JPH0340679A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent production of deterioration in the S/N by quantizing only a video signal component not including a synchronizing signal at recording and controlling a level of a reference signal for a prescribed period and quantizing only a signal component of a reproducing signal with the synchronizing signal eliminated therefrom at 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. Reference signals of levels V1, V2 are added to the resulting signal. Moreover, the levels of the reference signals are controlled to be respectively V1, V2 by correction circuits 13a, 13b at reproduction. In this case the reproduction signal having the same characteristic between channels is inputted to clamp circuits 16a, 16b respectively. Then only the video signal part is accurately quantized in A/D converters 15a, 15b. Thus, the reproducing signal is brought into a permissible limit or a detection limit or below.

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. 6A
3→Y4→..., and the first transmission channel has an odd line video signal (Y, →Y8→...),
The second transmission channel has an even line video signal (Y2
→Y4→...), and the time axis is expanded during recording (the signal in Figure 6B is supplied to the first transmission channel, and the signal in Figure 6C is supplied to the second transmission channel). .

), by performing time axis compression during reproduction, it is possible to record and reproduce broadband signals 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 decoded signals as well.

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, in the above configuration, since the video signal is transmitted over multiple transmission channels during recording and playback, there may be problems when the recording circuit and the playback circuit have different characteristics between the channels (for example, , if there is a DC level difference between transmission channels, Δ
This results in a DC level difference of (2). ), 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 components that do not include the synchronization signal during recording, and quantizes the level v1 that the video signal can take and the video signal components. A reference signal having a level exceeding V2 is inserted and recorded in a predetermined period of each channel, and during playback, the level of the reproduced reference signal for the predetermined period is V, , V
a first AD converter that feeds back control JIJ data to the correction circuit when the input signal amplitude is at least from ■1 to ■2; A clamp circuit that operates so that the period of level V1 of the reproduction reference signal output from the circuit becomes a predetermined value, and a signal component connected to the output of the clamp circuit and excluding the synchronization signal of the reproduction signal as in the case of recording. This configuration includes a second AD converter that quantizes only the second AD converter.

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. In addition, by using two AD converters that quantize the reference signal and video signal during playback,
Only the video signal components that do not include the synchronization signal are quantized, suppressing the decrease in the signal amplitude that can be input, and preventing deterioration of the SN ratio.

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, l is a video signal input terminal, and 2 is an AD converter that converts only the video signal part (signal from Vsl to Vsh shown in Fig. 3 (A)) excluding the synchronization signal part 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 timing circuit that separates the horizontal synchronizing signal from the input video signal and sets the insertion period of the reference signal; 10a is a timing circuit that adjusts the level to period x 1 according to the output of the timing circuit 9;
(Vs I<V, <Vs h) (7) The first reference signal generation circuit 1, lob, which inserts the reference signal, changes the level V2 (V2<
This is a second reference signal generation circuit 2 which inserts a reference signal of Vs l) (each reference signal is shown in FIG. 3(B)). 4a and 4b are adders that add 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 are the DA = + converters, 5a, 5b
This is an adder that adds a second reference signal to the output signal of.

6 is a recording signal processing circuit that converts a signal converted into an analog signal into a signal suitable for recording on a tape, 7a and 7b are recording heads, and 8 is a magnetic tape.

With the above configuration, only the video signal portion can be quantized during recording, and as shown in FIG.
V, , V for a predetermined period within the period of (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 flb are reproduction heads, and 12 is a reproduction signal processing circuit having functions such as demodulation.

14a is the reproduction reference signal v2 to V shown in FIG. 4(A).
The AD converter 13a, which manually handles signals up to 1, adjusts the gain and DC level of the reproduced signal so that the level of the reproduced reference signal during a predetermined period becomes V, V2, respectively, according to the output signal of the D converter 14a. This is a correction circuit to control. 16a indicates the period of Xl of the reproduced signal whose gain and DC level have been corrected, as shown in FIG. 4(B).
15 a clamp circuit that operates so that the voltage becomes 1+Vref;
a is only the video signal part of the clamped signal (Fig. 4 (
This is an AD converter that quantizes the signal from Vsl to Vsh shown in B). The other channel (13b,
14b, 15b, 16b) are also the same. Furthermore, 17 is 2 of the AD converters 15A and 15b.
A channel synthesis circuit compresses the time axis of channel signals and synthesizes them into one channel, 18 is a DA converter, and 19 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 excluding the synchronization signal portion of the human input signal is quantized, time axis expansion is performed, and the signal is divided into two channels. In this signal, as shown in Fig. 3 (B),
A reference signal of level v1 is added to the period of Xl. It is assumed that the added level vl is set to a level that the video signal can take. That is, V sI < V r <
Let V S h. DA conversion is performed in this state. Furthermore, the signal of level V2 outputted from the reference signal generation circuit 2 is added to the adder 30a.

30b. The level v2 to be added is vl
Conversely, assume that the video signal is set to an impossible level. That is, it is assumed that V 2 <V s l. In this way, a signal shown in FIG. 3(B) which has been time-extended and has a reference signal added thereto is obtained.

During playback, the two-channel playback signals output from the playback signal processing circuit 12 are processed by correction circuits 13a and 13b such that the levels of the reference signals during periods X, X2 are set to V, respectively.
, V2. At this time, correction circuit 1
3a and 13b, the maximum amplitude of the input signal is shown in Fig. 4 (A).
AD converter 14a from V2 to ■1 as shown in
, 14b, the correction circuits 13a, 1
Output of 3b (data of No. 3 is fed banked.■
Signals with a level exceeding
The gain and D of the reproduced signal input to the AD converters 14a and 14b are
C level has the same characteristics between channels. These reproduced signals, which have the same characteristics among the channels, are input to the respective clamp circuits 16a16b and become signals at the level shown in FIG. 4(B). In other words, the level of period X1 is
It is controlled to be 1+Vref. At this time, the video signal portion has an amplitude from Vsl to Vsh. Only the video signal portion of the reproduced signal clamped in this manner is accurately quantized in the AD converters 15a and 15b.

As described above, according to this embodiment, a reference signal is inserted for a predetermined period during recording, and during playback, the reference signal is inserted using the first AD converter whose input maximum amplitude corresponds to the maximum amplitude of the reference signal. The level of the reproduction signal for a predetermined period is corrected to a predetermined value, and the gain and DC level of the reproduced signal are corrected, and the reproduced signal is clamped so that the portion excluding the synchronization signal has the maximum amplitude of the input to the second AD converter. Therefore, it becomes possible to reduce the level difference between each channel of the reproduced signal to a permissible limit or a detection limit or less, 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.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a configuration diagram of a clamp circuit in a recording/reproducing apparatus showing a second embodiment of the present invention.

In FIG. 5, 20 is an input terminal for a reproduction signal whose gain and DC level have been corrected, 22 is an input terminal for output data of the AD converter, 25 is a comparison circuit for comparing the output data of the AD converter 15a with a predetermined value, and 24 is an LPF that averages the output of the comparison circuit. 23 is an adder that adds the output signal of the LPF 24 to the reproduced signal, and 21 is the output terminal of the clamp circuit.

The operation of the clamp circuit configured as above will be explained.

A reproduced signal shown in FIG. 4(A) is input to the clamp circuit 16a. The level of the reference signal during the period X1 is set to V, +Vr.
ef, the output signal of the clamp circuit 16a is
The D converter 15a converts it into digital data, and the comparison circuit 25 detects the difference from a predetermined value. For example, when the comparison circuit 25 is configured to perform a magnitude determination with respect to a predetermined value, the time average of the results of the magnitude determination is determined by the LPF.
It is output from 24. The level of the reference signal during period X1 is V
, +Vref, the output level of the LPF 24 is configured to decrease, so that the level of the reference signal during the period X1 can be converged to a predetermined value.

As described above, by feeding digital data of a predetermined period of the reference signal to the clamp circuit, the second
The DC level of the reproduced signal input to the AD converter can be made the same between channels.

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 several H or 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 component not including the synchronization signal during recording, and quantizes the reference signal having the level V1 that the video signal can take and the level v2 exceeding the video signal component for each channel. Insert and record at a predetermined period of time,
During reproduction, a correction circuit is provided for each channel to control the gain and DC level so that the level of the reproduced reference signal during a predetermined period is V, V2, and the input signal amplitude is at least from ■ to ■2. a first AD converter that feeds control data to the correction circuit; a clamp circuit that operates so that the period of the level vl of the reproduction reference signal output from the correction circuit becomes a predetermined value; and the clamp circuit. The second quantizer is connected to the output of
By configuring it with an AD converter, it is possible to reduce the level difference between each channel of the reproduced signal to below the permissible limit or detection limit, and it is possible to eliminate image quality deterioration such as line crawling and line flicker. moreover,
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
This figure is an internal configuration diagram of a clamp circuit according to another embodiment of the present invention, and FIG. 6 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, 17...
Channel synthesis circuit.

Claims (2)

[Claims] (1) 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. During recording, only the video signal components that do not include synchronization signals are quantized, and the video signal is A reference signal having a possible level V_1 and a level V_2 exceeding the video signal component is inserted and recorded in a predetermined period of each channel, and during playback, the level of the reproduced reference signal during the predetermined period is V_1,
A correction circuit that controls the gain and DC level so that the input signal amplitude is at least V_1 to V_2.
a first AD converter that feeds back control data to the correction circuit up to _2; a clamp circuit that operates so that the period of the level V_1 of the reproduction reference signal output from the correction circuit becomes a predetermined value; 1. A recording and reproducing device comprising: a second AD converter connected to the output of the clamp circuit and quantizing only the signal components of the reproduced signal excluding the synchronization signal, as in the case of recording. (2) The recording/reproducing apparatus according to claim (1), wherein the clamp circuit is configured to be controlled according to output data fed back from the second AD converter.