DE2409477A1 - BANDWIDTH REDUCTION DEVICE FOR TELEVISION IMAGE CONVERTER - Google Patents

Description

Dr. Hans-Heinrich Willrath d - 62 Wiesbaden

Dr. Dieter Weber v / b ^{Postfadl 1327}

Gustav-Freytag-Strasse

Diploma Phys. Klaus Seifert » ^{(0δ121) 372720}

^r ** Telegram address: WILLPATENT

PATENT AGENCIES ^ _{February 1974}

Arvin Industries, Inc. a Corporation of Indiana 1531 East 13th Street, Columbus, Indiana, USA

Bandwidth reduction device for television imagers

Priority; March 7, 1973 in USA, serial no. 338 667

The invention relates to recording and transmission systems and more particularly relates to a video bandwidth reduction system for the transmission of television signals with high resolution and high bandwidth via low frequency transmission and / or recording systems and narrow bandwidth.

It is well known that the cost of recording and recording increases Transmission devices for high frequency signals

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substantially as the frequency capacity of the system is increased. It is therefore very desirable to reduce the bandwidth (the maximum frequency of the signal) as much as possible, in particular where in the system the need for a high frequency capacity is only temporary is. Where it is therefore not necessary, for example, a moving video image in real Transmit and / or record time (i.e. when it actually occurs or is to be viewed), or where the video signal is a fixed representation (e.g. a map or chart as part of a hint program) then it is possible to display the video information with a much slower Rate, - and thus with a lower bandwidth - in accordance with the frequency Tcapacity of a transmission and / or low bandwidth recording system.

Different systems for transmission and / or recording of low bandwidth video television signals have been proposed. With them is in general uses the fact that a video signal can be transmitted at a lower bandwidth without loss of resolution and / or can be recorded when viewing the signal at a lower rate on a picture-on-picture '

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Base transmits and / or records. This suggested approximation is quite useful in systems where playback or playback cannot be effected immediately, as well as in image recording systems in which the image, once built, is to remain unchanged for a considerable period of time later reproduction · Examples of the latter systems are exercise program · "me _r where a given image recording is repeatedly shown on a Videorähre. in the latter case, the duration sees the presentation adequate transmission time ago for the reconstruction of the next image or the next presentation, etc.

A method of reducing the bandwidth of a Such a signal simply consists of it being recorded on a magnetic recording tape or disk record and play the recording at a slower speed. After receiving it, it will Tape or disk accelerated to the original speed in order to reproduce the original signal. One difficulty with simply slowing down a videotape is the losses that result if the speed is reduced by a considerable factor, with a limit value of the belt

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spreading is set, which can be obtained.

Another approximation has the periodic sampling of the video field, an example of which U.S. Patent 3,567,127. See also U.S. Patents 2,695,748, 2,794,066, and U.S. Patents 2,695,748 2 817 701, However, the sampling systems require very high sampling speeds and usually require discrete and separate sampling of the entire video field or image and the separation of the extracted sample signal into a multitude of channels.

design and cost problems, since the sample or Prodie

implementation, / amplitude differences and phase differences can cause unwanted interference signals that have to be added to the video signal, and steps must be taken to compensate for this. This often requires an expensive facility required as well as filtering and pulse compensation circuits, ίcompensation networks),

In brief, this invention provides a method and apparatus for recording and / or transmitting of video television signals with high resolution (high bandwidth) via media of any narrow bandwidth, e.g.

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Telephone lines, house tape recorders, etc.

The television signal is converted (scan converted) individually per line by the fact that the entire video image line is read or charged individually into a changeable memory device or delay line.

The delay line can run at various speeds including high speed and speed Low speed mode. Every line of video is written to the delay line when operating in the high speed mode, and the delay line da, nn is operated in the low speed mode to recover the individual video line as a Signal with significantly reduced bandwidth, The signal with lower bandwidth is then recorded and / or transfer. After the entire video line has been recorded and / or transmitted, the next video line becomes read into the variable delay line at high speed and also for recording and / or transmission reduced in bandwidth. This means that the entire video signal is used for recording and / or scan converted.

The replay is guaranteed by the fact that the original

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signal is rebuilt and arranged individually per line with the original bandwidth frequency. The signal with the narrow bandwidth is initially stored individually per line in a changeable memory device or delay line operated at low speed type is input, and the loaded delay line is then used at high speed mode for recording the particular one Image line operated on a magnetic disk recorder at the original high bandwidth frequency. The television signal is then reconstructed individually per line on the magnetic disk recorder in the receiver, and the original High bandwidth signal is recovered without loss of resolution.

The number of storage elements required in the changeable delay line is determined according to the number of rows or lines determines the resolution that is desired along the horizontal axis, taking for a guard band bandwidth the possibility is created to provide adequate suppression of the noise that is generated by the sampling frequency.

It is therefore the object of the invention to provide a method and a device for transmission, recording and / or recording of television signals over narrow-band media

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wide by taking the television signal individually per line to a signal of lower bandwidth and then the signal of lower bandwidth reconstructed individually per line to play back the original signal with the original frequency; also a sand width conversion system with a device for controllable demonstration of a pre-recorded television signal individually per video scan line with a normal high frequency bandwidth; being a memory device or delay line with selectable types for high and low Speed is provided; wherein a control means for converting the television signal individually per line is provided and around all of the above Tasks and characteristics in an inexpensive, uncomplicated, practical and permanent system that is completely compatible with the existing recording and / or transmission conditions are compatible in order to handle the television signal without loss of resolution to be able to.

Further advantages, features and possible applications of the present invention emerge from the following Description in conjunction with the drawings, They show:

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1 shows a block diagram of a transmission system according to the invention,

2 shows a block diagram of a receiver system according to the invention and

Figure 3 is a graphical representation of practical considerations for a guard frequency band for the Noise reduction,

In the description of the preferred exemplary embodiment, FIG. 1 shows a transmitter system IO for scan converting a television video signal according to the invention »

A steady or steady picture of a television signal from a television camera 13 or from a recording disk 14 is continuously in the Transmitter 10 read to be processed by this to become. A synchronous stripper 16 carries synchronization pulse information to a logic circuit 18 via a 75% monostable pulse circuit 21, the 75% monostable pulse circuit 21 eliminates the Extra shear pulses that occur during the vertical interval, while the horizontal pulse

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information to a phase comparator 22 is running, which is a voltage controlled oscillator (VCO) 24 controls to set the VCO to a harmonic of horizontal synchronization. Since the VCO operates at a frequency that is greater than the horizontal sweep frequency (from below for good reasons) there is a feedback loop from the VCO for the phase comparator by an -N (divided by N ..) counter 26 to to count down the VCO rate to the horizontal synchronization rate for the comparison in the phase comparator.

An electronic switch 27 is controlled by a logic circuit 18 to connect the Magnetplattenauf recording signal source 14 to a variable delay line memory device. The variable memory device or delay line 30 is capable of receiving or transmitting signals at any rate including a wide range of controllable rates. Such devices are known as z. B. reads in the literature, in "The New Concept for Memory and Imaging" Charge Coupling "(Electronics Magazine, June, 1971 _f page 50), and in" Pass the Bucket "(The Electronic Engineer, December 71, page 12) . See also electronic magazine

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Jan. 18, 1973, pages 162-169 and U.S. Patent 3,553,356, column 6, lines 68 and 69. The changeable delay line can also be fulfilled in that the signal is passed through an A / D converter handles the digital information through digital shift registers (digital Delay lines) and then transmits the information back to an analog format thereby converts that the digital signal is prepared or processed by a D / A converter. Although it however, it is possible to use digital technology, the charge coupling and collection electrode brigade (bucket brigade) preferred embodiments of this invention. According to the invention, the delay line is either in a low speed or operated in a high speed mode.

When the delay line 30 is ready to receive a line of the video signal, the "logic." Circuit 18 the output of the camera 13 or the magnetic disk recorder 14 (via the synchronous stripper 16) to find the beginning of each video sample which is to be transferred. At the appropriate time, the logic circuit closes the electronic switch 27 and feeds the video signal to the variable delay line 30.

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The electronic switch 32 is also operated to the voltage controlled oscillator or the Clock 24 to delay line 30 to connect line 30 in the high speed mode clock to load the selected scan line into the delay line.

After the particular scanning line has been loaded onto the line 30, the logic circuit 18 opens the switch 27 and switches the electronic switch 32 to an electronic divider circuit Ί-N ₂ , which reduces the clock or timer frequency by the factor N_ to the scanning line clock out of delay line 30 at a lower rate or speed. N "is selected to control the low frequency of the delay line and is set according to the frequency capacity of the recording and / or transmission device (not shown) connected to the transmitter output terminal 35. The signal appearing at the output terminal 35 is then a signal with a frequency and a bandwidth which _{are reduced by the factor N 2} relative to the frequency at which the signal was clocked into the delay line 30. The optional FM modulator 37 is shown as the video signals are sometimes responsive up to DC

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require down. The FM modulator may therefore be necessary where the recording and / or transmission device, which is applied to the output terminal 35 does not have such a low frequency capability.

FIG. 2 shows a receiver 40 for receiving the narrow bandwidth television signal which is transmitted by the transmitter 10 (either through a link transmission line or via an intermediate recording device). The receiver 40 reconstructs the television video signal individually per touch line and composes it, using it at the original frequency the high bandwidth for the eventual playback of the original video image at the original frequency.

The receiver 40 has a variable delay line memory device 45 similar to delay line 30, which carries the signal with the low bandwidth from an input terminal 47 receives. An optional FM demodulator 49 may be provided, the Transmitter 10 includes an FM modulator 37. A logic circuit 50 controls the operation of the receiver 40, the synchronization information from a synchronization frequency sampling circuit 53 and a magnetic disk recorder 55 is recorded. If a her-

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einkommendes signal at the input terminal 47 appears, the logic circuit 50 operates an electronic switch 57, a clock signal or timing signal from the timer 60 to the delay line 45 to give up, via a divider circuit 63, which operates with the same -f W_ ratio as the transmitter circuit 34 . The timer 60 runs at the same frequency as the timer 24 and allows the scan line to be clocked and loaded onto the delay line 45 at the low bandwidth and low frequency.

The frequency of the timer 60 is controlled and determined by the FM synchronization center frequency, which can be selected to be harmonically related to the timer frequency of the voltage controlled oscillator 24 of the transmitter. This can be ensured with a circuit similar to the recovery of the color Syhchronsignalfrequenz from the video signals of the back porch of the hue, with additional binary _w .teilern and phase locked loops to the appropriate harmonic relationship between the receiver timing and synchronization center frequency to be restored. As noted, the timer frequency and 4-N _{2 are the} same for both transmitter 10 and 10

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for the recipient 40,

After the particular key line has been loaded into the delay line 45, the switches logic circuit 50 the switch 57 in the AE position, so that no timer pulses are applied to the delay line. The line 45 holds thus the touchline signal in readiness for loading into the magnetic disk recorder 55 at the appropriate Time, The logic circuit 50 simultaneously monitors the output of the magnetic disk recorder 55 to determine the appropriate time to scan the video line from delay line 45 into the recorder. At the appropriate moment the logic circuit switches the electronic circuit Switch 57 and connects the delay line 45 directly to the timer 60 and switches the electronic Switch 64 on recorder 55 of games on record, the one taken directly from timer 60 High frequency signal operates the delay line with the original high frequency way to make the special Record touch line therein in the recorder 55 of the receiver. The recorder 55 thus functions as a a device for signal reconstruction, which the video signal individually per scanning line in the normal high frequency bandwidth reconstructs and arranges,

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Once delay line 45 has been discharged and another scan line signal appears on input terminal 47, circuit 50 repeats the above cycle and loads the next video scan line into magnetic disk recorder 55 for signal reconstruction. As a result, an entire video signal received by the transmitter 10 via a recording and / or transmission device with a narrow bandwidth is reconstructed individually for each video scan line. The selection of the number of storage elements in the variable delay lines 30 and 45 determines the frequency of the timers 24 and 60. These in turn determine the 4 N ₁ factor for the electronic divider and determine the 4 * N factor for the dividers 34 and Biese are also influenced by the frequency capacity of the narrow bandwidth recording and / or transmission device which couples the transmitter output port 35 to the receiver input port 47. Timers 24 and 60 operate at a frequency such that the number of timer cycles per 63.5 microseconds (horizontal scan time) is equal to the number of storage elements in the delay line and the -Jr N ₁ factor is chosen to be equal to this Number is. The latter criterion allows an oscillator pulse to be applied to the phase comparator 27 for each horizontal synchronization pulse.

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the one from the magnetic disk recorder 14 is received.

The number of storage elements in the delay line is selected to be above the line resolution requirements (along the horizontal direction) because the delay line (a The bucket brigade (charge coupled device) is a sample system is. The sample frequency itself must have a minimum limit of twice that of the original, high frequency Have baseband signal according to the Nyquist criterion. However, the sampling process introduces noise and an interference of itself which in a practical system must be removed. The usage the minimum Nyqui ^ strate is therefore only possible when using the baseband reprocessing a theoretically perfect filter is guaranteed, which has an infinitely steep drop. Figure 3a shows an illustrative baseband frequency spectrum, Figure 3b shows the resulting output, the "trial operation (sampling) "by the delay line variable memory device follows and shows the shutdown that results from using a filter with an ideal Response results.

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However, as shown in Figure 3C, a realistic or actual filter has a finite one Waste, and therefore a sample rate greater than twice the baseband is necessary around a sufficient guard frequency band (Fig. 3C) between the desired baseband sample components and the higher frequency noise generated by the sample operation. Since thus the number of resolution lines is otherwise directly proportional to the bandwidth of the baseband more storage elements are required in delay lines 30 and 45 than theoretically required to process the baseband signal itself. (A memory element is the same as the amplitude information a sample.) In the case of the individual memory delay lines 30 and 45 according to this invention saved an entire video touchline, and the equation to determine the number of storage elements E is:

E = f x 1

f = 2f. + f
sbg

1 - T
f sync h

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Whereby: f = sample frequency
s

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f = frequency of the horizontal line h

f = bandwidth of the baseband b

f = bandwidth of the guard frequency band

L = total number of lines of resolution along the horizontal axis

T The for the horizontal Synchronisync =

sation and posterior and anterior

Black shoulder time required

("u 10 microseconds for the EIA format)

Knowing the number of lines of resolution required, the horizontal sampling rate and the required guard frequency band (a function of the filter), the number E of storage elements in the delay line can be calculated. N ₁ can then be calculated since its function in the phase-locked loop requires

that f = f, where N ₁ must be an integer sdn. h s_ ^Ί

^N 1

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It can be seen that the invention brings numerous advantages. It enables video television signals to be recorded and / or transmitted via media without loss of resolution, which have frequency and bandwidth capabilities that are orders of magnitude lower than for that Television signal itself would be required. The invention can therefore always be used if it is real or actual time reproduction of the television signal is not required as it obviously takes a long time to process the signal due to the low rate at which the information in the recording and / or or transmission media is handled. The invention is therefore particularly advantageous where a single image is to be displayed for a while, e.g. B. in teaching material, In such a case, the magnetic disk recorder 55 in the receiver 40 continuously record a previously reconstructed image while at the same time slowly recording the next image to be shown is reconstructed by having two record / reproduce transformers used, At the appropriate time, the next image is transmitted while the recipient 40 continues to process the incoming signal for the preparation of the next image to be recorded etc. TV recordings with high resolutions are therefore easily carried out on the inexpensive device and can be transmitted easily and inexpensively over low bandwidth media. The transmission and reception individually per line is very preferred because of switching and synchronization problems. It is of course possible

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Process the signal in sections or segments larger than a line or in sections, that are slightly shorter than a line, although this is not preferred.

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Claims (8)

Claims Γ1 J Device for the transmission of television signals via a recording and / or transmission device equipped with a narrow bandwidth, characterized by a signal source (13, 14) with a controllable demonstration device for a previously recorded television signal individually per video keypad with normal high frequency bandwidth, a memory device (30, 45) with selectable high and low speed modes, a connecting device (16, 27) between the Signal source (14) and the storage device (30, - 45), a connection (37) between the storage device (30, 45) with the narrow-band recording and / or transmission device (55) and a control device (18) for the signal source (14) and the memory device to on the one hand a video touch line with normal, high-frequency bandwidth and at the same time operate the storage device in the high speed mode to read a To load touch line into the storage device, and on the other hand, the loaded storage device in of the low speed type that operate with 4098 37/07 71 the narrow bandwidth of the recording and / or Transmission device for showing the video touch line as a signal of lower bandwidth matches, the control device (13) successively the signal source (14) and the Storage device (30, 45) for the "presentation of an entire video signal to the recording and / or controls transmission device with narrow bandwidth individually per video touch line. 2. Device according to claim 1, characterized in that that the signal source (14) comprises a magnetic disk recorder. 3. Apparatus according to claim 1 _f, characterized in that the connecting device to the recorder and / or transmitter has an FM modulator (37). 4. Device according to one or more of the preceding claims, characterized by a signal reconstruction device (55) with a controllable recording device for a television signal individually per video key line at normal high frequency bandwidth, the signal reconstruction device with the memory device (30, 45) connecting device (37) and a reconstruction device (55) and the memory device controlling device, on the one hand to control the storage device 409837/0771 240-77 to operate in the low-speed mode, which with the narrow bandwidth of the recording and / or transmission device for loading a video touch line matches which as a signal Lower bandwidth is received, and on the other hand, the storage device and the signal reconstruction device to operate simultaneously in normal high-speed mode in order to transfer the one scanning line from the memory device to the signal and recording construction means as a high bandwidth signal, the control means (18) successive reconstruction device (55) and the memory device (30, 45) for the reconstruction of an entire video signal controls which from the recording and / or transmission device is received individually per video keypad. 5. Apparatus according to claim 4, characterized in that that the signal reconstructor is a magnetic disk recorder (55) has, 6. Apparatus according to claim 4, characterized in that the connecting device for the recorder and / or Transmitter has an FM demodulator (37). 7 »Method for transmitting a television signal via a recording and / or transmission device with 409837/0771 "MkL narrow bandwidth, characterized by loading or entering a single line of keys of the television signal at normal, high frequency in a memory device with selectable high and low speed modes, operating the memory device at high speed modes while entering, operating the loaded storage device at low speed type, those with the narrow bandwidth of the recording and / or transmission device to show the video touch line as a signal of lower bandwidth and through Repeat the previous steps to demonstrate or present an entire video signal for recording and / or transmission device with narrow bandwidth individually per video touch line. 8. The method according to claim 7, in particular for receiving of a television signal from a recording and / or Transmission device with narrow bandwidth, marked by loading a single narrow-band scanning line of the television signal into a storage device with selectable high-speed and low-speed modes, operating the memory device in the low-speed mode, while charging, operating the loaded storage device at high speed type for reproduction 409837/0771 ORIGiNAL! NoPSCTED the scanning line from the memory device as a normal signal, high bandwidth and repetition of the above Steps for reconstructing an entire video signal from the recording and / or transmission device with narrow bandwidth, individually per video keypad. 409837/0771 te L e r s. E i t e