the synchronization signal is quantized, and the video signal part and the other two levels V_1 and V
A reference signal having _2 is inserted and recorded in a predetermined period of each channel, and during playback, the gain and DC level are controlled for each channel so that the level of the reproduced reference signal during the predetermined period becomes V_1 and V_2. a correction circuit to
It is characterized by being comprised of an AD converter that feeds back quantized data to the correction circuit, and a clamp circuit that is connected between the correction circuit and the AD converter and adds a predetermined DC voltage for a video signal period. Recording/playback device.