SU1285627A1 - Digital generator of colour strip signals for secam and pal systems - Google Patents

Abstract

The invention relates to television. The purpose of the invention is to increase the stability of the formed signals of the color bands (SCP) of the SECAM and PAL systems. The generator contains master quartz rr 1, two counters 2 and 16, shift register 3, D / A converter 4, Liltr 5 low frequencies, amplifier Jr distributor 6, read-only memory (ROM) 7 of the television signal, driver 8 write pulses, ROM 9 lowercase pulses, two logical adders 10 and 12, two multiplexes ora 11 and 15, a ROM 13 of field pulses and a switch 14 operating modes, which selects the cells of ROM 7 containing information about the PAL system signal (about four lines of the SCP image) or about signal system SECAM (about two lines of the image of the SCP). The goal is achieved by forming horizontal damping pulses and field damping pulses in SECAM and PAL systems. At the same time, when operating in the SECAM mode, the output NGN is not switching the phase of the color subcarrier across two lines. 1. i (L

Description

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The invention relates to the field of television and can be used in color band signal generators for testing and tuning color television devices of the SECAM and PAL systems.

The aim of the invention is to increase the stability of the formed signals of the color bars of the systems. SCECAM and PAL and cost effectiveness.

The drawing shows a structural electrical circuit of a digital signal generator of color bands of the -SECAM and PAL systems.

 The digital signal generator of color bands of the SECAM and PAL systems contains: a master oscillator 1, the output of which is connected to the counting input of the first counter 2, the clock input of the shift register 3 and the clock input of the digital-to-analog converter (DAC) 4. The output of the shift register 3 is connected to the information input DAC A, DAC 4 output through filter 5

 low pass is connected to the input of the amplifier-distributor 6, the outputs of which are the outputs of the digital signal generator of the color bands of the SECAM and PAL systems. The output of the first counter 2 is connected to the input of a permanent storage device (PZ

7 television signal, with the input of the imager 8 write pulses and

with ROM input 9 lower case pulses. The output of the ROM 7 of the television signal is connected to the information input of the register 3 shift, the output of the imager

8 write pulses are connected to the first control input of the shift register 3. The first output of the ROM of 9 horizontal pulses is connected to the first input of the first logical adder 10, the output of which is connected to the first input of the first multiplexer 11. The second input of the first multiplexer 11 is connected to the output of the second logical adder 12, the first output of which is combined with the second input the first logical adder 10 and is connected to the first output of the ROM 13 field pulses.

The control input of the first multiplexer 11 is combined with the first control input of the ROM 7 of the television signal and connected to the output of the switch 14 operating modes. The second control input ROM of the television signal is combined with the second

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the input of the second logic adder 1 2 and connected to the second output of the ROM 13 field pulses, the third output of which is connected to the first input of the second multiplexer 15. The second input of the second multiplexer 15 is combined with the third input of the first logical adder 10 and connected to the fourth output of the ROM 13 pulses fields. The third input of the second multiplexer 15 is combined with the input of the second counter 16 and connected to the second output of the ROM of 9 horizontal pulses, the third and fourth outputs of which are connected respectively to the fourth and fifth inputs of the second multiplexer 13. The output of the second counter 16 of the field pulses. The output of the second multiplexer 15 is connected to the setup input of the DAC 4. The output of the first multiplexer 11 is connected to the second control input of the shift register 3.

The digital signal generator of the color bars of the SECAM and PAL systems operates as follows.

The master oscillator 1 generates pulses with a frequency ff greater than 12 MHz so as to provide a video signal conversion with a DAC 4 with an upper cut-off frequency of at least 6 MHz times the double frequency of the second 2 of these pulses information from the ROM 7 television signal and from the ROM 9 small pulses. The ROM 7 of the television signal is recorded. Information on four lines of the image of the signal of the PAL systems color bars, on two lines of the image of the signal of the color bars of the SECAM systems (red and blue) and on two lines (red and blue) containing the color synchronization signals of the system SECAM. The selection of the cells of the TV signal ROM 7 containing information about the signal of the PAL system or the SECAM system is carried out by means of a switch 14 of operation modes, commands from which are sent to the first control input of the ROM 7 of the television signal.

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A parallel code, from the output of the ROM 7 of the television signal, arrives at the information input of the shift register 3. In shift register 3, the output code of the ROM 7 of the television signal and 31128 are multiplexed.

Equalization of the flow in time. A parallel 32-bit code from the output of the ROM 7 of the television signal is converted by the shift register 3 into an 8-bit input to the DAC 4. This reduces the performance requirements of the ROM 7 of the television signal, since it operates in this case at a frequency. From the shaper of 8 write pulses, one write pulse for every four clock pulses arrives at the first control input of the shift register 3.

sa f. With the arrival of this pulse, a parallel output 32-bit code of the ROM 7 of the television signal is recorded in the shift register 3 and promoted to the output of the shift register 3 with a frequency f, the pulses of which are fed to its clock input. In order to normalize the write pulses, the output signal of the first counter 2 is supplied to the input of the driver AND the write pulses.

When forming the SECAM system signals, the transition from the cells in which the signal of the color bands is recorded to the cells in which the color synchronization signals are recorded is performed with the arrival of 9H pulses, which determine the position of nine lines containing color synchronization signals.

The sync pulse information is not recorded in the ROM 7 of the television signal, but instead it is recorded with a code corresponding to the level of damping pulses of the output signal.

In the PAP 4 operating at the clock frequency, the 8-bit code is converted into an analog signal, which, having passed through the low-pass filter 5 with a passband of up to 6 MHz and through the distribution amplifier 6, is fed to the outputs of the digital generator the signal of the color bars of the SECAM and PAL systems.

The ROM of 9 horizontal pulses contains information about horizontal sync pulses, equalizing pulses, frame inserts, and gating pulses of the color subcarrier of the PAL system. The address input of the ROM 9 line pulses receives the same address as the address input of the ROM 7 of the television signal. Thus, their output signals are synchronized with each other. From the release of the ROM 9 lower case

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pulses to the other blocks are four signals with a frequency. The memory capacity of the ROM of 9 lower-case pulses is eight times less than the volume of the memory of the ROM 7 of the television signal.

Field pulses are formed by a ROM of 13 field pulses. It contains information about the pulses 2, 5H, 7, 5H, the damping pulse of the fields 25H and about the pulses 9H, which determine the position of the color lock signals in the SECAM system.

The position of the 9H pulses relative to other field pulses is different in two adjacent fields of the television frame. Therefore, in the ROM of 13 field pulses information is recorded on the field pulses of both the first and second fields of one frame.

Information is read from the ROM of the field pulses 13 in accordance with the addresses received from the output of the second counter 16, to the input of which pulses of the frames are fed, which follow with the double line frequency 2 from the ROM of the nine horizontal pulses. To reduce the memory size of the ROM 13 field pulses, its control is performed as follows. An address bit having a field frequency is generated in the form of a pulse, the duration of which slightly exceeds 25 N and overlaps the damping pulse of the fields. These pulses are fed to the address input of the ROM 13 of the field pulses and with their arrival the reading of all the field pulses begins. In the intervals between the pulses of the address bit having the frequency of the fields, at the output of the ROM of 13 pulses of the fields there is a constant high logic level corresponding to the interval between the generated pulses of the fields.

The sync signal is generated in the second multiplexer 15, which with the arrival of 7.5N pulses from the ROM 13 field pulses switches from the output of horizontal pulses to the ROM 9 horizontal pulses to the output of equalizing pulses from the ROM 9 horizontal pulses. With the arrival of the 2.5N pulses from the output of the ROM 13 of the field pulses, the second multiplexer 15 switches to the output of the pulses of the ROM inserts of the 9 horizontal pulses. At the end of the pulse 2,5N second multi

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the plexer 15 returns to the output of the equalizing pulses, and at the end of the 7.5N pulse, it returns to the output of the horizontal pulses and remains in this position until the next 7.5N pulse arrives. As a result, a sync signal is formed, which is fed to the setup input of the DAC 4 and sets the output of the DAC 4 to the level of the response to zero, which is chosen for the level of the clock pulses.

Formation of horizontal damping pulses occurs when reading information from the ROM 7 of a television signal, in which, at intervals of the absence of a color subcarrier on the horizontal damping pulses (for the SECAM and PAL systems), codes corresponding to the damping pulses are recorded.

The formation of damping field pulses in the SECAM system is performed as follows.

The second control input of the shift register 3 receives pulses from the output of the first multiplexer 11. With the arrival of the pulse, the beginning of which coincides with the beginning of the damping field pulse, the shift register 3 is transferred from the write-advance mode to the storage mode and is output to its output the code corresponding to the quench level. This state continues until the arrival of the pulse 9H, during which at the output of the second logic adder, a signal is generated that translates the shift register 3 into the write-advance mode. The impulse 9H also arrives at the second control input of the ROM 7 of the television signal and switches the ROM 7 of the television signal to read information from the cells with recording color synchronization signals. In the output at the output of the shift register 3, codes of the color synchronization signals are generated. At the end of the 9H pulse, the shift register 3 reverts to the storage mode and, at its output, the code corresponds to the blanking level before the end of the damping field pulse, after which the shift register 3 switches to the recording-advance mode of the information about the color bars signal from the ROM 7 tv signal.

During the formation of damped field pulses in the PAL system signal at

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The second control input of the 3 shift register receives 7.5N pulses, at which there are no color subcarrier spacing in the output signal of the color bars. In the remaining lines of the damping field pulse, the readout of the damping pulse level is interrupted for the time of the flash strobe pulses when the shift register 3 enters the write-advance mode, and the output of the color subcarrier flashes received at this time from the TV signal ROM 7.

The switching of the first multiplexer 11 from the output of the second logic adder 12 to the output of the first logic adder 10 occurs by a command coming to the control input of the multiplexer 11 from the switch 14 operating modes.

Since only four lines of the PAL system color bars image are recorded in the TV signal ROM 7, the frequency of the color subcarrier in the output signal of the color I bands in this mode of operation is 25 Hz lower than the standard value. The blanking of the color subcarrier outbreaks in the interval of damped field pulses does not occur in the range of nine lines, and in the range of the pulse is 7.5N.

. When operating in the SCAM mode, there is no color subcarrier phase switching across two lines in the color bars output signal.

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Claims (1)

Formula iso.bren.and A digital signal generator of the color bands of the SECAM and PAL systems, containing the first counter and a persistent storage device (ROM) of the television signal, the second counter, and a digital-to-analog converter (DAC), characterized in that, in order to increase the stability of the formed color bar signals SECAM and PAL systems, serially connected write pulse shaper and shift register, the OUTPUT of which is connected to the information input of the D / A converter, which sets the quarter, are entered. the target genator, the output of which is connected to the counting input of the first account; - pin, to the clock input of the shift register 71 Heap and to the DAC clock input, series-connected low-pass filter and distribution amplifier, whose outputs are the outputs of the digital generator of color band signals of the SECAM and PAL systems, and the input of the low-pass filter connected to the output of the DAC, sequentially connected permanent memory (ROM) line pulses the first logic adder and the first multiplexer, the output of which is connected to the second control input of the shift register, the second multiplexer the second logic adder, mode switch In operation, a persistent storage device (ROM) of field pulses, the control input of the first multiplexer is combined with the first control input of the ROM of the television signal and connected to the output of the mode switch, the second input of the first multiplexer is connected to the output of the second logic adder, the first input of which combined with the second entrance eight the first logic adder and connected to the first output of the ROM of field pulses, and the second input is combined with the second control input of the ROM of the television signal and connected to the second input of the ROM of field pulses, the third output of which is connected to the first input of the second multiplexer, the second input of which is combined with the third input the first logical adder and is connected to the fourth output of the ROM of the field pulses,. The second output of the lowercase pulse ROM is connected to the third input of the second multiplexer and through the second counter to the ROM input of field pulses, the third and fourth output of the lowercase ROM ROM are connected to the fourth and fifth inputs of the second multiplexer, the output of which is connected to the MAP setup input, the ROM input the television signal is combined with the ROM inputs of the lower pulse and the input of the recording pulse generator, and the output with the information input of the shift register.