RU2042218C1 - Video-cassette/digital data recorder - Google Patents

Abstract

FIELD: instrumentation engineering. SUBSTANCE: trailer length files are recorded on video recorder tape under computer program control through interface unit, channel coder, shift register, record amplifier. RECORD mode is preceded by desired file search through reproduction of record made earlier and data transmission to computer through reproduction amplifier and channel coder. Detection of last track of desired file causes jump to RECORD mode without stopping magnetic tape so that no space is held between files. EFFECT: improved informative capacity of magnetic tape with provision for desired file search during digital video recording. 5 dwg

Description

 The invention relates to instrumentation and can be used as a drive for digital information for archival storage.

A device for digital audio recording containing a series-connected analog-to-digital converter, a coding and interleaving unit, a channel modulator, a switch, a playback amplifier, a corrector, a phase-locked loop, a channel demodulator, an error correction block, an interpolation unit, a digital-to-analog converter, and the output the switch is connected to the rotating heads, and the output of the playback amplifier with the engine control units of the capstan and the block of rotating heads [1]
This device provides a high recording density along the track (track), however, on the surface of the magnetic tape between the pairs of tracks there are unused gaps due to the orthogonal arrangement of a pair of rotating heads in the plane of rotation. In addition, with the file structure of the recorded data on the magnetic tape, unused intervals appear at each start, stop and synchronization of the drive of the magnetic heads and tape. All this reduces the utilization of the magnetic tape.

There is also known a device for digital magnetic recording of information on a VCR, comprising a generator connected through a frequency divider to the synchronizing inputs of the device, a switch whose inputs are connected to interface units and coded pulse modulation encoders, and the outputs are connected in series with a digital encoder, digital-to-analog converter, video signal conditioner, VCR, digital signal isolator, analog-to-digital converter, digital decoders and pulse decoders Modulation Code [2]
The specified device records tracks without gaps. However, the file structure of the recorded data also reduces the information capacity of the magnetic tape, since with a high recording density and relatively small file sizes, the useful recording area on the tape is incomparably smaller than the area of tape sections consumed during start-up, shutdown, and synchronization of the drive of magnetic heads and tape in the process records of each file.

 The purpose of the invention is to increase the information capacity of a magnetic tape with the ability to search for a given file during digital recording on a VCR.

 To achieve the goal, a device for digital magnetic recording of information on a VCR containing a data bus, an address bus, and a control bus connected to the interface unit, whose “Record Data” output is connected via a switch to the input of the channel encoder, a generator connected to the clock input of the first divider frequency, the first output of which is connected to the input "Request for recording data" of the interface unit, a VCR, the bus "switching pulses" of which is connected to the input of the first driver, the second frequency divider, deco data marker and channel decoder, the first and second shift registers, a recording amplifier, a playback amplifier, a clock recovery unit and a second driver, the input of which is connected to the input of the first driver, and the output with the field pulses bus of the VCR, the output is “Record sign” are introduced the interface unit is connected to the reset input of the first frequency divider, to the control input of the recording amplifier and to the "Record" bus of the VCR, the output of the channel encoder through the first shift register and the recording amplifier and connected to the "Record Data Input" bus of the VCR, the first output of the first frequency divider is connected to the address input of the switch, and the second output to the clock input of the first shift register, the "Control" output of the interface unit is connected to the "Remote Control" bus of the VCR, the "Output “through which the playback amplifier is connected to the inputs of the second shift register and the clock recovery unit, the output of which is connected to the clock inputs of the second frequency divider and the second shift the new register, the output of which is connected to the data input of the decoder of the data marker and the channel decoder, the output of which is connected to the input "Playback data" of the interface unit, the output of the first driver is connected to the input "Interrupt request" of the interface unit, the output of the second frequency divider is connected to the input "Request playback data "of the interface unit and with the reset input of the data marker decoder, the output of which is connected to the reset input of the second frequency divider.

 The set of features of the presented technical solution is necessary and sufficient to increase the information capacity of the magnetic tape during digital recording on a VCR, because they provide the maximum use of the magnetic tape without any gaps due to the search for a given file in playback mode and switching to recording mode with a moving tape in result of detection of the last track of the searched file.

 Figure 1 presents a block diagram of a device for digital magnetic recording of information on a VCR; figure 2 format of digital recording on magnetic tape of a VCR; figure 3 block pairing; figure 4 block recovery sync information; 5, a data marker decoder.

 A device for digital magnetic recording of information on a VCR contains a pairing unit 1, a switch 2, a channel encoder 3, a first shift register 4, an recording amplifier 5, a first frequency divider 6, a generator 7, a second driver 8, a first driver 9, a VCR 10, an amplifier 11 playback, sync recovery unit 12, second shift register 13, second frequency divider 14, data marker decoder 15, channel decoder 16, data bus 17, address bus 18, control bus 19.

 Switch 2 is designed to store and convert parallel code into parallel-serial and contains the register KP1533IR23 and the multiplexer K1533KP17. Channel encoder 3 is designed to convert parallel four-bit words into parallel six-bit words and is made in the form of read-only memory on the K155REZ microcircuit. The first shift register 4 is designed to convert parallel words into a sequence of pulses with subsequent encoding it according to the BVNM method and is performed on the K1533TM9 and K1533TM2 microcircuit, included in the counting mode. The recording amplifier 5 is designed for coordination with recording heads and is made in the form of a push-pull emitter follower on transistors of different conductivity. The first frequency divider 6 is designed to generate clock frequencies for recording and exchanging with computers and is made in the form of a serial connection of a binary counter K555IE5 and an annular shift register K555IR8. The ratio between the clock frequencies of recording and exchange is set as 24/1 in a two-word exchange. The generator 7 is made on two K1533LN1 inverters, closed in a ring through a quartz resonator.

 The second shaper 8 is designed to match the multi-level signals of the VCR 10 and is made on the emitter follower. The first driver 9 is designed to generate unipolar pulses along the edges of different polarity of the input signal and is made on an EXCLUSIVE OR K1533LP5 microcircuit. The playback amplifier 11 is designed to generate unit pulses for each transition of the magnetization of the magnetic tape and contains a series-connected linear amplifier, a peak detector in the form of a differentiating RC circuit, a K597CA2 comparator for generating a two-level signal from an analog, and a shaper on a K1533LP5 chip to generate unipolar pulses along the edges of different polarity.

 The second shift register 13 is designed to convert a serial code into a parallel word and is executed on the chip K555IR8. The second frequency divider 14 is designed to generate clock frequencies for reproduction and exchange with computers and is made in the form of a ring register K555IR8 and one bit of a binary counter K555TM2. Channel decoder 16 is designed to restore the original information by the inverse conversion of six-bit words into four-bit words and is made in the form of read-only memory on the KR556RT11 chip.

 The interface unit 1 (Fig. 3) is designed to provide asynchronous information exchange between the VCR and the computer and contains a data bus 17, an address bus 18, an output pulse bus 19.1 (from the computer), a response bus 19.2, a data request bus 19.3, an input pulse bus 19.4 ( in a computer), a bus 19.5 of the pulse request interrupt channel direct access to memory, register 20 data recording, register 21 commands, encoder 22 commands, elements 23 and 24, decoder 25 port numbers, elements OR 26 and 28, trigger 27, element And 29, read data register 30, bus 31-36.

 The register 20 of data recording is designed to convert an uneven sequence of information words into a uniform one and is performed on chips KR1533IR23. The encoder 22 commands is designed to generate code sequences for remote control of the VCR 10 and is executed on the chip K1506XL1, the truth table of which corresponds to the command system of the VCR. The decoder 25 port number is designed to activate the necessary direction of exchange in accordance with the operating mode and is executed on the chip K555ID7. The read data register 30 is intended for storing information words in the intervals between exchanges, has three states and is executed on the KR1533IR23 chip.

 The sync information recovery unit 12 (Fig. 4) contains an input bus 37, an And 38 element, a charging resistor 39, a charging diode 40, an operational amplifier 41, a controlled generator 42, an output bus 43, an inverter 44, an AND-NOT element 45, a discharge resistor 46 , discharge diode 47, filter capacitor 48, filter resistor 49. The operational amplifier 41 with a high input resistance is designed to eliminate the influence of the load on the filter time constant and is made on the KR544UD2 microcircuit. The controlled generator is made on a chip K531GG1P.

 The decoder 15 of the data marker (figure 5) is designed to determine the beginning of the data group and contains the input bus 50 of the playback data, the input bus 51 of the request for playback data, the element And 52, the block of elements NOT 53, the trigger 54, the output bus 55, the counter 56. Number inputs of the element And 52 corresponds to the number of bits of the data marker (two bytes). Elements are NOT included in the lines corresponding to the zero bits of the data marker. The capacity of the counter 56 corresponds to the number of words in the data group (including the data marker itself). As counter 56, the K555IE7 chip is used.

 The device (figure 1) works as follows.

 Recording and playback are carried out on a pre-formatted magnetic tape, for which a video recorder 10 with an installed video cassette is turned on in recording mode using its own controls. As a result, throughout the entire magnetic tape, pulses of a frequency of 25 Hz are recorded on its control track from the output of the “Pulses of switching” of the VCR to its input “Pulses of the fields” through the second driver 8. When the device is in other modes, the VCR 10 always remains in playback mode and synchronized by the pulses of the formatted track, and the recording mode is provided by turning on the external recording amplifier 5.

 Recording and playback of digital information in the form of files of finite length is carried out using a personal computer (not shown) loaded with the corresponding program and connected to the device with data buses 17, addresses 18 and control 19. Files are recorded on the magnetic tape of the VCR 10 with a serial code using the BVNM method .

 In accordance with the principle of oblique line recording of the VCR 10, files are placed on tracks (tracks), the recording format of which is created programmatically. This format (figure 2) provides packages of units at the beginning and end of the track for synchronization restorer sync information, data blocks and markers for their identification during playback.

 In the first data block of each track, overhead information is recorded containing the track number and file name required when searching for a given file. Search is used both during playback and during recording. The recording mode may be preceded by a playback mode with the search for the file after which the next file must be recorded without any intervals. Detection of the last track of the file searched initiates the transition from playback to recording at the beginning of the next track with a moving tape. The described algorithm of work is carried out under the control of a computer program bypassing the control system built into the VCR, which does not provide such a change of modes without stopping the tape.

 When you start the program on the corresponding register of block 1 pairing from the computer receives the command word, which determines the desired mode of operation. Depending on it, a sequence of command pulses is generated in the interface block of the KR1506XL1 microcircuit, which sets the magnetic tape drive to the required mode (operating speed or fast forward and backward) on the bus of the VCR “Remote control”, and if the operation involves recording or playback, it starts also a rotating head unit of the VCR 10. It generates switching pulses that connect the rotating heads to the track recording or playback circuits. According to the switching pulses at the beginning of each track, the shaper 9 generates a request signal for interrupts of the direct access channel to the computer memory. The program perceives this request after the time necessary for acceleration and synchronization of the magnetic tape drive and rotating heads, after which the direct access channel is programmed in accordance with the interrupt vector for the desired operating mode.

 Record Mode On the "Control" bus of the computer interface unit 1, the VCR 10 is set to playback mode, and its rotating heads are connected to the output of the recording amplifier 5 by a high signal level on the "Record flag" bus. This starts the tape drive and synchronizes it from a pre-formatted control track. The potential of the bus "Record sign" also allows the operation of the recording amplifier 5 and the first frequency divider 6, launched by the generator 7.

 Frequency divider 6 generates data request pulses of the direct memory access channel with a period sufficient to convert the parallel data word to serial. The program begins to process these requests after programming the direct access channel and recording a unit package at the beginning of the track. For each data request from the computer, a recording data word is received, which from the register of the pairing unit 1 is fed to the information input of the switch 2, controlled by the address input by a frequency divider 6. Switch 2 converts the parallel data word into parallel-consecutive four-bit words, each of which is transcoded into a six-bit word by the channel encoder 3 and is input to the parallel load of the shift register 4. Channel coding replaces each four-bit word with one six-bit combination that satisfies the balance condition, i.e. in every six-bit word that was encoded by the BVNM method before recording, there should be an equal number of positive and negative digital transitions th signal. This prevents errors due to a change in the DC component of the recorded signal. The frequency divider 6 also generates write clocks, with which the shift data register 4 is converted into a serial data code and encoded in accordance with the recording method BVNM, providing for a change in the direction of magnetization when recording each unit. The encoded data through the recording amplifier 5 is fed to the VCR bus “Record Data Input”.

 On each track, a predetermined number of data words are recorded, after which units are written until the end of the track, that is, until the next request for interrupts the direct access channel is generated. If the entire file is issued, then at the initiative of the program, the stop word of the VCR is sent to the command register of the pairing unit 1.

 Playback mode. VCR 10 is started and synchronized in the same way as the “Record” mode, but the operation of the recording amplifier 5 and the first frequency divider 6 is prohibited by the low signal level on the “Recording flag” bus. With the same potential, the rotating heads of the VCR are connected to the input of the playback amplifier 11, in which the level of the read signal is brought to the required level, the low-frequency component is excluded by the peak detector, and a two-level BVNM playback signal is formed by zero transitions by the comparator, on each edge of which an information unit pulse is generated using schemes EXCLUSIVE OR.

 In the synchronization information recovery unit 12, the phase-locked loop (PLL) system generates a sequence of clock pulses from the information pulses, with the help of which sequentially reproduced data are entered into the shift register 13. In parallel, they from the output of the register go to the decoder 15 of the marker and the channel decoder 16, restoring the original data for output to the computer through the block 1 interface. The exchange with the computer is carried out according to the signals "Request for playback data", which are generated by the second clock frequency divider 14 as the shift register 13 is filled with the next word. Phasing of the frequency divider 14 is performed by data markers, which are allocated by the marker decoder 15 from the reproduced data.

 Search mode. This mode always starts with the "Play" mode. The program compares the reproduced number of the current track with the given one and, depending on the sign and size of the result, either continues to play, or starts fast forward or rewind. The duration of the rewind is determined by the difference between the numbers of the current and the desired tracks. By rewinding the video tape, it is brought to the area of the specified track, and the "Search" mode is turned back on. When a specified track number is detected, the program switches to the desired operating mode (recording or playback), starting from the next track without stopping the tape.

 The interface unit (figure 3) works as follows.

 After programming the channel for direct access to the computer memory, a binary code of the port number is set on the address bus 18 through which the control word is sent to the data bus 17. It is recorded in the register 21 teams, the choice of which is carried out by the decoder 25 according to the port number and the pulse output 19.1 through the element And 23. One of the outputs of the register 21 commands is connected to the bus 32 "Record sign" and determines the operating mode of the device. Code combinations on other outputs of this register control the movement mode of the magnetic tape of the VCR. The encoder 22 commands, these codes are converted into a sequence of pulses, the intervals between which correspond to the control commands of the VCR.

 The exchange of data is carried out according to the signals "Request for recording data" 34 or "Request for playback data" 35, which through the OR element 28 are received at the installation input of the trigger 27 data request. In response, the computer issues a data output port number via the 18 address bus, and the decoder 25, through the And 23 element, is allowed to write to the write data register 20, where the data word is written by the output pulse 19.1. On bus 19.2 "Response" trigger request 27 is restored to its original state.

 During playback, the output impulse 19.1 is absent, and according to the input impulse 19.4 from the read data register 30, the data word is entered into the computer. The data on this register is updated according to the signals 35 of the request for playback data, and from the high-impedance state it is output through the AND element 29 by the input pulse 19.4 when the port number of the playback port is input to the decoder 25.

 Block recovery sync information (figure 4) works as follows.

 The generator 42, frequency-controlled by the output potential of the operational amplifier 41, generates clock pulses, which are in antiphase fed to the inputs of the phase detector (element And 38 and element AND-NOT 45). Their other inputs receive short pulses of 37 reproduced units. If they are ahead of phase in the reference sequence of the generator 42, then through the element 38 and the charging chain 39, 40, the capacitor 48 is charged. This leads to an increase in the frequency of the generator 42 until the phase difference becomes zero.

 If the reproduced pulses of 37 units are out of phase with the clock pulses, then the capacitor 48 is discharged through the AND-NOT element 45 and the discharge circuit 46, 47. This leads to a decrease in the frequency of the generator 42 to a value at which phase errors are eliminated. When the playback data fall out on the capacitor 47, the potential corresponding to the frequency before the dropout is preserved, since the input resistance of the operational amplifier 41 and the diodes 40 and 47 locked while this increase the time constant of the discharge circuit.

 The decoder data marker (figure 5) works as follows.

 The reproduced data 50 is sent in parallel to the data marker recognition circuit. Bits with single values of the bits of the marker go to the inputs of the AND 52 element, and bits with zero values through the elements NOT 53. After reading the last bit of the data marker, the And 52 element affects the setting input of the trigger 54. It allows the counter 56 and the second frequency divider 14 to work ( figure 1), which generates impulses for requesting playback data and thereby supports communication with a computer. The counter 56 at the same time counts the number of words played back by the request signals 51 of the playback data and after the last word of the data group resets the trigger 56. As a result, the exchange with the computer stops during the reading of the next marker and it is not transmitted to the computer.

Claims (1)

 DEVICE FOR DIGITAL MAGNETIC RECORDING OF INFORMATION ON A VCR, containing a data bus, an address bus, and a control bus connected to the interface unit, the recording data output of which through a switch is connected to the input of the channel encoder, a generator connected to the clock input of the first frequency divider, the first output which is connected to the input "Request for recording data" of the interface unit, a VCR, the bus "Switching pulses" of which is connected to the input of the first driver, the second frequency divider, the data marker decoder and anal decoder, characterized in that the first and second shift registers, a recording amplifier, a playback amplifier, a clock recovery unit, and a second driver are input into it, the input of which is connected to the input of the first driver, and the output is with the bus "Field pulses" of the VCR, the output is "Sign recording "interface unit is connected to the reset input of the first frequency divider, to the control input of the recording amplifier and to the bus" Record "of the VCR, the output of the channel encoder through the first shift register and amplifier the recorder is connected to the “Record data input” bus of the VCR, the first output of the first frequency divider is connected to the address input of the switch, and the second output is to the clock input of the first shift register, the “Control” output of the interface unit is connected to the “Remote control” bus of the VCR, the bus “Output "through which the playback amplifier is connected to the inputs of the second shift register and the clock recovery unit, the output of which is connected to the clock inputs of the second frequency divider and the second motor register, the output of which is connected to the data input of the decoder of the data marker and the channel decoder, the output of which is connected to the input "Playback data" of the interface unit, the output of the first driver is connected to the input "Interrupt request" of the interface unit, the output of the second frequency divider is connected to the input "Request reproduction data "of the shifting unit and with the reset input of the data marker decoder, the output of which is connected to the reset input of the second frequency divider.

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