GB2335817A - Film frame steadiness correction in film to video conversion - Google Patents

Abstract

A video signal-processing device, such as telecine film scanner, comprising an evaluation device (29, Fig.1) provided to generate a correction signal for compensating steadiness errors of each film frame from the scanned position of reference marks, such as sprocket holes, assigned to each film frame, 31-34. The evaluation device (29) generates at least two correction signals for each film frame. In this way, the scanned film frames can be corrected section by section, 41-44, in their horizontal position, eg via measured displacements x1 to x4. Scanning of the reference marks may be done optically, ultrasonically or capacitively.

Description

2335817 1

DESCRIPTION

VIDEO SIGNAL PROCESSING The invention relates to a video signal processing device, for processing a video signal produced by a film scanner, the video signal processing device comprising an evaluation device provided to generate a correction signal for compensating steadiness errors of each film frame from the scanned position of reference marks assigned to each film frame. The invention further relates to a video signal-processing device, for post-processing film material stored electronically, comprising a steadiness correction device provided to correct the frame position of each film frame on the basis of a correction signal. The invention still further relates to a film scanner. The invention yet further relates to a storage device for electronically storing film material and to a corresponding data carrier material on which film material is stored.

A film scanner is used to convert cinematographic film material into electronic signals by passing, a film beyond or through an optoelectronic scanning device. A problem which always occurs in this case is to maintain the frame position of consecutively scanned frames constant. The partly periodical, partly statistical fluctuations of the frame position may have different causes. For example there may be positioning errors in the pick-up camera as well as in the negativelpositive copying machine. Additionally, frame position errors and tracking errors of the film scanner may also lead to further steadiness errors.

Different solutions have been proposed to attempt to reduce the frame position errors, as is known from, inter alia, DE 37 36 789 C2, in which a reference mark assigned to a film frame is scanned as a reference point for each scanned film frame. Reference marks may be, inter alia, the sprocket holes, the contour of each film frame or, for example, also marks simultaneously illuminated during illumination of the film. A scanning device for example, a line sensor, which is arranged at a given inclined angle with respect to the film drive direction, generates pulsatory signals which are 2 compared with stored reference patterns. The horizontal and vertical offset of the scanned reference mark are determined in a computer as horizontal and vertical vector signals from the temporal offset of the currently scanned pulsatory signal with respect to the stored reference pattern. These vector signals are applied to a correction circuit in which the scanned film frame is moved in opposite directions in accordance with the measured horizontal and vertical offset of the reference mark. The use of such reference marks as reference points for the film frames has the advantage that mechanically conditioned positioning errors of the film can be substantially compensated io because the positions of the scanned reference marks and the assigned film frame are coupled together with generally very small tolerance and are also substantially maintained when copying the film.

However, the display accuracy is also negatively influenced by tracking fluctuations of the film scanner. As is common practice, the drive motor provided for the film transport is therefore adjusted, using, for example sprockets as speed sensors engaging the sprocket holes. Tolerances of the sprocket and possible slip thus have a direct effect on the tracking stability.

It is an object of the invention to improve the display quality of video signals produced by film scanners.

The invention provides a video signal processing device comprising an evaluation device for generating a correction signal for compensating steadiness errors of each film frame from the scanned position of reference marks assigned to each film frame, in which the evaluation device is arranged to generate at least two correction signals for each film frame.

By generating a plurality of correction signals per film frame, each film frame can be subdivided into a plurality of sections, in which the frame position of each film frame section itself can be corrected rather than correcting the frame position of a film frame as a whole, as was hitherto the case. Whereas a frame position error is produced during frame-wise transport in a pick- up camera, which error has the same effect on the whole frame, frame position errors within a frame are produced through continuous transport of the film when copying the film or when the film is being displayed. Vertical position 3 errors then result, for example, from tracking fluctuations, and horizontal position errors result from a motion of the film transverse to its drive direction. By correcting sections of a film frame it is now possible to correct such frame position errors as well.

The positions of a plurality of reference marks can be applied per film frame to the evaluation device, i.e. a plurality of reference marks is available for each film frame, for example, the four sprocket holes on each side of a film frame whose positions are consecutively scanned and applied to an evaluation device. Already with a single scanning device for determining the position of io these reference marks, a plurality of positions may be determined for each film frame.

Another possibility is to apply a plurality of position values of the same reference mark per film frame to the evaluation device. To this end, a corresponding number of scanning devices is to be provided, with the number of scanning devices predetermining the number of individually correctable film frame sections. With a corresponding high resolution, it is possible to correct every single scanned picture line in this way.

The number of reference positions available may also be obtained in that a plurality of scanning devices for determining the position of the reference marks is provided for a plurality of reference marks per film frame. The number of reference positions which can be obtained in this case is the product of reference marks per film frame and the number of scanning devices used.

A two-dimensional arrangement of single sensors, for example a CCID array, is preferably chosen as a scanning device for a high resolution. With such a device, the position of a film frame can be continuously tracked during scanning. At one evaluated reference mark per film frame, the vertical extension of the scanning device is preferably chosen to be slightly larger than the film frame height, and when a plurality of reference marks are to be evaluated per film frame to be a corresponding fraction of the film frame height. The next reference mark can thus already be engaged before the reference mark which has just been scanned has left the scanning device.

4 The invention further provides a video signal-processing device, for post- processing film material stored electronically, comprising a steadiness correction device provided to correct the frame position of each film frame on the basis of a correction signal, in which the steadiness correction device is implemented in such a way that each film frame can be corrected section by section by means of the correction signals. This provides the possibility of dealing with the frame position only during the post- processing operation, which has the advantage that the correction of the frame position can be adapted to the format, if different formats are used such as, for example io standard format or HDTV format.

The invention still further provides to a film scanner including such a video signal processing device.

The invention yet further provides a storage device for electronically storing film material which is provided to store and reproduce, in addition to the scanning values (V) of a film frame, also reference information which can be assigned section by section or line by line.

The invention yet further provides a data carrier for electronically storing film material which stores, in addition to the scanning values (V) of a film frame, reference information (R) which can be assigned section by section or line by line.

These and other features and advantages of the invention will become apparent from the following description of embodiments of the invention, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 shows a film scanner for scanning a plurality of reference marks per film frame, Figure 2 shows a section of a film with a plurality of reference marks per film frame, Figure 3 shows a section of a film with a plurality of scanning sensors for a reference mark per film frame, Figure 4 shows a section of a film with a scannina sensor field,

Figure 5 shows a film scanner with a scanning sensor field and transport speed control by means of the scanned reference marks, Figure 6 shows an arrangement for archiving film material.

Figure 1 is a schematic view of the parts of a film scanner that co operate with a sensor circuit for detecting reference marks. A film 1 is continuously fed from a supply reel 2 in the direction of the arrow 3 by means of a capstan 4 to a take-up reel 5. Supply reel 2, capstan 4 and take-up reel 5 are driven by means of electric motors 6, 7, 8 which are controlled by a io transport control device 9. The film tension is measured by means of a first sensor lever 11 arranged in the film drive path proximate to the supply reel 2.

The measured film tension is applied to the transport control device 9 which controls the supply reel motor 6 by means of an internal control circuit in such a way that a substantially constant film run is ensured. During the take- up process, the film tension is similarly controlled via the take-up reel motor 8 by means of a second sensor lever 12 arranged proximate to the take-up reel 5.

Various rollers 10 are arranged in the film path, predetermining the film drive path of the film 1.

For the purpose of optically scanning a film 1, the film 1 is guided by means of a swivable roller 13 in such a way that it is partially wrapped around the capstan. The film transport speed is thereby exclusively predetermined by the capstan 4 or its capstan motor 7. In the case of fast forward winding or rewinding, the swivable roller 13 is swiveled away by the film 1 in the direction of the second arrow 14 so that the film is no longer wrapped around the capstan 4. In this case, the film transport is exclusively performed by the supply reel motor 7 and the take-up reel motor 9.

A sprocket 15 which is rigidly connected to a tacho disc 16, is arranged as a speed sensor in the film drive path to control the transport speed during the scanning operation. The tacho disc 16 supplies pulse signals corresponding to the film speed (hereinafter referred to as tacho pulses) which are applied to the transport control device 9. Control signals for controlling the 6 capstan motor 7 are generated that depend on parameters set on an operating panel 17 and the tacho pulses supplied by the tacho disc 16, During transport, the film 1 is passed through a scanning unit 18 in which the film 1 is illuminated by means of an illumination device shown diagrammatically as a lamp 19 and a condenser 20. The light modulated by the picture contents of the film 1 is scanned via frame scanning sensors 21, 22, 23 and 24. The first frame scanning sensor 21 is used for scanning a luminance signal W and the other frame scanning sensors 22, 23 and 24 are used for scanning the chrominance component signals RGB. Luminance io signal W and chrominance component signals RGB are applied to a video signal-processing unit 25 in which the received signals are converted into the desired video signal format and are available in the studio standard at an interface 26.

A sensor 28 for scanning the reference marks is further arranged in the scanning unit 18. In this embodiment, the sprocket holes of the film 1 are used as reference marks. The output signal of the sensor 28 is applied to a computer 29. The computer 29 evaluates the output signals of the sensor 28 and generates correction signals C for horizontal and vertical frame position errors applied to the video signal-processing unit 25. The signal conversion of every single video frame can be displaced accordingly by means of the correction signals C in known manner in its horizontal and vertical position and each frame position error can be corrected. The film scanner described in the embodiment comprises as a video signal-processing unit 25, a so-called spatial processor, by means of which frame sections can be offset or rotated with respect to each other. However, a technically equivalent solution is the one in which the video signal and the correction signals are applied via an external interface to an externally connected digital video effect apparatus. Simpler embodiments, for example for the control of the instants of read-out from a picture memory are feasible. Finally, the selection of a suitable device by means of which the film steadiness correction is to be effected depends on deration of technir-,:bi e-nmnnnents 'costs) and the required accuracy.

a consl 7 Dependent on the format and standard of the film material to be scanned, a plurality of sprocket holes, generally four, is arranged on the left and right beside each film frame. Since the sprocket holes associated with a film frame are generally produced by a punching tool in one punching process, the geometrical dimensions of the holes associated with every single film frame are mutually constant from film frame to film frame.

In the embodiment, the sensor 28 is inclined at a given angle with respect to the film drive direction and consists of a single CCD line. As is known from the state of the art mentioned in the opening paragraph, both the io horizontal and vertical position of a sprocket hole can be detected due to the inclination of the sensor. In accordance with Figure 2, the scanning of a film 1 with four left and four right sprocket holes 31-38 per film frame 30 with a single sensor 28 results for each film frame in four reference indications Xl, X2, X3 and x4 with respect to a reference position which is symbolized in Figure 2 by a reference line 39 for the horizontal alignment of the film frame 30. In this way, it is possible to subdivide each film frame into four horizontal film frame sections 41, 42, 43 and 44 and to correct the deviation of the frame position of every single film frame section by means of the individual horizontal and vertical correction signals.

The accuracy which can be achieved with this embodiment is, however, limited in that actually only the sprocket hole which was used in the pick-up camera for positioning the film is directly coupled to the illuminated film frame.

The other sprocket holes are only indirectly coupled to the film frame via the sprocket hole used for positioning. Their position with respect to the film frame may therefore change to a greater extent from film frame to film frame than the position of the sprocket hole used for positioning. The sprocket hole pair used for positioning in the pick-up camera is each time the lower pair of holes of a preceding film frame and is generally denoted as Mitchell hole.

In the second embodiment shown in Figure 3, an arrangement consisting of five individual sensors 45 to 49 instead of a single sensor is used on one film side. In this way, ft is possible to scan the relevant Mitchell hole 50 at five different positions, the first and the fifth individual sensors 45, 49 are 8 separated by a distance corresponding to the film frame height. It is true that this results in only four single sections which can be corrected, but in this embodiment intermediate values can be interpolated from two consecutively generated correction signals so that, in principle, the frame position of each scanned line can be corrected with an individual (interpolated) correction value for horizontal, vertical and rotational errors. For the sake of clarity of the Figure, only five sensors are chosen in this embodiment. By increasing the number of sensors used, the number of individually correctable film sections can be arbitrarily increased in conformity with the desired accuracy.

The most elaborate, but also most accurate correction values are obtained by means of a sensor field which extends vertically throughout the film frame height and horizontally at least through the horizontal frame position fluctuation to be expected. In this way, it is possible to track the selected marks uninterruptedly throughout the film frame. The vertical extension of the sensor field is preferably chosen to be even slightly larger than the film frame height. In this way, the Mitchell hole of each next film frame can already be detected before the next film frame passes the scanning device. This simplifies, for example, the synchronization with the Mitchell hole. In contrast to the preferably obliquely arranged single sensors of the embodiment described hereinbefore, the sensor field may be formed from single sensors arranged in a regular grid, for example a CCD array, without having a detrimental influence on the accuracy.

In the embodiment shown in Figure 4, a sensor field 53, 54 is even arranged on each side of the film. By scanning the right Mitchell hole 51 and the left Mitchell hole 52, a rotational steadiness error can also be detected in known manner by means of this arrangement. At a corresponding resolution of the scanning sensors for scanning the reference marks, which may be advantageously chosen to be even larger than the scanning resolution of the film frame, each scanned frame line can be corrected even in the sub-pixei range.

By forming individual correction values for the vertical deviation of sinale film frame sections, or even every single scanned film frame line, the 9 requirements imposed on film tracking can be alleviated because tracking fluctuations can be corrected with a greater resolution than was hitherto the case, or than can be corrected by controlling the scanning time for the scanned frame.

Moreover, it is even possible to directly control the transport speed of the film by means of the computed positions of the scanned marks. Figure 5 shows a film scanner which is similar to the film scanner shown in Figure 1. However, no sprocket 15 and tacho generator 16 are used in the film scanner shown in Figure 5. In contrast, the transport control device 9 receives the io vertical position of the Mitchell hole as an actual value signal. The precision of this signal is only dependent on the geometrical accuracy of the sensor field and is not dependent on mechanical tolerances and wear of a mechanical value-measuring device such as for a sprocket.

The correction signals C may also be used for a mechanical correction of the film guiding, as is known from, for example DE 19636393.4. In this method, the film is continuously aligned before scanning so that a correction of the scanned film is no longer necessary. In Figure 5, the correction signals C are therefore no longer applied to a picture memory but to two film- setting elements 55, 56. By using two setting elements, the film not only can be displaced in the horizontal position upon a corresponding control, but even the angle of the film drive direction can be changed so that rotatory errors can also be compensated.

The sprocket holes of a film were used as reference marks in the embodiments. However, the invention is not limited to this type of reference mark, and neither to the scanning principle suitable for this purpose. In addition to the optical scanning of sprocket holes, a capacitive scanning is also suitable, or, as also already proposed, ultrasonic scanning. Moreover, neither is the use of correction signals limited to the correction of the scanned film frame.

Generally, frame position errors are corrected simultaneously during scanning in a film scanner. However, the invention is also suitable for post processing scanned and stored or archived film frames whose reference marks are also available as scanning values or in a suitably converted form. Figure 6 shows such a filing system which consists of a film scanner 61, a storage device 62 and a post-processing device 63. The film scanner applies a video signal V, for example, in a digital form with the scanned film material.

Additionally, the film scanner supplies either the scanning values R of the reference marks or values which have already been converted into reference positions. Since the reference marks R or reference positions R are stored together with the video data V, a film scanner suitable for this archiving system should not comprise its own arrangement for steadiness correction. A io correction of the frame position of the stored video frame in accordance with the invention by means of the equally stored reference marks R or reference positions R is not performed until the post- processing operation in the postprocessing device 63. This device comprises a computer 64 whose function corresponds to the computer 29 used in the previous embodiments of the described film scanners. This computer 64 computes the required correction signals C from the reference marks R or reference positions R supplied by the storage device 62. These correction signals are also applied to a steadiness correction device 65 known from the previously described embodiments, in which unit a corresponding frame position correction is performed section by section or line by line on the basis of the correction signals C.

All known storage devices which principally allow storage of data in addition to the video frame are suitable for storing video data V and a plurality of reference information values R for each stored film frame. Because of the large quantity of data, magnetic tape recording devices, disc arrays or also digital versatile disc recorders are particularly suitable. The information stored on the corresponding storage media such as magnetic tapes, hard disks and digital versatile discs thus does not only comprise the actual video data but also the additional information according to the invention.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the design and use of video signal processing circuits, film scanners and component parts thereof and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation of one or more of those features which would be obvious to persons skilled in the art, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated io to such features andlor combinations of such features during the prosecution of the present application or of any further application derived therefrom.

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Claims (1)

1. CLAIMS.

   1. A video signal-processing device for processing a video signal produced by a film scanner, the video signal processing device comprising an evaluation device for generating a correction signal for compensating steadiness errors of each film frame from the scanned position of reference marks assigned to each film frame,in which the evaluation device is arranged to generate at least two correction signals for each film frame.

   2. A video signal-processing device as claimed in claim 1, in which the positions of a plurality of reference marks per film frame are applied to the 10 evaluation device.

   3. A video signal-processing device as claimed in claim 1, in which a plurality of position values of the same reference mark is applied per film frame to the evaluation device.

   4. A video signal-processing device as claimed in claim 1, 2 or 3 in which for scanning the position of the reference marks, a two-dimensional sensor field is provided in a film scanner.

   5. A video signal-processing device as claimed in claim 1, 2, 3 or 4, in which the correction signals are provided to control a steadiness correction device.

   6. A video signal-processing device as claimed in any one of the preceding claims, in which the correction signals are applied to mechanical setting members of a film scanner.

   13 7. A video signal processing device for processing signals produced by a film scanner, the video processing device being substantially as described herein with reference to the accompanying drawings.

   8. A film scanner including a video signal processing device as claimed in any preceding claim.

   9. A video signal-processing device, for post-processing film material stored electronically, comprising a steadiness correction device io provided to correct the frame position of each film frame on the basis of a correction signal, in which the steadiness correction device is implemented in such a way that each film frame can be corrected section by section by means of the correction signals.

   10. A video signal processing device for post processing film material stored electronically, the video signal processing device being substantially as described herein with reference to the accompanying drawings.

   11. A storage device for electronically storing film material which is provided to store and reproduce, in addition to the scanning values (V) of a film frame, also reference information which can be assigned section by section or line by line.

   12. A data carrier for electronically storing film material which stores, in addition to the scanning values (V) of a film frame, reference information (R) which can be assigned section by section or line by line.

   13. Any novel feature or novel combination of features disclosed herein either implicitly or explicitly whether or not it relates to the same invention as that claimed in any preceding claim.