DE949350C - Method for testing transmission properties in television - Google Patents

Description

The description has been changed as follows: a) Page 2, lines 3 and 4 have been replaced as follows: The leveling of the white value during the Consignment is not due to the picture content alone b) page 2, between the lines 16 and 17 the following words have been inserted: without additionally keyed in Test signals c) Page 2, line 17: At the end of the line a »point« has been placed.

d) Page 2, lines 18 to 37 are deleted and replaced by the following text has been replaced: it is known to be additional during the ongoing television broadcast To transmit information, for example signals for monitoring purposes, a Standard frequency for color television or reference values for brightness, in particular a reference value for the white level during the line sync pulses or before and / or after the line synchronization pulses, but still within the Line blanking times.

In a method for testing the transmission properties at Television in which signals are keyed in while the television broadcast is on, which are not absolutely necessary components of the television signal mixture belong and the time outside of the occupied by the line sync pulses Time segments and in terms of amplitude lie in the range of the image signal are according to the invention one or more lines - so-called test lines - with a number of known, defined and quantitatively measurable test voltages provided in such a way that these signals are accommodated in the time segment that is limited by the End of a line blanking pulse and the beginning of the next line blanking pulse, and that the test lines lie within the vertical blanking pulse or in the Take the place of active lines near a horizontal edge of the picture. e) page 2, Lines 54 to 6o: The previous sentence has been replaced by the following sentence: The test line can also be used to identify a specific studio, a relay station or a clock or for message transmission with the aid of code signals be used. f) Page 2, lines 64 to 77 have been deleted. g) side 2, lines io4 and io5 have been replaced as follows: Do not fall below may and is not included in the composite video signal. The brightest h) side 2, line io7: The word "first" has been replaced by the word "only".

i) Page 2, line io8: The words "in the test line" have been deleted been.

k) page 2, lines 113, and 114: the word "dem" is through "this" and the words "the test line" have been deleted.

1) Page 2, line 117: The words "The test line" are identified by "the white level" been replaced.

m) Page 2, lines 118 to i23: The sentence "So far, the white value ... is suitable" has been deleted.

The claims have been amended as follows: a) The claim i has been replaced by the following version: Procedure for testing the transmission properties in television, in which signals are keyed in while the television broadcast is in progress that are not absolutely necessary components of the television signal mixture belong and the time outside of the occupied by the line sync pulses Periods of time and in terms of amplitude lie in the range of the image signal, characterized in that that one or more lines - so-called test lines - with a number of per se known, defined and quantitatively measurable test voltages provided in this way are, -that these signals are accommodated in the period of time which is limited by the end of a line blanking pulse and the beginning of the next line blanking = impulses, and that the test lines lie within the vertical blanking impulse or take the place of active lines near a horizontal edge of the picture.

b) Claim 7 has been deleted.

c) The previous claims 8 to 13 have been renumbered with a corresponding change in the back-reference in claims 7 to 12. . Method for testing transmission properties in television The invention relates to a method for testing transmission properties in television, in which the composite signal can be observed as an oscillogram. As is well known, the entire signal mixture, including the image signal, blanking signal and synchronizing signal, is recorded on the fluorescent screen of a Braun tube as an amplitude curve as a function of time. The width and height of the vertical and horizontal blanking and synchronizing signals can be measured, the deformation of these pulses can be determined and the blackest and brightest value of the image signal can be determined according to its voltage value.

This procedure is used to monitor a television broadcast during program transfer, but has the disadvantage that it is very imprecise and incomplete as will be explained in more detail below. Every composite signal should theoretically a sync level, a blanking level, a black level, and a white level contain. These levels are checked before transmission with test signals or with the help of a Testbiktes leveled for the entire transmission path. It has now turned out that these levels both in their absolute size and during transmission vary greatly in their relationship to one another. One must consider. That a television broadcast from the studio mostly worse an extended hundreds of kilometers long relay section with many transmitters and receivers connected in series, via cable lines with repeater:; erns, routed via multi-level television stations and maybe received again via a ball receiver, and then before the Transfer the broadcast on. will. Hence a Regulating this Level desirable during transmission.

In addition, the leveling of the white value is the same as previously usual Television process not possible because there is no defined white value in the composite signal is available. In the composite signal there is indeed the brightest point in the picture or in the Line can be recognized, but it cannot be determined whether ur.d when this point denotes the White level reached. Hence it is also not possible to find the linearity between black and white to check during transmission.

Also is the quantitative traversal of a television broadcast connection in. with respect to Im-. pulse deformation, according to amplitude and phase response and, if necessary, according to occurring reflections during the program transmission not possible, rather have to. these measurements have so far been carried out outside of the program times, d. In other words, the transmission links must be put into operation specifically for this test.

For this reason you can also see the television route outside of the actual Program not to the extent desired for other possible purposes, for example for carrying a wide variety of long distance calls or television advertisements etc., exploit.

In order to avoid the disadvantages described, therefore, according to the invention proposed a single or multiple lines of the composite signal, so-called Test lines with a number of defined, quantitatively measurable test voltages that are not included in the composite signal of the television picture, consisting of picture, Blanking and sync signals, are included, while the other lines are at the same time of the signal mixture are available for the transmission of the television picture. the Test line can, for example, show the white level, sawtooth or staircase voltages Testing of linearity, pulses and sinusoidal voltages for testing pulse deformations and the amplitude and phase response, pulses for measuring reflections on the It can contain a whole line or just part of it the same include. The test line can also be transmitted continuously or temporarily it can be used to test the entire transmission path or a part of it serve., In this case the test line is in the composite signal before the part to be tested keyed in and then keyed out again. The signals contained in the test line can be transferred either by agreement or upon special request.

The introduction of a test line also creates a new one at the same time News channel opened up for television operations, as this is used to identify a certain. Studios, a relay station or a clock generator or for the transmission of messages can be used with the aid of code signals. Furthermore, in the test line Control voltages are included, which are used to regulate a wide variety of voltages and facilities serve on the transmission path. In this way, the so far required control and reporting lines can be saved.

With the introduction of the test line, not only the initially Avoided disadvantages described, but there are also a number of advantages. Through the perfect detection of transmission errors and the location of the error as well as immediate elimination without disrupting the ongoing program transmission the quality of the television broadcasts is significantly improved. As the television routes can no longer be used for test purposes outside of the program times, the Profitability of these lines can be increased significantly.

The figures show exemplary embodiments of the new test line. In Fig. i is the content of such a line for the European television standard with 625 lines and interline displayed. According to this standard, the test line is negative Modulation is drawn, but it can also be shown in positive modulation and can be applied analogously to any other standard. It's the signal amplitude A shown as a function of time t. The total time i of a line is calculated from the beginning of a horizontal blanking pulse 2 to the beginning of the next pulse 3. The duration of this line extends from the end of 5 of the horizontal blanking pulse 2 to the beginning of 6 of the horizontal blanking pulse 3 and is in the 625-line norm about 52, usec. During the period 4 are generally in the transmission of the television picture either the picture signal with the fluctuations in the line brightness or transmit the black level of the vertical blanking pulse. In this section 4 only the test voltages are accommodated.

In its first place is the white level 7, that is the level that is not the residual level in the transmitter with ioo / o of the total RF amplitude may not be exceeded and was not previously included in the composite signal. Of the The brightest point in the picture fluctuates very strongly with the picture content. Only through introduction of the white value in the test line, it is possible during the transmission of the respective Set the limit of the greatest image brightness. The studio alone can judge when the brightest point of the image is to be regarded as the defined white value. The studio therefore regulates the image according to the white value of the test line and ensures that the permissible Limits are respected. On the entire transmission path is therefore not more according to the image signal, but only adjusted according to the test line. Until now the white value was adjusted with a measuring slide before the broadcast, but that wegern: the fluctuations in its transparency as well as because of its dependence on the brightness of the light source is poorly suited as a standardized white value.

The test line also contains a staircase 8, which is better than a sawtooth is suitable for checking the linearity of the transmission path. Here can not only a ruler can be created, but the steps can also be set individually with a Reticle are measured. The steps are of such a size that in the Sew the lower and upper. Limit of the amplitude range a possibly occurring S-shape of the characteristic can be determined; also the individual step heights can be measured precisely.

For the detection of pulse deformations such as overshoot, small Flank steepness, roundings, indentations, sloping ceilings. etc., has become a Pulse. 9 proved to be suitable by i, usec - With suitable oscillographs, pull this pulse from white to black so far apart that its quantitative measurement is possible. There can also be impulses of other latitudes accommodate, but not those whose pulse repetition frequency is less than the line frequency is.

Four additional pulses io, ii, 12, and 1 3 of a duration of each i, usec serve for identification of the clock and for signaling. Each of these impulses can have five different amplitudes, so that 5 '- 5' 5 = 625 different ways of sending messages are available. That should be enough to identify all European clocks and to give the broadcast an identifier from the studio so that unnecessary queries can be avoided in the event of malfunctions in the studio. In practice, the technical operating staff has an important communication channel in the direction of transmission.

The longest time must be reserved on the test line for the flow measurement (from point 1q. To point 15, ie 29, usec). Confluence is understood to mean the entirety of all those interference signals that occur as a result of reflections at incorrectly matched transmission points during line transmission or on conductive surfaces during wireless transmission and that arrive later than the main signal at the end of the transmission path. These interfering signals, also known as late signals, can also occur several times and cause blurring on the television picture with short transit times, and double edges and double images, so-called ghost images, with longer transit times. The co-flow can either amplify or weaken the main signal at the end of the transmission path, depending on whether it arrives in phase or out of phase with the main signal. A short pulse 16 in the form of a single sine wave is sent if from the previous one. Test pulses every reflection decayed. is. The pulse must be so narrow that reflections arrive briefly one after the other. can be clearly differentiated from one another. However, it must not be narrower than the limit frequency of the transmission path allows. In the case of very narrow square-wave pulses, it is known that the higher harmonics lie outside this cut-off frequency, which is why a short square-wave pulse is unsuitable for measuring the co-flux. For the actual flow measurement, about 15 .usec are available; a time that is sufficient to be able to evaluate distance differences of 4.5 km. The path difference calculated from the measured transit time of the late signal is used to determine the location of the fault in cable transmissions and the local position of the interfering reflective surfaces in wireless transmission: The flow measurement is first of all necessary in order to determine interfering reflections on television transmitters on the way from the transmitter to the antenna can. '' Mismatches after the occurrence of storms or water ingress can be identified immediately. There are circuits with which you can compensate for any unforeseen reflection on the television transmitter; How far this has been achieved can be checked on the test line on a receiver immediately adjacent to the transmitting antenna.

Furthermore, it can be determined immediately whether at a certain receiving location Late signals occur or not. Let the late signals. itself in term and Measure the amplitude precisely. The receiving antenna can be measured after the test line. and swivel until the minimum of late signals is reached. This is for example then the case when the directional diagram in the direction of the interfering reflective surface the receiving antenna has a zero point. Without a test line oscilloscope is a good one Customer service hardly conceivable.

The flow measurement is also extraordinary for transmitter monitoring Importance. First of all, with the help of the test line, a suitable reflection-free one is made The installation site of the control station is determined. Then the quality of the broadcast Quantitatively monitored for reflections. With the help of a graticule you could The transit time and amplitude of the late pulses can be measured precisely at any time. Since the co-flow impulses lie in the 5% gray value (point 1q. to i5), the phase position can also be determined agree with the reflection, in the 5% gray value it can be seen whether the Reflection same or opposite polarity to the main signal Has. In addition, the 5% gray value even with an S-shape of the The control characteristic always lies in the linear part of this curve and therefore with the usual amplitudes the late pulses provide more accurate attenuation values for these late pulses.

Since the test line continuously monitors the transmission quality during the transmission reproduces must have uniform designations, for example in form. and figures, to identify the fault.

Because the previously used test pattern has been replaced by the _ test line is, it must be ensured in the television studio that the image content corresponds to the The black and white level specified in the test line matches. To this end are on the screen of a control oscillo, graphs the image content and the Test line, for example, written one on top of the other. The picture is correct leveled, if the amplitude limit values of the image signal are at the respective brightest and darkest: Place the image exactly with the white value and the black value on the test line cover. For the reasons given above, it is advantageous to use the check line to be inserted in the modulation device, because this is where the composite is created for the first time Composite signal. With this video-frequency mixture, the intermediate frequency, for example the frequency of 21 MHz as the subcarrier frequency for long-distance transmission over cable routes, or the bern: seeing, it modulates. To the check line to be able to use the modulation device by a Prüfzeil_en.einastgerät and a test line generator which .synchronized from the clock generator Test line generated.

The composite signal that is now available, including the test line, works now not only on the transmission path, but also becomes a distribution amplifier supplied, which supplies all control receivers or control oscillographs of the studio. These control devices are provided with a test line selection switch to each To be able to compare image content and test line.

The amplitude levels of the between the black and white values Image signals are recorded in the studio for a specific camera with the help of an optical Adjusted the test image, which is set up in front of the lens of the camera.-This The test image has as many precisely defined brightness levels as the staircase 8 the test line has amplitude levels. Those involved in the upcoming broadcast Studio equipment such as cameras, camera amplifiers and line amplifiers, can be set by comparing the oscillograms of the image signal with the test line that the image signal conforms to each individual step height of the test line is brought. The studio devices adjusted in this way are now used for recording and transmission of the television picture. This ensures that these tested devices the brightness levels of the image in proportional amplitude levels of the image signal convert, .that together. is given with the test line on the transmission path. During the broadcast, all you need to do is take the stairs on the test line to check the Linearity of the other links of the transmission path to be used.

In the case of external transmissions, the composite signal including the test line broadcast either via a special channel or via the normal television channel and received in the OB van. At the output of the receiver used for this purpose is the same test line control device as in the studio, so that too here the white and black level can be regulated according to the test line.

For testing parts of the transmission path using the The test line must have a test line generator and a test line keying device at these points to be available. Since the test line does not appear disruptive in the television picture should, the test line is keyed in in a further embodiment of the inventive concept, that it lies outside the edge of the picture and is covered by the picture frame.

The test line should have a permanent place under the lines of the image received, so their distance from the vertical sync pulse should be one of the two Fields be constant. This constant distance is especially guaranteed if the time interval from the vertical sync pulse is not too great. This Distance is smaller in the upper edge of the picture than in the lower edge of the picture, therefore. the Test line placed in the upper edge of the picture.

Because the steep edge of the saw tooth for the image change within of the vertical blanking pulse at the top of the screen. flat, for several line lengths sometimes even runs horizontally, there is no risk that one by the Test line interrupted. To see a slanted light line in the picture is. The test line should therefore be in the last, horizontally running part of the vertical blanking pulse be placed.

At this point it is sufficient. There is space for the test line. According to the 625-line standard, the blanking pulse is 18.75 lines wide. According to the older standard, a total of g lines are required for 6 early pulses, 6 synchronous pulses and 6 late pulses. A duration of 9.75 lines is therefore available for accommodating the test line. According to the new form with 5 early pulses, 5 sync pulses and 5 late pulses, even 11.25 lines are available. These last lines within the image blanking are no longer usable for the image, since if it were visible it would no longer be linear for the vertical deflection due to the curvature of the sawtooth. However, this area is extremely suitable for testing the test line.

It is possible to use a group of several lines for the test line. One can. Furthermore, key in a test7 for each field or for each frame.

With today's oscilloscope technology it is easily possible display a single line of the image on the screen. Since the Check line is an almost invariable periodic process, a long afterglow period for filling in the breaks and a great post-acceleration of the electron beam can be used. It is therefore also possible to only use a part the test line for analyzing the pulse shapes.

In summary it can be said that one of the last times or the last line within the vertical blanking pulse of the first field for keying in the test line is most suitable. Here the test line does not take any Line of the usable image height away. Since the scrolling does not start there yet, it remains invisibly behind even in the light test due to the white value of the test line the upper picture frame. In Figs. 2 to 6, for example Principle of test line keying explained.

In Fig. 2 the usual composite television signal is at the end of the vertical Blanking pulse of the first field shown. This place is after the previous ones Explanations particularly suitable for keying in the test line. . To the left of the point 17 is the vertical blanking pulse, to the right of which is the image signal with the horizontal blanking and sync pulses.

3 shows the composite television signal including the test line again. Instead of the last line of the. vertical. Blanking pulse of the first. The test line 18 is entered, which is relatively simple. is built, she consists only of the white level 7 and the staircase B.

The test line is now keyed into the television signal device, that from the periodic test line signal mixture of Figure 4 a piece of the duration of test line 18 with. With the help of a line: one-key pulse ig of FIG. 5 cut out will. With the help of the same. Line input pulse is in the composite signal of Fig. 2 cut a gap the length of the test line. The cut out Test line is inserted into the gap by mixing, so that the signal mixture including test line.

In Fig. 6, for example, is a block diagram of the test line keying shown. The television signal generator fed in via line 2o is used for generation of a line keying pulse ig according to FIG. 5 with the aid of a keying pulse generator 2i used. A test line generator synchronized by the same composite signal 22 generates the periodic test line signal mixture shown in FIG. The composite television signal is through a blanking modulator B and the composite test line signal through a One-key modulator C modulates. The outputs of both modulators are shared Output rail 23 supplied. Both modulators are in this way from the line insertion pulse ig modulates that during the duration of the line input pulse ig the modulator B locked and the modulator C is open. In this way -will during the duration this pulse is replaced by the test line in the composite television signal.

For example, FIG. 7 shows a simple line selection switch again how it is used to make a test line visible. Via a line 25 the composite signal is supplied with the test line. Herewith. is using a Line blanking pulse generator 26 modulates a line selection modulator 27 so that only the test line is displayed on the screen of the oscilloscope 28. The row selection pulse generator 26 is a simplified row input pulse generator 21 as shown below.

At. The generation of the line selection pulse and of the line insertion pulse explained. The generator 26 for the line selection pulse 52 is a part of the line selection switch of FIG. 7 and at the same time a part of the generator 2i for the line insertion pulse according to FIG. 6.

The description of the generator is therefore sufficient for clarity 21 for the line insertion pulse, because. the. Obtaining this pulse is the line selection in advance. Mark the reference numbers with a prime (e.g. 57 '). the part in because the associated signal (e.g. 57) is available. Figure 8 is as follows. broken down: Ha, lbbildwahl I, line selection II and obtaining the line insertion pulse III.

every line selection technique must start from the vertical sync pulse, which is contained twice in each picture as a result of the zen @ jump method. This is where field selection comes in and makes the unwanted field ineffective. The composite television signal is fed to the circuit via line 2o. Through the switching element 29, the differentiated field pulses 31 shown in curve 3o are prepared in known manner, recovered .. The half: picture; selection based on the fact that after the interlacing according to each field image of the Horizonitalsynchronimpulse are shifted by a half line with respect to the vertical sync pulse. Since the differentiated field pulse 31 is obtained from the trailing edge of the vertical sync pulse, the five late compensation pulses, ie three whole line lengths, must first elapse. until the horizontal sync pulses emerge. As a result, the signals must be differentiated for the purpose of field selection. Field pulses 34 as shown in curve 32 are delayed by a transit time 33 .. This transit time must be a multiple of half a line duration, but at least six half lines. The pulses 34 delayed with the aid of a delay chain 35 are. fed together with the horizontal sync pulses of the television signal mixture to a mixer 36, every other field signal 134 coinciding with a horizontal sync pulse. The mixture is now carried out in such a way that the horizontal synchronizing pulses cancel the signals 34; this is only possible if both signals occur at the same time. From the schematic curve 37 it can be seen that pulse 38 coincides with signal 34, but pulses 39 and 40 do not. These are shifted by half line 4i. every second field signal 34 is thus extinguished, so that only half the number, that is, the signals 43 shown in curve 42, remain. The field selection is now carried out.

The line selection II is now carried out in such a way that.B the signals 43 again be delayed until they are about half a line before the at which the test line is to be keyed in. At the selected Digit in the last line of the vertical blanking pulse of the first field delay 44 is nine whole lines, as shown in curve 45. The one with the help the delay chain 46 delayed pulse 47 synchronizes a. Pulse generator 48, the pulses 52 with approximately twice the line duration 49 of this Impulse one line in the composite television signal is replaced by the test line.

9. The method according to the claims. i to 8, characterized in that .that the line input pulse differentiated from two by means of a flip-flop circuit Horizontal sync pulses is formed.

ok Process according to claims i to 9, characterized in that that the two horizontal sync pulses with the help of a line selection pulse your sync signal can be selected.

i i. Process according to claims i to io, characterized in that that "the line selection pulse is caused by a signal delayed by a delay element, that from the differen.tiation. won the trailing edge of the vertical sync pulse is turned on. 1a. Method according to claims i to ii, characterized in that that every second delayed signal is canceled by, that every second off signal obtained by differentiating the trailing edge of the vertical sync pulse after delaying an integer half a line from that at that time existing horizontal sync pulses is scanned away, so that after the interlace process .. only those assigned to a specific field, for example those assigned to the first field delayed signals remain and d; a.-d performed by field selection will.

13. The method according to claim i, characterized in that the test line is keyed in at any point on the IT transmission path and at another point: is blanked again. ,