Patent Publication Number: US-8982189-B2

Title: 3D video reproduction device, non-transitory recording medium, 3D display device, 3D imaging device, and 3D video reproduction method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application and claims the priority benefit under 35 U.S.C. §120 of PCT Application No. PCT3P2011/077759 filed on Dec. 1, 2011 which application designates the U.S. , and also claims the priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2011-022046 filed on Feb. 3, 2011, which applications are all hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a stereoscopic video reproduction device, a stereoscopic video reproduction program and a non-transitory computer-readable recording medium therefor, a stereoscopic display device, a stereoscopic imaging device and a stereoscopic video reproduction method. Especially, the present invention relates to a technique of reproducing a stereoscopic video of a stereoscopic video file in which a stereoscopic image formed with a plurality of viewpoint images is consecutively recorded in a time axis direction. 
     2. Description of the Related Art 
     A stereoscopic imaging device takes images of an object in right and left viewpoints using two right and left imaging units arranged with parallax, acquires the viewpoint image for the left eye and the viewpoint image for the right eye respectively and records them in a recording medium. When these acquired right and left viewpoint images are read from the recording medium, input in a 3D display that can perform three-dimensional (3D) display, and are displayed such that the viewpoint image for the left eye and the viewpoint image for the right eye can be visually checked by right and left eyes respectively, it is possible to recognize the result as a stereoscopic video. 
     By the way, the parallax amount between the recorded right and left viewpoint images varies depending on the change in an imaging scene, the movement of the object, the change in the zoom magnification or the like, and, meanwhile, the 3D display has various screen sizes. Therefore, in a case where reproduction display of a stereoscopic video is to be performed, there is a case where the parallax amount for the stereoscopic video is not suitable for the size of the 3D display. In such a case, there arises a problem that the pop-up amount and pop-down amount from the screen are excessive and it is not possible to recognize the stereoscopic video as a natural stereoscopic video. 
     Japanese Patent Application Laid-Open No. 2004-180069 discloses a technique of: acquiring suitable screen size information related to the screen size suitable for reproduction of a stereoscopic image, display screen size information of a 3D display, suitable visual distance information related to the suitable distance to a display screen for an observer to view the display screen at the time of reproduction, and visual distance information related to the distance from the observer to the display screen of the 3D display, in addition to image information that can be stereoscopically viewed; setting the shift amount (offset) between the left eye image and the right eye image based on these items of information; and adjusting the stereoscopic feeling of the displayed image. 
     It is not clear whether the stereoscopic image disclosed in Japanese Patent Application Laid-Open No. 2004-180069 is a still image or a video. In the case of a stereoscopic video, the parallax amount of right and left viewpoint images varies depending on the change in an imaging scene, the movement of an object, the change in the zoom magnification, and so on. Even if, for the sake of argument, the parallax amount of a stereoscopic video is adjusted by the technique disclosed in Japanese Patent Application Laid-Open No. 2004-180069 such that the stereoscopic video has a natural pop-up amount, it is considered to adjust the parallax amount in units of frames of the stereoscopic video. However, in this case, there is a problem that a feature as the stereoscopic video in which the stereoscopic feeling varies is lost and an unnatural stereoscopic video is provided. 
     By the way, on a display screen of a 3D display, in a case where the right eye image has a parallax in the right direction with respect to the left eye image, a stereoscopic image is visually checked as an image with a larger depth than the display screen, but, when the screen size of the 3D display increases, this parallax increases too. When the parallax exceeds a man&#39;s binocular interval, binocular fusion is impossible (i.e. binocular vision is impossible). 
     Although Japanese Patent Application Laid-Open No. 2004-180069 discloses acquiring a stereoscopic image in which the optimal stereoscopic degree (i.e. depth amount) is adjusted in proportion to the display screen size of the 3D display, it does not disclose adjusting the shift amount between the left eye image and the right eye image such that the above-mentioned binocular fusion is not impossible. Further, since it does not contain description related to the maximum parallax amount of the distant view side (or depth side) of a stereoscopic image either, the stereoscopic image display device disclosed in Japanese Patent Application Laid-Open No. 2004-180069 cannot adjust the shift amount between the left eye image and the right eye image such that the parallax does not exceed the man&#39;s binocular interval regardless of the screen size of the 3D display. 
     SUMMARY OF THE INVENTION 
     The present invention is made in view of such a circumstance and it is an object to provide a stereoscopic video reproduction device, a stereoscopic video reproduction program and a recording medium therefor, a stereoscopic display device, a stereoscopic imaging device and a stereoscopic video reproduction method that can: adjust the parallax amount of a stereoscopic video such that binocular fusion is possible regardless of the screen size of a stereoscopic display at the time of stereoscopically displaying the stereoscopic video read from the stereoscopic video file on the stereoscopic display with an arbitrary screen size; and reproduce a natural stereoscopic video. 
     To achieve the above object, a stereoscopic video reproduction device according to the present invention includes: a first acquisition unit configured to read a stereoscopic video file and acquires a stereoscopic video and attached information from the stereoscopic video file, where the stereoscopic video in which a stereoscopic image formed with a plurality of viewpoint images is consecutively provided in a time axis direction and the attached information are recorded in the stereoscopic video file and the attached information includes an intra-interval maximum display size which is the largest in each of consecutive predetermined intervals in the time axis direction of the stereoscopic video among the maximum display sizes every frame in which a binocular fusion is possible when displaying each frame of the stereoscopic video on a stereoscopic display; a second acquisition unit configured to acquire a display size of a stereoscopic display of output destination; a decision unit configured to compare the intra-interval maximum display size acquired corresponding to every predetermined interval of the stereoscopic video and the acquired display size of the stereoscopic display, and, based on a comparison result, decides whether the binocular fusion is possible every predetermined interval when displaying the stereoscopic video on the stereoscopic display; a parallax correction unit configured to correct a parallax when the decision unit decides that the binocular fusion is impossible, such that the binocular fusion becomes possible in the stereoscopic video in a predetermined interval in which the binocular fusion is decided to be impossible; and an output unit configured to: when outputting the acquired stereoscopic video to the stereoscopic display, output, to the stereoscopic display, the stereoscopic video in which the parallax is corrected in the stereoscopic video by the parallax correction unit in the predetermined interval in which the binocular fusion is decided to be impossible in a case where the decision unit decides that the binocular fusion is impossible; and output the acquired stereoscopic video as is to the stereoscopic display in a case where the decision unit decides that the binocular fusion is possible. 
     According to the present invention, the display size of the stereoscopic display and the intra-interval maximum display size acquired form the stereoscopic video file are compared, and, based on the comparison result, it is possible to decide whether a binocular fusion is possible at the time of displaying the stereoscopic video in the interval on a stereoscopic display, and, when it is decided that the binocular fusion is impossible, since the parallax is corrected such that the binocular fusion becomes possible in the stereoscopic video in the interval to output the result, it is possible to display the stereoscopic video with an adequate parallax amount. Also, by using the intra-interval maximum display size recorded as attached information of the stereoscopic video file, it is possible to decide whether the binocular fusion is possible in a case where the stereoscopic video in the interval is stereoscopically displayed on the stereoscopic display of output destination, and it is possible to reduce the load of image processing. 
     A stereoscopic video reproduction device according to the present invention includes: a first acquisition unit configured to read a stereoscopic video file and acquires a stereoscopic video and attached information from the stereoscopic video file, where the stereoscopic video in which a stereoscopic image formed with a plurality of viewpoint images is consecutively provided in a time axis direction and the attached information are recorded in the stereoscopic video file and the attached information includes an intra-interval maximum parallax amount which is the largest in each of consecutive predetermined intervals in the time axis direction of the stereoscopic video among maximum parallax amounts on a distant view side in each frame of the stereoscopic video; a second acquisition unit configured to acquire a display size of a stereoscopic display of output destination; a decision unit configured to, based on the intra-interval maximum parallax amount acquired corresponding to every predetermined interval of the stereoscopic video, the acquired display size of the stereoscopic display and a predetermined value indicating man&#39;s binocular interval, decide whether a binocular fusion is possible every predetermined interval when displaying the stereoscopic video on the stereoscopic display; a parallax correction unit configured to correct a parallax when the decision unit decides that the binocular fusion is impossible, such that the binocular fusion becomes possible in the stereoscopic video in a predetermined interval in which the binocular fusion is decided to be impossible; and an output unit configured to: when outputting the acquired stereoscopic video to the stereoscopic display, output, to the stereoscopic display, the stereoscopic video in which the parallax is corrected in the stereoscopic video by the parallax correction unit in the predetermined interval in which the binocular fusion is decided to be impossible in a case where the decision unit decides that the binocular fusion is impossible; and output the acquired stereoscopic video as is to the stereoscopic display in a case where the decision unit decides that the binocular fusion is possible. 
     According to the present invention, based on the intra-interval maximum parallax amount acquired corresponding to every predetermined interval of the stereoscopic video, the display size of the stereoscopic display and a predetermined value indicating man&#39;s binocular interval, it is possible to decide whether a binocular fusion is possible when displaying the stereoscopic video in the interval on the stereoscopic display, and, when it is decided that the binocular fusion is impossible, since the parallax is corrected such that the binocular fusion becomes possible in the stereoscopic video in the interval to output the result, it is possible to display the stereoscopic video with an appropriate parallax amount. Also, by using the intra-interval maximum parallax amount recorded as attached information of the stereoscopic video file, it is possible to decide whether the binocular fusion is possible in a case where the stereoscopic video in the interval is stereoscopically displayed on the stereoscopic display of output destination, and it is possible to reduce the load of image processing. 
     In the above stereoscopic video reproduction device, the decision unit calculates an allowable parallax amount based on the display size of the stereoscopic display and the predetermined value indicating the man&#39;s binocular interval, and, depending on whether the plurality of intra-interval maximum parallax amounts are equal to or less than the allowable parallax amount, decides whether the binocular fusion is possible, for each of the plurality of intra-interval maximum parallax amounts and each of the predetermined intervals. 
     In the above stereoscopic video reproduction device, the decision unit includes an image shift amount calculation unit configured to calculate an image shift amount on a stereoscopic display corresponding to the intra-interval maximum parallax amount based on the acquired intra-interval maximum parallax amount and the display size of the stereoscopic display, and decides whether the binocular fusion is possible, depending on whether the calculated image shift amount exceeds the predetermined value indicating the man&#39;s binocular interval. 
     In the above stereoscopic video reproduction device, the parallax correction unit corrects the parallax by shifting between viewpoint images corresponding to the stereoscopic video in the predetermined interval by a predetermined parallax shift amount such that the intra-interval maximum parallax amount on the stereoscopic display does not exceed the predetermined value indicating the man&#39;s binocular interval, for the stereoscopic video in the predetermined interval in which the binocular fusion is decided to be impossible. Accordingly, the stereoscopic video in which the binocular fusion is decided to be impossible can be subjected to easy parallax correction to be stereoscopically viewed. 
     In the above stereoscopic video reproduction device, the attached information of the stereoscopic video file includes an intra-interval maximum parallax amount on a near view side in the stereoscopic video in the predetermined interval, further including: an addition unit configured to add the interval maximum parallax amount on the near view side and the predetermined parallax shift amount in the parallax correction unit; and a decision unit configured to decide whether an image shift amount corresponding to the added interval maximum parallax amount on the near view side exceeds a binocular fusion limit at the time of displaying on the stereoscopic display; and in a case where the decision unit decides that the image shift amount exceeds the binocular fusion limit, the output unit outputs, to the stereoscopic display, any one of the viewpoint images of the stereoscopic video acquired by the first acquisition unit to display a plane image. 
     When the parallax amount on the distant view side is reduced by parallax shift, the parallax amount on the near view side increases. Therefore, from an addition result of the interval maximum parallax amount on the near view side and the parallax shift amount by the parallax correction unit, it is decided whether an image shift amount corresponding to the interval maximum parallax amount on the near view side exceeds the binocular fusion limit at the time of displaying on the stereoscopic display, and, in a case where it is decided that it exceeds the binocular fusion limit, by outputting, to the stereoscopic display, any one of viewpoint images of the stereoscopic video, a plane image is displayed. 
     In the above stereoscopic video reproduction device, the stereoscopic video file is an MPEG file in which a plurality of viewpoint images are sequentially recorded every one GOP formed with a plurality of frames, and the predetermined interval of the stereoscopic video is an interval corresponding to a predetermined number of GOPs equal to one or two, or greater than two. 
     In the above stereoscopic video reproduction device, the predetermined interval of the stereoscopic video is an interval distinguished every scene. 
     In the above stereoscopic video reproduction device, the stereoscopic video file is an MPEG file in which a plurality of viewpoint images are sequentially recorded every one GOP formed with a plurality of frames, and the predetermined interval of the stereoscopic video includes a first interval corresponding to a predetermined number of GOPs equal to one or two, or greater than two and a second interval longer than the first interval distinguished every scene. 
     The above stereoscopic video reproduction device includes: a calculation unit configured to calculate a first ratio of an intra-interval maximum display size or intra-interval maximum parallax amount of the first interval in the second interval to an intra-interval maximum display size or intra-interval maximum parallax amount in the second interval, when the decision unit decides that the binocular fusion is impossible based on the intra-interval maximum display size or intra-interval maximum parallax amount acquired in accordance with the second interval of the stereoscopic video; and a parallax correction coefficient acquisition unit configured to acquire a parallax correction coefficient which includes the first ratio as a parameter and which approaches a second ratio of the intra-interval maximum display size in the second interval to the display size of the stereoscopic display of output destination from 1 when the first ratio approaches 1 from 0, where, when the decision unit decides that the binocular fusion is impossible based on the intra-interval maximum display size or intra-interval maximum parallax amount acquired in accordance with the second interval of the stereoscopic video, the parallax correction unit acquires a parallax correction coefficient corresponding to the first ratio calculated by the calculation unit from the parallax correction coefficient acquisition unit, multiplies the parallax correction coefficient and the intra-interval maximum display size or intra-interval maximum parallax amount of the first interval, and, based on a result of the multiplication, corrects a parallax such that the binocular fusion becomes possible in the stereoscopic video in the second interval in which the binocular fusion is decided to be impossible. 
     By this means, it is possible to: perform parallax correction such that the binocular fusion is possible in the stereoscopic video in the scene; reduce and stereoscopically display the parallax amount as it becomes closer to the intra-interval maximum display size or the intra-interval maximum parallax amount; and, by contrast, perform parallax correction to reduce (or makes it closer to the original) the decrement of displayed parallax as it becomes distant from the intra-interval maximum display size or intra-interval maximum parallax amount. 
     The above stereoscopic video reproduction device includes a decision unit configured to decide whether the second interval is sufficiently long with respect to the first interval, where, when the decision unit decides that the second interval is sufficiently long with respect to the first interval, the parallax correction unit corrects the parallax using the parallax correction coefficient, and, when the decision unit decides that the second interval is not sufficiently long with respect to the first interval, corrects the parallax based on the intra-interval maximum display size or intra-interval maximum parallax amount acquired in accordance with the first interval in the second interval. 
     A stereoscopic video reproduction program according to the present invention causes a computer to realize the above stereoscopic video reproduction device. A non-transitory computer-readable recording medium that records this stereoscopic video reproduction program is included in the present invention too. 
     A stereoscopic display device according to the present invention includes the above stereoscopic video reproduction device and the stereoscopic display of output destination. 
     A stereoscopic imaging device according to the present invention includes: an imaging unit configured to acquire a stereoscopic video in which a stereoscopic image formed with a plurality of viewpoint images is consecutively provided in a time axis direction; a parallax amount calculation unit configured to calculate a parallax amount indicating a shift amount between feature points with a common feature, from a plurality of viewpoint images every frame of the acquired stereoscopic video; a maximum parallax amount acquisition unit configured to acquire a maximum parallax amount on a distant view side from the calculated parallax amount of each feature point every frame; an intra-interval maximum parallax amount acquisition unit configured to acquire an intra-interval maximum parallax amount which is the largest in every predetermined interval of the stereoscopic video, in the acquired maximum parallax amount on the distant view side; an intra-interval maximum display size acquisition unit configured to acquire an intra-interval maximum display size in which binocular fusion is possible when the stereoscopic image is displayed on a stereoscopic display every predetermined interval, based on the intra-interval maximum parallax amount acquired every predetermined interval of the stereoscopic video; a recording unit configured to generate a stereoscopic video file in which the stereoscopic video is recorded, and records the stereoscopic video file in a recording medium, wherein the recording unit records the stereoscopic video in the stereoscopic video file and records the intra-interval maximum display size every predetermined interval in the stereoscopic video file as attached information; and the above stereoscopic video reproduction device, where the first acquisition unit reads a stereoscopic video file from the recording medium. 
     A stereoscopic imaging device according to the present invention includes: an imaging unit configured to acquire a stereoscopic video in which a stereoscopic image formed with a plurality of viewpoint images is consecutively provided in a time axis direction; a parallax amount calculation unit configured to calculate a parallax amount indicating a shift amount between feature points with a common feature, from a plurality of viewpoint images every frame of the acquired stereoscopic video; a maximum parallax amount acquisition unit configured to acquire a maximum parallax amount on a distant view side from the calculated parallax amount of each feature point every frame; an intra-interval maximum parallax amount acquisition unit configured to acquire an intra-interval maximum parallax amount which is the largest in every predetermined interval of the stereoscopic video, in the acquired maximum parallax amount on the distant view side; a recording unit configured to generate a stereoscopic video file in which the stereoscopic video is recorded, records the stereoscopic video file in a recording medium, records the stereoscopic video in the stereoscopic video file and records the intra-interval maximum parallax amount every predetermined interval in the stereoscopic video file as attached information; and the above stereoscopic video reproduction device, where the first acquisition unit reads a stereoscopic video file from the recording medium. 
     A stereoscopic video reproduction method according to the present invention causes a stereoscopic video reproduction device to execute: a step of reading a stereoscopic video file and acquiring a stereoscopic video and attached information from the stereoscopic video file, where the stereoscopic video in which a stereoscopic image formed with a plurality of viewpoint images is consecutively provided in a time axis direction and the attached information of the stereoscopic video are recorded in the stereoscopic video file and the attached information includes an intra-interval maximum display size which is the largest in each of consecutive predetermined intervals in the time axis direction of the stereoscopic video among the maximum display sizes every frame in which a binocular fusion is possible when displaying each frame of the stereoscopic video on a stereoscopic display; a step of acquiring a display size of a stereoscopic display of output destination; a decision step of comparing the intra-interval maximum display size acquired corresponding to every predetermined interval of the stereoscopic video and the acquired display size of the stereoscopic display, and, based on the comparison result, deciding whether the binocular fusion is possible every predetermined interval when displaying the stereoscopic video on the stereoscopic display; a parallax correction step of correcting a parallax when the decision step decides that the binocular fusion is impossible, such that the binocular fusion becomes possible in the stereoscopic video in a predetermined interval in which the binocular fusion is decided to be impossible; and a step of: when the acquired stereoscopic video is output to the stereoscopic display, outputting, to the stereoscopic display, the stereoscopic video in which the parallax is corrected in the stereoscopic video by the parallax correction step in the predetermined interval in which the binocular fusion is decided to be impossible in a case where the decision step decides that the binocular fusion is impossible; and outputting the acquired stereoscopic video as is to the stereoscopic display in a case where the decision step decides that the binocular fusion is possible. 
     A stereoscopic video reproduction method according to the present invention causes a stereoscopic video reproduction device to execute: a step of reading a stereoscopic video file and acquiring a stereoscopic video and attached information from the stereoscopic video file, where the stereoscopic video in which a stereoscopic image formed with a plurality of viewpoint images is consecutively provided in a time axis direction and the attached information of the stereoscopic video are recorded in the stereoscopic video file and the attached information includes an intra-interval maximum parallax amount which is the largest in each of consecutive predetermined intervals in the time axis direction of the stereoscopic video among maximum parallax amounts on a distant view side in each frame of the stereoscopic video; a step of acquiring a display size of a stereoscopic display of output destination; a decision step of, based on the intra-interval maximum parallax amount acquired corresponding to every predetermined interval of the stereoscopic video, the acquired display size of the stereoscopic display and a predetermined value indicating man&#39;s binocular interval, deciding whether a binocular fusion is possible every predetermined interval when displaying the stereoscopic video on the stereoscopic display; a parallax correction step of correcting a parallax when the decision step decides that the binocular fusion is impossible, such that the binocular fusion becomes possible in the stereoscopic video in a predetermined interval in which the binocular fusion is decided to be impossible; and a step of: when the acquired stereoscopic video is output to the stereoscopic display, outputting, to the stereoscopic display, the stereoscopic video in which the parallax is corrected in the stereoscopic video by the parallax correction step in the predetermined interval in which the binocular fusion is decided to be impossible in a case where the decision step decides that the binocular fusion is impossible; and outputting the acquired stereoscopic video as is to the stereoscopic display in a case where the decision step decides that the binocular fusion is possible. 
     According to the present invention, it is possible to read the intra-interval maximum display size or intra-interval maximum parallax amount every predetermined interval of the stereoscopic video, which is recorded as attached information of the stereoscopic video file, and decide whether a binocular fusion is possible when displaying the stereoscopic video in the corresponding interval on the stereoscopic display, based on this read added information and the display size of the stereoscopic display. When it is decided that the binocular fusion is impossible, since the parallax is corrected such that the binocular fusion becomes possible in the stereoscopic video in the interval to output the result, it is possible to display the stereoscopic video with an appropriate parallax amount regardless of the screen size of the stereoscopic display of output destination. Also, by using the intra-interval maximum display size or intra-interval maximum parallax amount recorded as attached information of the stereoscopic video file, it is possible to easily decide whether the binocular fusion is possible in a case where the stereoscopic video in the interval is stereoscopically displayed on the stereoscopic display of output destination, and it is possible to reduce the load of image processing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a state where viewpoint images at two viewpoints are imaged. 
         FIG. 2  is a diagram illustrating a first example typically showing a data structure of a 3D video file. 
         FIG. 3  is a flowchart illustrating imaging/recording processing. 
         FIG. 4  is a diagram illustrating an example of viewpoint images at two viewpoints. 
         FIG. 5  is a diagram illustrating a second example typically showing a data structure of a 3D video file. 
         FIG. 6  is a diagram illustrating a third example typically showing a data structure of a 3D video file. 
         FIG. 7  is a diagram illustrating a fourth example typically showing a data structure of a 3D video file. 
         FIG. 8  is a diagram illustrating a state where viewpoint images at four viewpoints are imaged. 
         FIG. 9  is a diagram typically showing a data structure of a 3D video file in which viewpoint images at four viewpoints are recorded. 
         FIG. 10  is a diagram for explaining a virtual viewpoint. 
         FIG. 11A  is a diagram illustrating a front appearance of a stereoscopic imaging device. 
         FIG. 11B  is a diagram illustrating a rear appearance of a stereoscopic imaging device. 
         FIG. 12  is a block diagram illustrating an internal structure of a stereoscopic imaging device. 
         FIG. 13  is a flowchart illustrating the first embodiment of 3D video reproduction. 
         FIG. 14  is a diagram for explaining the principle of parallax shift. 
         FIG. 15A  is a diagram illustrating parallax shift of right and left viewpoint images. 
         FIG. 15B  is a diagram illustrating parallax shift of right and left viewpoint images. 
         FIG. 16  is a flowchart illustrating the second embodiment of 3D video reproduction. 
         FIG. 17  is a flowchart illustrating the third embodiment of 3D video reproduction. 
         FIG. 18  is a graph illustrating an example of a parallax correction table. 
         FIG. 19  is a flowchart illustrating the fourth embodiment of 3D video reproduction. 
         FIG. 20  is a flowchart illustrating the fifth embodiment of 3D video reproduction. 
         FIG. 21  is a flowchart illustrating the sixth embodiment of 3D video reproduction. 
         FIG. 22  is a flowchart illustrating the seventh embodiment of 3D video reproduction. 
         FIG. 23  is a diagram illustrating the whole structure of a stereoscopic video reproduction device and 3D display. 
         FIG. 24  is a block diagram illustrating an internal structure of a stereoscopic video reproduction device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, preferable embodiments of the present invention are explained in detail according to the accompanying drawings. 
     {First Embodiment of 3D Video File} 
     A stereoscopic video file (3D video file) according to the first embodiment is explained. 
       FIG. 1  is a diagram illustrating a state where viewpoint images (or videos) at two viewpoints (i.e. the left viewpoint and the right viewpoint) are imaged from different viewpoints with respect to an object  100  by two imaging devices  101 - 2  and  101 - 3 , and  FIG. 2  is a diagram typically showing a data structure of a 3D video file recording a 3D video formed with the left viewpoint and right viewpoint videos imaged in the imaging devices  101 - 2  and  101 - 3  illustrated in  FIG. 1 . 
     The 3D video file illustrated in  FIG. 2  is a MPEG file in conformity to the MPEG (moving picture expert group) format, and the viewpoint image at the left viewpoint and the viewpoint image at the right viewpoint are alternately coupled in units of one GOP (group of picture: in the MPEG compression, combination of several frames of video signals that are a unit at the time of compression and at the time of reproduction/edit) and formed as one file. 
     A header area is provided in the head of an area recording the viewpoint image of each GOP, and this header area records attached information such as the image size, the aspect ratio and the frame rate. Also, in the present embodiment, as attached information, all or part of the following attached information is further recorded.
         GOP maximum display size (width, height, unit: mm)   Assumed visual distance (distance between a viewer at the time of observing a stereoscopic video and a 3D display) (unit: mm)   GOP maximum parallax amount (near view): parallax amount with respect to image width (%)   GOP maximum parallax amount (distant view): parallax amount with respect to image width (%)   Convergence angle, base line length and imaging unit arrangement (viewpoint number) of device that takes each viewpoint image       

     Imaging/recording processing to record such a 3D video file is explained using the flowchart in  FIG. 3 . 
     First, right and left viewpoint images for one frame in a plurality of frames of one GOP corresponding to the left viewpoint and the right viewpoint are acquired (step S 11 ). Here, by the two imaging devices  101 - 2  and  101 - 3  as illustrated in  FIG. 1 , right and left viewpoint images for one frame of a 3D video subjected to 3D video imaging with respect to the object  100  are acquired. Here, it is assumed that the imaging device  101 - 2  has a viewpoint number  2  and the imaging device  101 - 3  has a viewpoint number  3 . 
     Next, a plurality of feature points are extracted from right and left viewpoint images (step S 12 ) and the parallax amount in each feature point is calculated (step S 13 ). Here, the parallax amount denotes the difference between the distances from the left ends of the respective viewpoint images in the corresponding feature point between the viewpoint images, and the unit is pixel. From the parallax amount in each feature point calculated in this way, the maximum parallax amount on the near view side and the maximum parallax amount on the distant view side are acquired (step S 14 ). 
       FIG. 4  is a diagram illustrating an example of right and left viewpoint images, (a) portion of  FIG. 4  illustrates a left viewpoint image  201 - 2  and (b) portion of  FIG. 4  illustrates a right viewpoint image  201 - 3 . 
     In the example of  FIG. 4 , the maximum parallax amount on the near view side is  213 N, and feature points (i.e. maximum parallax amount positions (near view)) with this parallax amount are  211 N and  212 N, respectively. Also, the maximum parallax amount on the distant view side is  213 F, and feature points (i.e. maximum parallax amount positions (distant view)) with this parallax amount are  211 F and  212 F, respectively. That is, in a case where a stereoscopic image based on these right and left viewpoint images is stereoscopically viewed, it is viewed such that the maximum parallax amount positions (near view) are the nearest and the maximum parallax amount positions (distant view) are the most distant. 
     The ratios (%) of the maximum parallax amount  213 N on the near view side and the maximum parallax amount  213 F on the distant view side to the image width are the maximum parallax amount (near view) (%) and the maximum parallax amount (distant view) (%). 
     Subsequently, it is decided whether to finish acquiring the maximum parallax amounts in all frames of one GOP (step S 15 ), and, in a case where it is not finished (i.e. “in the case of NO”), it returns to step S 11  to perform the processing in steps S 11  to S 14 , and, in a case where it is finished (i.e. “in the case of YES”), it proceeds to step S 16 . 
     In step S 16 , the largest maximum parallax amount among the maximum parallax amounts in all frames of one GOP is acquired as a GOP maximum parallax amount. Further, based on this GOP maximum parallax amount, the GOP maximum display size is acquired. 
     When the parallax amount on the distant view side exceeds man&#39;s binocular interval, binocular fusion is impossible in the position of the image and it cannot be stereoscopically viewed. Therefore, according to the ratio (%) of the GOP maximum parallax amount (distant view) to the image width, the maximum display size (i.e. the GOP maximum display size) is acquired within the display size in which the parallax does not exceed the man&#39;s binocular interval. 
     For example, it is assumed that the man&#39;s binocular interval is 50 mm, and, if the ratio of the GOP maximum parallax amount (distant view) to the image width is 10%, the maximum display width allowed for binocular vision is 500 mm. That is, in the case of a display with a width of 500 mm or less, right and left images corresponding to the GOP maximum parallax amount (distant view) are displayed without exceeding a binocular interval of 50 mm, and, as a result, the viewer can perform binocular vision. 
     Here, in a case where a display with an aspect ratio of 16:9 is assumed, the maximum display height is 281.25 mm. 
     Here, the man&#39;s binocular interval may be arbitrarily determined according to the target viewer. For example, when only adults are targeted, a wide value such as 65 mm may be set. 
     For example, it is assumed that the man&#39;s binocular interval is 65 mm, and, if the ratio of the GOP maximum parallax amount (distant view) to the image width is 15%, the GOP maximum display size allowed for binocular vision is about 433 mm. Also, in a case where a 3D display with an aspect ratio of 16:9 is assumed, the height of the GOP maximum display size is about 244 mm. 
     Also, instead of performing calculation from man&#39;s binocular interval, a table recording the maximum display size corresponding to the maximum parallax amount is prepared in advance, and, by referring to this table, the GOP maximum display size may be acquired. 
     Next, the left viewpoint images and right viewpoint images for one GOP are respectively subjected to MPEG compression, alternately coupled as illustrated in FIG.  2  and recorded as a 3D video file, and, in the first header area of an area in which the viewpoint images in each GOP are recorded, for example, the GOP maximum display size, the GOP maximum parallax amount (distant view) (%) and the GOP maximum parallax amount (near view) (%) acquired in step S 16  are recorded as attached information (step S 17 ). Subsequently, by performing the above processing for all GOPs of the 3D video, it is possible to record the 3D video file illustrated in  FIG. 2 . 
     The 3D video file recorded as above is read by a stereoscopic video reproduction device at the time when it is displayed on a 3D display. In this case, in the stereoscopic video reproduction device, by comparing the GOP maximum display size recorded in the attached information of the 3D video file and the display size of a 3D display on which it is to be displayed, it is possible to easily decide whether a binocular vision is possible. In a case where it is decided that the binocular vision is possible, the recorded 3D video may be displayed as is, and, in a case where it is decided that the binocular vision is not possible, it is possible to correct the parallax of right and left viewpoint images in the corresponding GOP using the GOP maximum display size and the GOP maximum parallax amount, and it is possible to reduce parallax correction processing in a stereoscopic video reproduction device. 
     Here, in the present embodiment, although the GOP maximum display size is determined based on only the GOP maximum parallax amount on the distant view side, it may be determined taking into consideration the GOP maximum parallax amount on the near view side. By taking into consideration the GOP maximum parallax amount on the near view side, it is possible to determine the GOP maximum display size that enables appropriate binocular vision on not only the distant view side but also the near view side. 
     For example, the display size in which the near-view parallax amount is equal to or less than 50 mm may be set as the GOP maximum display size. This is because, when the parallax amount on the near view side increases, the viewer feels fatigued for the binocular vision and therefore it is preferable to be equal to or less than a predetermined amount. 
     Also, in the present embodiment, the GOP maximum parallax amount and the GOP maximum display size are recorded in the first header area of a GOP from which the GOP maximum parallax amount and the GOP maximum display size are acquired, as attached information. However, it is not limited to this, and, as illustrated in  FIG. 5 , they may be recorded in the first header area of a GOP two GOPs before (i.e. the time for one GOP minute before). Also, as illustrated in  FIG. 6 , the GOP maximum parallax amounts and GOP maximum display sizes acquired from all GOPs may be collectively recorded in the first header area of the 3D video file. According to this, a stereoscopic video reproduction device that reads the 3D video file can detect in advance whether to adjust the parallax of the stereoscopic video in one GOP, and can calculate in advance the parallax amount to be adjusted. 
     Further, in the present embodiment, the GOP maximum parallax amount and GOP maximum display size which are the largest in one GOP are acquired. However, it is not limited to this, and the intra-interval maximum parallax amount and intra-interval maximum display size in each of a predetermined number of GOPs (intervals) set in advance may be acquired and recorded as attached information with respect to the 3D video in the interval. 
     {Second Embodiment of 3D Video File} 
     In the second embodiment, in a case where a 3D video scene changes as illustrated in  FIG. 7 , all or part of following attached information is recorded as attached information of the head of the scene.
         Flag indicating scene head   Scene maximum display size (width, height, unit: mm)   Assumed visual distance (i.e. distance between the viewer at the time of observing a stereoscopic video and a 3D display) (unit: mm)   Scene maximum parallax amount (near view): parallax amount with respect to image width (%)   Scene maximum parallax amount (distant view): parallax amount with respect to image width (%)   Convergence angle, base line length and imaging unit arrangement (viewpoint number) of device that takes each viewpoint image   Convergence angle, base line length and imaging unit arrangement (viewpoint number) of device that takes each viewpoint image       

     Further, a flag indicating zoom-in/zoom-out and a flag indicating ON/OFF/Reset of blurring correction may be recorded as attached information. 
     It is possible to change a scene by a scene change detection unit configured to detect the scene change from an acquired 3D video. For example, the detection is possible in cases where: the times of time stamps indicating the recording times are separated from each other in previous and subsequent 3D video frames; the correlation of previous and subsequent 3D video frames is checked and there is no correlation; the GOP maximum parallax amount changes over a predetermined threshold in adjacent GOPs; and the blurring correction state changes (ON--&gt; OFF, OFF--&gt; ON, Reset). Here, the scene change detection method is not limited to the above example and various methods are possible. 
     The scene head flag denotes a flag indicating the head of each scene in a 3D video file coupling each scene of the 3D video as illustrated in  FIG. 7 , the scene maximum parallax amount is the parallax amount which is the largest in the 3D video in the scene, and the scene maximum display size is the maximum display size within the display size in which binocular fusion is possible at the time of displaying the scene on a stereoscopic display and which is acquired based on the scene maximum parallax amount in the scene. 
     Also, as illustrated in  FIG. 7 , in the 3D video file in which each scene of the 3D video is coupled, for each scene, attached information such as the scene head flag, the scene maximum parallax amount in the scene and the scene maximum display size is recorded at the head of the scene. Here, in addition to the above information, scene length information of the scene is recorded in the attached information at the scene head. The scene length information can be expressed by the number of GOPs forming the scene. 
     {Third Embodiment of 3D Video File} 
     In the first embodiment, an example has been explained using right and left viewpoint images taken from two viewpoints, the number of viewpoints for a 3D video according to the present invention is not limited to two viewpoints and viewpoint images at multiple viewpoints equal to or greater than three viewpoints is possible. 
       FIG. 8  is a diagram illustrating a state where four imaging devices  101 - 1  to  101 - 4  take four viewpoint images at different viewpoints with respect to the object  100 . Here, it is assumed that the viewpoint numbers of the imaging devices  101 - 1  to  101 - 4  are  1  to  4  in order. 
       FIG. 9  is a diagram typically showing a data structure of a 3D video file recording viewpoint images at four viewpoints taken by these four imaging devices  101 - 1  to  101 - 4 . Similar to the file illustrated in  FIG. 2 , this 3D video file is a MPEG file, and, regarding the viewpoint images at four viewpoints, in units of one GOP, viewpoint images ( 1 ) to ( 4 ) corresponding to viewpoint numbers  1  to  4  are sequentially and repeatedly coupled and formed as one file. 
     Also, in the first header area of the record area in which each viewpoint image per GOP is recorded, similar to the first embodiment, attached information is recorded, such as the GOP maximum display size, the GOP maximum parallax amount, the assumed visual distance and the convergence angle, base line length and imaging unit arrangement (i.e. viewpoint number) of the device that takes each viewpoint image. 
     Also, as for the GOP maximum display size and the GOP maximum parallax amount or the like recorded in the head of each of the viewpoint images ( 1 ) to ( 4 ), values calculated between the viewpoint image and other viewpoint images are recorded. To be more specific, regarding the GOP maximum display size and GOP maximum parallax amount with respect to viewpoint image ( 1 ), on the basis of viewpoint image ( 1 ) taken at the left end reference viewpoint as illustrated in  FIG. 8 , for example, the GOP maximum parallax amount calculated from a viewpoint image with the largest parallax amount (viewpoint image ( 4 ) in this case) and the GOP maximum display size and assumed visual distance acquired from this maximum parallax amount are recorded. Even regarding the convergence angle and the base line length, the convergence angle and base line length of a device that takes the same viewpoint image (viewpoint image ( 4 ) in this case) are recorded. 
     As attached information of viewpoint image ( 2 ), for example, the GOP maximum display size, GOP maximum parallax amount, assumed visual distance, convergence angle, base line length and viewpoint number calculated from this viewpoint image ( 2 ) and viewpoint image ( 1 ) taken at the reference viewpoint are recorded. 
     As attached information of viewpoint image ( 3 ), for example, the GOP maximum display size, GOP maximum parallax amount, assumed visual distance, convergence angle, base line length and viewpoint number calculated from this viewpoint image ( 3 ) and viewpoint image ( 1 ) taken at the reference viewpoint are recorded. 
     As attached information of viewpoint image ( 4 ), for example, the GOP maximum display size, GOP maximum parallax amount, assumed visual distance, convergence angle, base line length and viewpoint number calculated from this viewpoint image ( 4 ) and viewpoint image ( 1 ) taken at the reference viewpoint are recorded. 
     Thus, a 3D video file recording viewpoint images at multiple viewpoints equal to or greater than three viewpoints is read by a stereoscopic video reproduction device when it is displayed on a 3D display. In this case, in the stereoscopic video reproduction device, by comparing the GOP maximum display size per viewpoint image recorded in attached information of the 3D video file and the display size of the 3D display on which it is to be displayed, it is possible to easily decide whether a binocular vision is possible. 
     The recording order of multiple viewpoint images is not limited to the order illustrated in  FIG. 9 , and recommendation images (e.g. two viewpoint images) when it is displayed on the 3D display may be recorded earlier. For example, in a case where stereoscopic display by viewpoint images ( 2 ) and ( 3 ) at the two viewpoints in the center is recommended, viewpoint images ( 2 ) and ( 3 ) may be recorded earlier and viewpoint images ( 1 ) and ( 4 ) may be subsequently recorded, and, meanwhile, in a case where stereoscopic display by viewpoint images ( 1 ) and ( 4 ) at the two viewpoints at both ends is recommended, viewpoint images ( 1 ) and ( 4 ) may be recorded earlier and viewpoint images ( 2 ) and ( 3 ) may be subsequently recorded. 
     {Fourth Embodiment of 3D Video File} 
     All of the multiple viewpoint images as in the third embodiment need not be images that are actually taken, and a virtual viewpoint image corresponding to a virtual viewpoint may be included. 
     For example, as illustrated in  FIG. 10 , two viewpoint images at different viewpoints (i.e. viewpoint number  1  and viewpoint number  4 ) with respect to the object  100  are taken by two imaging devices  101 - 1  and  101 - 4 . 
     Further, it is possible to generate viewpoint images  2  and  3  of viewpoint numbers  2  and  3  at virtual viewpoints, which are different viewpoints from viewpoint numbers  1  and  4  and which are not actually present. To generate a virtual viewpoint image, there are a method of internally dividing each pixel of a plurality of taken images and a method of generating it using a parallax map generated from a plurality of taken images and one taken image, but it is not specifically limited. 
     In a 3D video file recording viewpoint images at multiple viewpoints including a viewpoint image at a virtual viewpoint, as attached information of first viewpoint image ( 1 ) among the viewpoint images at the multiple viewpoints, information indicating whether the viewpoint image at each viewpoint is the viewpoint image at an actual viewpoint or the viewpoint image at the virtual viewpoint, is collectively recorded (see  FIG. 9 ). Here, it is not limited to a case where information of the actual viewpoint and the virtual viewpoint is collectively recorded as attached information of first viewpoint image ( 1 ), and, as the attached information of each of viewpoint images ( 1 ) to ( 4 ), information indicating whether it is the viewpoint image at the actual viewpoint or the viewpoint image at the virtual viewpoint may be individually recorded. This information indicating whether it is the viewpoint image at the actual viewpoint or the viewpoint image at the virtual viewpoint can be used in a case where a 3D video is displayed as a 2D video. 
     {Appearance of Stereoscopic Imaging Device} 
       FIG. 11A  and  FIG. 11B  are diagrams illustrating an appearance of a stereoscopic imaging device according to the present invention,  FIG. 11A  is a perspective view seen from the front surface side of the stereoscopic imaging device and  FIG. 11B  is a rear view. 
     This stereoscopic imaging device (i.e. compound eye camera)  10  is a digital camera that can record and reproduce 2D/3D still images and 2D/3D videos, and, as illustrated in  FIG. 11A , a shutter button  11  and a zoom button  12  are provided on the upper surface of the thin camera body having a rectangular parallelepiped shape. 
     As illustrated in  FIG. 11A , a lens barrier  13  having substantially the same width as the width in the horizontal direction of the camera body is provided in the front surface of the camera body so as to be freely moved in the vertical direction of the camera body, and, by moving this lens barrier  13  in the vertical direction between the position indicated by the alternate long and two dots lines and the position indicated by the solid lines, it is possible to open and close the front surfaces of a pair of right and left imaging optical systems  14 - 1  and  14 - 2  at the same time. Here, as the imaging optical systems  14 - 1  and  14 - 2 , a zoom lens of folded optics is used. Also, in tandem with the opening and closing operation of the front surface of the lens by the lens barrier  13 , it is possible to turn on or off the camera power supply. 
     As illustrated in  FIG. 11B , a liquid crystal monitor  16  for 3D is provided in the center part of the back of the camera body. The liquid crystal monitor  16  can display a plurality of parallax images (i.e. right viewpoint image and left viewpoint image) as directivity images having predetermined directivities by a parallax barrier, respectively. Also, as the liquid crystal monitor  16  for 3D, it is possible to apply the one using a lenticular lens or the one in which it is possible to individually view the right viewpoint image and the left viewpoint image by wearing dedicated glasses such as polarized glasses and liquid crystal shutter glasses. 
     Various operation switches are provided on the right and left of the above liquid crystal monitor  16 . An operation switch  18 A is a switching switch to switch between the still image imaging and the video imaging, an operation switch  18 B is a parallax adjustment switch to adjust the parallax amount between the right viewpoint image and the left viewpoint image, and an operation switch  18 C is a switching switch to switch between the 2D imaging and the 3D imaging. Also, an operation switch  18 D is a seesaw key combining a MENU/OK button and a reproduction button, an operation switch  18 E is a multi-function arrow key and an operation switch  18 F is a DISP/BACK key. 
     The MENU/OK button is an operation switch combining: a function as a menu button to give an instruction to display a menu on the screen of the liquid crystal monitor  16 ; and a function as an OK button to give an instruction to confirm and execute selection content. The reproduction button is a button to switch from an imaging mode to a reproduction mode. The arrow key is an operation switch to input an instruction for four directions of top, bottom, right and left, to which a macro button, a flash button and a self-timer button or the like are assigned. Here, in a case where a menu is selected, the arrow key functions as a switch (i.e. cursor movement operation unit) to select an item from the menu screen or give an instruction to select various setting items from each menu. Also, the left/right key of the arrow key functions as a button for frame feeding (forward direction/backward direction feeding) in a reproduction mode. The DISP/BACK key is used at the time of switching a display format of the liquid crystal monitor  16 , cancelling instruction content on the menu screen or returning to the previous operation state. 
     Also, reference numeral “ 15 ” is a stereo microphone in  FIG. 11A . 
     {Internal Structure of Stereoscopic Imaging Device} 
       FIG. 12  is a block diagram indicating an internal structure of the above stereoscopic imaging device  10 . 
     As illustrated in  FIG. 12 , this stereoscopic imaging device  10  is formed mainly of: a plurality of imaging units  20 - 1  and  20 - 2 ; a central processing unit (CPU)  32 ; an operation unit  34  including the above shutter button  11 , the zoom button  12  and various operation switches; a display control unit  36 ; the liquid crystal monitor  16 , a record control unit  38 ; a compression/decompression processing unit  42 ; a digital signal processing unit  44 ; an AE (Automatic Exposure) detection unit  46 ; an AF (Auto Focus) detection unit  48 ; an AWB (Automatic White Balance) detection unit  50 ; a VRAM  52 ; a RAM  54 , a ROM  56 ; and an EEPROM  58 . Here, although the imaging units  20 - 1  and  20 - 2  take two parallax images of the left eye image and right eye image with parallax therebetween, there may be three or more imaging units  20 . 
     The imaging unit  20 - 1  that takes a left eye image includes: a prism (not illustrated); an imaging optical system  14 - 1  ( FIG. 14 ) formed with a focus lens and a zoom lens  21 ; an optical unit formed with a diaphragm  22  and a mechanical shutter  23 ; a solid-state imaging element (CCD)  24 ; an analog signal processing unit  25 ; an A/D converter  26 ; an image input controller  27 ; a lens drive unit  28  that drives the above optical unit; a diaphragm drive unit  29 ; a shutter control unit  30 ; and a CCD control unit  31  that controls the CCD  24 . Also, the imaging unit  20 - 2  that takes a right eye image has the same structure as the imaging unit  20 - 1  that takes the above left eye image, explanation of the specific structure is omitted. 
     The CPU  32  performs integration control of the overall camera operation according to a predetermined control program based on an input from the operation unit  34 . Further, the CPU  32  calculates the parallax amount by feature point extraction, acquires the maximum parallax amount, calculates the GOP maximum display size, calculates the scene maximum display size, calculates the GOP maximum parallax amount, calculates the scene maximum parallax amount, detects the scene change, performs parallax shift and generates a virtual viewpoint image, and so on. 
     Also, the ROM  56  stores a control program executed by the CPU  32 , various kinds of data required for control, a 3D video processing program and a 3D video reproduction program or the like. The EEPROM  58  stores various kinds of information indicating an adjustment result at the time of adjustment before the product is shipped, such as pixel defect information of the CCD  24 , correction parameters used for image processing and the like, and a correspondence table between the maximum parallax amount, and the maximum display size. 
     Also, the VRAM  52  is a memory that temporarily stores display image data displayed on the liquid crystal monitor  16 , and the RAM  54  contains a computation work area of the CPU  32  and a temporary storage area of image data. 
     The focus lens and the zoom lens  21  included in the imaging optical system are driven by the lens drive unit  28  and moved back and forth along the optical axis. By controlling the drive of the lens drive unit  28 , the CPU  32  controls the position of the focus lens and performs focus adjustment such that the object is focused on, and changes the zoom magnification by controlling the zoom position of the zoom lens according to a zoom instruction from the zoom button  12  in the operation unit  34 . 
     For example, the diaphragm  22  is formed with an iris diaphragm, and is driven and operated by the diaphragm drive unit  29 . The CPU  32  controls the aperture amount (i.e. diaphragm value) of the diaphragm  22  through the diaphragm drive unit  29 , and controls the incident light amount to the CCD  24 . 
     The mechanical shutter  23  decides the exposure time in the CCD  24  by opening and closing the optical path, and prevents smear from being caused such that unnecessary light is not incident on the CCD  24  at the time of reading a video signal from the CCD  24 . The CPU  32  outputs a shutter close signal synchronized with the exposure end timing corresponding to the shutter speed, to the shutter control unit  30 , and controls the mechanical shutter  23 . 
     The CCD  24  is formed with a two-dimensional color CCD solid-state imaging element. On the light receiving side of the CCD  24 , many photodiodes are arrayed in a two-dimensional manner, and, in each photodiode, a color filter is arranged in a predetermined array. 
     An object optical image formed on the CCD light receiving side through the optical unit having the above structure is converted into a signal electric charge corresponding to the incident light amount by this photodiode. The signal electric charge accumulated in each photodiode is sequentially read from the CCD  24  as a voltage signal (or image signal) corresponding to the signal electric charge, based on a drive pulse given from the CCD control unit  31  according to an instruction of the CPU  32 . The CCD  24  includes an electronic shutter function and controls the exposure time (or shutter speed) by controlling the electric charge accumulation time for the photodiode. Here, the electric charge accumulation start timing corresponding to the shutter speed is controlled by the electronic shutter, and the exposure end timing (i.e. electric charge accumulation end timing) is controlled by closing the mechanical shutter  23 . In this embodiment, although the CCD  24  is used as an imaging element, it is possible to use an imaging element of another structure such as a CMOS sensor. 
     After analog signals of R, G and B read from the CCD  24  are subjected to correlated double sampling (CDS) and amplification in the analog signal processing unit  25 , they are converted into digital signals of R, G and B in the A/D converter  26 . 
     The image input controller  27  incorporates a line buffer of predetermined capacity, and, after temporarily accumulating the image signals of R, G and B (i.e. CCDRAW data) subjected to A/D conversion in the A/D converter  26 , stores them in the RAM  54  through a bus  60 . 
     The CPU  32  controls the imaging unit  20 - 2  that takes a right viewpoint image as well as the imaging unit  20 - 1  that takes a left viewpoint image, in a 3D imaging mode. 
     The AE detection unit  46  calculates the object luminance required for AE control based on a video signal imported at the time of a half push of the shutter button  11 , and outputs a signal indicating the object luminance (i.e. imaging EV value) to the CPU  32 . The CPU  32  sets the shutter speed (i.e. exposure time), diaphragm value and imaging sensitivity in a plurality of imaging units  20 - 1  and  20 - 2 , according to a predetermined program diagram based on the input imaging EV value. 
     The AF detection unit  48  integrates the absolute value of the high-frequency component of an image signal of an AF area imported at the time of a half push of the shutter button  11 , and outputs this integrated value (i.e. AF evaluation value) to the CPU  32 . The CPU  32  moves the focus lens from the near side to the infinity side, searches for the focusing position in which the AF evaluation value detected by the AF detection unit  48  is the maximum, and, by moving the focus lens to the focusing position, performs focus adjustment to the object (i.e. main object). Also, at the time of taking videos, so-called mountaineering control is performed to move the focus lens such that the above AF evaluation value always has the maximum value. 
     The AWB detection unit  50  automatically finds the light source type (color temperature of the field) based on image signals of R, G and B acquired at the time of the imaging, and reads the corresponding white balance gain from a table storing the white balance gains (i.e. white balance correction values) of R, G and B which are set in advance for respective light source types. 
     The digital signal processing unit  44  includes: a white balance correction circuit; a gray scale conversion processing circuit (e.g. gamma correction circuit); a synchronization circuit that compensates for a spatial gap of color signals such as R, G and B according to a color filter array of a single panel CCD and aligns the position of each color signal; a contour correction circuit; and a luminance and color difference signal generation circuit, and so on, and performs image processing on the image signals (i.e. CCDRAW data) of R, G and B stored in the RAM  54 . That is, in the digital signal processing unit  44 , the CCDRAW data of R, G and B is multiplied by the white balance gain detected in the AWB detection unit  50 , subjected to white balance correction, and, after predetermined processing such as gray scale conversion processing (e.g. gamma correction) is subsequently performed, converted into a YC signal formed with the luminance signal (Y signal) and the color difference signal (Cr and Cb signals). The YC signal processed by the digital signal processing unit  44  is stored in the RAM  54 . 
     Also, the digital signal processing unit  44  includes: a distortion correction circuit that corrects lens distortion correction in the imaging optical systems of the plurality of imaging units  20 - 1  and  20 - 2 ; and an image extraction processing circuit that corrects the optical axis shift of the imaging optical systems of the plurality of imaging units  20 - 1  and  20 - 2  by extracting an image of a predetermined extraction area from the right and left viewpoint images respectively. 
     The compression/decompression processing unit  42  performs compression processing on the YC signal stored in the RAM  54  according to an instruction from the CPU  32  at the time of recording in the memory card  40 , and performs decompression processing on the compressed compression data recorded in the memory card  40  and produces the YC signal. 
     The record control unit  38  records the compression data compressed by the compression/decompression processing unit  42  in the memory card  40  as a predetermined format image file (e.g. records a 3D still image as an MP file and a 3D video as a video file of MPEG4, MPEG4-MVC, motion JPEG or H.264), or reads the video file from the memory card  40 . 
     Also, when a 3D video file according to the present invention is recorded, as explained in the first embodiment to the fourth embodiment, in addition to attached information such as the image size, the aspect ratio and the frame rate, the record control unit  38  records, as attached information in the memory card  40 : the GOP maximum display size; the scene maximum display size; the assumed visual distance; the GOP maximum parallax amount (near view) (%); the GOP maximum parallax amount (distant view) (%); the scene maximum parallax amount (near view) (%), and the scene maximum parallax amount (distant view) (%). 
     In this case, at the time of taking a 3D video, in addition to a case where a 3D video file is created and recorded as explained in the first embodiment to the fourth embodiment, a case is possible where it is temporarily recorded as a normal 3D video file in the memory card  40 , and, after that, the 3D video file is read from the memory card  40  to create the 3D video file explained in the first embodiment to the fourth embodiment and record it in the memory card  40  again. 
     The liquid crystal monitor  16  is used as an image display unit to display a taken image, and is used as a GUI (Graphical User Interface) at the time of various settings. Further, the liquid crystal monitor  16  is used as an electronic viewfinder that displays a live view image (hereafter referred to as “through image”) to confirm the angle of view in an imaging mode. In a case where a 3D video is displayed on the liquid crystal monitor  16 , the display control unit  36  alternately displays the left viewpoint image and right viewpoint image held in the VRAM  52  one pixel by one pixel. By the parallax barrier provided in the liquid crystal monitor  16 , the right and left eyes of the user who observes the monitor from a predetermined distance individually have visual contact with the right and left images that are alternately arrayed one pixel by one pixel. By this means, binocular vision is possible. 
     By the stereoscopic imaging device  10  configured as above, it is possible to realize the above embodiments. Here, although the stereoscopic imaging device  10  explained herein includes two imaging units to take images at two right and left viewpoints, it may be configured to include three or more imaging units and take viewpoint images at three or more points. For example, as illustrated in  FIG. 8 , it may be configured such that, by including four imaging units such as four imaging devices  101 - 1  to  101 - 4 , viewpoint images at four viewpoints are taken. 
     {First Embodiment of 3D Video Reproduction} 
     Next, using the flowchart in  FIG. 13 , an explanation is given to processing of reading a 3D video file recorded as above and performing 3D video reproduction. 
     First, the output display size of a 3D display of the output destination to display a 3D video is acquired (step S 21 ). This output display size can be acquired from an HDMI terminal of the 3D display. Subsequently, GOP_L of a left viewpoint and GOP_R of a right viewpoint are read from the 3D video file, these are held in a cache (step S 22 ), and GOP_L of the left viewpoint and GOP_R of the right viewpoint are added to the cache until the cached amount reaches a predetermined maximum cache amount (step S 23 ). 
     When the cached amount reaches the predetermined maximum cache amount, it is decided whether the reading of GOP_L of all left viewpoints and GOP_R of all right viewpoints in the 3D video file is finished (step S 24 ), and, in a case where the reading is not finished (in the case of “NO”), the GOP maximum display size is read from attached information of GOP_L of the left viewpoint and GOP_R of the right viewpoint, which are to be output to the 3D display, among cached GOP_L of left viewpoints and GOP_R of right viewpoints, and temporarily stored (step S 25 ). Subsequently, the width of the output display size acquired in step S 21  and the width of the GOP maximum display size stored in step S 25  are compared (step S 26 ). 
     When the width of the GOP maximum display size is equal to or greater than the width of the output display size, there is no problem for binocular vision even if GOP_L of the left viewpoint and GOP_R of the right viewpoint are displayed as is, and therefore GOP_L of the left viewpoint and GOP_R of the right viewpoint are output as is to the 3D display (step S 27 ). 
     By contrast, in a case where the width of the output display size is greater than the width of the GOP maximum display size, if GOP_L of the left viewpoint and GOP_R of the right viewpoint with the GOP maximum display size as attached information are displayed, the parallax amount at the maximum parallax position on the distant view side exceeds man&#39;s binocular interval and that part cannot be stereoscopically viewed. Therefore, it is necessary to correct the parallax amount of the right and left viewpoint images. 
     The parallax amount correction is performed by parallax shift (step S 28 ). 
       FIG. 14  is a diagram for explaining the principle of the parallax shift. Also,  FIG. 15A  is a diagram illustrating the left viewpoint image and  FIG. 15B  is a diagram illustrating the right viewpoint image. Here, it is assumed that the left eye of the viewer is on coordinate (0,D) and the right eye of the viewer is on coordinate (XB,D). In the right and left viewpoint images displayed on Z=0, the object displayed on coordinate (XL,0) of the left viewpoint image and coordinate (XR,0) of the right viewpoint image is visually checked as being in coordinate (XP,YP). 
     In this state, as illustrated in  FIG. 15B , if the right viewpoint image is shifted only by XR-XR′ in the left direction, the coordinate of the right viewpoint image of the object becomes (XR′,0) as illustrated in  FIG. 10 , and, as a result, the object is visually checked as being in coordinate (XP′,YP′). 
     Thus, by performing parallax shift, it is possible to adjust the parallax amount. Therefore, in a case where the parallax amount on the distant view side exceeds man&#39;s binocular interval, it is possible to set the parallax amount within the man&#39;s binocular interval by performing parallax shift and appropriately perform binocular vision. 
     To be more specific, when the width of the output display size is W1, the width of the GOP maximum display size is W2 and the GOP maximum parallax amount is P, GOP maximum parallax amount after parallax correction P′ is set to the following equation.
 
 P′={W 2/ W 1}* P   {Equation 1}
 
     Therefore, by performing pixel shift on one or both of the right and left viewpoint images in the approaching direction only by the parallax amount (%) shown in the following equation, the parallax on the 3D display for a 3D video in one GOP can be set within man&#39;s binocular interval.
 
Parallax amount (%)= P−P′   {Equation 2}
 
     Also, parallax correction is not limited to the above parallax shift but may be performed by parallax compression. As explained using  FIG. 10 , the parallax compression can be performed by generating an image at a virtual viewpoint with a smaller parallax amount than right and left viewpoint images and displaying the generated image at the virtual viewpoint. Which way is adopted to correct the parallax amount may be decided in advance or configured such that the user can select it. At least the parallax on the distant view side can be reduced by any parallax amount adjustment. 
     GOP_L of the left viewpoint and GOP_R of the right viewpoint subjected to parallax correction in above step S 28  are output to the 3D display (step S 27 ). 
     Thus, it is possible to always display an appropriate 3D video by: reading the GOP maximum display size recorded as attached information; comparing it with the output display size; outputting GOP_L of the left viewpoint and GOP_R of the right viewpoint as is to the 3D display with an assumption that there is no problem for binocular vision in a case where the GOP maximum display size is larger; and outputting GOP_L of the left viewpoint and GOP_R of the right viewpoint subjected to parallax correction with respect to all frames of GOP_L of the left viewpoint and GOP_R of the right viewpoint with a determination that there is an area in which the binocular vision is impossible in a case where the output display size is larger. 
     In parallel with an output of above GOP_L of the left viewpoint and GOP_R of the right viewpoint to the 3D display, by reading and adding GOP_L of a new left viewpoint and GOP_R of a new right viewpoint into a cache, it is possible to reproduce the 3D video by performing the above processing. 
     In step S 24 , when the reading of GOP_L of all left viewpoints and GOP_R of all right viewpoints in the 3D video is finished (“in the case of YES”), GOP_L of the left viewpoint and GOP_R of the right viewpoint in the cache are output to the 3D display (step S 29 ), and reproduction of the 3D video is ended. Here, even when GOP_L of the left viewpoint and GOP_R of the right viewpoint in the cache are output to the 3D display, the processing in steps S 25  to S 28  is performed. 
     In this embodiment, although the GOP maximum display size recorded in attached information of a 3D video file is used to decide whether the stereoscopic video of each GOP displayed on a 3D display of output destination can be stereoscopically viewed, it is not limited to this and it can be similarly performed even by using the GOP maximum parallax amount. 
     That is, an allowable parallax amount is calculated based on the display size of the 3D display of output destination and a predetermined value (e.g. 50 mm) indicating man&#39;s binocular interval. The allowable parallax amount is expressed by (man&#39;s binocular interval)/(display size) (%), and, in a case where the man&#39;s binocular interval is 50 mm and the display size (i.e. width) is 1300 mm, the allowable parallax amount is 3.85(%). 
     Also, depending on whether the GOP maximum parallax amount (%) is equal to or less than the above allowable parallax amount, it is possible to decide whether a binocular fusion is possible. 
     Also, as another method, it is possible to calculate the image shift amount corresponding to the GOP maximum parallax amount on the 3D display based on both the GOP maximum parallax amount and the display size of the 3D display of output destination, and, depending on whether this calculated image shift amount exceeds a predetermined value indicating man&#39;s binocular interval, decide whether a binocular fusion is possible. 
     Also, in the first embodiment, although parallax correction can be performed every one GOP, it is not limited to this, and the parallax correction may be performed based on the maximum display size and the maximum parallax amount or the like in a predetermined number of GOPs every predetermined number of GOPs set in advance. 
     {Second Embodiment of 3D Video Reproduction} 
       FIG. 16  is a flowchart indicating the second embodiment of 3D video reproduction processing. Here, the same step numbers are assigned to the common parts with the first embodiment illustrated in  FIG. 13  and their detailed explanations are omitted. 
     Although the first embodiment targets a 3D video file in which the GOP maximum display size and the GOP maximum parallax amount are recorded as attached information every one GOP, the second embodiment is different from it in targeting a 3D video file in which the scene maximum display size and the scene maximum parallax amount are recorded as attached information every scene as illustrated in  FIG. 7 . 
     In  FIG. 16 , step S 30  decides whether there is a scene head flag. When the scene head flag is detected (“in the case of YES”), the scene maximum display size is read from the first header of the scene and temporarily stored (step S 31 ). Subsequently, the width of the output display size acquired in step S 21  and the width of the scene maximum display size stored in step S 31  are compared (step S 32 ). 
     In a case where the width of the scene maximum display size is equal to or greater than the width of the output display size, since there is no problem for binocular vision even if the 3D video in the scene is displayed, it is output as is to the 3D display (step S 27 ). 
     By contrast, in a case where the width of the output display size is greater than the width of the scene maximum display size (“in the case of NO” in step S 32 ), the parallax of the 3D video in the scene is corrected such that the parallax of the 3D video in the scene on the 3D display is set within man&#39;s binocular interval. 
     Here, using the scene maximum parallax amount instead of the scene maximum display size, it may be decided whether it is possible to stereoscopically view the 3D video of the scene. 
     {Third Embodiment of 3D Video Reproduction} 
       FIG. 17  is a flowchart illustrating the third embodiment of 3D video reproduction processing. Here, the same step numbers are assigned to the common parts with the first embodiment illustrated in  FIG. 13  and their detailed explanations are omitted. 
     The first embodiment targets a 3D video file in which the GOP maximum display size and the GOP maximum parallax amount are recorded as attached information every one GOP. In contrast, the third embodiment is different from it in targeting a 3D video file in which the GOP maximum display size and the GOP maximum parallax amount are recorded as attached information every one GOP and the scene maximum display size and the scene maximum parallax amount are recorded as attached information every scene as illustrated in  FIG. 7 . 
     In  FIG. 17 , in step S 40 , the GOP maximum parallax amount is read from attached information of cached GOP_L of the left viewpoint and GOP_R of the right viewpoint and temporarily stored. In step S 41 , it is decided whether there is a scene head flag. When the scene head flag is detected (“in the case of YES”), the scene length, the scene maximum display size and the scene maximum parallax amount are read from the first header of the scene and temporarily stored (steps S 42 , S 43  and S 45 ). 
     Subsequently, it is decided whether the scene length stored in step S 42  is sufficiently longer than one GOP (step S 45 ). When it is decided to be shorter (“in the case of NO”), in the same way as in the first embodiment, parallax correction is performed every one GOP (step S 46 ) and GOP_L of the left viewpoint and GOP_R of the right viewpoint subjected to the parallax correction are output to the 3D display (step S 47 ). Here, in a case where the maximum display size in the GOP is equal to or greater than the output display size, they are output as is to the 3D display without performing the parallax correction. 
     Meanwhile, in step  45 , when the scene length is decided to be longer (“in the case of YES”), it returns to step S 22 , and thereafter, through the processing in step S 41  and step S 48 , GOP_L of a left viewpoint and GOP_R of a right viewpoint are cached until it reaches a predetermined maximum cache amount from the scene head. 
     Subsequently, when the cached amount reaches the predetermined maximum cache amount (i.e. when it is decided as “in the case of YES” in step S 48 ), parallax correction with respect to the 3D video in the scene is performed using the following parallax correction tables (step S 49 ). 
       FIG. 18  is a graph illustrating an example of the parallax correction table. In the graph illustrated in  FIG. 18 , the horizontal axis indicates the GOP maximum parallax amount/scene maximum parallax amount, and the vertical axis indicates a parallax correction coefficient (0 to 1). 
     Here, when it is assumed that the ratio of the scene maximum display size stored in step S 43  to the output display size acquired in step S 21  (i.e. scene maximum display size/output display size) is X, the parallax correction coefficient is set to a value that changes from 1 to X as the GOP maximum parallax amount/scene maximum parallax amount approaches 1 from 0. 
     Here, the parallax correction coefficient is multiplied by each GOP maximum parallax amount in the scene. The parallax correction is performed such that each GOP maximum parallax amount in the scene is set to the above multiplied value (i.e. corrected GOP maximum parallax amount). 
     For example, GOP_L of the left viewpoint and GOP_R of the right viewpoint with the GOP maximum parallax amount corresponding to “GOP maximum parallax amount/scene maximum parallax amount=1” as attached information are subjected to parallax shift so as to provide the GOP maximum parallax amount P′ after parallax correction illustrated above in {Equation 1} (i.e. parallax shift by the parallax amount illustrated in {Equation 2}), and, by this means, it is possible to set the parallax of the 3D video in the GOP on the 3D display within man&#39;s binocular interval. 
     Meanwhile, even regarding GOP_L of the left viewpoint and GOP_R of the right viewpoint with the GOP maximum parallax amount less than “GOP maximum parallax amount/scene maximum parallax amount=1,” the parallax correction coefficient is determined such that parallax correction is performed based on the degree of the GOP maximum parallax amount. 
     In step S 49 , by performing the parallax correction using the above parallax correction table, the parallax correction is performed such that the parallax amount is gradually decreased as the maximum parallax amount in each GOP becomes closer to the maximum parallax amount in the scene (i.e. scene maximum parallax amount), while the parallax decrement is reduced (or made closer to the original) as it becomes more distant from the maximum parallax amount in the scene. 
     GOP_L of the left viewpoint and GOP_R of the right viewpoint subjected to parallax correction in above step S 49  are output to the 3D display (step S 47 ). In a case where the scene maximum display size is equal to or greater than the output display size (i.e. in a case where there is no problem in 3D display), the above parallax correction is not performed, and GOP_L of the left viewpoint and GOP_R of the right viewpoint without the parallax correction are output to the 3D display. 
     By the above parallax correction, even if there is a parallax as a problem in 3D display in a partial GOP in a scene, it is possible to prevent other GOP parallaxes from being subjected to parallax correction uniformly, suppress an excessive parallax and ensure the stereoscopic feeling in the whole scene. 
     Also, in the first embodiment to the third embodiment of 3D video reproduction described above, the parallax shift processing may be performed taking into consideration the maximum parallax amount (near view). 
     That is, in a case where the parallax amount on the distant view side becomes excessive and binocular fusion is impossible, when parallax shift is performed by the calculated necessary shift amount, the parallax amount on the near view side accordingly increases. Therefore, the necessary shift amount is added to the product of the display size (i.e. width) of the 3D display of output destination and the maximum parallax amount (near view), and it is decided whether the additional value is equal to or less than a binocular interval (e.g. 50 mm). Here, it is decided that binocular vision is adequately possible in a case where the parallax amount in the near view is 50 mm or less, but, this value of 50 mm may be adequately determined. 
     Subsequently, parallax shift is implemented in a case where the parallax amount is 50 mm or less, and viewpoint images at two viewpoints subjected to the parallax shift are stereoscopically displayed on the 3D display. By contrast, in a case where it is greater than 50 mm, there is a part in which binocular vision is impossible on the distant view side unless parallax shift is performed, and, since appropriate binocular vision on the near view side is not possible if the parallax shift is performed such that the maximum parallax amount on the distant view side becomes appropriate, 2D display is performed on the 3D display instead of 3D display. This 2D display is performed by outputting one of the viewpoint images recorded in the 3D video file to the 3D display. Also, together with the 2D display, warning display may be performed to show that the 3D video is not stereoscopically displayed since the display size is too large. 
     Thus, by adjusting the parallax amount taking into consideration not only the maximum parallax amount (distant view) but also the maximum parallax amount (near view), it is possible to display an appropriate 3D video. 
     {Fourth Embodiment of 3D Video Reproduction} 
     Next, using the flowchart in  FIG. 19 , an explanation is given to processing of: reading a 3D video file in which viewpoint images at three or more viewpoints are recorded as illustrated in  FIG. 9 ; and reproducing and displaying it. 
     In  FIG. 19 , first, the display size (i.e. horizontal width) of a 3D display on which a 3D video is displayed is acquired (step S 51 ). Here, it is assumed that the acquired horizontal width of the display is 600 mm. Also, GOPs for four viewpoints illustrated in  FIG. 9  are read (step S 52 ). 
     Next, the GOP maximum display size is acquired from each of the header areas of the read GOPs in order of the viewpoint number (step S 53 ). 
     Here, it is assumed that the GOP maximum display sizes, assumed visual distances and GOP maximum parallax amounts (distant view) of the GOPs for four viewpoints are as illustrated in Table 1 listed below. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Maximum 
               
               
                   
                   
                   
                 Assumed 
                 parallax 
               
               
                   
                 Viewpoint 
                 Maximum 
                 visual 
                 amount 
               
               
                   
                 number 
                 DSP size 
                 distance 
                 (distance view) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Viewpoint image (1) 
                 1 
                 500 mm 
                 2000 mm 
                 10% 
               
               
                 Viewpoint image (2) 
                 2 
                 1200 mm  
                 4000 mm 
                  4% 
               
               
                 Viewpoint image (3) 
                 3 
                 700 mm 
                 2500 mm 
                  7% 
               
               
                 Viewpoint image (4) 
                 4 
                 500 mm 
                 2000 mm 
                 10% 
               
               
                   
               
            
           
         
       
     
     In the example illustrated in above Table 1, first, the GOP maximum display size, 500 mm, of viewpoint image ( 1 ) with viewpoint number  1  is acquired. 
     Next, it is decided whether this acquired GOP maximum display size is equal to or greater than the display size acquired in step S 51  (step S 54 ). Here, since the GOP maximum display size is 500 mm while the display size is 600 mm, it proceeds to step S 56 . 
     In step S 56 , it is decided whether the GOP maximum display size has been acquired with respect to all viewpoint images. 
     Here, since it has not been finished with respect to all viewpoint images yet, it returns to step S 53 . 
     In step S 53 , the viewpoint number is incremented by one and the GOP maximum display size, 1200 mm, of viewpoint image ( 2 ) with viewpoint number  2  is acquired next. 
     Next, it proceeds to step S 54 , and it is decided whether the acquired GOP maximum display size is equal to or greater than the display size. This time, since the GOP maximum display size is 1200 mm and greater than the display size of 600 mm, it shifts to step S 55 . In step S 55 , the current viewpoint number is acquired. Here, viewpoint number  2  is acquired. 
     Thus, the processing in step S 53  to step S 55  is repeated with respect to all viewpoint images. By this processing, only the viewpoint number of a viewpoint image whose GOP maximum display size is equal to or greater than the display size is acquired. Here, viewpoint number  2  and viewpoint number  3  are acquired. 
     Next, from the viewpoint images of the viewpoint numbers acquired in step S 55 , viewpoint images at two viewpoints to be output to a 3D display are selected (step S 57 ). Here, viewpoint image ( 1 ) as an image at a reference viewpoint and either of the image with viewpoint number  2  (i.e. viewpoint image ( 2 )) or the image with viewpoint number  3  (i.e. viewpoint image ( 3 )) are selected. 
     As a selection criterion, the viewpoint image with the largest parallax amount, the viewpoint image with the smallest parallax amount or the viewpoint image closest to the central viewpoint or the like can be considered. Also, an actual viewpoint image that is actually taken is selected more preferentially than an image at a virtual viewpoint. This criterion may be decided in advance, or a configuration may be employed such that the viewer can freely set it. Here, it is assumed that an image with the largest parallax amount is selected, and, as a result, viewpoint image ( 1 ) and viewpoint image ( 3 ) are selected. 
     The viewpoint images at two viewpoints selected in step S 57  are stereoscopically displayed on the 3D display (step S 58 ). That is, here, 3D display is performed based on viewpoint image ( 1 ) and viewpoint image ( 3 ). 
     Next, it is decided whether the reading of all GOPs from the 3D video file is finished (step S 59 ). In a case where it is not finished (“in the case of NO”), it proceeds to step S 52  and the above processing is repeated, and, in a case where it is finished (“in the case of YES”), reproduction of the 3D video is ended. 
     Here, in a case where there is no viewpoint number acquired in step S 55 , that is, in a case where the GOP maximum display sizes of all viewpoint images are smaller than the display size, 2D display is performed. Although a criterion to select a viewpoint image subjected to 2D display may be adequately determined too, a viewpoint image at an actual viewpoint and reference viewpoint is preferable. 
     Thus, it is possible to always display an appropriate 3D video by reading the GOP maximum display size recorded as the attached information of each viewpoint image, comparing it with the display size of a 3D display of output destination and selecting and displaying a pair of viewpoint images in which the GOP maximum display size is larger. 
     Here, such processing can be performed based on the GOP maximum parallax amount recorded in the attached information of each viewpoint image of the 3D video file. 
     {Fifth Embodiment of 3D Video Reproduction} 
       FIG. 20  is a flowchart in the case of selecting a pair of viewpoint images subjected to 3D reproduction display based on the GOP maximum parallax amount. Here, the same reference numerals are assigned to the common parts with the flowchart illustrated in  FIG. 19  and their detailed explanations are omitted. Also, it is assumed that the GOP maximum display size is not recorded in the attached information of each viewpoint image of the read 3D video file and other attached information is the same as in the file illustrated in Table 1. Also, it is assumed that the horizontal width of a 3D display of output destination is 600 mm. 
     Similar to the case of  FIG. 19 , the display size is acquired (step S 51 ) and GOPs for four viewpoints are read from the 3D video file illustrated in  FIG. 9  (step S 52 ). Next, (a pair of) viewpoint images at two viewpoints are selected from each header area of the read GOPs (step S 61 ). Since combinations of all viewpoint images are finally selected, the selection order may be adequately determined Here, first, it is assumed that viewpoint image ( 1 ) and viewpoint image ( 2 ) are selected. 
     The GOP maximum parallax amount (distant view) for these selected images at two viewpoints is acquired (step S 62 ). The GOP maximum parallax amount (distant view) recorded in the attached information of each viewpoint image is a parallax amount with respect to the reference viewpoint image. Therefore, in a case where the reference viewpoint image is not included in the selected viewpoint images at two viewpoints, it is necessary to calculate the GOP maximum parallax amount again. 
     Here, since one of the selected viewpoint images at two viewpoints is viewpoint image ( 1 ) of the reference viewpoint image, the GOP maximum parallax amount (distant view) recorded in the attached information of viewpoint image ( 2 ) is the GOP maximum parallax amount (distant view) for these two viewpoints. 
     Next, it is decided whether the product of the display width acquired in step S 51  and the GOP maximum parallax amount (distant view) for the viewpoint images at two viewpoints acquired in step S 62  is equal to or less than man&#39;s binocular interval of 50 mm (step S 63 ). Also, the man&#39;s binocular interval is not limited to 50 mm, and, for example, a numerical value of 65 mm can be used. 
     In a case where this product is greater than 50 mm, since it is not possible to stereoscopically view the GOP maximum parallax position on the distant view side in an appropriate manner, it is decided that the combination of the viewpoint images at two viewpoints is not a suitable combination for binocular vision, and it proceeds to step S 65 . 
     Here, the GOP maximum parallax amount (distant view) is 4% and the product of it and the display width of 600 mm is 24 mm Therefore, the condition of 50 mm or less is satisfied and it proceeds to step S 64 . In step S 64 , the viewpoint numbers of these viewpoint images at two viewpoints are acquired. That is, in this case, a combination of viewpoint numbers  1  and  2  is acquired. 
     In step S 65 , it is decided whether the GOP maximum parallax amount has been acquired with respect to all combinations. Here, since it has not been finished for all combinations yet, it returns to step S 61 . 
     In the next step S 61 , (a pair of) different viewpoint images at two viewpoints are selected. Here, it is assumed that viewpoint image ( 2 ) and viewpoint image ( 3 ) are selected as the viewpoint images at two viewpoints. 
     In step S 62 , the GOP maximum parallax amount (distant view) for these two viewpoints is acquired. As described above, since the maximum parallax amount (distant view) recorded in each attached information of viewpoint image ( 2 ) and viewpoint image ( 3 ) is the maximum parallax amount with respect to viewpoint image ( 1 ) of the reference viewpoint image, it is necessary to calculate the GOP maximum parallax amount in two viewpoints of viewpoint image ( 2 ) and viewpoint image ( 3 ) again. 
     The GOP maximum parallax amount in two viewpoints is calculated by the difference between the GOP maximum parallax amounts (distant view) recorded in the respective attached information. Therefore, in this case, 7%−4%=3% is the GOP maximum parallax amount (distant view) in two viewpoints of viewpoint image ( 2 ) and viewpoint image ( 3 ). 
     In step S 63 , it is decided whether the product of this calculated GOP maximum parallax amount (distant view) for the viewpoint images at two viewpoints and the display width is equal to or less than 50 mm. 
     Here, the GOP maximum parallax amount (distant view) is 3%, and the product of it and the display width of 600 mm is 18 mm. Therefore, the condition of 50 mm or less is satisfied and it proceeds to step S 64 . In step S 64 , the viewpoint numbers of these viewpoint images at two viewpoints, that is, a combination of viewpoint numbers  2  and  3  is acquired. 
     Thus, the processing in step S 62  to step S 64  is repeated with respect to all combinations of viewpoint images. By this processing, only the viewpoint numbers in a combination of viewpoint images in which the product of the GOP maximum parallax amount (distant view) and the display size is 50 mm or less is acquired. Here, combinations of viewpoint numbers  1  and  2 , viewpoint numbers  2  and  3 , viewpoint numbers  2  and  4  and viewpoint numbers  3  and  4  are acquired. 
     Next, viewpoint images at two viewpoints to be output to a 3D display is selected from the combinations of viewpoint numbers acquired in step S 64  (step S 57 ). 
     As a selection criterion, as described above, it may give priority to: a combination in which the GOP parallax amount is the largest; a combination in which the GOP parallax amount is the smallest; a combination including a viewpoint image close to the central viewpoint; and an actual viewpoint image. This criterion may be decided in advance, or a configuration may be employed such that the viewer can freely set it. Here, it is assumed that a combination of viewpoint number  2  and viewpoint number  3 , which is a combination in which the parallax amount is the smallest, that is, viewpoint image ( 2 ) and viewpoint image ( 3 ) are selected. 
     The viewpoint images at two viewpoints selected in step S 57  are stereoscopically displayed on a 3D display (step S 58 ). That is, in this case, the 3D display is performed based on viewpoint image ( 2 ) and viewpoint image ( 3 ). 
     Next, it is decided whether the reading of all GOPs from the 3D video file is finished (step S 59 ). In a case where it is not finished (“in the case of NO”), it proceeds to step S 52  and the above processing is repeated, and, in a case where it is finished (i.e. “in the case of YES”), the reproduction of the 3D video is ended. 
     Also, in a case where there is no viewpoint number acquired in step S 64 , that is, in a case where the condition in step S 63  is not satisfied in all combinations, 2D display is performed. Also, a criterion to select an image subjected to 2D display may be adequately determined. 
     Thus, it is possible to always display an appropriate 3D video by reading the GOP maximum parallax amount (distant view) recorded as the attached information of each viewpoint image, calculating the product of it and the display size of a 3D display of output destination and selecting and displaying a combination of viewpoint images in which the product is smaller than man&#39;s binocular interval. 
     {Sixth Embodiment of 3D Video Reproduction} 
     As explained in the fourth embodiment, in a case where a display image is selected based on the GOP maximum display size recorded in the attached information of each viewpoint image, the image can be selected only by a combination with a reference viewpoint image. By contrast with this, as explained in the fifth embodiment, in a case where a viewpoint image is selected based on the GOP maximum parallax amount (distant view) recorded in the attached information of each viewpoint image, a decision can be made on combinations of all viewpoint images but the processing becomes complicated. 
     Therefore, in the sixth embodiment, in a case where both the GOP maximum display size and the GOP maximum parallax amount (distant view) are recorded in attached information, a viewpoint image is selected using the both information. 
       FIG. 21  is a flowchart illustrating a case where a viewpoint image is selected based on the GOP maximum display size and the GOP maximum parallax amount (distant view). Here, the same reference numerals are assigned to the common parts with the flowcharts illustrated in  FIG. 19  and  FIG. 20 , and their detailed explanations are omitted. 
     As illustrated in  FIG. 21 , first, similar to the case of  FIG. 19 , a viewpoint image that can be stereoscopically displayed is selected based on the GOP maximum display size (steps S 53  to S 56 ). 
     After that, similar to the case of  FIG. 20 , a viewpoint image that can be stereoscopically displayed is selected based on the GOP maximum parallax amount (distant view) (steps S 61  to S 65 ). Here, at this time, it is not necessary to perform processing on a combination with the reference viewpoint image. 
     After that, viewpoint images at two viewpoints to be output to the 3D display are selected from the combination with the reference viewpoint image acquired in step S 55  and the combination of viewpoint images at two viewpoints acquired in step S 64  (step S 57 ). A selection criterion may be adequately determined in the same way as above. 
     As described above, by selecting viewpoint images at two viewpoints displayed based on the GOP maximum display size and the GOP maximum parallax amount (distant view), it is possible to shorten the processing time while performing 3D display using appropriate viewpoint images selected from all combinations. 
     Here, viewpoint images at two viewpoints to be displayed are selected based on only the GOP maximum parallax amount on the distant view side, it may be determined in consideration of the GOP maximum parallax amount on the near view side. By taking into consideration the GOP maximum parallax amount on the near view side, it is possible to determine a combination of images that can be stereoscopically viewed in an appropriate manner on not only the distant view side but also the near view side. 
     For example, from the combinations of viewpoint images at two viewpoints acquired in step S 64 , it is possible to select a combination in which the parallax amount in the near view is equal to or less than a predetermined value. This is because, when the parallax amount on the near view side increases, the viewer feels fatigued for binocular vision and therefore it is preferable to be equal to or less than a value such as 50 mm. 
     In a case where the GOP maximum parallax amount on the near view side is recorded in a 3D video file, the value can be used. Also, as explained using  FIG. 10 , it is possible to extract the feature point from each viewpoint image and calculate it from the maximum parallax amount position on the near view side. 
     {Seventh Embodiment of 3D Video Reproduction} 
       FIG. 22  is a flowchart illustrating image reproduction processing according to the seventh embodiment. 
     Here, it is assumed that a read 3D video file is similar to the file illustrated in Table 1. Also, it is assumed that the horizontal width of a display is 1300 mm. 
     Similar to the case of  FIG. 19 , the display size of the 3D display of output destination is acquired (step S 51 ). For example, it is possible to acquire the display size from the 3D display connected by an HDMI cable. 
     Next, GOPs for four viewpoints are read from the 3D video file illustrated in  FIG. 9  (step S 52 ) and the value of the reference viewpoint number tag is read from each header area of the read GOPs (step S 71 ). In the present embodiment, reference viewpoint number  1  is read. 
     Next, the GOP maximum display size is acquired from attached information of the viewpoint image of reference viewpoint number  1 , that is, viewpoint image ( 1 ) (step S 72 ). As described above, the value recorded herein is the GOP maximum display size in a viewpoint combination with viewpoint image ( 1 ) in which the parallax amount is maximum, specifically, it is the GOP maximum display size in a combination with viewpoint image ( 4 ). 
     This GOP maximum display size and the display size acquired in step S 71  are compared (step S 73 ). In a case where the GOP maximum display size is larger than the display size (“in the case of YES”), since there is no problem if viewpoint image ( 1 ) and viewpoint image ( 4 ) are stereoscopically displayed as is, these viewpoint images at two viewpoints are stereoscopically displayed on a 3D display (step S 74 ). 
     By contrast, in a case where the comparison result in step S 73  is “NO,” it proceeds to step S 75 . 
     In step S 75 , the viewpoint numbers of all read viewpoint images are acquired. Further, from the attached information of each viewpoint image, the value of the GOP maximum parallax amount of each viewpoint image is acquired (step S 76 ). As illustrated in Table 1, the GOP maximum parallax amount of 4% is acquired from viewpoint image ( 2 ), the GOP maximum parallax amount of 7% is acquired from viewpoint image ( 3 ) and the GOP maximum parallax amount of 10% is acquired from viewpoint image ( 4 ). 
     Next, the allowable parallax amount in the 3D display on which 3D display is performed is calculated (step S 77 ). The allowable parallax amount is calculated by following {Equation 3}. Here, the display size indicates the horizontal width of the display. Also, although man&#39;s binocular interval is 50 mm in this case, other numeral values may be used.
 
Allowable parallax amount [%]=50 mm÷display size [mm]×100  {Equation 3}
 
     In the present embodiment, since the display size is 1300 mm, the allowable parallax amount is 3.85%. 
     Next, arrangement of a reference viewpoint is confirmed (step S 78 ). In a case where the reference viewpoint is not around the center of all viewpoints, a viewpoint position around the center is set to a new reference viewpoint (step S 79 ), and the maximum parallax amount of each viewpoint image with respect to the new reference viewpoint is calculated (step S 80 ). 
     In the present embodiment, since the viewpoint numbers are as illustrated in  FIG. 8 , viewpoint number  1  of the reference viewpoint is not around the center. Therefore, in this case, viewpoint number  2  is set to a new reference viewpoint as a viewpoint around the center. 
     The GOP maximum parallax amount of each viewpoint image with respect to viewpoint number  2  corresponding to this new reference viewpoint is calculated. In the 3D video file example in Table 1, the absolute value of the difference between the GOP maximum parallax amount described in the attached information of each viewpoint image and the GOP maximum parallax amount described in the attached information of viewpoint image ( 2 ), is the GOP maximum parallax amount in the new reference viewpoint. Therefore, the GOP maximum parallax amount of each viewpoint image is as follows.
 
GOP maximum parallax amount of viewpoint image (1)=|0%−4%|=4%
 
GOP maximum parallax amount of viewpoint image (2)=|4%−4%|=0%
 
GOP maximum parallax amount of viewpoint image (3)=|7%−4%|=3%
 
GOP maximum parallax amount of viewpoint image (4)=|10%−4%|=6%
 
     Here, such processing is performed because a viewpoint image arranged closer to the center is suitable for 3D display. 
     In a case where the processing in step S 80  is finished or it is decided in step S 78  that the reference viewpoint is around the center of all viewpoints, a viewpoint with the maximum value equal to or less than the allowable parallax amount is selected from these GOP maximum parallax amounts (step S 81 ). In the present embodiment, since the allowable parallax amount is 3.85% or less, a viewpoint satisfying this condition is viewpoint number  3 . 
     Thus, in a case where a viewpoint satisfying the condition can be selected (step S 82 ), 3D display is performed using the reference viewpoint image and the selected viewpoint image (step S 83 ). In a case where it cannot be selected (“in the case of NO” in step S 82 ), 2D display is performed (step S 84 ). 
     For example, if the acquired display size is 1700 mm, the allowable parallax amount is 2.94%, and it is not possible to select a viewpoint having the largest maximum parallax amount value equal to or less than the allowable parallax amount. In this case, 2D display is performed. 
     Thus, since a pair of viewpoint images is selected based on the allowable parallax amount, it is possible to select viewpoint images suitable for binocular vision in an appropriate manner. 
     Next, it is decided whether the reading of all GOPs from the 3D video file is finished (step S 85 ). In a case where it is not finished (“in the case of NO”), it proceeds to step S 52  and the above processing is repeated, and, in a case where it is finished (“in the case of YES”), the reproduction of the 3D video is ended. 
     Also, in a case where it is decided in step S 82  that the selection is not possible, instead of performing 2D display, 3D display may be performed after performing parallax shift or parallax compression for adjustment to an appropriate parallax amount. Also, in the fourth to seventh embodiments of 3D video reproduction, although parallax correction is performed every one GOP, it is not limited to this, and parallax correction may be performed every scene using the scene maximum display size and the scene maximum parallax amount. 
     {Stereoscopic Video Reproduction Device} 
     The above first to seventh embodiments of 3D video reproduction may be realized by the 3D video reproduction function of the stereoscopic imaging device  10  illustrated in  FIG. 11A ,  FIG. 11B , and  FIG. 12 , or may be realized by a stereoscopic video reproduction device that does not have an imaging unit. 
       FIG. 23  is a diagram illustrating the whole structure of a stereoscopic video reproduction device  300  and 3D display  320 . As illustrated in the figure, the stereoscopic video reproduction device  300  and the 3D display  320  are devices that are separately provided, and are connected by a communication cable  310  such that communication is possible. 
     The 3D display  320  is a display of a parallax barrier system or lenticular system, and alternately displays the left viewpoint image and right viewpoint image input from the stereoscopic video reproduction device  300  to the 3D display  320  every one line. 
     Also, the 3D display  320  may alternately switches the left viewpoint image and the right viewpoint image in a temporal manner and displays them. In this case, the viewer visually checks the 3D display  320  using special glasses. 
       FIG. 24  is a block diagram illustrating an internal structure of the stereoscopic video reproduction device  300 . As illustrated in the figure, the stereoscopic video reproduction device  300  includes a CPU  301 , a record control unit  305 , a memory card  306 , a display control unit  307  and a communication interface  308 . 
     The CPU  301  performs integration control on the whole operation of the stereoscopic video reproduction device  300  based on a control program such as a stereoscopic video reproduction program recorded in a computer-readable recording medium (“non-transitory computer-readable medium”) such as a ROM  302 . 
     A RAM  303  is used as a computation work area of the CPU  301 . A RAM  303  is used as a computation work area of the CPU  301 . 
     The record control unit  305  and the display control unit  307  are connected to the CPU  301  through a bus  304 . The record control unit  305  controls the reading and writing of 3D video file data with respect to the memory card  306 . For example, the memory card  306  is the same as the memory card  40  of the stereoscopic imaging device  10  illustrated in  FIG. 12 , and records a 3D video file including the attached information of each viewpoint image taken in the stereoscopic imaging device  10 . 
     The communication interface  308  is a connector unit to which a communication cable  310  is connected, and the display control unit  307  displays a 3D video on the 3D display  320  through these. As the communication interface  308  and the communication cable  310 , the ones of the HDMI standard may be adopted. According to the HDMI standard, the stereoscopic video reproduction device  300  can acquire the display size of the 3D display  320  connected through the communication cable  310 . 
     Here, the stereoscopic video reproduction device  300  may be configured to: include a compound eye imaging unit to take each viewpoint image; and record the taken viewpoint image in the memory card  306 . Also, the stereoscopic video reproduction device  300  and the 3D display  320  may be formed as an integral device. Also, a stereoscopic video reproduction program may be installed in a personal computer so as to cause the personal computer to function as the stereoscopic video reproduction device  300 . 
     Further, it is needless to say that the present invention is not limited to the above embodiments and various changes are possible without departing from the spirit of the present invention.