FR2851395A1 - Cinematographic sequence viewing condition simulation method for e.g. digital cinematographic camera, involves effecting modification of viewing parameter based on comparison of shooting signal and regulating signal - Google Patents

Abstract

The method involves displaying a regulating image upon application of a regulating signal, during a regulating phase. The regulating image is captured by a shooting camera (10) to deliver a shooting signal. A comparison signal is produced by comparing the shooting signal and the regulating signal during the regulating phase. A modification of viewing parameter is effected based on the comparison signal. Independent claims are also included for the following: (a) a device for simulation of viewing condition on a visualization device (b) a shooting system comprising a recorder and a treatment unit.

Description

i i

  DEVICE AND METHOD FOR SIMULATING CONDITIONS

  VIEWING CINEMATOGRAPHIC SEQUENCES

  TECHNICAL FIELD The present invention relates to a device and a method for simulating the viewing conditions of cinematographic sequences. The terms of viewing of a cinematographic sequence are understood to mean all the external conditions that influence the way in which an observer perceives an image reproduced by a visualization system. The viewing conditions include in particular the lighting imposed by an environment in which an observer, possibly a spectator, can view a given sequence. The simulation of viewing conditions may simply involve the elimination or reduction of image perception defects. More sophisticatedly, the simulation may include, in addition to the elimination of defects, the artificial reproduction of a particular viewing environment, for example that of a movie theater. To the correction of the defects can thus be added the obtaining of particular renderings of the image.

  The invention has applications in the equipment of cameras, including digital cinematographic cameras.

  PRIOR ART Shooting cameras, and in particular digital cameras, are generally equipped with a monitor with a control screen. The control screen allows you to check the framing of shots. A control screen can also be used to preview the recorded scene. Such an overview is indeed useful to the director-director.

  The cameras, as well as the control screens associated with them, are calibrated equipment. In other words, the assembly formed by the camera and the screen is adjusted in such a way that the light, the colors, the contrast of the images displayed on the screen reflect, as accurately as possible, the scene exposed to the camera. Calibration of the camera and the screen can take place by means of parameter electronic filters and in particular software filters.

  An illustration of the state of the art, and in particular an illustration of the calibration devices can be found in documents (1) to (7), the references of which are specified at the end of the present description.

  Exposure of the invention Despite the calibration of the control screen, it turns out that the image visible on the screen can be very different from that which would be visible, for example, in a movie theater, if the viewing was in a movie theater.

  The image visible on the screen is indeed different from the displayed image. The visible image corresponds to the image displayed, but is largely affected by the 10 viewing conditions, including the external illumination of the screen. For example, the fact that the surface of the screen is subjected to a source of bright light can considerably modify the image visible to the operator.

  On a set, lighting conditions vary frequently depending on the scenes or sequences recorded. Thus, the control screen which is generally secured to the camera, or at least located near the filming location, also undergoes lighting variations. The viewing conditions vary so quickly and frequently.

  In order to provide the operator or the director with more uniform viewing conditions, the object of the invention is to propose a device and a method for simulating viewing conditions.

  In particular, a goal is to correct the variations of the viewing conditions, and at least to warn the user in case of remote viewing conditions of the desired conditions.

  Another goal is to propose a method and a device that can possibly simulate particular shooting conditions and display them on the control screen without changing the calibration of the screen.

  To achieve these aims, the invention relates more specifically to a method for simulating viewing conditions on a display device associated with at least one camera capable of delivering an electric shooting signal. The method comprises at least one adjustment phase and at least one shooting phase. During the adjustment phase, a control image is displayed on the control screen by applying a control signal, the adjustment image is captured with the camera, a comparison signal is produced at from the camera-derived image signal and the adjustment signal, and a modification of at least one viewing parameter is performed in response to the comparison signal.

  The display device can be of any type. This is, for example a control screen, cathode, plasma, or liquid crystal, a projection device or rear projection. In the rest of the text, the display device is designated by "control screen" for reasons of simplification. These terms, however, must not be understood in a limiting sense. By viewing parameter is meant a parameter that makes it possible to modify the visible image, ie the image perceived by the observer. The viewing parameter is for example a parameter capable of affecting the signal transmitted by the camera to the control screen, so as to modify the light, the colors, or the contrast of all or part of the screen. This is, in this case, for example, a setting value of an electronic filter, or a value of a look-up table ("LUT") of a processor. signal.

  It should be noted here that the modification of one or more viewing parameters is not related to any proper adjustment of the screen or the camera.

  In other words, if the camera and / or the screen are calibrated, the modification of the viewing parameters can take place without any modification of the calibration of these devices. The method, which is not intended to calibrate the screen, preferably applies to previously calibrated screens.

  The modification of a viewing parameter in response to the comparison signal can take very variable forms. It is possible, for example, to use the comparison signal to trigger a warning system that warns the operator of improper display. The warning can be very brief, in the form of a sound or light signal. It may also be preceded by a diagnosis of the comparison signal and specify, for example, the nature of the defects and / or their location. The signal is then an information display signal. It can be applied, for example, to any screen or camera display device.

  In a particular embodiment of the device, the warning system is actuated when the comparison signal exceeds a set range. In response to the warning, the operator can then change the outside lighting received by the control screen. The intensity, the orientation and the color of the outside lighting received, can be considered, in this case, as so many viewing parameters.

  In a much more sophisticated manner, and in the manner already mentioned above, it is also possible to modify, in response to the comparison signal, the setting of an electronic filter. It is connected between the camera and the control screen. It can be connected permanently or at least during a shooting phase following an adjustment phase. The term "filter" is used here in a generic sense to denote any adjustable device capable of modifying the signal supplied to the control screen and thus to modify the display of the latter. It may include one or more cascading filter elements. The filter may be a signal processor, in hard-wired form or in software form. It can affect the brightness, color and contrast of all or part of an image displayed on the screen. In this case, the viewing parameter is understood as a filter setting parameter acting on the color, the accutance (contrast of the high frequencies), the contrast, and / or the light of all or part of the screen. control.

  The modification of the viewing parameters can take place randomly, but preferably in a direction reducing the comparison signal.

  It can be continued until the comparison signal is canceled, or at least until this signal corresponds to a determined range of values.

  This is the case when the image visible on the screen, and more precisely that captured by the camera during the adjustment phase corresponds to the image to be obtained in response to the adjustment signal. The use of the camera during the adjustment phase makes it possible to capture the visible image, that is to say the combination of the displayed image 30 and the viewing conditions.

  During the shooting phases, the camera is no longer turned towards the control screen but towards a scene to be recorded. The shooting signals are then directed to appropriate recording means and to the control screen. It should be noted that the camera used during the adjustment phase and that used during the shooting phase, may be the same, or possibly a different camera.

  The operator can decide at any time, and in particular at each change of scene or lighting condition, to repeat the adjustment phase to adapt the visible image to the control screen to the new viewing conditions.

  The operations indicated above make it possible to simulate on the screen conditions for viewing a screen, freed from the hazards of lighting or, more generally, defects that modify the perception thereof. To these viewing conditions can be added special conditions simulating for example a given environment. This aspect is described in more detail in the rest of the text. The viewing conditions are determined by the adjustment signal used during the adjustment phase. This is for example a signal selected from a display signal, a display signal of one or more uniform images or not, intensity, color and / or determined contrast, or still a null signal corresponding to a lack of displayed image. For the adjustment of conversion tables of a LUT type filter, the adjustment signal may correspond to a succession of different images exploring the range of color and brightness display of each pixel of the screen or each display point of the display device.

  As mentioned above, the operator can take advantage of the simulation of viewing conditions to display on the control screen not only an image freed from external conditions, but also to give this image a particular aspect. For example, a director may decide to change color temperatures, or hues, to give the image a particular effect, an "atmosphere". Indeed, during the shooting phase, it is possible to send the shooting signal to the control screen via a second filter, or effect filter, different from the first filter or filter. correction mentioned above. In this case, the role of the first filter is to simulate neutral viewing conditions, that is to say freed from external conditions, and the role of the second filter is to add a special effect. It should be noted that the parameters of the second filter can be adjusted at any time, both during the adjustment phase and during the shooting phase. The parameters of the effect filter can optionally be saved or stored for later use, and especially for post-production use.

  The first and second filters may optionally be replaced by a single filter performing these two functions, by a series of cascade filters or, of course, by any suitable image processor. The second filter, or the image processor can be used in particular to increase the contrast of the image.

  The invention also relates to a device for simulating viewing conditions on a display device associated with at least one camera capable of delivering an electric shooting signal. The device comprises: - a control signal generator - a first comparator for comparing, during an adjustment phase, a recording signal coming from the camera, and a control signal from the signal generator setting, and for outputting a comparison signal, and - a correction filter, responsive to the comparison signal, connected between the camera and the control screen during a shooting phase according to the adjustment phase.

  It should be noted that the correction filter can be permanently connected between the camera and the display device, or only during the shooting phase.

  The correction filter receives the comparison signal during the adjustment phase so as to adjust the viewing parameters, ie the processing parameters of the image sent to the control screen. These parameters are maintained during a subsequent shooting phase, until a new adjustment phase.

  The invention finally relates to a shooting system comprising a camera, one or more viewing devices and a device as described above. The camera and the display device are preferably calibrated equipment.

  Other features and advantages of the invention will emerge from the description which follows, with reference to the figures of the accompanying drawings. This description is given for purely illustrative and non-limiting purposes. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic and simplified representation of a particular embodiment of a camera system equipped with a simulation device according to the invention.

  Figure 2 is a representation of a variant of the camera system 15 of Figure 1, also in accordance with the invention.

  Figure 3 is a diagram indicating the main steps of a simulation method according to the invention.

  DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION In the text that follows, identical, similar or equivalent parts of the different figures are identified by the same references, so as to avoid a repetition of their description. Moreover, the different parts of the figures are represented in free scale, for the sake of clarity of the figures.

  Figure 1 shows a system of shooting and indicates in the form of arrow links the transmission of signals between different organs of the system. Reference 10 in FIG. 1 represents a cinematographic camera. It is a camera capable of delivering an electrical signal, digital or analog, usable for controlling the display of an image on a control screen 12. In the example considered here, the camera 10 is a digital camera even if this characteristic is not in itself indispensable. Indeed, film cameras with "video recovery" are known which also generate an electrical signal corresponding to the captured images.

  The camera is provided with a generator 14 of adjustment signal. The generator 14, which may or may not be integrated with the camera, is a device capable of supplying the control screen with a setting signal corresponding to one or more determined images. The data of this signal are stored in a memory not shown. As indicated above, the adjustment image may be a uniform image or not, a pattern, a color image or, more simply, a display background corresponding to the absence of image.

  The adjustment signal is supplied to the control screen 12 during an adjustment phase in which the camera 10 is turned towards the control screen so as to capture an image of that screen. This operating state is symbolically represented by a switch 15 whose switching state is indicated by a solid line. When the screen and the camera are perfectly calibrated, which is generally the case for professional equipment, the shooting signal available at the output 16 of the camera should in principle be identical to the signal supplied by the generator 14. This situation is a theoretical situation corresponding to ideal conditions for viewing in the darkroom. It is often far from the real conditions of viewing on a set.

  Indeed the screen is subjected to external lighting conditions that affect the contrast, brightness and / or the color of the image actually visible on the screen. The external conditions of viewing are here represented by a source of stray light 18 which modifies the perception of the displayed image, so that the visible image captured by the camera has a defect D with respect to the displayed image. The defect D shown in the figure represents any type of defect independent of the setting or calibration of the display system. It may also be a stain, dust or yellowing of a projection surface.

  The camera's recording signal, when it captures the adjustment image visible on the screen 12, is directed towards a first comparator 20. The first comparator 20 also receives the adjustment signal directly from the generator 14 The comparison can relate to different parameters, such as color, light, contrast, etc. The comparison can be a point-by-point, area-based, or global comparison. The comparator delivers a comparison signal denoted A. It is a digital signal or an analog signal whose amplitude translates, for example, for a given pixel or a given zone, the difference between image corresponding to the adjustment signal and that corresponding to the shooting signal.

  In an adjustment phase, represented symbolically by a switch 22 closed, the comparison signal A is directed to a setting input of a parameter filter 24 also called correction filter. The filter comprises, for example, an image processor provided with LUT conversion tables The LUT conversion tables may be specific to the entire screen or to each pixel thereof. The correction filter 24 makes it possible to modify an image signal which passes through it so that the pixel value P ,, y of the visible image, captured by the camera, becomes Tx values, y by applying to them a matrix function. luty 15 such that Txy = luty (P,> y). Pxy here indicates the value of luminous intensity or luminance of a given pixel of the image captured by the camera. The value can be given globally or for each color. Similarly, TIy is the value of the luminous intensity of the same pixel when the signal has passed through the correction filter. During the adjustment phase, the functions luty of the conversion tables 20 are set or modified so that the value Ty of each pixel is equal to a set value Toxy given by the adjustment signal. In this case, the comparison made in the comparator 20 consists of comparing the values Pxy and Toxy and the setting of the filter consists in setting the values lutxy. A conversion table filter is a device known per se. Reference may be made here to document 25 (1) already mentioned.

  The filter 24 may also include a convolution filter. A convolutional filter is a filter or processor capable of performing a matrix product between a representative matrix of pixels of the image and a convolution matrix with coefficients. In this case the adjustment relates to the coefficients 30 of the convolution matrix. The convolution filter makes it possible, for example, to modify the contrast or sharpness of the image. In a much simpler way, the filter 24 can still be a filter allowing only to adjust the overall brightness of the image according to a comparison signal representative of a brightness difference. In the example of the figure, the output signal of the filter 24, directed towards the screen, is modified so as to reduce the comparison signal. This amounts to eliminating, or at least reducing, the defect D in the visible image. Although this characteristic is not indispensable, the signal coming from the output 16 of the camera and directed towards the comparator 20 passes through the filter 24.

  When the filter 24 is set, the system can be used in a "normal" shooting phase in which the camera is turned to a scene to be recorded. The shooting signal is then also directed to the control screen via the filter 2 previously set. In the symbolic representation of the switching state given by the switch 22 and the switch 15, the setting phase This view corresponds to the opening of the switch 22 and to a position of the switch 15 as indicated in dashed lines. Optionally, the shooting signal can also pass through an additional effect filter 26 used to deliberately modify the image. This is, for example, an effect generator that can also include a table LUT. The choice to direct or not the signal through the effect filter 26 is indicated by a switch 27.

  The shooting signal that has or not passed through the filters 24 and 26 is directed to recording means 30. It can also be recorded after passing through another filter or processing device 28, independent of the filters used for the recording. control screen. The processing device may also be used to perform encryption and / or watermarking compression operations. The recording means comprise, for example, a digital recorder with a magnetic or optical support. In the example described with reference to FIG. 1, the comparison signal A is also directed towards a second comparator 40. This second comparator, which receives, moreover, a set value denoted Ama, checks whether or not the comparison signal is within an acceptable range of values, that is to say if it corresponds to display deviations that can be corrected by the filter 24.

  By way of example, the comparator 40 can check whether the comparison signal A is included or not in a range from dAma to + A ,,. . If this is not the case, the correction provided by the filter is not sufficient to simulate the desired viewing conditions. A warning system 42, driven by the second comparator 40, then issues a warning. In the illustrated example, the warning system 42 includes a small speaker.

  The user of the camera, well informed, can also act to change the viewing conditions. It can, for example, slightly move the screen 12.

  The elements detailed in FIG. 1, such as the adjustment signal generator 14, the comparators 20, 40, the warning means 42 and / or the filters 24, 26 may be external to the camera of view or integrated into it.

  FIG. 2 illustrates another possible embodiment of a shooting system according to the invention, constituting an improvement of the shooting system of FIG. 1. The various members constituting the system of FIG. 2 are identical or at least similar to those in Figure 1. We can

  thus refer to the above description.

  The system of Figure 2 differs from that of Figure 1 by the arrangement of organs and the resulting operation. The switch 15, which symbolizes the switching between the adjusting phase and the shooting phase is moved. It allows, in the diagram of Figure 2, to connect to the input of the filter 24, sometimes the output of the generator 14 of the control signal, sometimes the output 16 of the camera 10. The output of the filter 24 is connected to the display screen.

  As a result, the signal supplied to the screen 12 is always a signal which has passed through the filter 24. It is recalled in this connection that the adjustment signal is directed directly to the screen in the system of FIG.

  The comparator 20 of FIG. 2 receives on one of its inputs the signal from the generator 14 of the control signal. It receives on the other input the signal of the camera. It can be observed that, unlike the figurel system, the camera signal supplied to the comparator does not pass through the filter 24.

  The diagram of Figure 2, makes it possible to make successive and iterative adjustments of the filter 24 taking into account in the control loop the assembly formed by the camera and the screen. A non-iterative single setting is still possible. Considering that the filter 24 is a conversion table filter, initially in a state which does not modify the signal passing through it, the setting can be summarized as follows.

  The adjustment signal supplied by the generator 14 first passes through the filter 24 without being affected. A corresponding image is displayed on the screen, the comparator 20 then compares the shooting signal available at the terminal 16 of the camera 10 and the adjustment signal. A comparison signal A is delivered and directed to the conversion table of the filter 24 to adjust its parameters. If, after this adjustment, the comparison signal becomes zero, or virtually zero, the switch can be switched to the shooting mode. If it is not, that is to say if the screen display has yet to be modified, a new modification of the parameters of the filter 15 can take place. The more complete operation of the adjustment is further described in the rest of the text, with reference to FIG.

  During the adjustment phase, the second comparator 40 and the warning system 42 may be used, as previously described, ie to inform the user of an excessive difference existing between the tap signal 20 from the camera and the adjustment signal. In this case the instruction Ama applied to one of the inputs of the second comparator is not zero.

  In a different use, the Aman instruction is null or at least very weak. In this case the warning system is operated as long as the comparison signal A is not zero or substantially zero. This allows the operator to know that the filter 24 is not yet fully tuned and that the system is not yet ready for switching to shooting mode.

  In a particular and improved embodiment of the system, the warning provided to the user may include identifying the nature or location of the defect, and displaying a corresponding information on the screen 10. This is then substituted for the warning system 42. This possibility is indicated by a link 41 in broken lines.

  During the shooting phase, the switch 15 is switched so as to apply to the filter 24, set, the direct shooting signal of the terminal 16 of the camera. Comparator 20 and warning system 42 may be disconnected or disabled and switch 21 may be opened.

  A link 31, in broken lines, between the recorder 30 and the input of the filter 24 indicates the possibility of viewing previously recorded images or scenes in viewing conditions set by the setting of the filter 24 and possibly the filter 26.

  The diagram of FIG. 3 illustrates an implementation possibility of the method of the invention.

  A first step 50 consists in turning the camera 10 towards the control screen 12 so as to be able to generate a shooting signal corresponding to all or part of the screen, or images visible on the screen .

  In a concomitant step 52, an adjustment signal is supplied to the control screen 12. A comparison of the adjustment signal and the shooting signal corresponds to the block 54. The comparison can relate to a control signal. view corresponding to all or part of the screen 12.

  The result of the comparison makes it possible to determine whether the camera and the screen can be used in a subsequent shooting phase 70 or whether a modification of the viewing parameters is necessary. This choice, made from the comparison signal, is indicated with the reference 58. By way of example, a modification of the viewing parameters may be considered necessary if the comparison signal is not zero or is not less than a specified setpoint. The modification of the viewing parameters 25 is indicated with the reference 60.

  The modification of the viewing parameters can take place at one time, ie with a single adjustment of the filter parameters during each adjustment phase. It can also take place step by step in an adjustment loop. In the case of a system according to FIG. 1, the loop comprises only the filter 24, the comparator 20 and the switch 22. In the case of a system according to FIG. 2, the adjustment loop also comprises the screen 12 and the camera 10. The adjustment loop is indicated in FIG. 3 by an arrow 62 ...

  The reference 61 indicates the emission of a warning signal when the comparison 54 reveals a non-compensable deviation of the viewing conditions by the adjustment of parameters of a filter. The warning can be limited to simply sounding. It may also include the display of information, for example on the screen 12, information allowing the user to identify the fault, or the location of the fault. In the latter case the warning system 42 and the screen 12 may be a single organ.

  During the shooting phase 70, the camera is turned towards a scene S and the shooting signal is directed to recording means 30 already mentioned.

  Reference 72 indicates a choice made by the user of the camera. It consists either in continuing the shooting with the viewing conditions as simulated by the previous adjustment of the viewing parameters, or in returning to the adjustment phase 50. This latter choice can be made frequently, for example, at each change of lighting conditions, at each change of sequence of a shoot or at each change of location.

  References 1) Digital Imaging, Theory and applications by Howard E. Burdick Mc GrawHill Chap. 4, pages 75 fq 2) US-A-5,918,192 3) US-B-6,292,228 4) WO 02/21440 5) US-A-2002/0057835 6) EP-A-0 975 150 7) US -A-5,803,570

Claims (16)

  1 - A method for simulating viewing conditions on a display device (12) associated with a camera (10) capable of delivering an electric shooting signal, comprising at least one adjustment phase and at least one phase of shooting, in which, during the adjustment phase is displayed on the display device an adjustment image by application (52) of a control signal, it captures the adjustment image with the camera (10), a comparison signal (A) is generated from the camera image signal (54) and the adjustment signal and a modification (60) of at least one parameter is performed. viewing in response to the comparison signal.   2 - The method of claim 1, wherein, the modification of at least one viewing parameter comprises modifying at least one parameter of a correction filter (24) in response to the comparison signal.   3 - Process according to claim 1, wherein a warning signal (61) is emitted when the comparison signal exceeds a set range.   4 - Process according to claim 3, wherein the modification of at least one viewing parameter comprises modifying a lighting received by the display device (12), in response to the warning signal.   5 - The method of claim 3, wherein the warning signal is a signal selected from a sound signal, a light signal and an information display signal.   The method of claim 1, wherein the control signal is a signal selected from a display pattern signal, a display signal of at least one intensity, color and / or contrast image. determined, a display signal of a sequence of images of intensity, color and / or contrast different, and a null signal corresponding to a lack of displayed image.   7 - The method of claim 1, wherein, during the shooting phase, the shooting signal is sent to the display device (12) and to a recorder (30).   8 - The method of claim 2, wherein, during the shooting phase, the shooting signal is sent to the display device 12 through the correction filter (24) and a filter d Effects (26) 9 - The method according to claim 1, wherein, during the adjustment phase, the viewing parameter is modified in a direction reducing the comparison signal.   - Method according to claim 9, wherein, during the adjustment phase, the viewing parameter is modified until the comparison signal is less than an absolute value in a set value.   1 1 - Method according to claim 1, wherein, to establish the comparison signal (A) is compared the camera's shooting signal and the adjustment signal, one of the shooting signals and setting having passed through the correction filter.   12 - Device for simulating viewing conditions on a display device 12 associated with a camera (10) capable of delivering an electric shooting signal, comprising: a generator (14) for a control signal a first comparator (20) for comparing, during a tuning phase, a camera-derived signal and a tuning signal from the tuning signal generator (14), and for outputting a comparison signal A, and a correction filter, sensitive to the comparison signal, connected between the camera and the display device, during a shooting phase following the adjustment phase.   13 - Device according to claim 12, wherein the correction filter (24) is a parameter filter that can be adjusted according to the comparison signal, in a reduction direction of the comparison signal.   14 - Device according to claim 13 wherein the correction filter (24) and a conversion table filter type LUT.   15 - Device according to claim 12, comprising a second comparator (40) for comparing the comparison signal of the first comparator (20) with at least one setpoint, and for delivering a warning signal when the setpoint is exceeded .   16 - Device according to claim 15, wherein the set value is zero.   17 - Device according to claim 12, comprising an effects filter (26), different from the correction filter (24), the effects filter (26) being connected between the camera (10) and the camera (17). control screen (12).   18 - Shooting system comprising a calibrated camera (10), a calibrated display device (12) and a simulation device according to claim 12.   19 - Shooting system according to claim 15 comprising a recorder (30) and a processing unit (28) connected between the camera and the recorder.