Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
  • G11B20/10—Digital recording or reproducing
  • G11B20/10009—Improvement or modification of read or write signals
  • G11B20/10046—Improvement or modification of read or write signals filtering or equalising, e.g. setting the tap weights of an FIR filter
  • G11B20/10203—Improvement or modification of read or write signals filtering or equalising, e.g. setting the tap weights of an FIR filter baseline correction
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
  • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
  • G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
  • G11B27/24—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by sensing features on the record carrier other than the transducing track ; sensing signals or marks recorded by another method than the main recording
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
  • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
  • G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
  • G11B27/28—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording
  • G11B27/32—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on separate auxiliary tracks of the same or an auxiliary record carrier
  • G11B27/322—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on separate auxiliary tracks of the same or an auxiliary record carrier used signal is digitally coded
  • G11B27/323—Time code signal, e.g. on a cue track as SMPTE- or EBU-time code
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
  • H03K5/01—Shaping pulses
  • H03K5/08—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding
  • H03K5/082—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding with an adaptive threshold
  • H03K5/084—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding with an adaptive threshold modified by switching, e.g. by a periodic signal or by a signal in synchronism with the transitions of the output signal

Definitions

• the invention relates to a method for recovering an encoded signal sequence and an apparatus for carrying out the method.
• Methods and devices for recording a coded signal sequence on a moving storage medium are known, in which the coded signal sequence is recorded together with further information on the storage medium and stored there.
• a coded signal sequence is recorded at the edge of the image window, which is coded in binary form and is referred to as two-phase marking.
• FIG. 1 shows a section of a motion picture film 1, in the edge area of which perforation holes 21, 22 are provided.
• the film images 3 Arranged between the perforations 21, 22 are the film images 3 exposed by means of a motion picture camera, the format of which depends on the film format used in each case.
• a coded signal sequence 4 for additional information is recorded between the film images 3 and the one row of perforations 22 and consists of optically recorded markings in the form of wide and narrow lines and is referred to as "time code", which is based on the so-called SMPTE -Norm is included.
• This time code contains, for example, time information for determining the time at which the associated film images 3 were recorded, and optionally information about the user, the camera used, the film title, the name of the operator and the type of film used.
• This information stored in the coded signal sequence can additionally be recorded on a tape recorder 5 or a video device 7 and recorded on a manually operated script 6, so that, for example, an exact assignment to the recorded sound and additionally recorded video images is created during image processing becomes.
• time information about the hour, minute, minute and second as well as the number of the film image and a user coding recorded which are stored both on the motion picture film 1 and on the tape recorder 5 and the video device 7 and are entered in a manuscript 6.
• a motion picture camera with an electronic additional device for recording a coded signal sequence is known from DE-OS 30 10 225 and has a microprocessor with a memory and a device for entering the relevant information.
• a device for marking this information on the movable recording material is provided, the information being the number of the camera used, the film title, the name of the operator and the type of film used, and special information about the various sequences of the start and end times each sequence, the rotational speed, the value of the aperture used or the value used of the focal length of the lens, etc. can be recorded.
• a timer or a real-time clock which can be controlled by the camera via a logic circuit and is connected to the memory in order to enter the exact start and end times for each rotation sequence, is used to record the coded information.
• FIG. 2 shows an enlarged section of a coded signal sequence according to the SMPTE standard, which consists of wide and narrow lines exposed on the motion picture film, which form a two-phase marking.
• the binary Information consists of logical zeros and logical ones, which are recorded at the same intervals on the moving carrier material.
• a Signalwech ⁇ sel that lies within an interval aufbelichtete a marker, this is interpreted as a logic one, while a constant within the interval mark 'is interpreted as a logic zero.
• the transition from a logical zero to a logical one is 75% of the interval length, ie if a signal change occurs before 75% of the interval length, this is interpreted as a logical one, while a possible signal change after 75% of the interval length is a logical zero is interpreted.
• Figure 3 shows two different types of coded Si ghal 'followed by the SMPTE standard, wherein Figure 3A is a 80- bit information indicates, while Figure 3B is a 112-bit information includes, from 8 Zeitgeberbits 0 to 7 , a synchronization word with bit positions 8 to 23, a real-time and user bit word with bit positions 24 to 87, a further synchronization word with bit positions 38 to 103 and timer bits 104 to 111.
• disturbances occur which can be attributed, for example, to the exposure of the film, so that due to the change during an interval, the logic ones with a small amplitude are not recognized, which leads to additional sources of error.
• the amplified scanning signal is additionally output to a peak value detector, which controls the trigger level of the Schmitt trigger via a threshold value circuit.
• the measure of the positive feedback of the Schmitt trigger corresponds to a fixed value plus a value that is proportional to the sensed peak voltage. This means that when the sampled input signal increases the trigger threshold voltage is raised accordingly. The resulting shift in the trigger threshold serves to influence the sampled signal sequence in such a way that it meets certain criteria.
• a particular problem with the recovery of optically recorded signals is that when there is a change in polarity within a period to represent logical ones, there is a lower output amplitude than when scanning logical zeros in which the polarity within a period to represent the logically see zeros remain the same. If, in addition to these lower amplitudes, there is also the problem of a zero line shift due to a constant interference factor such as a gray haze on the motion picture film, errors in the evaluation of the signals emitted by the reading device are inevitable.
• the solution according to the invention includes a method with which the original signal sequence recorded on the moving storage medium is restored in a simple manner from a distorted signal sequence which is subject to interference, the use of commercially available reading devices in conjunction with a simple additional device, is possible.
• An advantageous development of the solution according to the invention is characterized in that the recorded signal sequence is detected by a reading head and the AC voltage component of the signal sequence is filtered out, that the maximum and minimum peak values of the AC voltage half-waves are detected such that a difference in the peak values is formed and the difference between the peak values is multiplied by the constant factor, and that the AC voltage signals are digitized to form a rectangular output signal sequence.
• a device for carrying out the method is a reading head for detecting the signal sequence recorded on the moving storage medium, a device for detecting the AC voltage components of the signal sequence, a device for forming the difference between the peak values of the AC voltage half-waves, and a device for multiplication the difference of the peak values with a predeterminable constant factor for forming the measure of the shift in the trigger threshold of a downstream square wave generator for converting the AC voltage signals into rectangular output signals.
• This device can be implemented by means of operational amplifiers which have a filter element for decoupling the AC component of the input signal, a peak value detector for detecting the maximum and minimum value of the half-waves of the AC voltage signal, and a difference generator for forming the difference between the maximum and minimum Form peak values, an amplifier with an adjustable degree of amplification and a Schmitt trigger with an adjustable threshold.
• Figure 1 is a schematic representation of the principle of recording a time code on a motion picture film
• FIG. 2 shows an enlarged section of a signal sequence coded according to the SMPTE standard
• FIG. 3 shows a bit representation of different types of signal sequences
• FIG. 4 shows a temporal representation of the original coded signal sequence as well as distorted and disturbed signal sequences
• FIG. 5 shows a block diagram of a device for the recovery of a distorted and disturbed coded signal sequence.
• the ideal signal sequence shown in FIG. 4A of additional information recorded on a moving storage medium consists of a square-wave signal, in which the period of the individual pulses depends on whether it is a logic zero or a logic one.
• the logical zeros have no signal change during an interval, while the logical ones contain a signal change during an interval and thus consist of rectangles of shorter period than the period of the rectangles of the logical zeros.
• these timecodes recorded as bar codes of different widths on the moving carrier material have no sharp contours in the rectangular area due to distortions which are due to flowing boundaries and no longer present sharp edges when recording on the moving carrier material. Signal sequence on.
• a DC voltage component is added to these aforementioned distortions, which is attributable, for example, to the gray haze of the motion picture film.
• This DC voltage component manifests itself in a shift in the zero line of the detected vibration.
• the DC component of the detected signal is eliminated according to the invention by laying the zero line in such a way that the same voltage time areas are present on both sides of the zero line with respect to the half-waves with maximum amplitude. Compared to this zero line, a further shift of the zero line is necessary in order to take into account the shape component, ie the asymmetry of the detected signal sequence.
• the zero line 0 * shifted relative to the zero line of the signal curve freed from the DC voltage component takes into account the form factor of the distortions, the measure of the shift
• the measure ⁇ thus represents the size of the shift in the trigger threshold for the recovery of the coded signal sequence and is composed of the product of a constant factor and the difference between the peak values of positive and negative half-waves.
• the above equation is based on the knowledge that the difference between the two half-wave peak values is directly proportional to the shift and the trigger threshold by which the zero line has to be shifted relative to the zero line of the pure AC voltage component of the detected signal sequence, by distortions and the different amplitudes the logical zeros and ones to be taken into account when recovering the coded signal sequence.
• the size of the constant factor C is chosen so that the shifted zero line 0 is placed approximately in the middle of the half-waves of small amplitudes, ie in the middle of the vibrations representing the logical ones.
• This constant factor can be easily adjusted by changing the gain of an amplifier.
• the setting of the constant factor can also be subject to regulation by changing the degree of amplification, the equality of the voltage time areas of the vibrations representing the logical ones being used, for example, as the controlled variable.
• the trigger threshold shifted by the dimension ⁇ is used to trigger a square-wave generator, which converts the positive and negative half-waves in relation to this trigger threshold 0 * into rectangular signals, i.e. digitized.
• FIG. 5 shows a block diagram of a device for recovering an encoded signal sequence that is subject to interference and distortion.
• the device contains a reading device 10 into which the motion picture film 1 with the time code thereon is inserted.
• the optical signal sequence contained on motion picture film 1 is shown schematically in block A.
• the output signal of the reading device 10 consists of a signal voltage, the course of which is shown in block B and which is emitted to the input of a downstream signal amplifier 11.
• This signal amplifier can be implemented, for example, by operational amplifiers, which fulfill the above-mentioned tasks 1 to 5 and a device for decoupling the AC component of the detected signal sequence to eliminate the DC voltage component, a peak value detector for detecting the maximum and minimum values of the signal sequence, a difference ⁇ delimiter for forming the difference from the detected peak values, an amplifier with adjustable degree of gain for setting the constant factor C and a Schmitt trigger or a comparator circuit which contains the zero line on both sides of the shifted line lying half-waves are converted into square-wave signals in a manner known per se.
• a square-wave timecode signal is thus present at the output of the signal amplifier 11, which is shown in block C and can be applied to the input of a display unit 12.
• the display unit 12 then converts the entered time code signal sequence back into a decoded signal corresponding to the representation according to FIG. 1 and displays the desired information alphanumerically.
• the embodiment of the invention is not limited to the preferred exemplary embodiment specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types.
• the implementation is not limited to implementation with discrete logic modules, but can also advantageously be implemented with programmed logic, preferably using a microprocessor.

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• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Recording Or Reproducing By Magnetic Means (AREA)
• Signal Processing For Digital Recording And Reproducing (AREA)
• Optical Recording Or Reproduction (AREA)

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• 1988
  • 1988-11-25 DE DE19883839749 patent/DE3839749A1/de active Granted
• 1989
  • 1989-11-24 WO PCT/DE1989/000743 patent/WO1990006578A1/de not_active Application Discontinuation
  • 1989-11-24 EP EP19890913038 patent/EP0445170A1/de not_active Withdrawn

Non-Patent Citations (1)

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