Patent Publication Number: US-2011052138-A1

Title: Image recording device, camera, image reproduction device, image recording method, image reproduction method, program, and integrated circuit

Description:
TECHNICAL FIELD 
     The present invention relates to an image recording device which records images, and an image reproduction device which reproduces the recorded images. 
     BACKGROUND ART 
     Image recording devices such as camcorders include imaging devices such as Charge Coupled Devices (CCD), transfer images generated by the imaging devices, code the images, and records the coded images. When the image recording device performs high-speed capturing, it is necessary to speed up image transfer speed from the imaging device, coding speed, and image recording process. This causes a problem of increased cost for the image recording device. In order to solve this problem, an image recording device which performs high-speed capturing without speeding up the image transfer speed from the imaging device, coding speed and image recording process has been proposed (for example, see Patent Literature 1). 
       FIG. 19  illustrates the image recording device according to Patent Literature 1. 
     When capturing at normal speed, the image recording device transfers the frames  1  and  2  from an imaging device at a predetermined frame rate, codes the frames, and records the coded frames  1  and  2 . On the other hand, when capturing at high speed, the image recording device changes the size of the frames  1  to  4  to a size of sub screen, divide the screen and multiplex the frames, and records the image generated by the division and multiplexing as a regular image. More specifically, when capturing at 4× speed, the size of the frames  1  to  4  that are captured at high speed are changed to the size of sub screen which is one quarter in size, divides and multiplexes four successive ¼ sized sub screens into one image, and records the one image as a regular image. This allows high-speed capturing without speeding up image transfer speed from the imaging device, coding process speed, and image recording process. [Patent Literature 1] Japanese Patent No. 2718409 
     DISCLOSURE OF INVENTION 
     Problems that Invention is to Solve 
     However, the image recording device according to Patent Literature 1 records the frames after reducing their size, which causes a problem of lowered resolution and degradation in image quality. 
     The present invention has been conceived to solve the problem, and it is an object of the present invention to provide an image recording device that can lower image transfer speed from the imaging device, coding speed, and image recording speed that are necessary for high-speed capturing, and an image reproduction device. 
     Means to Solve the Problems 
     An image recording device according to the present invention is An image recording device which records an input image, the image recording device including: an image generating unit which generates the input image based on input electric signal; an image transforming unit which generates a group of first frames which can be independently reproduced, by extracting frames at a predetermined time interval from frames included in the input image generated by the image generating unit and by arranging, in chronological order, the extracted frames, and generates a group of second frames using frames that are not in the group of first frames but are in the frames included in the input image; an image coding unit which (i) codes the group of first frames generated by the image transforming unit and outputs a first stream, and (ii) codes the group of second frames generated by the image transforming unit and outputs a second stream; and a recording unit which records the first stream and the second stream coded by the image coding unit on a recording medium. With this, regular reproduction can be performed by decoding and reproducing only the first stream, and slow reproduction can be performed by decoding both the first stream and the second stream and reproducing the first and second streams. 
     In addition, the image transforming unit may arrange, in chronological order, synthesized frames to generate the group of second frames, each of the synthesized frames being synthesized from pixels extracted from different regions of frames that are between temporally adjacent frames of the group of first frames. With this, the first stream (main stream) at high resolution and the second stream (sub stream) at low resolution are recorded. This allows the reproduction of the high-resolution main stream at the time of regular reproduction, and reconstruction of a clear image using the high-resolution main stream and the low-resolution sub stream and reproduction of the reconstructed stream at the time of slow reproduction. 
     In addition, the image transforming unit may synthesize each of the synthesized files from pixels that are not skipped when skipping pixels in the frames at least one of per line and per column. As such, simply skipping pixels per line and/or per column allows transforming the frames other than the frames at the predetermined time interval into the synthesized frames. 
     In addition, the input image is a progressive image. Although the present invention is applicable to both progressive images and interlaced images, the embodiment described above is particularly effective for the progressive images. 
     In addition, the image transforming unit may (i) extract N frames for each N frames from the frames, where N being a natural number, to synthesize each of first synthesized frames from the N frames that are temporally successive, and arrange, in chronological order, the first synthesized frames to generate the group of first frames, and (ii) synthesize each of second synthesized frames from N temporally successive frames among frames that are not in the group of first frames but are in the frames included in the input image, and arrange, in chronological order, the second synthesized frames to generate the group of second frames. This also allows reducing the image transfer speed from the imaging device, coding speed, and image recording speed that are necessary for capturing at high speed without degrading image quality significantly. 
     In addition, the input image may be an interlaced image. Although the present invention is applicable to both progressive images and interlaced images, the embodiment described above is particularly effective for the interlaced images. 
     In addition, the group of first frames and the group of second frames may have an identical screen size and an identical frame rate. With this, it is possible to record the streams of the same coding format on the recording medium. 
     A camera according to the present invention includes the image recording device described above and an imaging unit configured to convert light into electric signals and output the electric signals to the image generating unit. 
     In addition, the image transforming unit may arrange, in chronological order, synthesized frames to generate the group of second frames, each of the synthesized frames being synthesized from pixels extracted from different regions of frames that are between temporally adjacent frames of the group of first frames. 
     In addition, the camera may further include a read-out control unit which controls the imaging unit to extract only electric signals corresponding to pixels composing the synthesized frame, from each of frames that are not in the group of first frames but are in the frames included in the input image. This reduces the pixel to be read for generating each of the frames, thereby reducing the image transfer speed from the imaging unit. 
     An image reproduction device according to the present invention is an image reproduction device which reproduces the image recorded by the image recording device described above, the image reproduction device including: a reproduction mode specifying unit which specifies either regular reproduction or slow reproduction as a reproduction mode; a read-out unit which reads a stream from the recording medium; a decoding unit which decodes the stream read by the read-out unit; and an image reconstructuring unit which reproduces a group of frames decoded by the decoding unit, in which, when the reproduction mode specifying unit specifies regular reproduction, the read-out unit reads the first stream recorded on the recording medium, the decoding unit decodes the first stream read by the read-out unit, and the image reconstructuring unit reproduces the group of first frames decoded by the decoding unit without any change, and when the reproduction mode specifying unit specifies slow reproduction, the read-out unit reads both the first stream and the second stream recorded on the recording medium, the decoding unit separately decodes the first stream and the second stream that are read by the read-out unit, and the image reconstructing unit arranges, in chronological order, the frames included in the group of first frames and the group of second frames that are decoded by the decoding unit, and reproduces the arranged frames. 
     An image recording method according to the present invention is an image recording method for recording an input image, the image recording method including: generating the input image based on input electric signal; generating a group of first frames which can be independently reproduced, by extracting frames at a predetermined time interval from frames included in the input image generated by the image generating unit and by arranging, in chronological order, the extracted frames, and generating a group of second frames using frames that are not in the group of first frames but are in the frames included in the input image; (i) coding the group of first frames generated by the image transforming unit and outputting a first stream, and (ii) coding the group of second frames generated in the generating, and outputting a second stream; and recording the first stream and the second stream coded in the generating on a recording medium. 
     An image reproduction method according to the present invention is an image reproduction method for reproducing the image recorded by the image recording device described above, the image reproduction method including: specifying either regular reproduction or slow reproduction as a reproduction mode; reading a stream from the recording medium; decoding the stream read in the reading; and reproducing a group of frames decoded in the decoding, in which, when regular reproduction is specified in the specifying, the first stream recorded on the recording medium is read, the first stream read in the reading is decoded, the group of first frames decoded in the decoding is reproduced without any change, and when slow reproduction is specified in the specifying, both the first stream and the second stream recorded on the recording medium are read, the first stream and the second stream that are read by the read-out unit are decoded separately, and the frames included in the group of first frames and the group of second frames that are decoded in the decoding are arranged in chronological order and the arranged frames are reproduced. 
     A program according to the present invention is a program causing a computer to record an input image, the program causing the computer to execute: generating the input image based on input electric signal; generating a group of first frames which can be independently reproduced, by extracting frames at a predetermined time interval from frames included in the input image generated by the image generating unit and by arranging, in chronological order, the extracted frames, and generating a group of second frames using frames that are not in the group of first frames but are in the frames included in the input image; (i) coding the group of first frames generated by the image transforming unit and outputting a first stream, and (ii) coding the group of second frames generated in the generating, and outputting a second stream; and recording the first stream and the second stream coded in the generating on a recording medium. 
     A program according to the present invention is a program causing a computer to reproduce the image recorded by the image recording device described above, the program causing the computer to execute: specifying either regular reproduction or slow reproduction as a reproduction mode; reading a stream from the recording medium; decoding the stream read in the reading; and reproducing a group of frames decoded in the decoding, in which, when regular reproduction is specified in the specifying, the first stream recorded on the recording medium is read, the first stream read in the reading is decoded, the group of first frames decoded in the decoding is reproduced without any change, and when slow reproduction is specified in the specifying, both the first stream and the second stream recorded on the recording medium are read, the first stream and the second stream that are read by the read-out unit are decoded separately, and the frames included in the group of first frames and the group of second frames that are decoded in the decoding are arranged in chronological order and the arranged frames are reproduced. 
     An integrated circuit according to the present invention is an integrated circuit which codes an input image, the integrated circuit including: an image transforming unit which generates a group of first frames which can be independently reproduced, by extracting frames at a predetermined time interval from frames included in the input image and by arranging, in chronological order, the extracted frames, and to generate a group of second frames using frames that are not in the group of first frames but are in the frames included in the input image; an image coding unit which (i) codes the group of first frames generated by the image transforming unit and outputs a first stream, and (ii) codes the group of second frames generated by the image transforming unit and outputs a second stream. 
     An integrated circuit according to the present invention is an integrated circuit which reproduces the image recorded by the image recording device described above, the integrated circuit including: a decoding unit which decodes an input stream; and an image reconstructuring unit which reproduces a group of frames decoded by the decoding unit, in which, when regular reproduction is specified upon input of the first stream recorded on the recording medium, the decoding unit decodes the first stream read by the read-out unit, the image reconstructuring unit reproduces the group of first frames decoded by the decoding unit without any change, and when slow reproduction is specified upon input of the first stream and a second stream that are recorded on the recording medium, the decoding unit separately decodes the first stream and the second stream that are read by the read-out unit, and the image reconstructing unit arranges, in chronological order, the frames included in the group of first frames and the group of second frames that are decoded by the decoding unit, and reproduces the arranged frames. 
     Note that, the present invention can be implemented not only as an image recording device and an image reproduction device, but also as an integrated circuit which implements the function of the image recording device and the image reproduction device, and as a program which causes a computer to execute the functions. Needless to say, such a program can be distributed via a recording medium such as CD-ROM and a transmission medium such as the Internet. 
     EFFECTS OF THE INVENTION 
     As described above, according to the present invention, the input image is divided into first and second streams and recorded on a recording medium. Thus, it is possible to implement an image recording device which lowers the image transfer speed from the imaging device, the coding speed, and the image recording speed that are necessary for high-speed capturing without significantly degrading image quality. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  illustrates the overview of an image recording device according to the first embodiment of the present invention. 
         FIG. 1B  illustrates the overview of an image reproduction device according to the first embodiment of the present invention. 
         FIG. 2  is a block diagram of the image recording device according to the first embodiment of the present invention. 
         FIG. 3  illustrates an image transform method according to the first embodiment of the present invention. 
         FIG. 4  illustrates an image transform procedure according to the first embodiment of the present invention. 
         FIG. 5  is a block diagram of the image reproduction device according to the first embodiment of the present invention. 
         FIG. 6  illustrates an image reconstruction method according to the first embodiment of the present invention. 
         FIG. 7  is a flowchart illustrating an image reconstruction procedure according to the first embodiment of the present invention. 
         FIG. 8  illustrates an image transform method according to the second embodiment of the present invention. 
         FIG. 9  illustrates an image reconstruction method according to the second embodiment of the present invention. 
         FIG. 10  illustrates an image transform method according to the third embodiment of the present invention. 
         FIG. 11  illustrates an image reconstruction method according to the third embodiment of the present invention. 
         FIG. 12  illustrates an image transform method according to the fourth embodiment of the present invention. 
         FIG. 13  illustrates an image reconstruction method according to the fourth embodiment of the present invention. 
         FIG. 14  is a block diagram of the image recording device according to the fifth embodiment of the present invention. 
         FIG. 15  is a block diagram of the image recording device according to the sixth embodiment of the present invention. 
         FIG. 16  illustrates an example of skipping pixels according to the present invention. 
         FIG. 17  illustrates an example of image recording integrated circuit according to an embodiment of the present invention. 
         FIG. 18  illustrates an example of image reproduction integrated circuit according to an embodiment of the present invention. 
         FIG. 19  is a diagram for explaining an image recording device according to Patent Literature 1. 
     
    
    
     NUMERICAL REFERENCES 
     
         
           100  Image recording device 
           110  Imaging device 
           120  Image generating unit 
           130  Image transforming unit 
           140  Image coding unit 
           141 ,  142  H.264 image coding unit 
           150  Recording unit 
           160  Read-out control unit 
           170 ,  250  LSI 
           200  Image reproduction device 
           210  Reproduction mode specifying unit 
           220  Image decoding unit 
           230  Read-out unit 
           240  Image reconstructing unit 
           300  Recording medium 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following describes embodiments of the present invention in detail with reference to the drawings. 
     First Embodiment 
       FIGS. 1A and 1B  illustrate overviews of an image recording device  100  and an image reproduction device  200  according to the first embodiment of the present invention, respectively. For example, the image recording device  100  is applicable to a video camera which records captured images on a Digital Versatile Disc (DVD) or a Blu-ray Disc (BD). Furthermore, the image reproduction device  200  is applicable to a DVD player which reads the images recorded on the recording medium and reproduces the images, as illustrated in  FIG. 1B . Note that, the video camera illustrated in  FIG. 1A  may include the image recording device  100  and the image reproduction device  200 . 
       FIG. 2  is a block diagram of the image recording device  100  according to the first embodiment of the present invention. 
     The image recording device  100  records images, and in terms of the function, includes an imaging device  110 , an image generating unit  120 , an image transforming unit  130 , an image coding unit  140 , and a recording unit  150 , as illustrated in  FIG. 2 . Note that, the image recording device  100  of the present invention may include an input terminal which inputs the electric signal which is a source of an input image from outside. 
     The imaging device  110  converts incident light into electric signal and outputs the electric signal. The image generating unit  120  generates the input image based on the electric signal converted by the imaging device  110 . The generated image is an image with a distinction between angles of view and interlace/progressive, such as 1920×1080 progressive, 1920×1080 interlaced, and 1280×720 progressive. 
     The image transforming unit  130  transforms frames at a predetermined interval (for example, intervals at the time of capturing at regular speed) into frames at the first resolution, among the frames included in the input image generated by the image generating unit  120  and outputs the transformed frames. Furthermore, the image transforming unit  130  transforms frames other than the frames at the predetermined interval (for example, intervals at the time of capturing at regular speed) among the frames included in an input image generated by the image generating unit  120  into frames at second resolution, and outputs synthesized frames that are obtained by synthesizing the frames at second resolution. The second resolution is lower than the first resolution. When the frames at the first resolution are arranged in chronological order, a group of first frames that can be independently reproduced is generated. On the other hand, when the synthesized frames are arranged in chronological order, a group of second frames is generated. 
     The image transforming unit  130  may output the input image without any change. For example, in the first embodiment, the frames at the predetermined time interval (for example, the interval at the time of capturing at regular speed) are output as originally input, without changing the resolution. 
     The image coding unit  140  codes the group of first frames output from the image transforming unit  130  and outputs the first stream (hereafter also referred to as “main stream” or “stream A”), and codes the group of second frames output from the image transforming unit  130  and outputs the second stream (hereafter also referred to as “sub stream” or “stream B”. Although the coding method is not particularly limited, coding methods such as H.264/AVC are used. The recording unit  150  records the stream A and stream B output from the image coding unit  140  on a recording medium  300  such as DVD and BD. 
       FIG. 3  illustrates an image transforming method according to the first embodiment of the present invention. 
     Here, a case where the imaging device  110  and the image generating unit  120  generate input frames G 0 , G 1 , G 2  . . . G 13 , G 14 , G 15  . . . shall be described (see  FIG. 4 , S 11  and S 12 ). The input image is a progressive image of 1280×720, and when 300 images are generated per second, it is denoted as 1280×720/300p. 
     First, the image transforming unit  130  transforms the input frames G 0 , G 1 , G 2  . . . G 13 , G 14 , G 15  . . . ( FIG. 4 , S 13 ). Here, among the input frames G 0 , G 1 , G 2  . . . G 13 , G 14 , G 15  . . . , the input frames G 0 , G 5 , G 10 , G 15  . . . are frames at the time intervals at the time of capturing at regular speed, and the input frames G 1 , G 2 , G 3 , G 4 , G 6 , G 7 , G 8 , G 9  . . . are frames other than the frames at the time intervals at the time of capturing at regular speed. 
     Thus, the image transforming unit  130  outputs the group of first frames A 0 , A 1 , A 2 , A 3  . . . , without transforming the input frames G 0 , G 5 , G 10 , G 15  . . . Furthermore, the image transforming unit  130  synthesizes the input frames G 1 , G 2 , G 3 , G 4 , G 6 , G 7 , G 8 , G 9  . . . , and outputs the synthesized frames as the synthesized frames B 0 , B 1 , B 2 , B 3  . . . , constituting the group of second frames. 
     More specifically, the pixel lines  0 ,  4 ,  8  . . . of the input frame G 1 , the pixel lines  1 ,  5 ,  9  . . . of the input frame G 2 , the pixel lines  2 ,  6 ,  10  . . . of the input frame G 3 , and the pixel lines  3 ,  7 ,  11  . . . of the input frame G 4  are used for generating a synthesized frame B 0 . Furthermore, the pixel lines  0 ,  4 ,  8  . . . of the input frame G 6 , the pixel lines  1 ,  5 ,  9  . . . of the input frame G 7 , the pixel lines  2 ,  6 ,  10  . . . of the input frame G 8 , and the pixel lines  3 ,  7 ,  11  . . . of the input frame G 9  are used for generating a synthesized frame B 1 . Synthesized frames B 2 , B 3  . . . are generated in the same manner. 
     Here, the group of first frames A 0 , A 1 , A 2 , A 3  . . . , and the group of second frames B 0 , B 1 , B 2 , B 3  . . . are both moving pictures of 1280×720/60p. In other words, the frame size and the frame rate of the group of first frames and the group of second frames are identical. 
     Subsequently, the image coding unit  140  codes the moving picture generated by the image transforming unit  130  ( FIG. 4 , S 14 ). More specifically, the group of first frames A 0 , A 1 , A 2 , A 3  . . . is coded as one moving picture to generate the stream A. Furthermore, the group of second frames B 0 , B 1 , B 2 , B 3  . . . is also coded as one moving picture to generate the stream B. 
     Finally, the recording unit  150  records the stream A and stream B generated by the image coding unit  140  on the recording medium  300  ( FIG. 4 , S 15 ). 
       FIG. 5  is a block diagram of the image reproduction device  200  according to the first embodiment of the present invention. 
     The image reproduction device  200  according to the first embodiment of the present invention reproduces images, and in terms of function, includes a reproduction mode specifying unit  210 , an image decoding unit  220 , a read-out unit  230 , and an image reconstructing unit  240 , as illustrated in  FIG. 5 . Here, the description shall be made for a case where the stream A and stream B at 1280×720/60p generated by the image recording device  100  are recorded on the recording medium  300 . 
     The reproduction mode specifying unit  210  specifies either regular reproduction or slow reproduction as a reproduction mode. When the regular reproduction is specified by the reproduction mode specifying unit  210 , the read-out unit  230  reads the stream A recorded on the recording medium  300 . On the other hand, when slow reproduction is specified by the reproduction mode specifying unit  210 , the read-out unit  230  reads the stream A and stream B recorded on the recording medium  300 . 
     When regular reproduction is specified by the reproduction mode specifying unit  210 , the image decoding unit  220  decodes the stream A read by the read-out unit  230 . On the other hand, when slow reproduction is specified by the reproduction mode specifying unit  210 , the image decoding unit  220  decodes the stream A and stream B read by the read-out unit  230 . 
     When regular reproduction is specified by the reproduction mode specifying unit  210 , the image reconstructing unit  240  reproduces the stream A decoded by the image decoding unit  220  without any change to generate the regular reproduction image. On the other hand, when slow reproduction is specified by the reproduction mode specifying unit  210 , the image reconstructuring unit  240  reconstructs images with the same angles of view and frame counts as the input image using the stream A and stream B decoded by the image decoding unit  220 , reproduces the reconstructed image to generate the slow reproduction video. In other words, the groups of first frames and second frames that are obtained by decoding the stream A and stream B, respectively, are rearranged in chronological order and reproduced. 
       FIG. 6  illustrates an image reconstructuring method according to the first embodiment of the present invention. 
     Here, it is assumed that the reproduction mode specifying unit  210  specifies slow reproduction. When the slow reproduction is specified, the stream A and stream B illustrated in  FIG. 3  are read from the recording medium  300  by the read-out unit  230 , decoded by the image decoding unit  220 , and reconstructed by the image reconstructing unit  240  as described below ( FIG. 7 , S 21  to S 22  to S 26  to S 27  to S 28 ). 
     First, the image reconstructing unit  240  determines the group of first frames A 0 , A 1 , A 2  . . . that are obtained by decoding the stream A as the output frames g 0 , g 5 , g 10  . . . without any change. Furthermore, the image reconstructing unit  240  separates the synthesized frame B 0  obtained by decoding the stream B, arranges the pixel lines in chronological order of recording to generate intermediate frames b 0 - 0 , b 0 - 1 , b 0 - 2 , and b 0 - 3 . The intermediate frame b 0 - 0  is generated by the pixel lines  0 ,  4 ,  8  . . . of the synthesized frame B 0 , the intermediate frame b 0 - 1  is generated by the pixel lines  1 ,  5 ,  9  . . . of the synthesized frame B 0 , the intermediate frame b 0 - 2  is generated by the pixel lines  2 ,  6 ,  10  . . . of the synthesized frame B 0 , and the intermediate frame b 0 - 3  is generated by the pixel lines  3 ,  7 ,  11  and so on. 
     Furthermore, the image reconstructing unit  240  generates pixels that were skipped at the time of recording the image using the four intermediate frames b 0 - 0 , b 0 - 1 , b 0 - 2  b 0 - 3  and the group of first frames A 0  and A 1 , using interpolation of the pixels and super resolution technology and others. The intermediate frames b 1 - 0 , b 1 - 1 , b 1 - 2 , b 1 - 3  are generated from the synthesized frame B 1  in the same manner, and the output frames g 6 , g 7 , g 8 , and g 9  are reconstructed from the intermediate frames and the group of first frames A 1  and A 2  to reconstruct the output frames g 6 , g 7 , g 8 , and g 9 . The output frames g 11 , g 12  . . . are reconstructed in the same manner. 
     The output frames g 0 , g 1 , g 2 , g 3  . . . are arranged in chronological order to generate the image with 1280×720 pixels; in addition, it is the video captured at high speed with 300 frames per second. When 60 frames of the video is displayed per second, a ⅕ slow reproduction image is reproduced. The slow reproduction image is clear and smooth. 
     Note that, when regular reproduction is specified by the reproduction mode specifying unit  210 , the stream A recorded on the recording medium  300  is read by the read-out unit  230 , decoded by the image decoding unit  220 , and reproduced by the image reconstructing unit  240  without any change, thereby generating a regular reproduction video ( FIG. 7 , S 21  to S 22  to S 23  to S 24  to S 25 ). 
     As such, according to the first embodiment, it is possible to reduce the image transfer speed from the imaging device, coding speed, and the image recording speed that are necessary for capturing at high speed without significantly degrading image quality. In other words, the stream A at high resolution and the stream B at low resolution are recorded. This allows reproduction of the high-definition stream A at the time of regular reproduction, and reproduction of the clear image using the high-resolution stream A and low-resolution stream B at the time of slow reproduction. 
     Second Embodiment 
     In the second embodiment, an image transform method different from the first embodiment is used. More specifically, although a method for skipping pixels per line is used in the first embodiment, a method for skipping pixels per line and column is used in the second embodiment. The following describes the image transform method according to the second embodiment focusing on the differences from the first embodiment. 
       FIG. 8  illustrates an image transforming method according to the second embodiment of the present invention. 
     As illustrated in  FIG. 8 , the image transform method according to the second embodiment is similar to the image transform method according to the first embodiment (see  FIG. 3 ) except for the difference in the transform method in the image transforming unit  130  of the synthesized frames B 0 , B 1 , B 2  . . . , constituting the group of second frames. More specifically, the synthesized image B 0  is generated using the pixels in even pixel lines and even pixel columns of the input frame G 1 , the pixels in even pixel lines and odd pixel columns of the input frame G 2 , the pixels in odd pixel lines and even pixel columns of the input frame G 2 , and the pixels in the odd pixel lines and odd pixel columns of the input frame G 4 . The same applies to the other synthesized frames B 1 , B 2 , B 3  and others. 
     In the second embodiment, an image reconstructuring method different from the first embodiment is used. The following describes the image reconstructuring method according to the second embodiment focusing on the differences from the first embodiment. 
       FIG. 9  illustrates an image reconstructuring method according to the second embodiment of the present invention. 
     As illustrated in  FIG. 9 , the image reconstructuring method according to the second embodiment is similar to the reconstructuring method according to the first embodiment (see  FIG. 6 ) except that the method for generating the intermediate frames b 0 - 0 , b 0 - 1 , b 0 - 2 , b 0 - 3  in the image reconstructing unit  240  is different. More specifically, the intermediate frame b 0 - 0  is generated from the pixel lines  0 ,  2 ,  4  of the synthesized frame B 0 , and the pixel columns  0 ,  2 ,  4  of the synthesized frame B 0 . Furthermore, the intermediate frame b 0 - 1  is generated from the pixel lines  0 ,  2 ,  4  . . . and the pixel columns  1 ,  3 ,  5  of the synthesized frame B 0 . Furthermore, the intermediate frame b 0 - 2  is generated from the pixel lines  1 ,  3 ,  5  . . . and the pixel lines  0 ,  2 ,  4  of the synthesized frame B 0 . Furthermore, the intermediate frame b 0 - 3  is generated from the pixel lines  1 ,  3 ,  5  . . . and the pixel columns  1 ,  3 ,  5  of the synthesized frame B 0 . The same applies to the intermediate frames b 1 - 0 , b 1 - 1 , b 1 - 2 , and b 1 - 3 . 
     As described above, although an image transform method and an image reconstructuring method different from the first embodiment are used in the second embodiment, the same effect as the first embodiment can be achieved. In other words, it is possible to reduce the image transfer speed from the imaging device, coding speed, and image recording speed that are necessary for capturing at high speed. 
     Third Embodiment 
     In the first embodiment, an example using a progressive image is described. In the third embodiment, an example using an interlaced image shall be described. The following describes the structure of the image recording device  100  and the image reproduction device  200  according to the third embodiment focusing on the differences from the first embodiment. 
     The image transforming unit  130  in the second embodiment extracts N (N is a natural number. N=2 in the third embodiment) frames from the frames included in the input image, arranges first synthesized frames that are obtained by synthesizing N temporally successive frames to generate the group of first frames. At the same time, the second synthesized frames generated by synthesizing N temporally successive frames among the frames not included in the group of first frames are arranged in chronological order to generate the group of second frames. 
       FIG. 10  illustrates an image reconstructuring method according to the third embodiment of the present invention. 
     Here, a case where the imaging device  110  and the image generating unit  120  generate input frames G 0 , G 1 , G 2  . . . G 7 , G 8 , G 9  . . . shall be described. The input image is an interlaced image of 1920×1080/240i. Note that the description shall be made assuming that the input frames G 0 , G 1 , G 2 , and G 3  are images in even lines, and the input frames G 4 , G 5 , G 6 , and G 7  are images in odd lines. 
     First, the image transforming unit  130  transforms the input frames G 0 , G 1 , G 2  . . . G 7 , G 8 , G 9 , and so on. In other words, the image transforming unit  130  generates the first synthesized frame A 0  using the pixel lines  0 ,  4 ,  8  . . . of the input frame G 0  and the pixel lines  2 ,  6 ,  10  . . . of the input frame G 1 . Similarly, the image transforming unit  130  generates the second synthesized frame B 0  using the pixel lines  0 ,  4 ,  8  . . . of the input frame G 2  and the pixel lines  2 ,  6 ,  10  . . . of the input frame G 3 . Furthermore, the image transforming unit  130  generates the first synthesized frame A 1  using the pixel lines  1 ,  5 ,  9  . . . of the input frame G 4  and the pixel lines  3 ,  7 ,  11  . . . of the input frame G 5 . Similarly, the image transforming unit  130  generates the second synthesized frame B 1  using the pixel lines  1 ,  5 ,  9  . . . of the input frame G 6  and the pixel lines  3 ,  7 ,  11  . . . of the input frame G 7 . 
     Repeating the process allows extracting of input frames G 0 , G 1 , G 4 , G 5  . . . for each two input frames of G 0 , G 1 , G 2  . . . G 7 , G 8 , G 9  . . . , and generating the group of first frames A 0 , A 1 , A 2  . . . generated by arranging the first synthesized frame A 0  obtained by synthesizing two input frames G 0  and G 1  that are temporally successive and the synthesized frame A 1  obtained by synthesizing the two input frames G 4  and G 5 . 
     Similarly, the group of second frames B 0 , B 1 , B 2  that is obtained by arranging the second synthesized frame B 0  obtained by synthesizing the two temporally successive input frames G 2  and G 3  among the input frames G 2 , G 3 , G 6 , G 7  . . . that are not included in the group of first frames, and the second synthesized frame B 1  obtained by synthesizing the two input frames G 6  and G 7  in chronological order is generated. 
     Note that, the group of first frames and the group of second frames share the same size and frame rate. 
     Subsequently, the image coding unit  140  codes the moving picture generated by the image transforming unit  130 . More specifically, the group of first frames A 0 , A 1 , A 2  . . . is coded as one moving picture to generate the stream A. Furthermore, the group of second frames B 0 , B 1 , B 2  . . . is coded as a successive moving picture to generate the stream B. The stream A and stream B constitutes a general high-definition video at 1920×1080/60i. Finally, the recording unit  150  records the stream A and stream B generated by the image coding unit  140  on the recording medium  300 . 
       FIG. 11  illustrates an image reconstructuring method according to the third embodiment of the present invention. 
     Here, it is assumed that the reproduction mode specifying unit  210  specifies slow reproduction. When slow reproduction is specified, the stream A and stream B illustrated in  FIG. 10  are read from the recording medium  300  by the read-out unit  230 , decoded by the image decoding unit  220 , and reconstructed by the image reconstructing unit  240  as described below. 
     First, the image reconstructing unit  240  separates the first synthesized frame A 0  generated by decoding the stream A, and generates the intermediate frames a 0 - 0  and a 0 - 1  by arranging the pixels lines in the order of the input picture. The intermediate frame a 0 - 0  is generated from the pixel lines  0 ,  4 ,  8  . . . of the first synthesized frame A 0 , and the intermediate frame a 0 - 1  is generated by the pixel lines  2 ,  6 ,  10  . . . of the first synthesized frame A 0 . Similarly, the second synthesized frame B 0  generated by decoding the stream B is separated to generate the intermediate frames b 0 - 0 , and b 0 - 1 . Furthermore, the first synthesized frame A 1  is separated to generate the intermediate frames a 1 - 0  and a 1 - 1 . The intermediate frame a 1 - 0  is generated from the pixel lines  1 ,  5 ,  9  . . . of the first synthesized frame A 1 , and the intermediate frame a 1 - 1  is generated by the pixel lines  3 ,  7 ,  11  . . . of the first synthesized frame A 1 . 
     Next, the image reconstructing unit  240  reconstructs the output frames g 0 , g 1 , g 2 , g 3  . . . from the intermediate frames a 0 - 0 , a 0 - 1 , b 0 - 0 , b 0 - 1 , a 1 - 0  . . . using pixel interpolation, super resolution technology and others. The output frames g 0 , g 1 , g 2 , g 3  . . . that are arranged in chronological order is a video of 1920×1080/240i, which makes ¼ slow reproduction video when displayed 60 fields per second. 
     As described above, interlaced images are processed in the third embodiment instead of progressive images. However, the same effect as the first embodiment can be obtained. In other words, it is possible to reduce the image transfer speed from the imaging device, coding speed, and image recording speed that are necessary for capturing at high speed. 
     Fourth Embodiment 
     The second embodiment describes a case where a method of skipping pixels per line or column is used, and the third embodiment describes a case where the interlaced images are processed. The fourth embodiment is a combination of the second embodiment and the third embodiment. 
     More specifically,  FIG. 12  illustrates an image transform method according to the fourth embodiment, and  FIG. 13  describes an image reconstructing method according to the fourth embodiment. As illustrated in these diagrams, even when the interlaced images are to be processed, it is possible to use the method of skipping pixels per line or column. Detailed description for the other points is omitted here, since they are identical to the second embodiment or the third embodiment. 
     Fifth Embodiment 
     In the first embodiment, all of the 1280×720 pixels are read by the imaging device  110  for generating the input image. However, pixels that the image transforming unit  130  does not use are also included. Thus, in the fifth embodiment, the imaging device  110  is controlled such that the imaging device  110  does not read the pixels that the image transforming unit  130  does not use. The following describes the structure of the image recording device  100  according the fifth embodiment focusing on the difference from the first embodiment. 
       FIG. 14  is a block diagram of the image recording device  100  according to the fifth embodiment of the present invention. 
     The image recording device  100  has the structure identical to  FIG. 2  except that the read-out control unit  160  is added. The read-out control unit  160  controls the imaging device  100  such that the imaging device  110  does not read the pixels that the image transforming unit  130  does not use. More specifically, the read-out control unit  160  is capable of selecting the pixels read from the imaging device  110 . The following describes the operation of the read-out control unit  160  when generating a stream illustrated in  FIG. 3 . 
     First, the read-out control unit  160  controls the imaging device  110  such that all of the pixels in the angle of view of 1280×720 when reading pixels from the imaging device  110  to generate the input frame G 0 . The imaging device  110  follows the instruction, and outputs all of the 1280×720 pixels to the image generating unit  120 . 
     Furthermore, the read-out control unit  160  controls the imaging device  110  to read the pixel lines  0 ,  4 ,  8  . . .  716  among the pixels in the 1280×720 angle of view, when reading the pixels from the imaging device  110  to generate the input frame G 1 . The imaging device  110  follows the instruction and outputs the pixels in the pixel lines  0 ,  4 ,  8  . . .  716  to the image generating unit  120 . 
     Similarly, when reading the pixels from the imaging device  110  to generate the input frame G 2 , the read-out control unit  160  controls the imaging device  110  to read the pixels in the pixel lines  1 ,  5 ,  9  . . .  717 . When reading the pixels from the imaging device  110  to generate the input frame G 3 , the read-out control unit  160  controls the imaging device  110  to read the pixels in the pixel lines  2 ,  6 ,  10  . . .  718 . When reading the pixels from the imaging device  110  to generate the input frame G 4 , the read-out control unit  160  controls the imaging device  110  to read the pixels in the pixel lines  3 ,  7 ,  11  . . .  719 . 
     As described above, the read-out control unit  160  according to the fifth embodiment controls the imaging device  110  such that the imaging device  110  does not read the pixels that the image transforming unit  130  does not use. With this, the number of pixels to be read out is reduced compared to the case where all of the 1280×720 pixels are read to generate an input image, thereby reducing the image transfer speed from the imaging device  110 . Furthermore, since the number of pixels to be read out is reduced, the consumption power of the image recording device  100  is reduced as well. 
     Sixth Embodiment 
     Not just the image coding units compliant with H.264, regular image coding units are configured to code only one moving picture. In contrast, an image recording device  100  including two coding units each of which codes one moving picture is used in the sixth embodiment. The following describes the structure of the image recording device  100  according the sixth embodiment focusing on the difference from the first embodiment. 
       FIG. 15  is a block diagram of the image recording device  100  according to the sixth embodiment of the present invention. 
     As illustrated in  FIG. 15 , the image recording device  100  according to the sixth embodiment is characterized by dividing a video at high frame rate into two moving pictures. Here, the two moving pictures to be coded have the same format. In order to simultaneously code the two moving pictures, an H.264 image coding unit  141  and an H.264 image coding unit  142  are provided as image coding units. Since the structure of the H.264 image coding unit  141  and the H.264 image coding unit  142  are identical, and thus the manufacturing process of the image recording device  100  would not become particularly complex. 
     As described above, the video at high frame rate may be divided into two moving pictures and coded. Furthermore, the structure of the H.264 image coding unit  141  and the H.264 image coding unit  142  are identical. Thus, there is another effect that the manufacturing of the image recording device  100  would not become particularly complex. 
     Note that, although skipping by lines is described in the first embodiment and skipping by lines and columns is described in the second embodiment, the method for skipping the pixels is not limited to these embodiments. In other words, the skipping methods for pixels may be any of skipping by line, skipping by columns, or skipping by lines and columns, as illustrated in  FIG. 16 , or another skipping method may be used. Thus, the skipping method may not be particularly limited. 
     Furthermore, the present invention may not only be implemented as the image recording device  100  and the image reproduction device  200 , but also as a program causing the computer to execute the image recording method and the image reproduction method. 
     Furthermore, the image recording device  100  and the image reproduction device  200  in the embodiments may be implemented using LSI, which is a typical integrated circuit. In this case, the LSI may constitute in one chip, or multiple chips. For example, the functional block other the memory may be constituted in a single-chip LSI. Furthermore, here, LSI is mentioned but there are instances where, due to a difference in the degree of integration, the designations IC, system LSI, super LSI, and ultra LSI are used. 
       FIG. 17  illustrates an example of the functional structure of the image recording device  100  implemented as an LSI  170 . The LSI  170  illustrated in  FIG. 17  is an example of the image recording integrated circuit according to the present invention, and constitutes a single-chip LSI. 
       FIG. 18  illustrates an example of the functional structure of the image recording device  200  implemented as an LSI  250 . The LSI  250  illustrated in  FIG. 18  is an example of the image decoding integrated circuit according to the present invention, and constitutes a single-chip LSI. 
     Note that, the functional structure of the LSI  170  and the LSI  250  illustrated in  FIG. 17  and  FIG. 18 , respectively, may be different from the functional structure illustrated in  FIG. 17  and  FIG. 18 . For example, the LSI  170  may further include a part of or both of the image generating unit  120  and the recording unit  150 . Similarly, the LSI  250  may further include a part of or both of the reproduction mode specifying unit  210  and the read-out unit  230 . 
     Furthermore, the means for circuit integration is not limited to an LSI, and implementation with a dedicated circuit or a general-purpose processor is also available. In addition, it is also acceptable to use a Field Programmable Gate Array (FPGA) that is programmable after the LSI has been manufactured, and a reconfigurable processor in which connections and settings of circuit cells within the LSI are reconfigurable. 
     Furthermore, if integrated circuit technology that replaces LSI appears thorough progress in semiconductor technology or other derived technology, that technology can naturally be used to carry out integration of the constituent elements. For example, biotechnology is anticipated to apply. 
     Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to camcorders and DVD players that are necessary to reduce the image transfer speed from the imaging device, coding speed, and image recording speed that are necessary for capturing at high speed.