DE3149293A1 - Method and circuit arrangement for representing an item of time information on a longitudinal track of a magnetic tape - Google Patents

Abstract

A method and a circuit arrangement which serve for the storage and retrieval of a plurality of types of information on a single track of a magnetic recording medium are specified. In particular, suitable pulse sequence frequencies are specified for the time-code basic clock rate and the control-track pulses, which are in an integral relationship with each other and therefore influence each other only little by crosstalk. In this case, editing marks and parity and check bits may also be included in a suitable way in the time-code pulse train. Furthermore, the circuit arrangement may be substantially the same for carrying out two colour television standards.

Description

Method and circuit arrangement for illustration

a time information on a longitudinal track of a magnetic tape the technology The invention is based on a method according to the preamble of the main claim. From the Journal of the SMPUE't, June 1973, Vol. 82, pages 482 to 491, is known to have a binary-coded data signal on a longitudinal track of a video magnetic tape that is representative of each tape location. This data signal is recorded in the form of a continuous pulse train as a sequence of 80-bit data words and contains time information in the form of hours, minutes, seconds and Image number specification, application-related information as well as synchronization information. The time information and application-related information take up 64 bits, the synchronous word the remaining 16 bits. Has for coding this data signal the European Broadcast Union with E.B.U. Document Tech.

3097 Bi-Phase-MarX-Code raised to the standard, a self-clocking Code, enforced.

In magnetic tape systems for storing #TV signals, in particular of color television signals, are commonly recorded on another long track of magnetic tape sync pulses derived from the head wheel revolutions are recorded. In addition an alternating pulse is generated once per head wheel revolution in a detector device generated. During playback, this pulse chain is used to synchronize the phase of the Head wheel used by the when playing in the same way as when playing Recording generated head wheel pulses with the control track pulses taken from the magnetic tape be compared. In the earlier common cross-track recorders ran the head wheels when recording black and white television signals and color television signals according to the CCIR standard at 250 Hz, while when recording television signals according to the American black and white standard or color television signals according to the NTSC standard the #opfraddrehzahl was 240 per second. As a result, the control lane contained in the first case a 250 Hz signal, while in the second case pulses with an average Frequency of 240 Hz were recorded.

When choosing the 80-bit word length of the benen, The data signal called time code was, among other things, decisive for the bit rate of 2000 (80 bit x 25 full frames) in the recording of images according to the European TV standard or

2400 (80 bits x 30 frames) when recording television signals according to the American standard, each in a simple 8: 1 or 10: 1 ratio to the selected control track frequency, so that undesired mutual interference the signals recorded in adjacent longitudinal tracks are largely avoided became. In the literature cited above, the possibility is already indicated Use the time code information in place of the control track for servo purposes. In the meantime however, recording methods using the magnetic tape have become popular with a sequence of track sections running obliquely to the tape edge becomes (helical recording method).

With these #ie head gears rotate at different speeds than with the At the time the time code standard was established, only cross-track magnetic tape recorders were used. As a result, the control track has a pulse repetition frequency other than 240 or 250 Hz and the simple numerical connection that was originally sought between control track frequency and bit rate has been lost.

Advantages of the invention The method according to the invention with the characterizing Features of the main claim has the advantage that by suitable choice of the code word format, the bit rate is an integer Multiples the control track frequency is. Another advantage is that the information both longitudinal tracks can be combined in a single track.

The hatreds listed in the subclaims are advantageous Further developments and improvements of the method specified in the main claim are possible. It is particularly advantageous that in suitable sections of the time code pulse train the cutting marks previously placed in the control track can also be included. Likewise, parity and check bits can advantageously be provided. Further is further advantageous that the circuit arrangement for performing the invention Procedure can be essentially the same for both standards. Finally, it is advantageous that the clock processing for time code and control track in a common circuit arrangement he follows.

Drawing exemplary embodiments of the circuit arrangement according to the invention are shown in the drawing and explained in more detail in the description below. There are shown Fig. 1 as a block diagram of a circuit arrangement for the win Bit rate and the control track basic frequency when processing PAL color television signals, # ~ # 2 also shows the same circuit arrangement with the processing of NTSC or PAL-M color TV signals occurring frequencies in the time code and control track, FIG. 3 is a block diagram of an arrangement for recovering Data information, cut marks and control track clock from the recorded time code format.

Description In Fig. 1 are used to generate the required control track frequency and the bit rate for the time code when recording PAL-encoded Color television signals to the first input 1 of a phase lock circuit 2 horizontal sync signals fed at the line frequency of 15 625 Hz. In the phase lock circuit (r # t = phase locked loop) 2 is multiplied by a factor of 4, so that a pulse train with a clock frequency of 62,500 at the output of the PLL circuit Hz occurs. This clock frequency is in a first divider circuit 3 with the divisor 4 fed back to the line-frequency clock and the second input 4 of the PLL circuit fed so that a phase lock between the output signal and the input signal at input 1 occurs.

The output clock sequence of 62 500 Hz of the PL circuit 2 is in a second divider circuit 5 with the divisor 25 to the desired bit rate divided down from 2500 Hz to generate the time code words.

The reset input to C R5 of the divider circuit 5 will be as well like the reset input R3 of the divider circuit 3 pulses at an interval of 2V (frame rate) = 25 Hz are supplied, which simultaneously creates the coupling with the vertical sync pulses he follows. The resetting of the divider circuit 5 marked in the pulse train of 2500 Hz after every 100 oscillations the beginning of a new time code word, which consequently has a length of 100 bits. The bit rate of 2500 Hz is in a third divider circuit 6 with the divisor 8 to that in a particular recording system desired control track frequency divided by 312.5 Hz. The reset input R6 of the Divider circuit 6 are supplied 4V-synchronous pulses of 12.5 Hz, whereby these can be coupled with the control track clock of 312.5 Hz. From the output signal of the Divider circuit 5 is obtained by modulating the numerically encoded time code. The actual time code word is 80 bits long, while the bits are 80 bits long the serial numbers 81 to 100 are freely available. In particular, can in bits number 81 to 100 (for PAL: 4 V cutting marks and 8 V color question pulse), Check bits or check words are accommodated.

As a result of the fixed, integer relationship of the control track frequency and the bit rate can be on a dedicated longitudinal track of the magnetic tape Control track information is merged with the time code, making the freely available Storage area on the magnetic tape and the degree of utilization can be improved. at the combination of time code and control track to form a common track on the tape the output of the divider circuit 6 is only used as a reproduction reference for the retrieved Control track used.

The circuit arrangement according to FIG. 2 corresponds in structure and mode of operation completely of the circuit of FIG. 1, but the input 21 of the PXL circuit 22 a frequency of 15,750 Hz corresponding to the line frequency in the NTSC system. Multiplication by a factor of 4 results in a base frequency at the output the PLL circuit of 63,000 Hz, which by division in the divider circuit 25 is divided down to the basic bit sequence frequency of 2 520 Hz. The reset input R23 of the divider circuit 23 and the reset input 25 of the divider circuit 25 2V-synchronous impulses are supplied according to the frame rate of 30 Hz. Through this the result is a word length in the time code of 2 520: 30 = 84 bits. The fundamental bit rate frequency of 2520 Hz is in the divider circuit 26 with the division 8 to the control track frequency divided by 315 Hz. The word length in the time code of 84 bits when storing NTSC-coded color television signals with a standard length of 80 bits per time code word 4 bits in each word for special use, such as the arrangement of Cut marks etc. (with NTSC: 2 V cut marks and 4 V color frame impulse).

In Fig. 3, for the recovery of the track in a single longitudinal of a magnetic tape 32, they are scanned by a magnetic head 31 and the data in the signal coil 33 converted into electrical signals. According to the appropriate Amplification in amplifier 34, they are fed to a pulse shaper stage 35 whose output 36 the master code basic clock is pending, while at output 37 the pulse shaper stage 35 after demodulation, the data contained in the recorded track is available stand. The clock on line 36 is the Clock input eeß shift register, 38 # <&? #Tet, which contains at least as many memory locations as bits are provided in the period of a television full screen. At the rate of the bit rate on line 36, the data on line 37 is passed through the shift register 38 pushed. The synchronous word detector is located at the first parallel outputs of the shift register 38 39, which sends an output signal to the reset input when the synchronous word is present the divider circuit 40 outputs, whereby the clock sequence of the clock output 36 of the pulse shaper stage 35 corresponding to the division ratio of 8 to a pulse train with the frequency 312.5 Hz (in the case of PAL) is converted. By resetting with the occurrence of the synchronous word in the time code data signal, the fixed coupling with the Time code word (2V video). The pulse at the output of the synchronous word detector circuit 39 is also fed to the set input of a buffer 41, which is connected to parallel Data outputs of the shift register 38 is located. When the pulse occurs at the set input the content of the shift register 38 is transferred to the intermediate memory 41 and can be read out there. Contain those marked with brackets 42 Outputs the standard time code word, while those marked with bracket 43 Outputs the cut marks, check bits, etc.

may contain. The pulse train with the control track clock from the output the TeiXr circuit 40 is fed to an input of a phase comparison circuit 44, while the second input of the phase comparison circuit 44 is reference control pulses from a reference clock source 45 derived from Figures 1 and 2 312.5 Hz (315 Hz) became. Depending on the phase deviation of the removed from the magnetic tape and The phase comparison circuit generates processed processed from the #drawal pulses 44 an output signal which, in a known manner, is used to regulate the synchronization of the magnetic tape recorder can be used.

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Claims (8)

Claims method for displaying time information on a Longitudinal track of a magnetic tape, characterized by the choice of the time code word clock greater than the time code word length. 2. The method according to claim 1, characterized in that the time code basic clock and the control track frequency in a simple integer ratio to each other stand. 3. The method according to claims 1 or 2, characterized in that Check bit in the bit positions available beyond the time code word length or check words are included. 4. The method according to any one of claims 1 to 3, characterized in that that cut marks in the bits going beyond the word length of the time code word are housed. 5. The method according to one or more of the preceding claims, characterized in that for grCW ew ns iS ezet Ly sw one Information contained in magnetic tape when reproducing in a shift register (38) inserted complete clock section by a sync word detector (39) is recognized and with the occurrence of the sync word in the time code an 'oil divider circuit (40) is reset, which is generated by a pulse shaper stage (35) of a magnetic tape (32) removed, converted time code basic clock into the control track clock, and that at the same time the data contained in the shift register (38) at this point in time be transferred to a buffer (41). 6. Circuit arrangement for performing the method according to the claims 1 to 4, characterized by a phase locking circuit (pol) (2) whose the first input is supplied with horizontal-frequency pulses from the respective television standard and which by multiplication generates a basic frequency, from which by single division the bit sequence frequency and by repeated division the control track frequency can be derived. 7. Circuit arrangement according to claim 6, characterized in that the reset input of the first divider circuit (5, 25) a 2 V-frequency pulse train, the reset # input of the second divider circuit (6, 26) a 4 V-frequency pulse train is fed. 8. Circuit arrangement for performing the method according to claim 5, characterized by a pulse shaper (35) for reshaping from the magnetic tape (32) by means of the magnetic head (31) into a time code basic clock Pulse train (56) and a Detensequence (37), through a shift register (38), whose Clock input the time code clock and its data input those contained in the time code track Data are supplied by a sync word detector (59) to detect a complete time code clock section, by a buffer (41) for takeover the information contained in the complete clock section and by a divider circuit (40) to obtain the control track clock from the time code clock.