JPH0144075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video signal reproducing device, and in particular, a luminance signal and a line-sequential color difference signal are each subjected to time axis compression.
The present invention relates to a device that reproduces a signal obtained by time-division multiplexing of both signals from a recording medium in order to copy and record (dubbing) it onto another recording medium.

BACKGROUND OF THE INVENTION Due to recent dramatic advances in semiconductor technology, precision processing technology, and small component technology, it has become possible to improve the image quality of recording and reproducing devices and to make devices smaller and lighter. Reducing the size and drum diameter of the cassette has a major impact on reducing the size and weight of the device, and in order to secure the necessary recording time for a small cassette, it is necessary to slow down the tape running speed.
In such a compact and lightweight recording/playback device,
In order to obtain high quality images, a new recording and reproducing method other than the current reduced conversion recording and reproducing method is now required.

Therefore, various recording and reproducing methods have been proposed to meet the above requirements, one of which is to time-base compress the two types of color difference signals obtained by FM demodulating the carrier color signal, and also compress the luminance signal. Compress the time axis,
These signals are time-division multiplexed, this time-division multiplexed signal is frequency-modulated, and recorded on a recording medium. During playback, signal processing is performed in the opposite manner to that during recording, and the original standard color video signal is reproduced. There was a recording/reproducing apparatus configured to obtain a reproduction output (for example, see Japanese Patent Laid-Open No. 53-5926). This recording/reproducing device takes into consideration the difference between the bands of the luminance signal and the color difference signal, and is designed to transmit the color difference signal, which is a signal with a narrower band, within the horizontal blanking period. The - color difference signal transmitted within the 1H period is compressed in the time axis to about 20% of the 1H period, and the luminance signal is compressed in the same band as the time axis compressed color difference signal, which is advantageous from the viewpoint of bandwidth utilization. Approximately 80% of the 1H period to account for
The two color difference signals are time-division multiplexed as line-sequential signals that are transmitted alternately every 1H, and this signal is supplied to the FM modulator, and the output of this FM modulator is Based on the recording and reproducing method (hereinafter referred to as the timeplex method) in which signals are recorded on magnetic tape, etc., and during playback, signal processing is performed in the opposite manner to that during recording to obtain a reproduced color video signal. It was composed of

According to the timeplex method for transmitting such time-division multiplexed signals, there is no period during which the luminance signal and the color difference signal are transmitted simultaneously, so the luminance signal and the carrier chrominance signal cannot be combined, as in the case of NTSC or PAL color video signals. There is no mutual interference or moiré between the luminance signal and the color difference signal, which can occur when transmitting the luminance signal and the color difference signal by band sharing multiplexing.
In the case of NTSC, PAL, and SECAM color video signals, even if they are recorded and played back on tracks that are not aligned in H by an azimuth recording and playback system, the time division multiplexed signals on adjacent tracks are azimuthal. Since it is recorded in the form of a frequency-modulated wave signal obtained by frequency modulating a high-frequency carrier wave with a large loss effect, almost no crosstalk occurs due to the azimuth loss effect, and the above-mentioned crosstalk can be avoided. No countermeasures are required, and high-quality playback images can be obtained.

Furthermore, the above-mentioned time-domain compressed luminance signal and time-domain compressed color difference signal in the timeplex method have an energy distribution in which the energy is large in the low frequency band and small in the high frequency band. Since the signal format is suitable for The reproduced image quality can be significantly improved compared to the current low frequency conversion recording and reproducing method.

When dubbing time-division multiplexed signals based on the timeplex method, two recording and reproducing devices are prepared, and the time-division multiplexed signal based on the timeplex method described above is first frequency-modulated and recorded using one of the devices. The reproduced frequency-modulated time-division multiplexed signal obtained by this is reproduced using a standard method for reproduction through a reproduction signal processing system such as an FM demodulator, a time axis expansion circuit, and an encoder. After converting it into a color video signal, it is supplied to the other recording/reproducing device. The other recording/reproducing device generates a frequency-modulated time-division multiplexed signal through the recording signal processing system having the above-mentioned configuration again from this reproduction standard color signal, and records this signal on another unrecorded recording medium to perform dubbing. was being carried out.

Problems to be Solved by the Invention However, when dubbing a standard color video signal, it passes through the recording system of one recording/playback device, the playback system, and the recording system of another recording/playback device, and then unrecorded magnetic signals. Since it will be recorded on tape,
As it passes through numerous filters, FM modulators, FM demodulators, time axis compression systems, and time axis expansion systems, the frequency characteristics, pulse characteristics, linearity, etc. of the dubbed color video signal deteriorate. There was a problem in that the quality of the reproduced image deteriorated.

Therefore, the present invention does not return to the standard color video signal, but by recording the reproduced time-division multiplexed signal in the time-plex format with the time-division multiplexed signal configuration corrected for variations in reproduction time.
It is an object of the present invention to provide a video signal reproducing device that solves the above problems.

Means for Solving the Problems The present invention provides two types of time-axis compressed color difference signals alternately every horizontal scanning period, and one time-axis compressed color difference signal within one horizontal scanning period. A reproduction means for reproducing a previously recorded signal of a recording medium in which a time division multiplexed signal, which is time-divisionally divided with a luminance signal, is frequency-modulated and recorded, and then performing FM demodulation to obtain a reproduced time division multiplexed signal; It has a memory circuit used to expand the time axis of the time axis compressed luminance signal when outputting, and supplies the reproduced time division multiplexed signal to the memory circuit during dubbing, and expands the reproduction time axis of the entire reproduced time division multiplexed signal. It has a structure that eliminates fluctuations, and one embodiment thereof will be explained below with reference to the drawings.

Embodiment FIG. 1 shows a block system diagram of a recording/reproducing apparatus having an embodiment of the apparatus of the present invention. Here, the color video signal dubbing device according to the present invention is composed of a part of the reproduction system of one of the two recording and reproduction apparatuses and a part of the recording system of the other recording and reproduction apparatus. However, for convenience of illustration, FIG. 1 shows one recording/reproducing apparatus including the above-mentioned dubbing apparatus. First, the recording operation of a standard color video signal by the recording/reproducing apparatus will be explained. In FIG. 1, for example, a SECAM color video signal (this is a composite video signal) having a waveform as shown in FIG. 2A or 3A, which has entered input terminal 1, is connected to terminal R. The luminance signal is supplied to a reduction filter 3 through a switch circuit 2, where the luminance signal is separated and supplied to a decoder 4. The decoder 4 separates and extracts the carrier color signal, which is a frequency modulated wave, from the SECAM color video signal using a band filter (not shown), and sends the color difference signal through a bell filter and an FM demodulator (both not shown). (RY) and (B
-Y) are synthesized alternately in time series every 1H to obtain a line-sequential color difference signal as shown in FIG. 2B.

This line-sequential color difference signal is based on the DC level b ₁ of the 4.9 μs wide achromatic part (non-modulated carrier part) in the back porch within the 1H period in which the color difference signal (B-Y) is transmitted, and the color difference signal (R-Y ) is transmitted next
There is a fixed value difference from the DC level _b2 of the 4.9 μs wide achromatic portion (non-modulated carrier portion) in the back porch within the 1H period. This is because the color subcarrier frequency of the carrier color signal is 4.25 MHz for the color difference signal (B-Y) transmission line and 4.406 MHz for the color difference signal (R-Y) transmission line. The line sequential color difference signals are supplied to the AD converter 14 through the switch circuit 13 after being subjected to a DC level shift so that the DC level of the achromatic color portion of one color difference signal matches that of the other color difference signal.

On the other hand, a luminance signal separated from the input SECAM color video signal is taken out from the reduction filter 3, and a synchronization signal is separated and extracted from this luminance signal by a synchronization separation circuit 6, while an analog-to-digital conversion is performed by an AD converter 5. After that, they are supplied to random access memories (RAM) 8 and 9, respectively. The control pulse generator 7 is supplied with the synchronization signal from the synchronization separation circuit 6, and is also supplied with the rectangular wave b as a color difference signal discrimination pulse.
It supplies the generated control pulses to the converters 5 and 14 and the DA converters 11 and 16, respectively, and also generates horizontal synchronization signals and various pulses with a width of about 4 μs, and further
A write clock and a read clock are generated and outputted to the RAMs 8, 9, and 15 at predetermined timing and at a predetermined repetition frequency, respectively.

That is, the control pulse generator 7
For example, by supplying an 8MHz write clock pulse to one of RAMs 8 and 9, a 1H worth of luminance signal transmitted in a video period of 52 μs is also written to one of the RAMs. Immediately after transmission of the 1H minute (52 μs) time axis compressed color difference signal is supplied to the other RAM and stored in the other RAM only during the period excluding the serial transmission period of the horizontal synchronization signal and the 1H minute time axis compressed color difference signal. The luminance signal for 1H before the current one is read out. The read operation and write operation of the RAMs 8 and 9 are alternately switched every 1H, and the switch circuit 10 on the output side of the RAMs 8 and 9 performs the read operation using control pulses from the control pulse generator 7. Since the output signal of the RAM 8 or 9 on the side that is present is selectively output, the luminance signal whose time axis has been compressed to 4/5 is intermittently taken out from the switch circuit 10 without any loss of information as shown in FIG. 2E. It will be done. This time-base compressed luminance signal is sent to the DA converter 1.
1 performs digital-to-analog conversion and is supplied to the switch circuit 12.

On the other hand, the line sequential color difference signal outputted from the switch circuit 13 is supplied to the RAM 15 after being analog-to-digital converted by the AD converter 14 .
Within 1H (=64 μs), the RAM 15 writes a line-sequential color difference signal transmitted during a 52 μs video period using a write clock pulse of, for example, 2 MHz from the control pulse generator 7, and waits for a certain period (for example, 1.6 μs) after the writing is completed. For example from 10MHz
The color difference signal whose time axis has been compressed to 1/5 is read out using the readout clock pulse (therefore, one readout period is 10.4 μs).

The switch circuit 12 receives a time-domain compressed line sequential color difference signal having a waveform as shown in FIG. 2C, a time-domain compressed luminance signal having a waveform as shown in FIG. Approx. taken out from the generator 7 as shown in Figure 2D
Switching control is performed to time-division multiplex the 4 μs width horizontal synchronizing signal based on the output control pulses of the device 7, respectively. The time-division multiplexed signal taken out from the switch circuit 12 is supplied to the discrimination burst signal addition circuit 18, where the discrimination burst signal generation circuit 1
The determination burst signal generated in step 7 is added. This discrimination burst signal is a color difference signal (B-
This is a burst signal for distinguishing the transmission line of (B-Y) and (R-Y), for example, a single frequency signal of approximately 1.5 MHz is a color difference signal of either (B-Y) or (R-Y). It is generated only on the transmission line R--Y (in this case) in correspondence with the generation period of the horizontal synchronizing signal, as shown in FIG. 2F.

In this way, when a SECAM system color video signal such as the color bar signal shown in FIG. 2A and FIG. As shown in B, a discrimination burst signal is superimposed on the horizontal synchronization signal every 1H (=64μs), and the horizontal synchronization signal, color reference level (DC level of the achromatic part of the first color difference signal) and time are superimposed on the horizontal synchronization signal. Axial compression color difference signal (RY)c
or (B-Y)c and the time-domain compressed luminance signal are time-division multiplexed, respectively, and the time-domain compressed color difference signal is extracted as a time-division multiplexed signal that is transmitted line-sequentially. This time-division multiplexed signal having a waveform as shown in FIG. The signal is supplied to the recording head 25 through a recording signal processing circuit, and is thereby recorded on the magnetic tape 26.

Next, the operation during reproduction will be described. At this time, the switch circuits 2 and 13 are connected to the terminal P side, respectively. The reproduction head 27 reproduces the time division multiplexed signal recorded on the magnetic tape 26 in the form of a frequency modulated wave, and this reproduced frequency modulated wave is transmitted to the reproduction amplifier 28, the equalizer 29, the high-pass filter 30, and the FM. The reproduced signal is passed through a known reproduced signal processing circuit comprising a demodulator 31 and a de-emphasis circuit 32 to produce a reproduced time division multiplexed signal as shown in FIG. 3B. This reproduced time division multiplexed signal passes through a switch circuit 38 which is controlled to pass the input signal as is when not dubbing, and further passes through a switch circuit 2 and a low-pass filter 3 connected to a terminal P, respectively. A switch circuit 13 is supplied to the converter 5, the synchronous separation circuit 6, and the discrimination burst signal detector 33, respectively, and is connected to the terminal P.
It is supplied to the AD converter 14 through. AD converter 5, RAM8 and 9, switch circuit 10 and
A circuit section including the DA converter 11 generates a reproduced luminance signal whose time axis is extended and returned to the original time axis based on the output signal of the control pulse generator 7. Here, when one of RAMs 8 and 9 is performing a write operation for the time-base compressed luminance signal of the reproduction time division multiplexed signal, the other one is performing a read operation, and RAMs 8 and 9 perform a read operation alternately every 1H. Performing the write operation and write operation are the same as during recording, but unlike during recording, the repetition frequency of the write clock pulse is, for example,
At 10MHz, the repetition frequency of the readout clock pulse is, for example, 8MHz, so the reproduced luminance signal whose time axis has been expanded by 5/4 (that is, whose time axis has been expanded by the amount of time axis compression) is alternately output from RAMs 8 and 9 every 1H. It is taken out.

On the other hand, the circuit section consisting of the AD converter 14, RAM 15, and DA converter 16 writes the time-axis compressed color difference signal in the reproduced time division multiplexed signal to the RAM 15 based on the output signal of the device 7, and then performs a read operation. A line-sequential color difference signal with the time axis returned to its original state is obtained. In other words, RAM15 is, for example, 10MHz
A digital signal of a reproduced time axis compressed color difference signal is written by a write clock pulse of 2 MHz, and a digital signal of a reproduced line sequential color difference signal whose time axis has been expanded five times and whose time axis has been restored is read out by a read clock pulse of 2 MHz. The read digital signal is converted into a reproduction line sequential color difference signal through the DA converter 16 and then supplied to the first input terminal of the encoder 34. Further, the 1.5 MHz discrimination burst signal is detected by the discrimination burst signal detector 33 and supplied to the second input terminal of the encoder 34 .

The encoder 34 applies a predetermined DC level difference to each line of the color difference signals (R-Y) and (B-Y) of the reproduction line sequential color difference signal, performs frequency modulation to obtain a frequency modulated wave, and further outputs the frequency modulated wave. Transmission of the frequency modulated wave is interrupted only during the horizontal synchronization signal of the frequency modulated wave and the period before and after the horizontal synchronization signal, and a carrier color signal that is the frequency modulated wave conforming to the SECAM system is generated.

taken out from the output terminal of encoder 34
The reproduced carrier color signal conforming to the SECAM method is
The signal is supplied to the mixing circuit 35 shown in the figure, where it is mixed with the reproduced luminance signal from the DA converter 11 and the synchronization signal from the control pulse generator 7, respectively.
After being converted into a reproduced color video signal conforming to the SECAM system, it is output to the output terminal 36.

In the recording and reproducing apparatus that performs such recording and reproducing operations, the operation when dubbing a recorded signal on the recorded magnetic tape 26 to the unrecorded magnetic tape 42 will be described next. During dubbing, a dubbing control signal is applied to the control pulse generator 7 from the input terminal 37.

By the way, the reproduction time division multiplexed signal outputted from the output terminal 39 is transmitted between the magnetic tape 26 and the reproduction head 2.
In general, there is playback time axis fluctuation (jitter) due to fluctuations in the relative linear velocity between the two. If this reproduction time axis variation is large, when the dubbed time division multiplexed signal is reproduced, the reproduction time axis variation in this reproduction system will also be added to generate a clock pulse that supplies a clock pulse to a circuit that expands the time axis. The circuit (this is in the control pulse generator 7) is unable to sufficiently follow the fluctuations in the reproduction time axis, and due to the difference in time axis expansion rate between the time axis compressed luminance signal and the line-sequential color difference signal, the luminance A shift may occur between the signal and the color difference signal on the screen.

Therefore, in this embodiment, the output reproduction time-division multiplexed signal of the switch circuit 38 is passed through the switch circuit 2 and the reduction filter 3, respectively, and the AD converter 5, the RAMs 8 and 9, the switch circuit 10 and the DA The time-base compressed luminance signal is supplied to a time-base expansion circuit composed of a converter 11. However, in this time axis expansion circuit, the dubbing control signal input to the input terminal 37 causes the control pulse generator 7 to generate a clock pulse at a frequency and timing different from those used during time axis expansion. The playback time axis variation is removed without performing axis extension.

That is, the RAMs 8 and 9 repeat write and read operations every 1H, but the write clock pulse has the same time axis variation as the reproduction time division multiplexed signal, the read clock pulse has the same repetition frequency as the write clock pulse, and The DA converter 11
A reproduced time division multiplexed signal from which reproduction time axis fluctuations have been removed is extracted.

This reproduced time division multiplexed signal is supplied from the output terminal 40 to a dubbing signal input terminal of another recording/reproducing apparatus.

The input terminal 41 in FIG.
0, a clamp circuit 21, an FM modulator 22, a high-pass filter 23, and a recording amplifier 24, and are supplied to a recording head 25, where they are recorded on an unrecorded magnetic tape 42. In this way, the recorded signal on the recorded magnetic tape 26 is dubbed onto the unrecorded magnetic tape 42 without being converted into a standard color video signal, and moreover, the playback time axis fluctuations are removed before dubbing. It is possible to dub signals of extremely high quality compared to

By the way, as mentioned above, the horizontal synchronizing signal in the playback time division multiplexed signal from the de-emphasis circuit 32 has a narrow pulse width of about 4 μs, so when it goes through the recording and playback process of a recording and playback device whose band is limited, its playback is difficult. The waveform becomes sluggish, and the discrimination burst signal in the reproduction time division multiplexed signal also deteriorates during the recording and reproducing process.

Therefore, in another embodiment of the present invention, the switch circuit 38 converts the horizontal synchronization signal (including the vertical synchronization signal component) in the reproduced time division multiplexed signal from the de-emphasis circuit 32 and the burst signal for discrimination into control pulse generators. The horizontal synchronizing signal generated by 7 without signal deterioration and the discrimination burst signal from the discrimination burst signal generation circuit 17 are used instead. As a result, a playback time division multiplexed signal in which the horizontal synchronization signal and the discrimination burst signal have been switched is taken out from the switch circuit 38, and is supplied from the output terminal 39 to the dubbing signal input terminal 41 of another recording/playback device. Ru.

Application Example The device of the present invention can also be applied to recording and reproducing color video signals of the PAL system and the NTSC system. However, in this case, the decoder 4 needs to demodulate the carrier color signal and then convert it into a line-sequential color difference signal, and the encoder 34 needs to perform processing to synchronize the reproduced line-sequential color difference signals.

Effects As described above, according to the present invention, a time-plex time-division multiplexed signal reproduced from a recording medium is converted into a time-base compressed luminance signal without converting it into a standard color video signal. Since the time axis expansion circuit is used to remove reproduction time axis fluctuations of the reproduced time division multiplexed signal, it is possible to prevent the occurrence of color shift due to reproduction time axis fluctuations, and it is possible to reduce dubbing compared to conventional methods. It is possible to reduce the number of times a color video signal passes through a filter, FM modulation/demodulation, etc., and the number of times it passes through a time-base compression circuit and a time-base expansion circuit can also be reduced by one, so the color video signal can be converted into a time-division multiplexed signal. This system has the characteristics that it is possible to perform dubbing with higher quality than the conventional method even in the signal format of .

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing a recording/reproducing apparatus having an embodiment of the device of the present invention, and FIGS. 2A to 3F and FIGS. 3A and 3B are signal waveform diagrams for explaining the operation of the block system shown in FIG. 1, respectively. It is. 1...Standard color video signal input terminal, 4...
... Decoder, 5, 14 ... AD converter, 6 ... Synchronization separation circuit, 7 ... Control pulse generator, 8, 9, 15 ... Random access memory (RAM), 11, 16 ... DA conversion vessel, 12,
38... Switch circuit, 17... Burst signal generation circuit for discrimination, 22... FM modulator, 26... Recorded magnetic tape, 31... FM demodulator, 34...
Encoder, 35...Mixing circuit, 36...Reproduction standard color video signal output terminal, 37...Dubbing control signal input terminal, 39, 40...Reproduction time division multiplex signal output terminal for dubbing, 41...Reproduction for dubbing Time division multiplex signal input terminal, 42...unrecorded magnetic tape.

Claims (1)

[Scope of Claims] 1. Two types of time-axis compressed color difference signals are alternately generated in each horizontal scanning period, and one time-axis compressed color difference signal and a time-axis compressed luminance signal are alternately generated in one horizontal scanning period. A reproducing means for reproducing a previously recorded signal of a recording medium in which a time division multiplexed signal is frequency-modulated and recorded, and then performing FM demodulation to obtain a reproduced time division multiplexed signal; A configuration that includes a memory circuit used to expand the compressed luminance signal in the time axis, supplies the reproduced time division multiplexed signal to the memory circuit during dubbing, and removes reproduction time axis fluctuations of the entire reproduced time division multiplexed signal. A video signal reproducing device characterized by: 2. The video signal reproducing apparatus according to claim 1, further comprising a terminal for outputting the reproduced time division multiplexed signal from which time axis fluctuations have been removed.