SU1172079A1 - Generator for correcting time distortions of television signal - Google Patents

Abstract

A TELEVISION TEMPORARY TIME CORRECTOR CORRECTOR, containing a row clock selector, a pulse counter, and a voltage controlled oscillator, the output of which is connected to the counting input of the pulse counter and being the generator output for the equalizer, in order to improve, a pulse counter is used to improve the pulse counter generator, so that, in order to improve the corrector, the generator has a correct output of the pulse counter. pulse frequency, a sync block, a digital integrator, and a digital-analog converter are entered into it, with the output of the clock pulse selector connected to the input of the block with synchronization and input of the voltage controlled oscillator, the first output of the synchronization unit is connected to the preset input of the pulse counter, the second and third outputs are connected respectively to the first and second control inputs of the digital integrator, whose information input is connected to the output of the pulse counter, and the output is connected through a digital-to-analog converter with a voltage controlled by the g input of the generator. (L

Description

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The invention relates to the communications industry and can be used in constructing correctors for the temporal distortions of black and white television signals received from a video recorder, a disk player, etc.

The goal. the invention is to improve the accuracy and stability of the pulse frequency.

FIG. Figure 1 shows the structural electrical circuit of the generator for correcting the temporal distortion of the television signal; in fig. 2 - time diagrams, as shown, his work.

The generator for the TV signal time warp corrector contains a row clock selector 1, a pulse counter 2 and a generator 3 controlled by a voltage, the output of which is connected to the counter input of the pulse counter 2 and is a generator output for the corrector, synchronization unit 4, a digital integrator 5 and digital-to-analog converter 6, and the output of the selector 1 clock pulses. lines connected to the input of the synchronization unit 4 and the input of the generator 3, voltage controlled, the first output of the synchronization unit 4 is connected to the preset input of the pulse counter 2, the second and third outputs are connected respectively to the first and second control inputs of the digital integrator 5, information input which is connected to the output of the pulse counter 2, and the output through the digital-to-analog converter 6 to the control input of the generator 3, which is controlled by the voltage.

The generator for the corrector of temporal distortions of the television signal works as follows.

At the end of the analysis of the previous line, counter 2 records the nominal number of cycles (Fig. 2e) corresponding to the number of decomposition elements along the line. The falling edge of the sync pulse line (Fig. 2a) starts the generator 3, and using a generator with hard excitation ensures the initial phase of the write clock pulses fed to the subtract input of counter 2. Until the leading edge of the next sync pulse arrives (Fig. 2a ) the counter content is reduced by one (Fig. 2e) for each clock recording pulse, since by the end of the analysis of the current line in the counter 2 a remainder is formed (Fig. 2e), equal to the difference between nominal and actual the number of clock pulses in the interval between the sync pulses of adjacent lines, carrying information about the time error.

On the leading edge of the sync pulse of the next row, the oscillations (Fig. 2h) of the generator 3 and the start of block 4 are broken. On the leading edge of the pulse (Fig. 26), the second output of the block 4 records the contents of counter 2 (Fig. 2d) to the digital integrator 5 The impulse (Fig. 2c) from the first output of block 4 prepares the counter 2 for the analysis of the next line by pre-recording the nominal number of ticks into it (Fig. 2e). On the leading edge of the pulse (Fig. 2d) from the third output of block 4, the result of summing (Fig. 2e) of the previous contents of the digital integrator 5 with the remainder carrying the information on the time error on the previous line is output from the digital integrator 5. The new value of the binary code (Fig. 2e) from the output of the digital integrator 5 is fed to the input of the D / A converter b, which converts the digital code (Fig. 2e) to the voltage (Fig. 2g). Output voltage

(Fig. 2g) of the digital-to-analog converter 6 is fed to the control input of the generator 3. This sets a new value for the frequency of the output pulses of the generator 3.

Changing the frequency of clock pulses

records compensate for the detected time error in such a way that the number of write clock pulses arriving in the interval between the sync pulses of adjacent lines is exactly nominal, while by the time the next clock arrives, the contents of counter 2 will be equal to zero, therefore, the content of the digital integrator 5 will not change, while the control code will not change, the frequency of write clock pulses will remain unchanged until the next time error is detected. In this case, the tuning of the frequency-driving circuits of the generator 3 is performed during the action of the sync pulse line (Fig. 2a), when there is no generation (Fig. 2h) and

account (Fig. 2d) clock recording pulses.

The generator for the corrector of temporal distortions of the television signal implements a rigid connection of the clock frequency with the row frequency of the input television signal, which divides the active part of the television line, which is not constant in duration, into a constant number of samples equal to

decomposition elements along the television line, while ensuring relative frequency setting error

clock pulses of no more than 0.7-10 with a permissible corrected error (the maximum permissible difference between the lengths of adjacent lines of the input television signal) equal to half the active part of the line (± 26 µs in the SECAM system) and frequency-of-action pulses of 13.5 MHz.

FIG. 2

Claims (1)

A GENERATOR FOR THE TEMPORARY DISTORTION CORRECTOR OF A TV SIGNAL, comprising a line clock selector, a pulse counter and a voltage controlled oscillator, the output of which is connected to the pulse counter counter input and is a generator output for the corrector, characterized in that, in order to increase the accuracy and stability of the pulse repetition rate , a synchronization block, a digital integrator, and a digital-to-analog converter are introduced into it, and the output of the line clock selector is connected to the input of the synchronization block to the voltage controlled oscillator input, the first output of the synchronization unit is connected to the pulse counter preset input, the second and third outputs are connected respectively to the first and second control inputs of the digital integrator, the information input of which is connected to the pulse counter output, and the output is connected via a digital-to-analog converter with the control input of a voltage controlled generator. FIG. 1 ί172079