JP2795343B2 - TV signal transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a television signal transmission or a television signal recording, in which a transmission path or recording having a band narrower than a required transmission bandwidth given by a television system. To the device,
The present invention relates to a system for transmitting or recording television signals in the entire band, and more particularly to a television signal transmission or recording system suitable for surveillance television recording using a small and inexpensive VTR such as a so-called VHS system-VTR. [Prior art] A TV signal has a signal band of 4 MHz or more, and it goes without saying that the same band is required for recording, but a small and inexpensive VTR, such as a VHS-VTR, is an NTSC TV signal. Is separated into Y and C, and the Y signal is flattened to about 2MHz. At 3MHz, it consists of a luminance channel that considerably reduces the response (more than 10dB) and a chromaticity channel that can pass the carrier chromaticity signal about ± 500kHz. Although such a VTR is used for recording on a surveillance television, the band, particularly the luminance signal band, is not sufficient. For monitoring records, VTRs are specially devised for monitoring, generally called time-lapse VTRs, but the signal system is almost the same as the VHS-VTR signal system described above.
The resolution is almost the same. [Problems to be solved] As described above, even a TV signal having a resolution of 4.2 to 4.5 MHz has a resolution that is reduced to about half by VTR recording, so it is difficult to use it in security monitoring records. Therefore, even if the offender is imaged by the camera and recorded on the VTR, the offender's face cannot often be specified due to lack of resolution. An object of the present invention is to provide a method of obtaining a resolution of 4.5 MHz or more by processing and deforming a signal itself even when using a VHS-VTR, thereby doubling the resolution of monitoring and recording. is there. [Means for Solving the Problems] In order to achieve the above object, the present invention divides a television signal to be transmitted into n channels into 1 / n sub-samples for an arbitrary natural number n. , Are transmitted in frame order. That is, the television signal transmission system of the present invention includes the following units. Source sampling means for sampling a television signal to be transmitted at a frequency twice or more the upper limit frequency thereof. Sub-sampling means for sub-sampling each of a plurality of continuous samples of the output sample sequence of the source sampling means into a plurality of sub-samples and dividing the sample into a plurality of channel signals. A means for rearranging a plurality of outputs of the sub-sampling means on a time axis and transmitting the outputs for each channel in a time-division manner for each scanning cycle of the television scanning method. Means for controlling the phase of the source sampling by obtaining PLL phase information from the subsampled result. Generally, surveillance records are recorded by dropping frames like a time-lapse VTR, and do not require recording of complete moving images. In such a case, one frame of the input signal to be recorded is divided into two frames, the bandwidth is reduced to one half, and the bandwidth is reduced to one half. By repeatedly sending out a wideband frame twice, there is no problem even if only 15 frames of information can be recorded per second. In addition, in a method of transmitting a sub-sampled signal in an analog manner, as is well known to those skilled in the art, it is required that the re-sampling phase at the receiving end be exactly the same as the sub-sampling phase at the transmitting end. However, the present invention provides a simple and effective new method especially in this regard. [Operation] According to the present invention, an NTSC television signal is
Without separation of Y and C, the entire band can be recorded and reproduced using only the luminance channel such as VHS-VTR.Therefore, in applications that do not require much smoothness of motion, for example, in monitoring recording, etc. An inexpensive recording device is provided, and its practical effect is extremely large. In addition, since so-called high-definition television signals having 1000 or more scanning lines can be recorded and played back while dropping frames, so-called "background pictures" mainly including still images and hi-fi music are provided at extremely low cost. It will also be. [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 3 is an explanatory diagram of signal sampling according to the present invention, showing a case where the number of channels is n = 2 as an example. The television signal waveform to be transmitted or recorded, indicated by the solid line, is sampled on the time axis at one cycle Ts of the Nyquist sampling frequency, and subsampled into two channels A and B every other sampling and divided. I do. If the resulting spectrum remains Nyquist sampling as shown in FIG. 4, the original TV signal component indicated by the solid line in FIG. 4, that is, the baseband component, and the sampling frequency fs
And fs above and below fs. Needless to say, a similar higher-order spectrum, that is, a repeat spectrum appears at a frequency that is an integral multiple of fs, but is omitted in FIG. As shown in FIG. 3, the two channels A and B separated by the subsample 1
In the channel signal spectrum, since sampling is further performed at fs / 2, the frequency of fs / 2 becomes a new sampling frequency, and a side band as shown by a dashed line in FIG. 4 is generated. The upper and lower sidebands are second harmonics. It is important to note here that the subsampling phase differs by 180 degrees for both A and B channels, as shown in Fig. 3, so the fs / 2 sideband also has a 180 degree phase difference for both A and B channels. It is different. Therefore, if the signals of both the A and B channels are transmitted using a general analog transmission path, and the signals resampled at the same phase as the source sampling phase are rearranged again into one sample sequence,
The upper and lower sidebands of fs / 2 cancel each other out, and the baseband component and the upper and lower sidebands of fs, and more precisely, the repetition spectrum at a multiple of fs Can be reproduced. It is self-evident that this is true not only for the two channels A and B, but also for any n channels, and the present invention makes it possible to use each of the n channels at a very low cost recently for home television reception. It uses a digital frame memory used for a video recorder and a home VTR to delay the required amount and transmit the frames in sequence. For this reason, the signal waveform on the transmission line has exactly the same shape as a general television waveform, which leads to a feature that a transmission line or VTR already existing in the world can be used as it is. However, most home VTRs that have already become widespread, as described above, separate the NTSC signal into a luminance signal component and a chrominance signal component, record them according to their characteristics, and record them separately before output. The luminance and chromaticity signals are synthesized and sent out as before, but the luminance signal band is almost flat, up to about 2 MHz, as shown by the solid line in FIG. Enter cutoff at ~ 3.3MHz. Therefore,
The frequency of 50% amplitude of the upper limit of the pass band is about 2.5 MHz, and fs may be selected so that the lower side band of fs / 2 has a positional relationship with the base band at this frequency. Then the sub-sampling frequency is about 5.3MHz, fs
Is around 10.7MHz. Since this fs almost coincides with the triple frequency of the NTSC color subcarrier, conversely, by selecting fs exactly three times the color subcarrier and performing coherent sampling, the color burst is used for sampling phase control and the whole is extremely It can be inexpensive. This is the most remarkable point in the present invention. The frequency components actually recorded and reproduced are only the baseband component indicated by the solid line in FIG. 5 and the portion indicated by the dotted line in the VTR luminance channel band among the lower side waves of fs / 2.
The component shown by the dotted line is that the baseband component is attenuated at fs / 4 or more, whereas the component at fs / 4 or more is folded at the frequency fs / 4 and becomes a folded signal, and the frequency spreads in the lower direction. is there. Next, FIG. 1 and FIG.
A specific description will be given based on the embodiment of the signal processing system shown in FIG. FIG. 1 is a block diagram of a pre-signal processing system for pre-processing a signal to be recorded prior to recording. The PAL method is also the same in principle, but the case of NTSC will be described here. Input signal is sampled by sampling circuit 1
After source sampling at fs and sub-sampling at the A and B switches 2, the B signal is delayed by one frame in a frame memory (such as a digital frame memory) 3 and
The signal is assembled into a frame sequential signal by the b switch 4, and an ID pulse (identification pulse) indicating the contents of the assembly is added by an ID adding circuit 5 and supplied to a VTR input. On the other hand, part of the input signal is synchronously separated by the synchronous separation circuit 6, and the composite synchronous signal (MS) and the burst gate pulse (BF)
Occurs. 7 in the figure is 6 of the color subcarrier frequency.
A variable frequency oscillator (6 × fscVCO) having twice the frequency, the oscillation output of which has been frequency-divided by a first frequency-dividing circuit 8, is supplied to a sampling circuit 1, and further a second frequency-dividing circuit 9.
The A / B switch 2 is driven by dividing the frequency by 2. A part of the output of the second divide-by-2 circuit 9 is divided by 3 by the divide-by-3 circuit 10, and the gate pulses corresponding to the 0th, 1st, and 2nd phases of the divide-by-3 are applied to the next stage. The signal is supplied to the gate circuit 11. The gate circuit 11 is also supplied with a clock of fs / 2 and a burst gate pulse (BF).
Is gated by a three-pulse gate pulse from the divide-by-3 circuit 10, and a triple-pulse pulse gated by a burst gate pulse is generated. The # 0 circuit 12, the # 1 circuit 13, and the # 2
Send to circuit 14. The # 0, # 1, and # 2 circuits are one type of memory, and a register is used for a digital circuit, and a sample holder is used for an analog circuit. The inputs of these three memories are sub-sampled signals, and the gate circuit
Since the three-pulse pulse from 11, which is also a pulse for the burst period, the # 0, # 1, and # 2 circuits accumulate the sample values of each of the three-time units of the subsampled burst. The triplet sample value of the accumulated burst is
Among them, # 1 and # 2 are arithmetically averaged by the arithmetic averaging circuit 15,
The value is subtracted by the value of $ 0 by the subtraction circuit 16 to become a PLL control signal for controlling the frequency of the variable frequency oscillator (6 × fscVCO) 7. As a result, the sample phase of ♯0 is always stable when the instantaneous value of the subsampled burst sine wave coincides with the zero cross point where the value changes from positive to negative. This will be described with reference to FIGS. 6 and 7. That is, FIG. 6 shows the source sampling A and B subsamples of the burst portion at the time of the preprocessing before recording, the solid line is the sine wave of the input burst signal, the dotted line is the sine wave of the burst subsampled to the B channel, Further, the B sample sequence is sequentially associated with # 0, # 1, # 2. FIG. 7 is a vector diagram illustrating the explanation of the sampling pulse phase control. In each of ♯0, ♯1, and ♯2, A0 is a direct current component (the pedestal level of the television signal) with respect to the burst phase error φ. ), ♯0 = A0 + sin (φ + π), ♯1 = A0 + sin (φ−π /
3) Since ♯2 = A0 + sin (φ + π / 3), subtracting ♯0 from the arithmetic mean of ♯1 and ♯2 gives (♯1 + ♯2) / 2-♯0 = (A0 + sin ( φ−π / 3) + A0 + sin (φ + π / 3)) / 2− (A0 + sin (φ + π)) = A0 + 0.5 · sin (φ) −A0 + sin (φ) = 1.5 · sin (φ) Irrespective of this, a signal proportional to sin (φ) to φ, that is, a phase error can be taken out, so that it can be effectively used as a PLL error signal. However, it should be noted that the burst sine wave has a phase difference of π every 1H, so the output of the divide-by-3 circuit 10 also runs at the same frequency and phase as the burst. When looking at the signal as a reference, the same is repeated with a phase shifted by a half cycle of the burst sine wave. In this respect, since the same operation as the PLL circuit of the general color receiver is performed, it is easily understood that the operation as the PLL phase control is also exactly the same as that of the general color receiver. The state of the power-on condition of the divide-by-3 circuit 10 or the like is unknown, but it is only necessary that the phase of fs / 2 matches the sample phase in the pre-recording pre-processing and the post-reproduction post-processing. Therefore, even if the initial value of the divide-by-3 circuit 10 is deviated, the PLL loop save destination is always sub-sampled for both the pre-recording pre-processing PLL and the post-reproduction post-processing PLL according to the above description. This is the zero cross point of the burst sine wave from negative to positive. The description returns to FIG. The switching / ID signal generation circuit 17 first promises A as the first source sampling of the frame to be transmitted by sub-sampling and B as the next, and sets the composite synchronization (MS).
The A / B switch 2 is supplied to the A / B switch 2 by determining from which of the A and B switches 2 to start from the output of the second divide-by-2 circuit 9. The second is an ID signal. A signal indicating the contents of a frame is determined by using a vertical blanking signal, for example, the 1H period of the 20th H, when the a signal is zero (0-IRE unit of the television signal), and when the b signal is one. (80 of TV signal
100100-IRE unit), a,
It is used as a synchronizing signal for the b frame cycle, and is used for control for assembling the reproduced a and b frames into one complete frame signal without fail. The reproduction signal from the VTR is subjected to the processing shown in the post-reproduction signal processing system block diagram shown in FIG. 2 to restore the original wideband signal. That is, the reproduction signal is resampled by the sampling circuit 18 and is
One with frame delay and one without delay,
The A and B switches 20 driven at a frequency of fs / 2 combine them into one unit.
This is repeated twice, and externally, unnecessary ID signals are removed and sent to the output. For clock generation and sample phase control, the same sampling circuit for pre-signal processing is used to make the re-sampling phase for post-processing the same. Therefore, the components denoted by the same reference numerals as those described above have the same configuration and operation as those of the prior signal processing system of FIG. 1, and the description of this portion will be omitted to avoid repeating the same description. What differs from the prior signal processing system is the ID detection by the ID detection circuit 22 and the control based on the detected result. First, the frame-sequential ID pulse superimposed on the 20H is a frame to be stored in the frame memory 19 because it indicates the signal a when it is zero, and the frame repeat circuit 21 is a frame to repeatedly send out the previously sent frame. is there. When the signal is 1, the signal is a b signal.
Switching to 0 indicates that the original sampling sequence should be restored, and the frame repeater 21 sends out the output of the A and B switches 20 as it is, and at the same time prepares to send out the same signal in the next frame. To accumulate. Another point is that in order to match the initial conditions of the A and B switches 20 with those of the pre-recording preprocessing, the A / B discriminating circuit 23 outputs the output fs / 2 of the second divide-by-2 circuit 9 at the frame start. Is to set the initial condition of the A, B switch control signal based on the promise to the pre-processing side that initially sets the A signal as the A signal. Although omitted in FIG. 1 and FIG. 2, in order to apply the digital frame memory, A /
It goes without saying that D / A converters are required for D converters and outputs. However, other parts can be configured digitally or analogly. The important points are 1) source sampling, 2) division into two channels by half sub-sampling, and 3) recording of the divided two channels in frame order. 4) In order to make the resampled phase after reproduction exactly the same as the sample phase of the preprocessing, the sample phase control signal is obtained from the subsample output in both the preprocessing and the postprocessing. That is the thing. As can be seen from this description, except for 3), it is easy to understand that 1), 2), and 4) can be configured in an analog manner, and in particular, according to the present invention, there is a feature that can also be configured in an analog form according to 4) Is done. According to the signal processing described with reference to FIGS. 1 and 2, components of 0.75 times (approximately 2.7 MHz) or less of the frequency of the color subcarrier are transmitted as baseband components, and frequency components higher than that are transmitted as color subcarrier frequencies. It is folded at 0.75 times the high frequency component of the video signal in the direction of lower frequency, which is superimposed and transmitted as a folded signal by sub-sampling, so the 3.58 MHz carrier color signal is converted to about 1.8 MHz. Transmitted as a composite signal,
The transmission is performed as a single unit, so that there is no resolution degradation due to the separation and synthesis of Y and C, and the full band transmission determined by the television system is performed. In the above, the case of the NTSC television signal has been described in detail as an example, but the same applies to the case of the PAL system. The strong and different point is that
The color subcarrier frequency is 4.43MHz, 8 times higher than NTSC
Since it is about 50 kHz higher, the luminance signal pass band of the VTR is 3.3 M
Hz is required. PAL signal has 1 color subcarrier
Since the phase is offset by / 4 cycle and there is also an offset in the frame direction, the phase differs by 180 degrees every 1H in the NTSC system. On the other hand, only the phase changes in the combination of the 8H cycle and the 8 frame cycle, and the operation of the present invention works exactly the same. In the above embodiment, the case where the color burst included in the color television signal itself is used to control the sampling phase and the sub-sampling phase has been described. However, the present invention is not limited to this. It is easily conceivable to configure by adding a signal. For example, when the luminance signal band and the television signal band to be recorded cannot be selected based on the color subcarrier frequency as in the embodiment and a different sampling / subsampling frequency is selected, a burst signal different from the original color burst is newly added. It is conceivable to add to the spectrum, but from another viewpoint, depending on the group delay characteristics of the transmission line, a wider spectrum than a gated sine wave and concentration of energy near the frequency of the sine wave is considered. In search of expansion,
A square sine wave pulse, or even a single pulse, can be used. In short, it is important to match the sampling phase of the pre-processing with the sampling phase of the post-processing. In the present invention, the point is to obtain the sampling phase control information (PLL phase information) from the result of the sub-sampling. Next, when a high-definition television signal of 1125 systems is recorded on a VHS-VTR, an 8-channel sub-sampling circuit can be used, and a band eight times the VHS-VTR band, that is, 2.6 MHz × 8 =
This is sufficient because a bandwidth of about 21 MHz will be obtained. However, the difference in horizontal frequency is that two scanning lines of a high-definition television should correspond to one scanning line of the 525 system, and the signal waveform should be changed to the waveform of the 525 system for recording. As a result, all the effective scanning lines of the high-definition television are not recorded, and the upper and lower portions of the screen are slightly cut off, which is sufficient for practical use. In the embodiment, the case of frame sequential has been described. However, the method is not limited to a frame as long as it is a repetitive element of constant synchronization, and a method of using line sequential using a line scanning cycle and field sequential using a field cycle is also available. Needless to say, any periodicity of the television system can be used. In the embodiment of the present invention, the VTR recording has been described as an example.
As will be easily understood from the description, it goes without saying that the present invention is also effective for so-called "communication transmission" by "disc recording", wired or wireless, or satellite, in addition to "VTR recording". [Effects] As described above in detail based on the embodiments, the present invention is applied to a general-purpose small and inexpensive VTR for a television application in which fineness is more important even if the smoothness of the movement is somewhat lacking. ,
High-definition recording can be achieved simply by performing simple signal processing using digital frame memories that are now widely used in home video equipment, and television signals with a wider signal band can be transmitted over a relatively narrow band transmission path. It provides a technology for transmission, and in the past, for application fields that remained unsatisfied,
It provides a solution to the problem at a very low cost, and the application range of the present invention is extremely wide.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a pre-signal processing system of the present invention, FIG. 2 is a block diagram of a post-signal processing system of the present invention, FIG. 4 is an explanatory diagram of sub-sampling, FIG. 5 is an explanatory diagram of VTR response and selection of a sampling frequency when the present invention is applied to a VTR, FIG. 6 is an explanatory diagram of color burst signal samples / sub-samples, FIG. 7 is an explanatory diagram of sampling pulse phase control. 1 ... sampling circuit, 2 ... A, B switch, 3 ... frame memory, 4 ... a, b switch, 5 ... ID addition circuit, 6 ... synchronization separation circuit, 7 ... variable frequency oscillator ( 6 × fscVCO), 8... First divide-by-two circuit, 9... Second divide-by-2 circuit, 10... Divide-by-3 circuit, 11... Gate circuit, 12. ... 1 circuit, 14 ... 2 circuits, 15 ... arithmetic mean circuit, 16 ... subtraction circuit, 17 ... switching, ID signal generation circuit, 18 ... sampling circuit, 19 ... frame memory, 20 ... … A, B switch, 21… Frame repeat circuit, 22… ID detection circuit, 23… A, B discrimination circuit.

Claims (1)

(57) [Claims] In a television signal transmission system for transmitting a television signal to a transmission line having a transmission band narrower than a required transmission band determined by the television system, a television signal to be transmitted is transmitted at a frequency twice or more the upper limit frequency thereof. Source sampling means for sampling, and for each of a plurality of consecutive samples of the output sample sequence of the source sampling means,
Sub-sampling means, and sub-sampling means for dividing the signals into a plurality of channels, and a plurality of outputs of the sub-sampling means are rearranged on a time axis, and time-division-by-channel in every television scanning cycle. Means for transmitting, and means for controlling the phase of the source sampling by PLL phase information obtained by sub-sampling a color burst separated from the television signal to be transmitted and then performing signal processing. A television signal transmission system characterized by the following.