Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/78—Television signal recording using magnetic recording
  • H04N5/782—Television signal recording using magnetic recording on tape
• • 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
  • G11B20/02—Analogue recording or reproducing
• • 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
  • G11B20/10527—Audio or video recording; Data buffering arrangements
  • G11B2020/10537—Audio or video recording
• • 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
  • G11B2020/10833—Copying or moving data from one record carrier to another
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
  • H04N5/93—Regeneration of the television signal or of selected parts thereof
  • H04N5/95—Time-base error compensation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/79—Processing of colour television signals in connection with recording
  • H04N9/7921—Processing of colour television signals in connection with recording for more than one processing mode

Definitions

• the present invention relates to analog magnetic tape recordings of videos and their digitization.
• analog signal formats FBAS composite video
• YPBPR component video
• RGB optically rewritable chrometic random access memory
• said signals have undergone analog signal processing of the reproducer (reproducing device), which adds additional errors to the signal by means of noise, faulty calibration and distortions. After the event, it is no longer possible or only very difficult to reduce said errors.
• said signal formats allow only very limited evaluation for quality control purposes.
• time base correctors time base correctors
• TBCs time base correctors
• the color and brightness components of the video signal are modulated to carrier frequencies.
• the resulting signals are subsequently supplied to the magnetic recording head, which produces corresponding magnetization of the magnetic tape.
• the relative velocity between the magnetic tape and the recording head (head-to-tape speed) and the width of the head gap are selected such that the frequency spectrum of the modulated video signal may be reliably recorded.
• Analog video signals in the common signal formats FBAS (composite video), YPBPR (component video) or RGB are now present at the output of the device.
• TBCs For some video systems, there are special TBCs which can additionally fall back on internal signals of the reproducing machine and may thus achieve better correction.
• said devices At their outputs, said devices typically again provide an analog standard video signal. Since said devices are designed together with the respective video systems, they typically are not in line with modern prior art. Their signal processing is not very powerful, and the computing accuracy in digital devices is limited. Analog devices and/or analog circuit parts in digital devices result in signal errors due to noise, non-linearities and matching errors. Since said devices are typically 20 to 40 years old, maintenance is difficult and expensive, as is procurement of replacement parts.
• TBCs typically provide no information about the specific type and intensity of the correction applied. However, said information is extremely important, in particular for archiving, so as to be able to automatically digitize large stocks while maintaining a high level of quality.
• One variant serves to analyze digital serial video signals (SDI - series digital interface) and determines characteristics for the electric signal quality of the SDI signal and evaluates the image content contained in terms of compliance with specific limiting values, such as defined upper and lower values for luminance or chrominance signals.
• the second variant serves to analyze the image content in terms of typical errors which may arise during recording, transmission and encoding. They may concern black image and still picture detection, for example, detection of block artifacts of compression systems, detection of scene changes, color and movement analyses and similar characteristics.
• Both variants of quality control systems typically relate to digital signals and file formats and their particularities. Specific errors of analog video signals and specific errors of certain analog video systems are not taken into account in this context. Since particularly the second variant described only has the image content available for analysis, quality parameters from modulated signals cannot be taken into account for analysis.
• US78537662B2 describes an automated system for migrating media data from one storage medium to another.
• the timing of the video signal, the video signal and the audio signal are analyzed. Analysis is performed in real time.
• US3931638 describes an analog time base corrector wherein the analog video signal is read into a delay line storage (CCD) at an irregular clock and is subsequently read out again at a regular reference clock. The above is implemented as an electronic circuit.
• CCD delay line storage
• US5260839 describes a digital time base corrector wherein an analog (baseband) video signal is initially digitized and written to a memory. Subsequently, the signal is read out of the memory, again in correct timing with the aid of a reference clock signal, is interpolated and converted back to an analog signal via a D/A converter. The above is implemented as a digital electronic circuit.
• US4287529 describes a digital time base corrector with drop-out correction. The demodulated video signal from a magnetic tape is digitized and written to a memory. A drop-out detector detects drop-outs in the modulated signal and stores the times in a separate memory. The memory comprising the video signal is read out by means of a reference clock. The locations where a drop-out has been detected are replaced by the image information of the preceding row.
• US5596364 describes a method of objectively measuring the quality of a video frame and of an audio signal which generates parameters that are related to a human viewer's impression of quality. The method is used for quantifying any losses in quality arising from transmission, encoding or storing of the AV signal. In particular, he synchronicity of image signals and sound signals plays a part here. It is required for both the source signal prior to transmission and the transmitted signal to be available.
• US6734898B2 describes a method serving to measure the quality of a video signal in a receiver. This involves transmitting a test signal along with the video signal to be assessed. Evaluation of the properties of said test signal allow conclusions to be drawn as to the quality of the video signal.
• US7170933B2 describes a method of being able to determine the visual quality of a DCT (discrete cosine transform) coded video signal without knowing the original, non-encoded source signal. In this method, the quantization error and the block effects are estimated. The method is suited, in particular, for analyzing the quality of MPEG and similarly coded video data streams.
• DCT discrete cosine transform
• WO2004/054274A1 describes a method of measuring the quality of compressed digital video signals which does without the uncompressed original version.
• the quality level is derived, above all, from the step size of the quantizer and from the number of code blocks that have been coded with only one transformation coefficient.
• WO2005/060272A1 describes a system of measuring the image quality which evaluates the visibility of blocks of the encoding, the colorfulness and the sharpness of the image and combines them into a common quality measurement value.
• US7876355B2 describes a method and a device for detecting undesired deviations in the video frame during reproduction or the ingesting process.
• the deviations may concern faulty level values below or above specific threshold values or frozen frames and the like.
• the system operator is notified. Analysis and notification may be effected automatically.
• the TBC Since the standard video signals that are present at the input of a modern TBC have already undergone analog signal processing of the reproducing machine, the TBC no longer has the original signal available to it for correction, and thus, the possibilities of correction are reduced. In addition, the cost for TBCs is high.
• TBCs which additionally fall back on internal signals of the reproducing machine have worked with low quantization depths and sampling rates due to the technical possibilities available at the time. Due to the low computing power available, signal processing is typically limited to simple operations in the time domain. Both circumstances result in that the achievable image quality is limited as compared to that which is technically possible today. In addition, they convert the internal digital signal back to an analog standard video signal that would now have to be re-digitized. This results in losses which impair the image quality achievable. Utilization of the internal digital signals of said TBCs is not practicable since they are not standardized video signals and video interfaces and since they typically are not accessible and not documented.
• drop-out indications of video reproducing machines may be utilized for detecting defective tapes and subjecting them to special treatment. It is the object of the present invention to provide a concept for creating a digital version of a video from an analog magnetic tape recording of the video which leads to higher-quality results, within the framework of digitization of video archives, at moderate or even reduced expense required on the part of the user. This object is achieved by the subject matter of the pending independent claims.
• An inventive apparatus for creating a digital version from an analog magnetic tape recording of the video includes an input interface for receiving a modulated magnetic tape recording high-frequency signal originating from a magnetic tape recording of a video, an analog-to-digital converter for digitizing the modulated magnetic tape recording high- frequency signal to obtain a digital version thereof, and a digital postprocessing unit for deriving a digital version of the video from the digital version of the modulated magnetic tape recording high-frequency signal.
• the idea underlying the present invention consists in the recognition that digitization of video archives may be achieved with a higher quality and less expenditure if the digitization is performed as early as possible, namely as early as on the modulated magnetic tape recording high-frequency signals.
• Fig. 1 shows a block diagram of an apparatus for creating a digital version of a video from an analog magnetic tape recording of the video in accordance with an embodiment in a state where the apparatus together with a video reproducer forms a system for creating a digital version of the video;
• Fig. 2 shows a schematic representation for illustrating processing steps performed in the digital postprocessing unit 16 in accordance with an embodiment
• Fig. 3 shows a block diagram of a possible implementation of the apparatus of Fig. 1.
• Fig. 1 shows an apparatus for creating a digital version of a video from an analog magnetic tape recording of the video in accordance with an embodiment.
• the apparatus is generally indicated by 10. It includes an input interface 12, an analog-to-digital converter 14 and a digital postprocessing unit 16.
• the input interface 12 is configured to receive a modulated magnetic tape recording high-frequency signal originating from a magnetic tape recording of a video.
• the analog-to-digital converter 14 is configured to digitize the modulated magnetic tape recording high-frequency signal to obtain a digital version thereof.
• the digital postprocessing unit 16 in turn is configured to derive a digital version of the video from the digitized version of the modulated magnetic tape recording high-frequency signal and to subsequently output same at an output 18 of the apparatus 10.
• Fig. 1 shows an apparatus for creating a digital version of a video from an analog magnetic tape recording of the video in accordance with an embodiment.
• the apparatus is generally indicated by 10. It includes an input interface 12, an analog-to-digital converter 14 and a digital postprocessing
• the apparatus 10 is intended to receive modulated magnetic tape recording high-frequency signals at the input interface 12 and to process same, said processing being illustrated in more detail below.
• the apparatus 10 may possibly be combined with different video formats during operation, i.e. in the production of digital versions of videos.
• the apparatus 10 is combined with a video reproducer 20 so as to form, together, a system for creating digital versions of videos. As is shown by way of example in Fig.
• a video reproducer 20 typically comprises a tape drive 22 which here has a motor 24, for example, and a winding pin 26 for creating a tape feed 28 of a magnetic tape 30, namely in relation to a head drum 32 of the video device 20 having at least two video heads 34, which is also rotated about an axis 36 via a motor (not shown in Fig. 1), which axis 36 is arranged in a tilted manner in relation to a tape width direction extending tangentially to the magnetic tape 30 and perpendicularly to the feed direction 28.
• the tape drive is configured to guide the tape 30 during playback in such a manner that the magnetic tape 30 is fed along a part, such as half, of a circumference of the head drum 32, so that the video heads 34 arranged in a distributed manner along said circumference scan - during simultaneous rotation 38 of the head drum 32 and feed of the magnetic tape 30 - slant tracks 40 on the magnetic tape 30, along which tracks the modulated magnetic tape recording high-frequency signal is recorded.
• the signal, which is induced in the video heads 34 in an order which is cyclic in accordance with their arrangement along the circumference of the drum 32, is subjected to a first preprocessing, intended for forwarding, by a module 42 of the video reproducer 20, which acts as a reproducing amplifier and head switching circuit, so as to obtain the modulated magnetic tape recording high-frequency signal which is tapped at an output of the module 42, namely at an internal node 44 of the video reproducer 20, in that the node 44 is electrically connected to the input interface 12.
• the video reproducer 20 may have further components which also receive and utilize the modulated magnetic tape recording high-frequency signal at the node 44.
• a motor controller 46 of the video reproducer 20 evaluates any synchronization pulses contained within the modulated magnetic tape recording high- frequency signal so as to perform closed-loop control on the feed rate of feeding of the magnetic tape 30 and the rotational speed of the rotation 38 of the head drum 32, namely in relation to one another and, e.g., matched to a specific image repeat rate.
• An analog postprocessing unit 48 which also obtains the modulated magnetic tape recording high- frequency signal at the node 44, is provided, for example, to output the analog video signal - in a version intended, for example, for reproduction on a TV set - at an analog video output 50 of the video reproducer 20.
• the analog postprocessing unit 48 comprises, e.g., a frequency-separating means, analog demodulators, amplifiers, etc.
• said problems involved in digitization are circumvented by tapping the signal, which is supplied to the analog-to-digital converter 14, very early and at a point very close to the video heads 34.
• the input interface 12 is connected to induction and/or head windings 52 of the video heads 34 via no electric components other than the reproducing amplifier and the head switching circuit in the module 42.
• the reproducing amplifier and the head switching circuit in the module 42 do not too heavily impair the quality of the obtained modulated magnetic tape recording high-frequency signal, however due to signal amplification, they prevent major losses in the transmission to the input interface 12 and/or ensure that tapping of the modulated magnetic tape recording high-frequency signal takes place at a location which is independent of the precise video format and/or video reproducer 20 since the head switching circuit provides, as a component dependent on the video format and/or the rotational speed of the drum rotation 38, an intermediate format shared by most magnetic tape recording formats for videos.
• Fig. 2 shows a possibility of processing steps which may be performed in the digital postprocessing unit 16 to obtain the digital version 56 of the video from the modulated magnetic tape recording high-frequency signal 54.
• the video information is written into the slant tracks 40 of the magnetic tape 30 slant track by slant track in that magnetic material of the magnetic tape 30 is polarized accordingly along the track.
• the changing polarization along the track 40 creates - in the video heads 34, or, more specifically, in the head windings 52 - a high-frequency induction signal which yields, by means of the module 42, the modulated magnetic tape recording high-frequency signal 54.
• the temporal stringing together of the slant tracks 40 is indicated by the lettering t in Fig. 2.
• the modulated magnetic tape recording high-frequency signal 54 thus represents the curve of the change in polarization of the magnetic tape 30 along the series of slant tracks 40.
• the modulated magnetic tape recording high-frequency signal 54 typically carries the video information of the recorded video in the form of row-by-row sampling of the video frames 56, so that the modulated magnetic tape recording high-frequency signal 54 comprises a sequence of portions 58, each of which is associated with a row of an image 56 of the video, immediately consecutive ones of such portions 58 resulting in an image 56 and being followed by a further sequence of portions 58 of a subsequent video frame, etc.
• the portions 58 may have time gaps between them wherein the signal 54 is set in a predefined manner.
• each row portion 58 and/or each image 56 and/or each sequence of N images may have a synchronization pulse associated therewith, such a pulse being indicated by an arrow 60 by way of example.
• the video format contemplated is a color video format wherein the video information is modulated onto the modulated magnetic tape recording high-frequency signal 54 within two different frequency bands 62 and 64; however, other video formats wherein this is not the case would also be feasible.
• the signal bandwidth 66 of the modulated magnetic tape recording high-frequency signal 54 will be larger or smaller.
• the signal/noise ratio typically exhibited by the modulated magnetic tape recording high-frequency signal 54, which reaches the analog-to-digital converter 14 prior to being forwarded to the digital postprocessing unit 16, may also depend on the video format.
• the analog-to-digital converter 14 performs digitization at a bit depth and at a sampling frequency which depend on the video format underlying the modulated magnetic tape recording high-frequency signal 54, namely in that, e.g., one always uses the smallest bit depth and sampling frequency possible, or one always uses - at least among the maximally possible combinations of bit depth and sampling frequency as are provided by the A/D converter 14 - one of the combinations which meet both criteria.
• the sampling frequency should be double that frequency of the signal 54 that is to be maximally expected.
• the digital postprocessing unit 16 may be configured to detect the video format by means of a user input or to detect it automatically, such as by means of an analysis of the digital version of the modulated magnetic tape recording high-frequency signal 54.
• the target of such an analysis may be, e.g., a frequency analysis of the spectrum or any other evaluation of typical features of the video formats which differ among the video formats.
• Derivation of the digital version 56 of the video by the digital postprocessing unit 16 may also depend on the video format detected; with reference to Fig. 2, a typical example applying to many video formats will be provided below.
• the digital postprocessing unit 16 As was already mentioned above, a possible mode of operation of the digital postprocessing unit 16 will be described below for an exemplary case of the underlying video format. Consequently, the subsequent description might concern the mode of operation of the digital postprocessing unit 16 in the event that the video material currently to be digitized is a video format of the exemplary kind.
• the digital postprocessing unit 16 might have different modes of operation for different video formats.
• the modulated magnetic tape recording high-frequency signal 54 carries the video information in separate frequency bands 62 and 64 in accordance with the video format contemplated by way of example.
• Both frequency bands contain information about different brightness/color components of the video, for example.
• the higher-frequency frequency band carries the information about the brightness component of the video in a, e.g., frequency-modulated form
• the lower- frequency frequency band 62 carries the information about color components of the video, such as two chroma components, via quadrature amplitude modulation.
• a frequency band separation 68 for separating the two frequency bands 62 and 64 with a demodulation 70 of the frequency band components.
• Steps 68 and 70 may be serially performed in this order or may be inherently performed in one step.
• one possibility would be to realize the frequency band separation by a digital filter so as to obtain digital modulated brightness/color component signals 72 and 74 from the digital version of the modulated magnetic tape recording high- frequency signal 54.
• the signal component 74 would contain, e.g., only that signal portion of the high-frequency signal 54 that relates to the frequency band 64, whereas the signal 72 would include only that portion concerning the frequency band 62.
• Demodulation 70 would then depend on the type of modulation of the respective component, such as the frequency demodulation in the case of the brightness signal 74, and QAM demodulation in the case of the color component signal 72, as was described above.
• the result of the demodulation 70 would be digital demodulated color component signals, i.e. digital sequences of samples describing the brightness/color information of the video in the row sampling order of the signal 54.
• demodulation 70 of the signal component 74 would result, e.g., in a sequence 76 of brightness values of the video along the original row-by-row sampling of the signal 54, and demodulation 70 of the signal 72 would result in a sequence 78 of pairs of values specifying the color component of the video in the same sampling order.
• the digital postprocessing unit 16 in accordance with the embodiment of Fig. 2 also performs resampling 80 of the sequences 76 and 78 so as to obtain digital pixel values 82 of the digital version 56 of the video, namely one brightness value and two color values per pixel.
• resampling 80 the number of rows per image 56 of the video is maintained in resampling 80, and only the number of samples per row is adjusted, e.g. reduced, by the resampling 80, to the number of columns per image 56 of the video.
• the postprocessing unit 16 can operate and be implemented digitally is now showing positive effects in the most diverse instances.
• any filter operations performed for signal improvement or interpolations may take into account such signal portions of said signals which come after - in the sampling direction of the original signal 54 - the signal portion currently to be filtered, or even come before same by relatively large time periods, such as in one of the preceding rows of the same image 56 or in a preceding image, for example.
• Resampling 80 may use an FIR filter, for example, the filter kernel of which extends, in terms of position, about the pixel to be filtered and into the image 56 of the pixel currently to be filtered, and/or extends, in terms of time, about the pixel to be filtered into the future and into the past and into corresponding areas, in terms of location, of temporally adjacent images of the video.
• FIR filter for example, the filter kernel of which extends, in terms of position, about the pixel to be filtered and into the image 56 of the pixel currently to be filtered, and/or extends, in terms of time, about the pixel to be filtered into the future and into the past and into corresponding areas, in terms of location, of temporally adjacent images of the video.
• Anti-causally operating IIR filters would also be applicable, i.e. IIR filters operating counter to the order of rows and/or to the row scanning direction of the original signal 54. The same applies to filters employed, e.g., in frequency band separation 68 and/
• the previous processing steps of the digital postprocessing unit 16 are such processing steps as are equally performed for all of the videos of a video format contemplated, for example, since e.g. the locations of the frequency bands 62 and 64 are specified by the video format, the demodulation is specified by the video format, and resampling 80 is also specified, namely by the transition to the digital video format.
• the digital postprocessing unit 16 may also be configured to correct time base errors of the modulated magnetic tape recording high-frequency signal 54 and/or of the digital version. Such kinds of time base errors may occur in that - e.g. during recording - the rotational speed of the head drum fluctuated, the tape feed fluctuated, or such things happened during reproduction in the video reproduction device 20, i.e.
• the digital postprocessing unit 16 may be configured to correct said time base errors while evaluating the synchronization pulses 60.
• Temporal positional deviations of the synchronization pulses 60 from expected target positions having an expected time interval are corrected, e.g., by resampling using an interpolation filter in that the sequence of deviations occurring at the individual synchronization pulses 60 is continually temporally interpolated between said synchronization pulses 60. Said resampling takes place, e.g., prior to the frequency band separation 68 or demodulation 70.
• correction of time base errors of the digital version of the modulated magnetic tape recording high-frequency signal 54 is also possible in that the digital postprocessing unit 16 checks the carrier signals of the digitally modulated brightness/color component signals 72 and 74 in terms of a variation of the frequencies, for example, and tries to counteract said variation in that the sampling frequency of said digital modulated brightness/color component signals is decreased and/or increased accordingly, such as by resampling or, in the case of the frequency-modulated component 76, by means of a corresponding correction and/or by taking into account the demodulation, i.e. by changing the mapping of frequencies to amplitudes of the samples of the brightness component 76.
• time base errors mostly change continually over time.
• time base errors additionally have a specific time pattern in most cases, such as a specific frequency at which the time base errors change, and the digital postprocessing unit 16 may be configured to detect such time patterns within the time base error and to take them into account in the time base error correction so as to improve the correction.
• many magnetic tape recordings also have test images therein which may be detected by the digital postprocessing unit 16 and may be used in deriving the video frames of the digital version 56 of the video in order to improve the quality of the derivation.
• the digital postprocessing unit 16 uses, e.g., a relationship between the detected text image in the pixelated form following resampling 80 and stored characteristics of the test image. Deviations may then be used for performing corrective interventions in the individual processing steps for the subsequent video frames of the video, such as interventions in the demodulation, such as the frequency demodulation for adapting the frequency/amplitude mapping or the like.
• the apparatus 10 it is also possible for the apparatus 10 to process several modulated magnetic tape recording high-frequency signals 54 originating from a magnetic tape recording of the video so as to thereby improve the derivation of the digital version 56 of the video, namely by taking into account, in the derivation, all of said several modulated magnetic tape recording high-frequency signals 54.
• errors which occur irregularly in a non-reproducible manner such as varying tape-head distances which occur during playback of the magnetic tape 30 may be corrected, e.g. by suitable averaging over the several recording signals 54 or by averaging over other intermediate signals, such as 72, 74, 76, 78 and/or 82, for example.
• the digital postprocessing unit 16 may also cause targeted repeated playback of specific portions of the magnetic tape 30.
• the apparatus 10 may be configured to output, along with the digital version 56 of the video, data which is a measure of the quality of the signal obtained from the internal node 44, such as data which obtains this measure from the degree of influence exerted by the above corrective measures on the final result or on one or more of the intermediate results, i.e. the degree of corrective influence.
• the archive operator may use said data to draw conclusions as to the quality of the video material, conclusions as to possible problems of the video reproducer 20 or conclusions as to any maintenance work to be performed, such as maintenance on the video reproducer 20 or maintenance and/or cleaning of the magnetic tape 30, etc.
• Fig. 3 is to represent one possible implementation of the embodiment of Fig. 1 , showing what a typical implementation of the embodiment of Figs. 1 and 2 might look like.
• the apparatus 10 may temporarily store the digitized version of the modulated magnetic tape recording high- frequency signal, i.e. the digital data stream 84, in a suitable storage medium 86 of the apparatus 10 halfway between the analog-to-digital converter 14 and the digital postprocessing unit 16.
• the storage medium 86 may be any memory such as a volatile or non-volatile memory, a FIFO memory or the like.
• the digital postprocessing unit 16 may be configured as a computer or as an FPGA or ASIC.
• the digital postprocessing unit 16 may comprise dedicated hardware for digital signal processing.
• the postprocessing unit 16 stores the digital version 56 in a storage medium 88 of the apparatus 10, for example.
• This storage medium may belong to a working memory of the computer 16 or be a portable storage medium, such as a portable hard disc, a DVD, a memory stick or the like.
• the digital postprocessing unit 16 may output the digital quality control data, which has also already been mentioned above, to a storage medium 90 in accordance with the embodiment of Fig. 3. Said storage medium may physically coincide with the storage medium 88.
• the digital quality control data 92 may form side information on the digital image/video data 56.
• the apparatus 10 may comprise a user interface 94 by means of which it is possible for the user of the apparatus 10 to interact with the apparatus 10, such as to input the video format or to receive messages of the apparatus 10 and/or of the digital postprocessing unit 16, such as the message about any problems, which have already been mentioned above, in terms of the quality of the magnetic tape recording high-frequency signal read in, which allow conclusions to be drawn as to any maintenance measures that may be required.
• the analog-to-digital converter 14 digitizes the modulated high-frequency signal 54 as close as possible to the magnetic reproducing head 34, which reads the information from the tape. Close means, e.g., that there are no, if possible, or few electronic components or circuits such as filters, amplifiers, change-over switches, etc., located between the reproducing head(s) 34 and the analog-to-digital converter 14.
• the analog electric high-frequency signal 54 is sampled, for example, at a sampling frequency corresponding to its signal bandwidth 66, and is quantized with a bit count corresponding to its signal-to-noise ratio.
• a suitable filter is employed prior to sampling so as to reliably adhere to the sampling theorem. This filter might be part of the analog-to-digital converter 14 as is indicated in Fig. 3, or it may be connected upstream from the converter 14. However, over-sampling may also be employed in order to improve the signal quality.
• the computing unit performing the digital postprocessing i.e. the computing unit 16 to which the digital signal 84 is supplied, may be a PC or a GPU, DSP or FPGA realization.
• Said computing unit 16 is capable of applying any signal processing steps required for retrieving a color image signal or a black-and-white image signal to the digitized high- frequency signal 84.
• the specific computing steps involved depend on the respective video system and/or video format, as was mentioned above.
• said computing steps are FM and QAM demodulation, de-emphasis filtering, weighting of reference phase information for QAM demodulation, synchronization and matching of the demodulation, automatic gain control (AGC), obtaining row, image and image sequence and field synchronization information, and others.
• AGC automatic gain control
• the modulated digital (color) video signal 56 is subsequently converted to a suitable image or video data format and may be stored as a file on a hard disc or a different storage medium 88.
• the unit 16 may correct such errors in that the signal is analyzed in the frequency range with regard to the frequency of the carrier signals, such as the carrier signals of the FM and of the QAM. Preceding and subsequent rows, fields and frames which are at a larger direct and temporal distance may be incorporated in the analysis. In addition, the unit 16 may perform an analysis of the time curve of the demodulated signals while also incorporating preceding and/or subsequent rows, fields and frames. The unit 16 may also employ a combination of the analysis in the time as well as in the frequency domains. The time base errors may be combined by resampling the modulated or demodulated signal.
• level errors which make themselves felt by means of time base errors, particularly in a demodulated FM signal such as the signal 76, may be compensated for by means of level adjustment.
• the unit 16 may include functions of detecting and analyzing periodic patterns in the time base errors and their compensation.
• the periodic errors may arise, among other things, due to so-called impact effects wherein the regular tape run is impaired by the periodic contact of the rotating video head 34 with the magnetic tape edge. Any time base error corrections may be created, stored and/or transmitted in the quality control information 92 in addition to and synchronized to the image data 56.
• the unit 16 analyzes the RF signal 54 and its time curve. Said analysis may be performed in the time domain, in the frequency domain or, as a combination, both in the time and frequency domains.
• the RF signal 54 may be temporarily stored in a storage medium 86 for this purpose. The latter enables, both for signal analysis and for demodulation 70, the application of non-causal methods, i.e.
• Errors which may arise due to the reproducer 20 are, among others, clogging of the magnetic heads due to tape abrasion, tape-head contact errors during reproduction, mechanically deformed tapes, such as due to creases in the magnetic tape 30, and drop-outs.
• Errors which occur during recording already and which are therefore stored on the magnetic tape 30 together with the image information are, among others, errors arising in the recording due to an erroneous mechanical setting of the video recorder, track position errors, tape-head contact errors, errors caused by erroneous electric setting (matching) of the recorder as well as drop-outs.
• the apparatus 10 may calibrate an adaptive digital signal processing chain, such as the chain of processing steps which was described above with reference to Fig. 2, with the aid of test images which have frequently been recorded during the original recording on the tapes 30 to be digitized, and thus to compensate for any errors that were stored during recording on the tape, e.g. due to maladjustments of the recorder.
• Common test images are color-bar images, for example.
• the unit 16 may draw conclusions, in particular, as to original signal level ratios in the recording, such as black and white levels, and as to the setting of the pre-emphasis filters.
• Analysis may be effected either in the time domain or in the frequency domain or in the time and frequency domains simultaneously. In this manner, the level ratios may be counted back to the correct value within the framework of digital signal processing during the digitization process in the event of errors.
• Analysis of overshoots on edges in a test image may be used, e.g., by the unit 16 for adapting the de-emphasis in the digitization accordingly and for correcting any errors occurring here.
• the de-emphasis is performed, e.g., on the pixel values and/or in the pixelated domain of the digital image data 56.
• the corrections and compensations applied may be created, in turn, by the unit 16 as part of the quality control data 92 in their types and intensities and may be stored, for example.
• the quality control information 92 may also be used for pointing out to the operator of the apparatus 10 any necessary manual intervention in the process which otherwise operates in a fully automatic manner.
• the digitized high-frequency signal 84 output by the analog-to-digital converter 14 may also be stored directly to obtain a digital replacement original for long-term storage, such as in the storage medium 86.
• the necessary signal processing steps may then be applied, possibly with further improved technology, to the stored file having this digitized version 84 at a later point in time. The same applies to signal analysis for quality control.
• the demodulated video signals may be stored either in a suitable file format, for example on a hard disc or a different storage medium 88, or may be transferred to other systems via suitable interfaces.
• file formats both single-image formats such as TIFF, DPX, JPG, JPEG 2000, PNG, etc., or video formats and video container formats such as AVI, Quicktime and the like, are possible.
• output interface 18 both network interfaces such as Ethernet having suitable protocols such as TCB/IP, UDP, RTP, RTSP, etc., but also digital video interfaces such as SDI or HDSDI are possible.
• the demodulated video signal be compressed together with an audio signal and be transmitted, in reduced quality, into a further device such as the operating workplace 94, for example.
• the quality control information 92 may be stored in a file together with the image data 56. It is also possible to store said information and data in separate files. In this context, synchronization between image data and QC data is realized via of time code, image numbers or similar mechanisms.
• the QC data 92 may be transmitted, at the same time as the demodulation 70 of the image data, to further devices such as the operator's workplace, for example, via network interfaces with the aid of suitable protocols such as TCP/IP, UDP, etc.
• the operator may be made aware, in the event that specified threshold values of significant analysis parameters are fallen short of or exceeded, of any problems occurring in the digitization process or in the video signal so as to be able to take appropriate corrective measures.
• the above embodiments have the following positive properties, in particular.
• the above embodiments In comparison with digital video recorders, which may also play back relatively old analog formats and are available for several video tape formats, the above embodiments have the advantage that the computing power of current PC systems is higher and is available at lower cost. In addition, it is only for few video tape formats that digital video recorders are available which can play back analog tapes. Moreover, the above embodiments provide the possibility of directly storing the digitized data stream and of performing processing in non-real time at a later point in time. Thereby, signal processing steps of any degree of expenditure may be used and, consequently, e.g. very high-quality restoration of defective sections may be achieved, which would not be possible with a real-time system.
• Storing the RF signal also enables analyzing and reconstructing the signal while contemplating samples located further in the past or future with regard to the current value (several seconds or even longer periods are possible). It is also possible to process the signal in several runs, e.g. in an analysis run and a further processing run. Recursive processing, wherein the result is improved with each run, also becomes possible.
• the digitized RF signal is stored for the long term, one will be able to exploit future improvements in signal processing algorithmics to perform renewed image reconstruction or signal restoration.
• the RF signal can nevertheless be stored on hard discs. If, during reconstruction, problems arise and if individual images or portions cannot be reconstructed, one may fall back on the stored RF signal and process same with further restoration algorithms without having to re-digitize the video tape.
• the above embodiments may be employed, in particular, in automated digitization of large stocks of archival video material, it being important to achieve high throughput and degree of automation while attaining maximum image quality.
• the above embodiments enable using normal existing video recorders of the different systems and tapping the signals to be digitized via a cable which is additionally connected internally at the suitable location of the already existing circuit, and supplying said signals to the interface 12.
• the details concerning the precise location where the signal may be tapped depend on the specific video recorder 20, of course.
• signal processing differs depending on different video systems and formats, there being three fundamental principles which may then vary with different parameters depending on the video format and in accordance with the television system (PAL, NTSC, etc.).
• the component 48 might be omitted.
• the unit 16 uses a time period oriented toward both the past and the future. This includes the possibility of employing the principle of non-causal signal processing, which basically cannot be realized with analog systems without the possibility of signal storage. This means that calculating an initial value of a signal processing system is performed while using input values that may be located in the past or in the future with regard to the output value. In practical terms, this means that the input signal is stored over the period under observation, and that there may possibly be a time delay between the input and the output.
• a specific example is the application of digital FIR (finite impulse response) filters, which exhibit a non-causal pulse response.
• filters that are easier to control, e.g. for clearing the signal of spurious components, for separating individual signal components located in different areas of the overall spectrum, etc.
• Observation of relatively long time periods, i.e. across several image rows or video frames also enables signal correction of defective sections arising, e.g., from dropouts.
• image distortions arising from the RF signal breaking away because, e.g., the video tape was no longer in contact with the recording or reproducing head for a brief moment. They may also be caused by defects in the magnetic coating of the tape.
• the above embodiments also provided the possibility of reading out and iteratively postprocessing a pure digitized readout signal several times in each case.
• problems occurring during reproduction may be detected and computationally reduced.
• One example relates to the above-mentioned drop-outs, which may arise, e.g., due to grains of dust located between the tape and the head during reproduction. In the event of repeated playback, they would presumably not always lead to an error at the same location. These errors may then be compensated for via averaging (filter).
• Another field of application is the reduction of the noise influences of the analog reproducing amplifiers in the video recorder, which are normally always required before the signal is directed into the analog-to-digital converter. By repeated playback and by employing corresponding filters, the noise influence of said amplifiers may be reduced. However, the signal noise that has already found its way onto the tape as a result of the recording cannot be reduced in this manner.
• the above embodiments also provided the possibility of the unit 16 evaluating test images.
• a color-bar test image may be found at the beginning.
• the properties of said test image such as the signal levels at the individual locations of the image and the desired sharpness of the edges between the color bars, for example, are known.
• conclusions may then be drawn as to the adjustment of the recorder during the recording, and any errors that have possibly been caused by poor adjustment may be corrected.
• a further field of application is the production of a specific adjustment tape with a set of standard test images common in television technology, with which the reproducer employed for the digitization may then be set mechanically and, as far as required for digitization, electrically.
• This tape may then be played back and analyzed in an automatic process, for example daily, in order to assess the state of the reproducer.
• Any test images that may be considered contain, above all, color bars, sweeps, multibursts, 2T/10T pulse ramps, modulated ramps, and several other signals.
• the above embodiments described a system for digitization with automatic quality control for analog video tapes and cassettes, the signal stored on the magnetic tapes being digitized, if possible, directly after readout via the magnetic reproducing heads.
• Demodulation of the signals for luminance and chrominance may be performed with the aid of digital signal processing and leads to the reconstruction of the television images, which are stored on the magnetic tape, as digital image files.
• Typical signal errors may be corrected within the framework of digital signal processing.
• the information obtained during this process may be used for quality control of the signal and of the process.
• the above embodiments manage to achieve the best quality possible in the digitization of analog video tapes and cassettes. Time base errors resulting from wow and flutter can be corrected. In addition, it is possible to monitor the quality of the digitized signals in the best possible manner. Also, due to the evaluation of different signal portions, the quality analysis may make a statement about possible error sources, which may then be made known to the operator, so that same may intervene in the digitization process as required. Moreover, the digitized data itself may form a basis for automatic error correction and signal improvement. With reference to the above description it shall once again be pointed out that it has been frequently assumed that the video material is a color video material. However, the apparatus 10 would not be limited to being able to deal with color video materials only. The apparatus 10 might also digitize black-and-white video formats.
• aspects have been described within the context of a device, it is understood that said aspects also represent a description of the corresponding method, so that a block or a structural component of a device is also to be understood as a corresponding method step or as a feature of a method step.
• aspects that have been described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.
• Some or all of the method steps may be performed by a hardware device (or while using a hardware device), such as a microprocessor, a programmable computer or an electronic circuit. In some embodiments, some or several of the most important method steps may be performed by such a device.
• embodiments of the invention may be implemented in hardware or in software. Implementation may be effected while using a digital storage medium, for example a floppy disc, a DVD, a Blu-ray disc, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, a hard disc or any other magnetic or optical memory which has electronically readable control signals stored thereon which may cooperate, or cooperate, with a programmable computer system such that the respective method is performed. This is why the digital storage medium may be computer- readable.
• a digital storage medium for example a floppy disc, a DVD, a Blu-ray disc, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, a hard disc or any other magnetic or optical memory which has electronically readable control signals stored thereon which may cooperate, or cooperate, with a programmable computer system such that the respective method is performed. This is why the digital storage medium may be computer- readable.
• Some embodiments in accordance with the invention thus comprise a data carrier which comprises electronically readable control signals that are capable of cooperating with a programmable computer system such that any of the methods described herein is performed.
• embodiments of the present invention may be implemented as a computer program product having a program code, the program code being effective to perform any of the methods when the computer program product runs on a computer.
• the program code may also be stored on a machine-readable carrier, for example.
• Other embodiments include the computer program for performing any of the methods described herein, said computer program being stored on a machine-readable carrier.
• an embodiment of the inventive method thus is a computer program which has a program code for performing any of the methods described herein, when the computer program runs on a computer.
• a further embodiment of the inventive methods thus is a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program for performing any of the methods described herein is recorded.
• a further embodiment of the inventive method thus is a data stream or a sequence of signals representing the computer program for performing any of the methods described herein.
• the data stream or the sequence of signals may be configured, for example, to be transferred via a data communication link, for example via the internet.
• a further embodiment includes a processing means, for example a computer or a programmable logic device, configured or adapted to perform any of the methods described herein.
• a processing means for example a computer or a programmable logic device, configured or adapted to perform any of the methods described herein.
• a further embodiment includes a computer on which the computer program for performing any of the methods described herein is installed.
• a further embodiment in accordance with the invention includes a device or a system configured to transmit a computer program for performing at least one of the methods described herein to a receiver.
• the transmission may be electronic or optical, for example.
• the receiver may be a computer, a mobile device, a memory device or a similar device, for example.
• the device or the system may include a file server for transmitting the computer program to the receiver, for example.
• a programmable logic device for example a field-programmable gate array, an FPGA
• a field-programmable gate array may cooperate with a microprocessor to perform any of the methods described herein.
• the methods are performed, in some embodiments, by any hardware device.
• Said hardware device may be any universally applicable hardware such as a computer processor (CPU), or may be a hardware specific to the method, such as an ASIC.

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