JPH0530355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a recording and reproducing apparatus such as a VTR or a disk that records and reproduces television signals of the NTSC system, PAL system, etc., and high-definition television signals.

BACKGROUND TECHNOLOGY SMPTE type C format VTRs, which are commonly used in broadcasting stations, can record signals with a bandwidth of about 8M. However, so-called high-definition television signals with a large number of scanning lines are 20MHz
When recording and playing back this high-quality television signal using the above-mentioned VTR, or in order to prevent deterioration of frequency characteristics due to recording and playback of the VTR, it is necessary to divide the input video signal into multiple channels. A method of recording and reproducing by lowering the frequency band may be used.

One method for this is to extend the time axis of the video signal, divide it into multiple channels, narrow the video signal bandwidth per channel, record it on tape, and compress the time axis when playing back. There are some (for example, Japanese Patent Laid-Open No. 57-97281).
FIG. 4 is a block diagram of the recording system, and FIG. 5 is a block diagram of the reproduction system.

Figure 4 shows the brightness signal of the NTSC television signal.
Sy is connected to A-D converter 1 through input terminal 11.
2 and a synchronization pulse is supplied to input terminal 18.
The signal is supplied to the pulse forming circuit 19 through the pulse forming circuit 19. The pulse forming circuit 19 forms various pulses such as a clock necessary for signal processing.The pulse forming circuit 19 supplies the clock to the A-D converter, and the luminance signal Sy is converted into an 8-bit parallel digital signal Sd. converted. This signal S _d is supplied to the memories 13A to 13D having a capacity for one horizontal period, and a write clock and a read clock are supplied from the pulse forming circuit 19 to the memories 13A to 13D at a predetermined frequency and timing. Memory writing and reading are performed as shown in FIG.

That is, each horizontal period T ₁ , T ₂ , shown in FIG. 6A
When the signal S _d at T ₃ , T ₄ . . . is S ₁ , S ₂ , S ₃ , S ₄ . is read at a speed of

The output signals of the memories 13A and 13C are supplied to the switch circuit 14A, and the output signals of the memories 13B and 13D are supplied to the switch circuit 14B, as well as a control signal. The signal shown in FIG. 6 Sb is output as the output, and the D-A converter 15
A and 16A convert it into an analog signal. The frequency of this analog signal is 1/2 of the frequency of the original signal Sy
And the bandwidth is also /1/2.

This analog signal is then transmitted to the FM modulation circuit 16.
A, 16B is supplied as an FM signal, and this
FM signals are supplied to rotary heads 1A, 1B through recording amplifiers 17A, 17B and recorded on tape 2 simultaneously.

During playback, the FM signal is played back from the tape 2 by heads 1A and 1B in FIG. 5, and this FM signal is sent to playback amplifiers 21A and 21B and limiter 22A
22B to FM demodulation circuits 23A and 23B, the analog signal is demodulated, and this analog signal is supplied to A-D converters 24A and 24B, and is also supplied to a pulse forming circuit 29 to form pulses for clocks, etc. The clock pulses are supplied to A-D converters 24A and 24B, and the analog signals are converted into digital signals S _a and S _b .

These signals Sa and Sb are transmitted to memories 25A, 25C and 25B having a capacity for one horizontal scanning period.
and 25D, a write clock and a read clock are supplied from the pulse forming circuit 29 to the memories 25A to 25D, and the signals S ₁ ,
S ₂ , S ₃ , S ₄ . . . are written in the memories 25A to 25D, and read from the memories 25A to 25D at the writing speed during recording. Then, the read signals S ₁ , S ₂ , S ₃ , S ₄ . . . are supplied to the switch circuit 26, and the signals S ₁ , S ₂ , S ₃ , S ₄ . The signals Sd arranged in the order of are extracted. And this signal Sd
is supplied to the D-A converter 27, where Sd is converted into the original luminance signal Sy and taken out to the output terminal 28.

Problems to be Solved by the Invention However, in this case, the nonlinear distortion and output level of the DA converters 15A and 15B in FIG. 4, the input voltage versus frequency nonlinear distortion and sensitivity of the FM modulators 16A and 16B, Non-linear distortion and sensitivity of frequency versus output voltage of FM demodulators 23A and 23B in Fig. 5, and A-
The characteristics of the non-linear distortion and input range of the D converters 24A and 24B vary, and even if the level of the brightness signal input during recording is constant, the level of the reproduced output brightness signal differs for each horizontal scan. Also, the number of scanning lines in one frame is 525 in NTSC,
A high-definition television signal has 1125 lines, which is usually an odd number, and when divided into two channels, lines with the same number change channels every frame, as shown in FIG.

Therefore, fluctuations in the luminance signal level due to variations in characteristics between channels will cause the luminance to differ between lines on the screen, and furthermore, the luminance of the same line will change between frames. In particular, this inter-frame luminance change has a long period of change, so flickering becomes noticeable.

The present invention provides a video signal recording and reproducing apparatus that solves the problem of unsightly screens caused by brightness changes between frames.

Means for Solving the Problems In order to solve the problems, the present invention includes the following steps at the time of recording.
An A-D converter that converts an input video signal into a digital signal, and a channel divider that divides this digital signal line by line into m channels (m is an even number) and distributes lines with the same number between frames to the same channel. the input video signal is divided and recorded on a recording medium using a means for dividing the input video signal, an expanding means for expanding the time axis of the divided digital signal, and a D-A converter for converting the expanded digital signal into an analog signal. During playback, an A-D converter converts each of the m-channel signals reproduced from the recording medium into a digital signal, a compression means that compresses the time axis of this digital signal, and a synthesis means that synthesizes the m-channel digital signals. and a D-A converter that converts the synthesized digital signal into an analog signal to reproduce the original video signal.

Effects According to the present invention, lines having the same number are arranged in the same channel even if the frames change sequentially due to the above-described configuration. Therefore, even if there are variations in the characteristics between channels, such as the sensitivity of the FM modulator or non-linear distortion, the brightness changes between frames, which is the problem with the conventional example described above, do not occur, and flickering is not visible. be.

Embodiment FIG. 1 is a block diagram showing a recording system of a VTR according to an embodiment of the present invention, and FIG. 2 is a block diagram showing its reproduction system. The configurations shown in FIGS. 1 and 2 are the same as the conventional example shown in FIGS. 4 and 5 except that a switch is provided. Switches 30A and 30B are supplied with the output signals of switches 14A and 14B, and are also supplied with a control signal from pulse forming circuit 19 for switching on a frame-by-frame basis. As _shown in FIG. 3, the output signals _S
is supplied to the computer, converted to an analog signal, and recorded on tape.

Also, during playback, A-D converter 24A and 2
Switch 31 newly provided with 4B output signal
A and 31B, and a control signal for switching every frame is supplied from the pulse forming circuit 29. Therefore, the output signals of the switches 31A and 31B are outputted with the channels changed every frame as shown in the third _Sa and Sb, and are supplied to the memories 25A, 25C, 25B, and 25D.
The time axis is compressed. Therefore, the original video signal is taken out at the output terminal 28 in the same manner as in the conventional circuit.

However, in this embodiment, when switching for each frame, the switching is performed within the video section of the expanded signal, but there is no problem if the switching for each frame is performed within vertical blanking.

Effects of the Invention As explained above, according to the present invention, lines with the same number are arranged in the same channel even if the frame changes, so the brightness does not change even if the frame changes, which is a problem with conventional circuits. There is no unsightly screen flickering, and the effect is great.

The present invention also applies to NTSC television signals, PAL
It can be used for television signals, NHK high-definition television signals with 1125 scanning lines, and even MUSE signals, which are a type of NHK high-definition television signals. In particular, the MUSE signal is a line-sequential signal in which the color difference signal is compressed on the time axis within the horizontal blanking of the luminance signal and the order is reset for each frame, so when recording and reproducing this MUSE signal by dividing it into two channels, With the configuration of the present invention, it is possible to eliminate color flickering for each frame.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording system of a recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a reproducing system of the same embodiment, FIG. 3 is an operating waveform diagram of the same embodiment, and FIG. 4 5 is a block diagram of a recording system of a conventional recording and reproducing apparatus, FIG. 5 is a block diagram of a reproducing system of the conventional example, and FIG. 6 is an operating waveform diagram of the conventional example. 12, 24A, 24B...A-D converter, 1
3A-13D, 25A-25D...Memory, 15
A, 15B, 27...D-A converter, 30A,
30B, 31A, 32B...Switch.

Claims (1)

[Claims] 1 During recording, an A-D converter converts the input video signal into a digital signal, and an A-D converter converts the input video signal into a digital signal.
channel dividing means for dividing each line into m channels (m is an even number) and distributing lines with the same number between frames to the same channel; and expanding means for expanding the time axis of the divided digital signal. The input video signal is divided and recorded on a recording medium using a D-A converter that converts a digital signal into an analog signal, and during playback, each of the m channel signals reproduced from the recording medium is converted into a digital signal. An A-D converter, a compression means for compressing the time axis of this digital signal, a synthesizing means for synthesizing the digital signals of m channels, and a D for converting the synthesized digital signal into an analog signal.
- A video signal recording and reproducing device characterized in that it is configured to reproduce an original video signal using an A converter.