RU2107410C1 - Method measuring parameters of signals of television broadcasting - Google Patents

Abstract

FIELD: instrumentation, television and radio broadcasting, measurement and control of quality indications of television path and sound transmission channel. SUBSTANCE: realization of proposed method is based on joint usage of device for input to personal computer and analog-to-digital conversion of TV and radio broadcasting signals and programming complex. Employment of method ensures high-speed of measurements with obtainment of results in real time, high accuracy of measurements, expansion of range of measured parameters, possibility of expansion of this range thanks to build-up of complex of programs, visualization and display of measured parameters with restoration of analog form of measured signal with the aid of digital-to-analog conversion. Personal computer carries out program realization of processes of control, measurement and test due to avoidance of analog processing of measured signal, its replacement with digital processing and usage of all advantages given by digital computing technology. EFFECT: enhanced authenticity of method. 1 dwg

Description

 The invention relates to the field of instrumentation of television and radio broadcasting and can be used to measure and control the quality of the television path and the sound transmission channel.

 A known method of measuring the parameters of television broadcast signals [1]. This method includes switching measuring television signals, fixing a constant level of a television signal, frequency filtering television signals with the formation of a luminance signal, a color signal, with the allocation of color subcarriers, storing the level of the television signal in the form of fixing instantaneous values. Further, in the course of analog-to-digital transformations, the measured signal undergoes stroboscopic time sampling and level quantization, intermediate storing in the form of a sample of instantaneous amplitudes at the characteristic points of the selected signal section, which is recorded from frame to frame when many frames are included in the measurement cycle. Memorized measurements and preset algorithms serve as source material for calculating estimates of the values of the controlled measuring signal using statistical methods. The need to include in the measuring cycle many similar measurements is caused by inevitable errors due to non-linearity and instability of processes in the analog processing channel.

 When calculating the parameters, the method [1] provides for the assessment and indication of the reliability of the results, as well as the correction of the measurement results according to the characteristics of the results of analog processing and analog-to-digital signal conversion. Method [1] has the variability of both measurements and their digital indication. The inherent disadvantages of analog processing are partially eliminated by correcting the measurement results in the above types.

 The method [1] uses an adaptive measurement algorithm, and the functions of logical analysis, control and calculation are implemented by an electronic computer complex based on the use of a microprocessor controller controlled by a read-only memory with the corresponding program.

 Nevertheless, the method [1] does not completely eliminate all the disadvantages that are fundamentally inherent in measurements with analog processing of the signal under study: it does not provide the required accuracy of measurements of the parameters of television broadcasting signals, nor does it cover measurements of the entire set of normalized parameters of the television path and does not provide completeness and clarity in the indication of the measurement results. Measurement of sound parameters remains outside the scope of the method. The low accuracy is explained by the fact that when stroboscopic sampling by time and when quantizing by level are used, some of the information related to the measured signal is inevitably lost, as well as the fact that the choice of the number of averaged measurements is not sufficiently justified, as is the method for selecting the sampling and quantization sections. As a result, the method does not provide the required measurement accuracy for all conditions of operation of the television paths, does not provide measurements of the entire set of normalized parameters of the television path, as well as completeness and clarity in the indication of the measurement results. Stroboscopic time sampling and multiple measurements of the same type do not allow the results to be linked to a real time scale; for the same reasons, the method does not provide the necessary practice for the speed of the measurement process. The method does not provide an oscillographic display of the analog form of the measured signal: the number of samples of instantaneous values of the measured signal at characteristic points and the computational and information-indication base used to implement the method do not allow to restore the analog form of the measured signal.

 Closest to the claimed is a method of measuring the parameters of television broadcasting signals [9]. The method involves measuring the parameters of both a television signal and a sound signal. It includes switching of measuring television and audio signals, fixing a constant level of a television signal, frequency filtering of television signals with the formation of a luminance signal, a color signal, with the allocation of color subcarriers, storing the level of the television signal in the form of fixing instantaneous values, analog-to-digital conversion of television and audio signals with time discretization and quantization by level, intermediate storing of digital values, calculation of parameters by the bar of instantaneous values, moreover, the calculation of the parameters of the audio signal is interleaved in time with the calculation of the parameters of the television signal, the intermediate storage of the measurement results and their conversion with reference to the specified information-display model for displaying on the display panel. At the same time, both television and sound signals commute in a cycle, the instantaneous values of the measured signal are recorded only at a characteristic point, this fixation takes place before analog-to-digital processing. The digital values of several signal levels, recorded during the analog-to-digital conversion, and adaptive algorithms embedded in read-only memory, recorded during intermediate storing, and adaptive algorithms embedded in a permanent storage device, are the source material for calculating the values of the parameters of the measured signals and, subsequently, the parameters of the television transmitter via the image channel, and on the sound channel. This data is subjected to intermediate storage for display and tabular data, and then must be converted to generate a signal on the display. Likewise, the obtained and stored results of comparing the measured parameters with the corresponding tolerances embedded in the permanent storage device of one of the links of the measuring channel are found on the display panel. These results are also converted to display and generate tabular data according to the information and display model selected by the operator.

 The previous analog-to-digital processing of determining a constant level of a television signal, using low-pass filtering, extracting color subcarriers using a band-pass filter, and detecting them — these and other operations of analog signal processing add filtering and error detection due to the non-linearity and stability of the processes, to reduce which the method provides calculation of estimates of the values of the controlled parameters of the measured signals using statistical methods using by reusable measurements. This also applies to measurements in the sound measuring channel, since each of the measured sound signals undergoes peak detection before being digitized by analog-to-digital conversion.

 The reusability of the measurement of parameters and the temporal characteristics of sound signals lead to a noticeable limitation of the capabilities of the method in terms of measurement in a single cycle and in a single measuring channel of the parameters of the image and sound signals. The measurement time of each parameter is about 0.5-2 s, so the total measurement cycle time of ten parameters is about 10 s. For this reason, it is also impossible to include measurements of the quasi-peak span of the input dynamic sound signals and the maximum deviation of the average frequency of the sound radio signal in the parameter measurement cycle [9, column 10]. Thus, only the amplitudes of the sound signal radio signal [9, column 4] and its power [9, column 5] fall into a single channel for measuring the parameters of video and audio signals from the latter.

 Like any other method of measuring the parameters of television broadcasting signals, based on analog processing of the measured signal, the method [9] requires a relatively capacious hardware implementation, first, for analog processing as such, and, secondly, to reduce the influence of errors along the way analog processing.

 The selection of instantaneous values of the amplitudes of the measured signal only at the so-called characteristic points does not allow us to study the shape and spectral characteristics of the measured signal, a significant part of the information about the measured signal remains, thus, without coverage by the measuring process, which makes it impossible to obtain the entire set of normalized parameters, as well as required measurement accuracy.

 The implementation of the method does not provide for displaying on the display board the analog form of the measured signal, since it does not include either digital-to-analog conversion or the corresponding techniques for restoring the analog form of the signal between its measured values.

 The method [9] does not cover the broadcasting signals by the measuring process, but provides a separate measuring channel for measuring the parameters of the sound signal.

 To measure the parameters of the sound transmission channel in the television channel, the transmitted reference sound signal in the form of current is used, and in the broadcasting channel, the signals of the time stamps (MTV) are used. These signals consist of six rectangular radio pulses filled with a harmonic signal with a frequency of 1000 Hz. The duration of each radio pulse is 100 ms with a repetition period of 1 s. The beginning of the sixth signal in the MTV series corresponds to the beginning of each hour of Moscow time [2]. Known control methods using MTB involve the isolation of a tonal measuring signal by analog processing methods [3], [2], which requires relatively capacious equipment and reduces the accuracy of the measurement itself. The determination of the beginning of the measurement process in the prototype is based on switching on a cycle, which is not consistent with either the temporary waiting for the MTV measurement signal, or using the analytical capabilities of the electronic computing unit. The audio signal is discretized in time with a predetermined fixed frequency.

 The method [9] does not contain an operational reserve for building up a set of measured and controlled parameters.

 The aim of the invention is to increase the speed and accuracy of measurements, expanding the range of measured parameters and the visibility of their display, expanding the measuring capabilities to measure broadcast signals. The visibility of the display of the measured parameters implies the expansion of the possibilities of displaying the necessary data on the display with a specified degree of detail of measurements.

 The expansion of the measuring capabilities of the proposed method also lies in the applicability of any measuring signals used in television and broadcasting measurements, covering a set of normalized parameters while improving the reliability and accuracy of measurements. The nomenclature of the measured and controlled parameters, as well as the variability of the measuring signals, can be expanded by expanding the software packages.

 This goal is achieved by the use of a number of technical methods that allow implementing on a personal computer (hereinafter referred to as a PC) the control, measurement and control processes, in other words, abandon the analog processing of the measured signal, replacing it with digital processing using all the advantages provided by digital computing.

 Converting the analog form of the measured signal to digital without losing all the completeness of the information contained in the signal requires the fulfillment of the conditions of the Kotelnikov theorem, which makes it possible to obtain complete information about the signal throughout its duration or in a predetermined segment of this duration.

 Switching the measured audio signal in a cycle switch to switching in time.

 The sampling frequency in the measurement channel of the audio signal is subjected to switching, since two different sampling frequencies are used for measurements: one in the mode of detecting the beginning of the measuring signal and the other in the mode of digitizing the measured signal and its intermediate storage.

 Both switchings are made at the moment the sound measuring signal is detected, and the moment itself is determined by the results of the computational processing of the memorized sequence of digital values of the sound signal. This processing consists in sequential filtering of instantaneous signal values using a band-pass recursive filter implemented on a PC [5, p. 141 and 52], for example, Butterworth filter [5, p. 253], the characteristics of which are calculated from a priori information about the frequency of the measuring signal [5, 141, 89, 235], and ultimately comes down to detecting the measuring signal from the filtered sequence of instantaneous signals using the criterion for the ratio of the likelihood maximums about the presence and absence of measuring signals [6 , p.31, 32].

 Switching control, fixing a constant level of a television signal, storing and calculating, converting measurement results is carried out on a PC using software (procedures and functions) of standard library modules for a PC [7, p. 250, 256, 259, 266, 268] and programs transforming data that implements these tools in any programming language, for example, in the Turbo-Pascal language [7]. The measurement of television and sound signals is carried out in one measuring cycle, the intermediate storage of instantaneous values is carried out exclusively in digital form, and the entire sequence of digital values of the television signal is stored in one step, and the sound signal in several steps with time intervals used to calculate its parameters , the frequency filtering of the television signal in whole or in part is carried out by computing the stored sequence of their digital values, they perform digital-to-analog conversion of the measurement results with the calculation for analog interpolation of the intermediate between the measured instantaneous values of a television or sound signal using the Kotelnikov series [8, p. 46-49] and the oscillographic display of the corresponding analog form in the form of a quasi-continuous signal.

The drawing explains the process of measuring the parameters of the sound broadcasting signals according to the proposed method, where
a) - an example of a received audio signal containing a section with a measuring signal - a signal from the MTV series; b) - a temporary diagram of the process of measuring the parameters of an audio signal (option).

 The possibility of implementing the proposed method is illustrated as follows. The control of the measurement process is reduced to the management of switching, which is carried out by entering commands that define the measurement program, which, in turn, is determined by the number of monitored TV channels, sound and broadcasting, and the choice of measurement mode.

 For each monitored image transmission channel, the following modes are provided: full (according to the complete set of measuring signals), operational (according to the reduced set of measuring signals), functional (according to the complete set of measuring signals generated at the control point).

 For sound broadcasting channels, there are modes for monitoring the signal level, monitoring signal parameters from a series of MTV signals, a complete set of normalized parameters (the so-called periodic monitoring), as well as selecting the composition of measuring signals for operational monitoring modes and the time for measuring signal parameters from a series of MTV signals.

 In the proposed method, the switching of the measured signal in the television path is carried out in two stages: the selection of a given test line and the detection of test signals in this line. The number of the test line is determined by the established channel control mode. The specified line number is used for its switching by selecting and counting the clock pulses of the lines of the TV frame. The detection of measuring signals in this line is carried out after sampling the instantaneous values (digitization) of the signals and their digital processing, which is reduced to detecting the measuring signal by the criterion of the ratio of the maximum likelihood of hypotheses about the presence and absence of measuring signals [6, p.31, 32].

 TV measuring signals, for example B2, B1, F and D1, transmitted in the corresponding line of the television frame, undergo distortion when passing through the TV path. It is these signals that are the subject of measurement and comparison with the initial measuring signals, and the TV channel quality assessment is reduced to determining the parameters of the measured signals [4].

 The measurement results obtained as a result of the calculations are subjected to intermediate storage and formed in relation to a given indication model to be displayed on the display panel.

 To measure the characteristics of sound channels in the proposed method use accurate time signals (MTV) of high information content.

 Figure (a) shows an image of a received conventional sound broadcasting signal, turning into an accurate time signal of high information content. According to the proposed method, the length of interest to us is determined by the sequence of test samples obtained with a time interval (sampling frequency) that provides digital filtering of the frequency of the test signal, which (filtering) is used to detect the desired measured signal and to determine the start of digitization of the signal and its intermediate storage with switching the sampling frequency according to the conditions of sampling, that is, according to the Kotelnikov theorem. The choice of this option is due to the identity of its content with the main measuring process embedded in the inventive method.

 The calculation of the parameters of the measured sound signal is produced in the time intervals between calculations of the values of the parameters of the measured television signal.

 Digitization of the measured signal and its intermediate storing allows following this storing to measure the parameters of both the television and sound measured signal in a single measuring channel.

 The transition to measuring signal parameters by performing computational operations is carried out immediately after the intermediate storage of the next sample.

 Switching the audio signal in a cycle determines the initial moment of the interval of the set duration of the intermediate storage of the measured signal.

 The proposed method allows to obtain a gain in the accuracy of the measurement results in those cases when the object of study is not a special measuring, but any transmitted signal of both television and radio broadcasting.

 Consider the process of measuring the parameters of audio broadcasting signals using the example of a broadcast program signal and the MTV signal following it.

In drawing (a), a sound signal in the broadcasting channel is shown along the time axis, the level of which in pauses drops to the noise level, and at the time of transmission of the MTB signal rises to the maximum permissible value. The MTB signal consists of six tonal premises. The time axis is interrupted by a dotted line at those time intervals where the essence of the processes is the same as in the previous one. The drawing (b) shows a temporary diagram of the process of measuring the parameters of an audio signal in a broadcasting channel, where
T _s - the time of storing the digital values of the sampled signal;
T _ISM - time calculation of the parameters of the measured signal from a stored sequence of digital values;
T _OBN is the time of detection of the next sending of the signal of marks of exact time (MTB);
T _CPR - lead time of the expected MTV signal;
t _tv is the exact hour of the expected start of the MTV signal;
t _p - the moment of switching the sampling step;
i is the order number of switching the sampling step, and t _p1 is set as t _p1 = t _tv - T _exercise .

Let us trace the measurement of the sampling step Δt, following the time axis from left to right and designating Δt _{1 the} sampling step of the portion of the measured signal and Δt ₂ in the waiting (detection) portion of the measured signal, with Δt ₁ << Δt ₂ .

So, following from left to right along the time axis, we note that
on site T $\genfrac{}{}{0ex}{}{\text{I}}{\text{3}}$ digitization and storage of the usual broadcast signal,
on site T $\genfrac{}{}{0ex}{}{\text{I}}{\text{ism}}$ - calculating the parameters of the measured signal (conventional broadcast) from the stored sequence of discrete digital values taken with a sampling step Δt,
on site T $\genfrac{}{}{0ex}{}{\text{II}}{\text{s}}$ - digitization and storage of a conventional broadcast signal, taken with a sampling step Δt
on site T $\genfrac{}{}{0ex}{}{\text{II}}{\text{ism}}$ - calculation of the measured signal parameters from the stored sequence of discrete digital values taken with a sampling step Δt,
on site T $\genfrac{}{}{0ex}{}{\text{I}}{\text{update}}$ - obtaining a separate digital signal value, filtering it and making a decision on the presence of the first sending of the MTV signal in the time interval Δt ₂ , waiting for the next digital value,
on site T $\genfrac{}{}{0ex}{}{\text{III}}{\text{s}}$ - digitization and storage of the first transmission of the MTB signal with a sampling step Δt ₁
on site T $\genfrac{}{}{0ex}{}{\text{III}}{\text{ism}}$ - calculation of the parameters of the measured signal from the first transmission of the MTV signal from a sequence of digital values stored in the section T $\genfrac{}{}{0ex}{}{\text{III}}{\text{s}}$ ,
on site T $\genfrac{}{}{0ex}{}{\text{II}}{\text{update}}$ - "listening" to the device pause until the second transmission of the MTV signal is detected,
on site T $\genfrac{}{}{0ex}{}{\text{IV}}{\text{s}}$ - digitization and storage of the final section of the second sending signal MTV,
on site T $\genfrac{}{}{0ex}{}{\text{IV}}{\text{ism}}$ - calculation of the measured signal parameters from a sequence of digital values stored in section T $\genfrac{}{}{0ex}{}{\text{IV}}{\text{s}}$ at a sampling step Δt ₁ ..

Similar explanations could be given for sections T $\genfrac{}{}{0ex}{}{\text{IV}}{\text{update}}$ , T $\genfrac{}{}{0ex}{}{\text{VIII}}{\text{s}}$ and T $\genfrac{}{}{0ex}{}{\text{VIII}}{\text{ism}}$ . .

The process of measuring the parameters of the MTB signal on the third, fourth and fifth premises on the conducted time scheme is not shown, respectively, to which a gap is made on the time axis between the fifth (t _p5 ) and eleventh (t _p11 ) moments of switching the sampling step.

 Used sources.

 1. Auto USSR N 1297260, class H 04 N 17/02.

 2 / Broadcasting and electroacoustics. M .: Radio and communication. 1989, p. 416, 417.

 3. M. G. Ioffe. Automatic control of sound channels. M .: Communication. 1980.

 4. GOST 18471-83. The image transmission path of broadcast television. Links of a path and measuring signals.

 5. Rabiner L., Gould B. Theory and application of digital signal processing. M .: World. 1978.

 6. Vilenchik L.S., Katulev A.N., Mikhno G.A. Fundamentals of the theory of algorithmic control of a television channel. Scientific and technical collection "Technique of communications", a series of "Technique of television", issue 6, 1992, p.29-39.

 7. Faronov V.V. Basics of Turbo Pascal. M .: Publishing house MVTU - "Festo-didactic". 1992.

 8. Gutnikov V.F. Filtering measuring signals. L .: Energoatomizdat. 1990.

 9. Auth. St. USSR N 1584126, cl. H 04 N 17/00 (prototype).

Claims (1)

 A method for measuring the parameters of television broadcasting signals, including switching measuring television and sound signals, fixing a constant level of a television signal, frequency filtering television signals with the formation of a luminance signal, a color signal, with the allocation of color subcarriers, storing the level of the television signal in the form of fixing instantaneous values, analog-to-digital conversion of television and audio signals with time sampling and quantization by level, intermediate storing digital values, calculating parameters from a sampling of instantaneous values, moreover, calculating the parameters of the audio signal are interleaved in time with calculating the parameters of the television signal, intermediate storing of the measurement results and their conversion as applied to the specified information-display model, characterized in that the signals in the sound channel are low-pass filtering, and their analog-to-digital conversion is alternately switched from one sampling frequency to another, and about ba switching is performed at the moment of detecting the sound measuring signal, and the moment itself is determined by the results of the computational processing of the memorized sequence of digital values of the sound signal, switching control, fixing a constant level of the television signal, storing and calculating, converting the measurement results is carried out on a personal electronic computer, measurement television and sound signals are performed in one measuring cycle, intermediate memorizing instantly digital values, and the entire sequence of digital values of the television signal is stored in one step, and the sound signal in several steps with time intervals used to calculate its parameters, the frequency filtering of the television signal is fully or partially carried out by computing the stored sequence its digital values, carry out digital-to-analog conversion of the measurement results with the calculation for the analog int rpolyatsii intermediate between the measured instantaneous values of a television or audio signal and oscillographic display its analog to form a quasi-continuous signal.