JPS59149485A - Recording and reproducing device for video signal - Google Patents

Abstract

PURPOSE:To prevent the lateral movement of a reproduced picture and timing deviation between a luminance and a chroma signal by using two phase-synchronizing clock signals which differ in frequency and then expanding the luminance signal and chroma signal on the time axis. CONSTITUTION:The luminance signal, horizontal synchronizing signal, and chroma signals are all converted into time compressed signals as compared with the original signal, and they are composed together to generate a time-division multiplex signal. The horizontal synchronizing signal and luminance signal are equalized in time compression rate, and the time compression rate of the chroma signal which may have band width only a half as wide as the luminance signal is set more than twice as high as that of the luminance signal. Further, when the signal of a television camera is recorded, the deflection frequency of the television camera is set as specified and the horizontal blanking period is made far longer than specified, thus generating the time compressed luminance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for recording and reproducing a video signal, and particularly to a device suitable for recording and reproducing a luminance signal and a chroma signal in a video signal by time-division multiplexing. .

[Prior art]

In conventional technology for recording and reproducing luminance signals and chroma signals by time division multiplexing, insertion of synchronization signals is insufficient.
This makes it difficult to restore the time-compressed signal to its original state.

Hereinafter, conventional problems will be explained in detail using drawings. Figure 1 shows JEER, Tran, s CE-22, Al(1
FIG. 9 is a diagram showing a time division multiplexed signal waveform described in "Time division multiplexed color signal for video discs and VTRs using semiconductor memory" published in December 976. In FIG. 1, A is a luminance signal waveform including a horizontal synchronization signal, B is a line-sequential chroma signal waveform, and C is a signal waveform in which B is time-division multiplexed on A.

To make the explanation more concrete, A is an NTSC TV.

, the case of a vision signal will be explained as an example. 1 is the front porch, 2 is the horizontal sync signal, 5 is the back porch, 4
is a luminance signal, 5 is a horizontal blanking period of about 13 μs,
9 is a video period of about 50 μs.

6 is a front porch period of about 21ts, 7 is a horizontal opening) jA period of about 5 μs, F3 is a back porch period of about 6 μff, io is a R-Y signal, and 11 is a B-Y signal.
It's a signal.

In the conventional technology, the horizontal blanking period 5 in AM type
It is characterized in that the time-compressed synchronization signal and the time-compressed chroma signal are time-division multiplexed, and the luminance signal 4 of the video period 9 is used as its core. Therefore, as shown in waveform C, the front porch 1 has a front porch period 21 of about 1 μs.
2. Horizontal synchronization 16. Horizontal synchronization period 22 is approximately 6μ9. Back porch 14. Back porch period 25 is approximately 1 μs. Chroma period 19 is approximately 8 μs, guard period 2 between chroma and brightness
0 is a guard 16 of about 1 μs. signal j5A'', B-Y・1 word 11 is time-compressed B
This means that it has been converted to -Y0 signal 17.

The problem here is the front porch, horizontal synchronization.

The back porch pulse width is narrow. That is,
Since the energy of the synchronization signal has been significantly reduced, the influence of waveform distortion and noise in the transmission system is large, causing horizontal fluctuations in the reproduced image and timing discrepancies between the luminance signal and chroma signal.

After all, in the case of an NTSC TV signal, for example, there is not enough energy for the synchronization signal, and the multiplexing ratio between the synchronizing signal and the video signal is an appropriate value, and changing this multiplexing ratio is important for overall performance. unfavorable to

[Purpose of the invention]

The object of the present invention is to provide a device for recording and reproducing luminance signals and chroma signals by time division multiplexing, which is less susceptible to the effects of waveform distortion and noise received in a transmission system, and which is less likely to cause horizontal fluctuations in reproduced images or timing shifts between luminance signals and chroma signals. is to provide.

[Summary of the invention]

In the present invention, a luminance signal is used for the original signal.

After converting all the horizontal synchronization signals and chroma signals into time-compressed signals, these signals are combined to form a time-division multiplexed signal. If the time compression ratio of the horizontal synchronization signal and the luminance signal are made equal in order to prevent horizontal image shaking, the time compression ratio of the chroma signal, which requires a bandwidth of 1 or less compared to the luminance signal, is equal to the compression ratio of the luminance signal. Set it to 2 times or more. Furthermore, when recording a signal from a television camera, a time-compressed luminance signal is generated by keeping the deflection frequency of the television camera as standard and making the horizontal blanking period much longer than the standard.

[゛Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing an embodiment in which the present invention is used when a signal from an NTSC television camera is recorded and reproduced on a two-head helical scan type video tape recorder.

FIG. 5 is a waveform diagram of the main part of FIG. 2.

In FIG. 2, 24 is a television camera, 25 is an image sensor consisting of a solid-state image sensor or an image pickup tube, and 27
is a deflection circuit for converting two-dimensional image information into a one-dimensional electrical signal; 28 is a synchronization signal generation circuit for driving the deflection circuit; and 26 is a process amplifier that generates a luminance signal D and a line-sequential color difference signal E. .

As shown in Figure 5, D is approximately 25/! Z,? It consists of a horizontal blanking period of 61 and a video period of about 40 ttr. E
Similarly, it has horizontal blanking of about 23 μm and a video period of about 40 μs. This E signal is sent to the time compression circuit 29.
B-Y(T(No. 59 becomes 64, R-
The Y signal 60 is converted to 66 and time-division multiplexed to the D signal to obtain the waveform F or G in FIG. Front porch in F65. Horizontal synchronization 66 and back porch 67 are combined with pulses from synchronization signal generation circuit 28.

In FIG. 6, the video period is set to about 40 μs, and the time axis of the signal must also be selected to be one time the regular N'rSC synchronization signal. Therefore, the front porch 65 is about 1.6 μs, the horizontal synchronization 66 is about 4 μs, and the back porch 6 is about 4 μs.
7 is approximately 4.8N. In this way, F or G is obtained as the output of the waveform synthesizer 50.

The F (G) signal is band-limited by an LPF 51, the horizontal synchronization tip is clamped by 52, dynamism and quenching is performed by 53, and emphasis is applied by 54. After the overshoot caused by the emphasis is amplitude-limited by a clip circuit 65, 66, the signal is converted into an angle modulated signal. The angle modulation signal is sent to the write amplifier 57. rotary transformer 68
．． Video head 59α.

39'6 and recorded on videotape 40.

Next, playback will be explained. Signals recorded on the video tape 40 are input to the preamplifier 41 via the video heads 39α, 59h and the rotary transformer 58. The output signal of the preamplifier 41 is guided to an FM equalization circuit 42 to compensate for frequency characteristic distortion caused by the tape head system, and then passed through a limiter 43. Demodulator 45. By passing through the de-enfax circuit 45, a waveform similar to F(0) in FIG. 3 is obtained. That is, the output waveform of the de-emphasis circuit 45 (F'(
G')) does not perform dynamic de-emphasis.

The waveform shown in FIG. 6F (G) is applied with dynamic emphasis. F'(G') is applied to a synchronization separation circuit 47 and a synchronization signal is extracted.

Further, the F'(G') signal is converted into a digital signal by the converter 46. Since the input signal to the color converter 460 is subjected to dynamic emphasis as described above, sufficient image quality can be obtained with 6 to 7 bits as a converter. 49 is a time axis expander, memory 50, D
The A converter 51 has a luminance signal memory 52. DA converter 56
is for the chroma signal.

In the time axis expander 49, the time axes of the luminance signal and the horizontal synchronization signal are multiplied by 1, and the time axes of the chroma signal are multiplied by 5. By expanding in this manner, the horizontal synchronization and luminance signals of the NTSC standard shown at H in FIG. 3 are obtained at the terminal 56, and the line-sequential chroma signal shown at I in FIG. 6 is obtained at the terminal 57. In the end, there is no need to replace the horizontal synchronization signal in the regeneration circuit,
Therefore, problems such as the above-mentioned lateral vibration do not occur.

The basic principle of the time axis expander 490 is to read out the input signal (the output signal of the A converter 46) at a speed slower than the speed at which it is written into the digital memory 50.52. Therefore, a write clock and a read clock are required, and these clocks are generated by the clock generator 48.

A block diagram showing one embodiment of the clock generator used in the present invention is shown in FIG. In FIG. 4, 73 is an input terminal for a horizontal synchronization signal, 74 is an output terminal for the read clock of the memory 50, 75 is an output terminal for the read clock of the memory 52, 76 is an output terminal for the write pulse of the memories 50 and 52, and 77 is a phase comparator, 78 is a VCO179,
80, 81, 82, and 83 are frequency dividers. To create the B signal from the G signal shown in Figure 6, it is sufficient to perform one time expansion, and to create the I signal from the G signal, it is necessary to perform five times time expansion. =4, N2=1, N4=
5, #S=5. In this case, the write clock is N5fH (71T: horizontal synchronous frequency), and the read clock is for the memory 50 = #3fu
For the t memory 52, l'/s fu is obtained. The purpose of frequency divider 85 is to offset the write clock.

If an offset is not required, it is not required.

FIG. 5 is a waveform diagram showing an embodiment in which chroma signals are time-division multiplexed in a simultaneous manner. In Fig. 5, A is the regular synchronization signal and luminance signal (Y signal), J is the regular RY signal,
K is a regular BY signal, and L is a time division multiplexed signal. L
84 is a horizontal synchronization signal that has been time-compressed by a factor of 1, 85 is a luminance signal that has been time-compressed by a factor of 100, 86 is an R-Y signal that has been time-compressed by a factor of 1, and 87 is a time-compressed signal that has been compressed by a factor of 1. B-Y
It's a signal. In Figure 5, there are diamonds Y, RY, B-
The bandwidth of Y is 6:1.1, but a preferable value is Y:R-
Y=2-6+1, RY:B-1'=I:1. If L in FIG. 5 is input to the LPF 51 in FIG. 2, it will be recorded similarly to G in FIG. 3. The regeneration circuit is a ΔD converter 4
6 output IAK connection! It is necessary to configure the circuit to be used as shown in FIG. In FIG. 6, 84 is a terminal to which the output signal of the sword converter 46 is marked 7711; 85.
89 is R-Y, B-Y memory, 86゜90 is R-Y
, DA converter for B-Y, 87.91 is R-Y, B
-Dynamic de-emphasis circuit for Y, 88.92
95 is a write clock terminal, 94 is R-Y, a BY signal read clock terminal, and 95 is a Y signal read clock terminal. To restore A, J, and K from L, in Figure 4, #t=3. N2=1, A'a=#5=5, and the deviations are good.

The features of Figure 2 are that time compression of the luminance signal is achieved by devising the deflection of the television camera, eliminating the need for expensive high-speed aluminum converters and memory; The number of AD converter and DA converter bits is reduced by applying a common '+'C to the color difference signals and by placing a dynamic de-emphasis circuit at the output terminal of the DA converter.

The feature of Figures 4 and 6 is that the luminance signal and color difference signal are transmitted from the same station?
i; t, the luminance signal and color difference signal are read out in the memory using two specific frequency clocks that are 9-phase synchronized.

The above explanation has been made using the NI'SC system video signal as an example, but the present invention can also be applied to video signals of the PAL U5 system, SE(, 'A'vf system, and medium-high definition television system). Needless to say.

〔Effect of the invention〕

According to the present invention, it is possible to completely eliminate the horizontal shaking of an image and the timing shift between a luminance signal and a chroma signal, which are drawbacks of conventional time division multiplexing systems.

[Brief explanation of drawings]

FIG. 1 is a signal waveform diagram showing an example of a conventional time division multiplexed signal, FIG. 2 is a block diagram showing an embodiment of the video signal recording and reproducing apparatus of the present invention, and FIG. FIG. 5 is a waveform diagram showing an example of the signal waveform of the main part of FIG.
FIG. 4 is a block diagram showing an embodiment of a clock generator used in the present invention, and FIG. 6 is a block diagram showing an embodiment of a time axis expander used in the present invention. 2...Horizontal synchronization signal, 4...Brightness signal, 10...
- Color difference signal (RY signal), 11... Color difference signal (B-Y signal), 25... Image sensor, 28... Synchronization signal generator. 27... Deflection circuit, 29... Time axis compressor, 46...
・Notification converter. 48... Clock generator, 49... Time axis expander, 65... Dynamic emphasis circuit, 54.55
,87.91...Dynamic de-emphasis circuit, 50.52,85.89...Memory, 51.55,8
6.90...DA Konno Kuichita. Representative Patent Attorney Akio Takahashi Figure 7 Figure 2 Figure 3 (6) I Figure 4

Claims (1)

[Claims] 1. In an apparatus for recording and reproducing a time-division multiplexed luminance signal and chromaticity signal or color difference signal on a distribution medium,
An image characterized in that the horizontal synchronization signal and the luminance signal have the same time axis extension characteristics, and the time axis of the luminance signal and the chrominance signal are respectively extended using two phase-synchronized clock signals having different frequencies. Signal recording and reproducing device. 2. Select the deflection characteristics of the image sensor so that the horizontal blanking period of the output signal from the image sensor is longer than the regular period, and add a horizontal synchronizing pulse with a narrower pulse width to the luminance signal than the regular pulse audience. . The video signal recording and reproducing apparatus according to claim 1, wherein time-compressed color signals are multiplexed within the horizontal blanking period.