JPH0588039B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a component video signal (consisting of a luminance signal of a color television video signal and two types of color signals or three primary color signals (R, G, B)). (all or part of the signal) or transmission method,
In particular, it relates to a signal band compression method that enables recording or transmission using a recording device or a narrowband transmission path that has a bandwidth that is approximately half of the highest frequency of the original component video signal.

[Summary of the Disclosure] The present invention is a signal band compression method that enables recording or transmission of an input component video signal whose maximum frequency is approximately twice that of a VTR having a narrowband recording/reproducing system or a narrowband transmission line. In one embodiment of the present invention, an input component video signal is converted into a two-channel signal with half the band by time-axis expansion, and the lower side band side of each signal is converted to prevent aliasing components from occurring. Converting the residual sideband AM signal into the removed residual sideband AM signal, and changing the carrier frequency of one of the carrier waves to a frequency 1/2n _H , which is an integer (n) times 1/2 of the horizontal scanning frequency _H of the input component signal,
In addition, by setting the number of transport cycles on the other side to 1/4 (2n + 1) _H or 1/4 (2n - 1) _H , they are multiplexed while maintaining a mutual frequency interleaving relationship, thereby configuring a signal for recording or transmission. It is something.

[Prior Art] Examples of frequency interleaving multiplexing in television video signals include the NTSC system and PAL system for color television signals (for example, the ``Digital signal processing of images''
(Published by Nikkan Kogyo Shimbun on May 25, 1982) Chapter 2 p.18-20
reference).

The case of the NTSC system will be briefly explained. In the NTSC system, color subcarriers are quadrature-two-phase modulated using color signals (I, Q signals) and multiplexed onto a luminance signal.
At this time, the frequency sc of the color subcarrier is sc=455× _H /2. Here, _H : Horizontal scanning frequency (15.75kHz
, the carrier color signal has a frequency interleaved relationship with the luminance signal. Therefore, the luminance signal is 4.5 MHz and the chrominance signal (I signal 1.5 MHz, Q signal
0.5MHz), the overall transmission bandwidth is reduced to 4.5MHz.

In the MTSC system, the bandwidth of the chrominance signal is less than half that of the luminance signal, so the transmission bandwidth can be reduced using the above method. On the other hand, for signals having the same signal bandwidth, such as luminance signals, the transmission bandwidth cannot be reduced by the above method.

[Problems to be Solved by the Invention] Therefore, in order to eliminate the above-mentioned drawbacks, signals of each τ period are sequentially extracted from the original component video signal, and the signals that are sequentially extracted are Simultaneously generate two adjacent signals 2
After changing the signal of the two channels to a signal of the two channels, multiplexing the signals of the two channels while maintaining a mutual frequency interleaving relationship, and then extending the time axis to a signal of 2τ period, or converting the changed two channel signals to a signal of each 2τ period. It is conceivable to perform band compression of the original component video signal by extending the time axis and then multiplexing the signal while maintaining a frequency interleaving relationship (although it was not yet publicly known at the time of this application, it was already disclosed in the patent application filed in 1983). -4267 filed by the present applicant).

However, in order to achieve a 1/2 _H frequency shift or a 4/1 _H frequency shift over a wide band to maintain frequency interleaving, the circuit configuration is extremely complex (for example, a wide band Hilbert transformer is required). The problem arises that

The reason why such a wideband frequency shift circuit becomes complicated is that aliasing components occur in a low frequency region near direct current, and complicated processing is performed to remove them.

Therefore, an object of the present invention is to simplify the signal processing circuit by using residual sideband AM with a defined carrier frequency, thereby reducing the band of the component video signal to approximately 1/2.
The purpose of this invention is to provide a band compression method that compresses the bandwidth to 2.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides, on the input side, τ
Sequentially extracting signals of each period as a unit, converting two adjacent signals among the sequentially extracted signals into two-channel signals that occur simultaneously,
Each of the obtained two-channel signals is converted into a vestigial sideband amplitude modulation (VSB-AM) signal in which the lower sideband is removed so that no aliasing components occur, and the converted two-channel signals are The carrier frequency of one of the two channel signals is set to A·n _H (where _H is the horizontal scanning frequency of the input component video signal, and n is a positive integer), and the carrier frequency of the other of the two channel signals is set to , B・(2n+1) _H or B・(2n−1)
By making it _H , the frequency interleave relationship is maintained and multiplexed signals are extracted from the output side, and the time axis of the signal is doubled on either the input side or the output side. Time axis extension to double (however, on the input side, A = 1/2, B = 1/4, on the output side, A
=1, B=1/2), and the signal extracted from the output side is used as a signal for recording or transmission.

In addition, in a preferred embodiment of the present invention, the luminance signal of the sum of even lines is divided by 1 for the luminance signal of the even line.
After delaying the horizontal period, the signals at each odd corner are
After stretching the time axis to a signal with half the bandwidth,
Each of them is converted into an amplitude modulated (AM) signal with carrier frequency _c , and each of them is converted into a vestigial sideband amplitude modulated (VSB-AM) signal through a bandpass filter. is _c + 1/2 ( _H is the line frequency, n is a positive integer), and the other carrier frequency is _c + 1/4 (2n + 1).
Perform balanced modulation as _H or _c + 1/4 (2n - 1) _H to obtain a VSB-AM signal that has a mutual interleaving relationship and has lower sidebands removed so that aliasing components do not occur. Multiplexing allows narrowband recording or transmission.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a block diagram showing an embodiment of a signal processing circuit to which the present invention is applied. In this figure,
1 is a delay device, 2 and 3 are time base expansion circuits, 4 and 5 are AM modulators, 6 and 7 are bandpass filters, 8 and 9 are balanced modulators, and 10 is an adder. Further, SG1 to SG10 indicate output signals of each of the above-mentioned components.

FIG. 2 is a signal spectrum diagram illustrating the signal processing process performed by the embodiment shown in FIG.

Next, the signal processing process in this embodiment will be explained with reference to FIGS. 1 and 2.

First, the input component video signal SG1 such as a luminance signal is divided into two, and one of the signals is sent to the delay device 1.
is introduced and delayed by time τ. Next, the time axis expansion circuit 2 doubles the time axis using the timing signal T which is generated every 2τ to form a signal SG2 whose frequency band is halved. At this time,
Information about half the period τ of the period 2τ is lost.

On the other hand, the other divided input signal is supplied to the time axis expansion circuit 3. As a result, a signal SG3 is formed by expanding the signal of the period that disappeared in the time axis expansion circuit 2 when the time axis was expanded to twice the time axis.

The above-mentioned time axis expansion divided signals SG2 and SG3
is a carrier wave with a frequency _c that is sufficiently high compared to the highest frequency _n that these signals SG2 and SG3 have.
AM modulated in AM modulators 4 and 5,
It is sent out as AM signals SG4 and SG5. Furthermore, these signals SG4 and SG5 are respectively ( _c −
_n ) to ( _c + _L ), and the residual sideband wave is
AM signals SG6 and SG7 are formed. Here, the frequency _L is set to the lowest possible value.

Then signal SG6 changes the carrier frequency to _c + 1/2n _H
The signal is introduced into a balanced modulator 8 having a carrier frequency of 1/2n _H , and is converted into a residual sideband AM signal SG8 having a carrier frequency of 1/2nH. On the other hand, signal SG7 has a carrier frequency of _c + 1/4
(2n + 1) _H or _c + 1/4 (2n - 1) _H , and the carrier frequency is 1/4
It is converted into a residual sideband AM signal SG9 of (2n+1) _H or 1/4(2n-1) _H .

Since these signals SG8 and SG9 have a frequency interleaving relationship, by multiplexing them in the adder 10, a band-compressed component video signal SG10 can be obtained.

Here, the above-mentioned n (integer) is set so that _L < 1/2n _H or f _L < 1/4 (2n-1) _H.

FIG. 3 shows an embodiment of a signal processing circuit that restores the band compressed signal SG10 obtained by the signal processing circuit shown in FIG. 1 to the original component video signal SG1. Since this circuit restores signals according to the reverse process to that shown in FIG. 1, each signal shown in FIG. 3 is the same as signals SG1 to SG10 shown in FIGS. It corresponds to each. In addition, in this figure, 11 and 12 are comb filters,
13 and 14 are balanced modulators, 15 and 16 are bandpass filters, 17 and 18 are residual sideband AM demodulators, 19 is a delay device, 20 and 21 are time-base compression circuits, and 22 is a signal switch.

Next, the signal processing process performed in FIG. 3 will be explained.

First, the band compressed signal SG10, which is an input signal, is divided into two and applied to comb filters 11 and 12, and signals SG8 and SG9 are taken out.
This signal SG8 is passed through a balanced modulator 13 whose carrier frequency is _c + 1/2n _H and a bandpass filter 15.
via the residual sideband AM signal at carrier frequency _c
Changed to SG6. The other signal SG9 has a carrier frequency _c + 1/4 (2n + 1) _H or _c + 1/4 (2n -
1) It is converted into a residual sideband AM signal SG7 of carrier frequency _c via the balanced modulator 13 and bandpass filter 16 set to _H.

These signals SG6 and SG7 are introduced into residual sideband AM demodulators 17 and 18, respectively, and the signals
SG2 and SG3 are obtained as demodulated outputs. This signal SG2 is supplied to the time base compression circuit 20.
The other signal SG3 is delayed by the time τ in the delay device 19, and then supplied to the time-base compression circuit 21. In the time-base compression circuits 20 and 21,
In response to the timing signal t〓, the time axis is compressed to 1/2.

The output signals of these time axis compression circuits 20 and 21 are supplied to a signal switch 22. Then, the outputs of the time axis compression circuits 20 and 21 are alternately taken out from the signal switch 22 in synchronization with the timing signal t, and the restoration of the component video signal is completed.

Further, the signal processing circuit to which the present invention is applied on the recording or transmitting side is not limited to that shown in FIG. 1, but may be configured as shown in FIG. 4, for example. That is, FIG. 4 is an example in which time axis expansion is performed on the output side of the signal processing circuit, and the time axis expansion circuits 2 and 3 in FIG. 1 are omitted, and instead, the time axis of the output signal SG10 of the adder 10 is A time axis expansion circuit 23 is provided to expand the image by a factor of two. In addition, in the case of this example, the local oscillation frequencies supplied to the balanced modulators 8 and 9 are respectively _c +n _H and _c +1/2 (2n+1) _H or _c +1/2 (2n-1)
You need to change it to _H.

Furthermore, in the signal processing circuits shown in FIGS. 1 and 4, before multiplexing the two channel signals while maintaining the interleaving relationship, each signal is converted into a VSB-AM signal by a bandpass filter, but the signal processing circuit shown in FIG. In the AM modulators 4 and 5, signals with frequencies having the same relationship as those added to the balanced modulators 8 and 9 described above are added, amplitude modulated, and then added, thereby creating two channels that maintain a frequency interleave relationship. Multiplex the signal and pass it through a bandpass filter to produce one VSB-
The AM signal may then be added to a balanced modulator and transferred to a lower frequency range to obtain a signal for recording or transmission.

In addition, according to the above embodiment, the band is wider by 1/2nf _H compared to the method (Patent Application No. 61-4267) described earlier in the [Problems to be Solved by the Invention] section. However, since this value can be made negligible compared to the highest frequency of the band compression signal, the practical merit is extremely large.

[Effects of the Invention] As described above, according to the present invention, the band of a component video signal can be compressed to approximately 1/2 using a signal processing circuit having a relatively simple circuit configuration. This not only simplifies the configuration of the playback system, but also facilitates the achievement of wide-density recording and narrow-band transmission of component video signals.
This is an advantage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a signal processing circuit to which the present invention is applied; FIG. 2 is a signal spectrum diagram explaining the signal processing process in FIG. 1;
FIG. 3 is a block diagram showing an embodiment of a signal processing circuit for inputting a band-compressed signal according to the present invention and restoring the original component video signal, and FIG. 4 is a signal processing circuit to which the present invention is applied. FIG. 7 is a block diagram showing another embodiment of the circuit. 2, 3... Time axis expansion circuit, 4, 5... AM modulator, 6, 7... Band pass filter, 8, 9...
... Balanced modulator, 10 ... Adder, 11, 12 ...
Comb filter, 13, 14...Balanced modulator, 1
5, 16...Band pass filter, 17, 18...
... Residual sideband AM demodulator, 19 ... Delay unit, 2
0, 21... Time axis compression circuit, 22... Signal switch, 23... Time axis expansion circuit.

Claims (1)

[Claims] 1. Two channels in which, on the input side, signals of each τ period are sequentially extracted from the input component video signal, and two adjacent signals among the sequentially extracted signals are simultaneously generated. Convert each of the obtained two-channel signals into a vestigial sideband amplitude modulation (VSB-AM) signal with the lower sideband removed so that no aliasing components occur, and the converted two-channel signal. The carrier frequency of one of the two channel signals is A·n _H (where _H is the horizontal scanning frequency of the input component video signal, and n is a positive integer), and the carrier frequency of the other of the two channel signals is By setting the carrier wave frequency to B·(2n+1) _H or B·(2n−1) _H , a mutual frequency interleaving relationship is maintained and the signal is extracted from the output side in the form of a multiplexed signal. , A component characterized in that time axis expansion is performed to double the time axis of the signal on either the input side or the output side, and the signal extracted from the output side is used as a signal for recording or transmission. Bandwidth compression method for video signals. 2. The component according to claim 1, wherein when the time axis expansion is performed on the input side, the coefficients A and B are set to A=1/2 and B=1/4. Video signal band compression method. 3. The component video signal according to claim 1, wherein when the time axis expansion is performed on the output side, the coefficients A and B are set to A=1 and B=1/2. Bandwidth compression method.