Abstract:
To provide a technology capable of transmitting image information at a high speed under the same physical conditions as those in the prior arts. An image information transmitting method of the present invention includes replacing, in data with a plurality of gradations that form image information, high-order data with low-order data, thinning out the data with the plurality of gradations that form the image information by deleting the low-order data, and consecutively outputting the post-thinning-out image information or the post-replacing image information. Further, an image information receiving method of the present invention includes consecutively receiving post-replacing image information or post-thinning-out image information, extracting the low-order data from the post-replacing image information, supplementing the low-order data extracted from the post-replacing image information to the post-thinning-out image information received after the post-replacing image information, replacing at least part of the high-order data of the post-thinning-out image information received just before the post-replacing image information with the low-order information in the way of being attached to the post-replacing image information, and outputting the post-supplementing image information and the post-replacing image information.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a technology of transmitting image information by an information processing device (computer) and so on. 
         [0002]    The information processing device such as a personal computer transmits image information obtained as a result of processing by an arithmetic processing unit to an image display device, wherein the image display device displays the image information. Especially, with spread of liquid crystal display devices over the recent years, such a case increases that digital data are transmitted between interfaces of the information processing device and the display device. 
         [0003]    The interface with this liquid crystal display device has a basic configuration of including a power source, ground, four lines of timing signals (Hsync, Vsync, DataEnable, DotClock) and 18 through 24 lines of RGB image signals. 
         [0004]    In the present technologies, the image transmission is conducted based on fast serial transmission by using a differential transmitting method such as LVDS (Low Voltage Differential Signaling) and TMDS (Transmission Minimized Differential Signaling). Then, it is desired from a highly refined structure etc of the display device to further increase a transmission speed. There is naturally, however, a limit on increasing the transmission speed due to physical problems such as impedance matching and a material of a transmission cable. 
         [0005]    Further, the technology disclosed in the following Patent document 1 and 2 are given as the prior art related to the invention of the present application. 
         [0006]    [Patent document 1] Japanese Patent Application Laid-Open Publication No. 8-179740 
         [0007]    [Patent document 2] Japanese Patent No. 3018329 
       SUMMARY OF THE INVENTION 
       [0008]    As described above, if the increase in the transmission reaches its limit, it is considered to change a physical configuration (condition) such as doubling signal lines (transmission mediums) in order to attain further speedup. 
         [0009]    For doubling the transmission speed, however, if simply the transmission mediums are doubled, there arises a problem, wherein the device is sized up, and so on. 
         [0010]    Further, if the physical configuration is changed, such a problem occurs that the compatibility is deteriorated. 
         [0011]    Such being the case, the present invention provides a technology capable of transmitting the image information at a high speed even under the same physical conditions as those in the prior arts. 
         [0012]    The present invention adopts the following configurations in order to solve the problems. 
         [0013]    Namely, an image information transmitting device of the present invention comprises a replacing unit replacing, in data with a plurality of gradations that form image information, at least part of high-order data with low-order data, a thinning-out unit thinning out the data with the plurality of gradations that form the image information by deleting the low-order data, and an output unit consecutively outputting the post-thinning-out image information or the post-replacing image information. 
         [0014]    The replacing unit may replace, in the consecutive pieces of image information, the image information delimited at a predetermined cycle. 
         [0015]    The image information transmitting device may comprise an identifying information generating unit generating a piece of identifying information for identifying the post-replacing image information, wherein the output unit may output the identifying information together with the image information. 
         [0016]    The output unit may output the identifying information in place of the data with the plurality of gradations during a non-display period. 
         [0017]    The output unit may output, in the case of outputting, as the image information, the data with the plurality of gradations and a timing signal, the identifying information in place of the timing signal during the non-display period. 
         [0018]    Further, an image information receiving device of the present invention comprises a receiving unit consecutively receiving post-replacing image information obtained by replacing at least part of high-order data with low-order data in data with a plurality of gradations that form image information, or post-thinning-out image information obtained by thinning out the data with the plurality of gradations that form the image information by deleting the low-order data, a data extracting unit extracting the low-order data from the post-replacing image information, a supplementing unit supplementing the low-order data extracted from the post-replacing image information to the post-thinning-out image information received after the post-replacing image information, a re-replacing unit replacing at least part of the high-order data of the post-thinning-out image information received just before the post-replacing image information with the low-order information in the way of being attached to the post-replacing image information, and an output unit outputting the post-supplementing image information and the post-replacing image information. 
         [0019]    The re-replacing unit may replace the image information delimited at a predetermined cycle in the consecutively-received image information. 
         [0020]    The re-replacing unit may make the replacement on the basis of identifying information for identifying the post-replacing image information. 
         [0021]    The receiving unit may receive the identifying information in place of the data with the plurality of gradations during a non-display period. 
         [0022]    The receiving unit may receive, in the case of receiving, as the image information, the data with the plurality of gradations and a timing signal, the identifying information in place of the timing signal during the non-display period. 
         [0023]    Moreover, an image information transmitting method of the present invention by which an image information transmitting device executes a step of replacing, in data with a plurality of gradations that form image information, at least part of high-order data with low-order data, a step of thinning out the data with the plurality of gradations that form the image information by deleting the low-order data, and a step of consecutively outputting the post-thinning-out image information or the post-replacing image information. 
         [0024]    In the image information transmitting method, the data replacing step may include replacing, in the consecutive pieces of image information, the image information delimited at a predetermined cycle. 
         [0025]    The image information transmitting method may further comprise a step of generating a piece of identifying information for identifying the post-replacing image information, wherein the image information outputting step may include outputting the identifying information together with the image information. 
         [0026]    In the image information transmitting method, the image information outputting step may include outputting the identifying information in place of the data with the plurality of gradations during a non-display period. 
         [0027]    In the image information transmitting method, the image information outputting step may include outputting, in the case of outputting, as the image information, the data with the plurality of gradations and a timing signal, the identifying information in place of the timing signal during the non-display period. 
         [0028]    Still further, an image information receiving method of the present invention comprises a step of consecutively receiving post-replacing image information obtained by replacing at least part of high-order data with low-order data in data with a plurality of gradations that form image information, or post-thinning-out image information obtained by thinning out the data with the plurality of gradations that form the image information by deleting the low-order data, a step of extracting the low-order data from the post-replacing image information, a step of supplementing the low-order data extracted from the post-replacing image information to the post-thinning-out image information received after the post-replacing image information, a step of replacing at least part of the high-order data of the post-thinning-out image information received just before the post-replacing image information with the low-order information in the way of being attached to the post-replacing image information, and a step of outputting the post-supplementing image information and the post-replacing image information. 
         [0029]    In the image information receiving method, the data replacing step may include replacing the image information delimited at a predetermined cycle in the consecutively-received image information. 
         [0030]    In the image information receiving method, the replacement may be made based identifying information for identifying the post-replacing image information. 
         [0031]    In the image information receiving method, the image information receiving step may include receiving the identifying information in place of the data with the plurality of gradations during a non-display period. 
         [0032]    In the image information receiving method, the image information receiving step may include receiving, in the case of receiving, as the image information, the data with the plurality of gradations and a timing signal, the identifying information in place of the timing signal during the non-display period. 
         [0033]    Further, the present invention may also be an image information transmitting program for making a computer execute the image information transmitting method. Still further, the present invention may also be an image information receiving program for making the computer execute the image information receiving method. Yet further, the present invention may also be a readable-by-computer storage medium stored with this program. The computer is made to read the program from the storage medium and to execute the program, whereby a function thereof can be provided. 
         [0034]    Herein, the storage medium readable by the computer, etc. connotes a storage medium capable of storing information such as data, programs, etc. electrically, magnetically, optically, mechanically or by chemical action, which can be read from the computer. Among these storage mediums, for example, a flexible disc, a magneto-optic disc, a CD-ROM, a CD-R/W, a DVD, a DAT, an 8 mm tape, a memory card, etc. are given as those demountable from the computer. 
         [0035]    Further, a hard disc, a ROM (Read-Only Memory), etc. are given as the storage mediums fixed within the computer. 
         [0036]    According to the present invention, there is provided the technology capable of transmitting the image information at the high speed even under the same physical conditions as those in the prior arts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a schematic view of a computer including an image information transmitting device and an image information receiving device of the present invention. 
           [0038]      FIG. 2  is a diagram showing a physical configuration of a connection between an interface on the side of a liquid crystal panel and an interface on the side of the computer. 
           [0039]      FIG. 3  is an explanatory diagram of image information (frame). 
           [0040]      FIG. 4  is an explanatory diagram of a thinning-out process. 
           [0041]      FIG. 5  is an explanatory diagram of a replacing process. 
           [0042]      FIG. 6  is an explanatory diagram of the thinning-out process and the replacing process. 
           [0043]      FIG. 7  is a schematic diagram when transmitting data signals. 
           [0044]      FIG. 8  is an explanatory diagram of a timing signal. 
           [0045]      FIG. 9  is an explanatory view of the image information transmitting device and the image information receiving device in a first embodiment. 
           [0046]      FIG. 10  is a flowchart showing a processing flow of restoring and displaying the image information. 
           [0047]      FIG. 11  is an explanatory view of the image information transmitting device and the image information receiving device in a second embodiment. 
           [0048]      FIG. 12  is an explanatory view of the image information transmitting device and the image information receiving device in a third embodiment. 
           [0049]      FIG. 13  is an explanatory view of the image information transmitting device and the image information receiving device in a fourth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First Embodiment  
       [0050]      FIG. 1  is a schematic view of a computer including an image information transmission system configured by an image information transmitting device and an image information receiving device according to the present invention. 
         [0051]    A computer  1  has a display device (liquid crystal panel)  2  openable and closable with respect to a main body  3 . The main body  3  includes a CPU  31 , a main memory  32 , a storage device (hard disk)  33 , an input device (a keyboard, a pointing device, etc)  34 , a network control unit (NCU)  35  and an image control unit (corresponding to the image information transmitting device)  40 . 
         [0052]    The image control unit  40  is a computer-sided interface that transmits the image information to the display device  2 , thereby displaying the image information on the display device  2 . In the first embodiment, the image control unit  40  transmits, based on an LVDS (Low Voltage Differential Signaling) method, as shown in  FIG. 2 , the image information to a liquid crystal panel sided interface (the image information receiving device)  20  by use of three pairs of lines L 1 , L 2 , L 3  for transmitting data signals and a pair of lines L 4  for transmitting a clock signal. Herein, the image control unit  40  transmits the image information in a way that reduces an information quantity (data size) while thinning out the data by deleting part of this data with a plurality of gradations that form the image information, thereby enabling speedup or stability. 
         [0053]    To begin with, a principle of an image information transmitting method of transmitting the image information in a way that reduces the information quantity, will be explained with reference to  FIGS. 3 through 6 . 
         [0054]    The image information has such a structure as to contain values of respective pixels arrayed in a horizontal direction and in a vertical direction thereby to form frames, and timing signals for forming the frames. In the first embodiment, as illustrated in  FIG. 3 , 1024 pixels  11  are arrayed in the horizontal direction, and 768 pixels  11  are arrayed in the vertical direction, thus forming 1 frame. 
         [0055]    The pixel  11  is depicted in three primary colors (R, G, B) (each having 6 bits in this example) with a plurality of gradations. To be specific, as shown in  FIG. 4 , data signals per pixel have 18 bits of R 0 -R 5 , G 0 -G 5 , B 0 -B 5 . In those bits, “0” is the least significant bit, while “5” is the most significant bit. 
         [0056]    The image control unit  40  in this example, as illustrated in  FIG. 4 , thins out the original 18-bit data of R 0 -R 5 , G 0 -G 5 , B 0 -B 5  by deleting the low-order bits (corresponding to low-order data) R 0 , R 1 , G 0 , G 1 , B 0 , B 1 , whereby the image data are reduced down to 12 bits (which will hereinafter be also termed a thinning-out process). 
         [0057]    Further, the image control unit  40 , as shown in  FIG. 5 , deletes and replaces part (which will hereinafter be also referred to as intermediate-order bits) of the high-order data with the low-order data for every 15 frames, and thus transmits the data (which will hereinafter be also termed a replacing process). 
         [0058]    Namely, as illustrated in  FIG. 6 , the pixels forming the frames ranging from the first frame to fourteenth frame are transmitted as the data of R 2 , R 3 , R 4 , R 5 , G 2 , G 3 , G 4 , G 5 , B 2 , B 3 , B 4 , B 5  into which the original data are thinned out by the low-order bits of R 0 , R 1 , G 0 , G 1 , B 0 , B 1 . Moreover, the pixels forming the fifteenth frame are transmitted as data of R 0 , R 1 , R 4 , R 5 , G 0 , G 1 , G 4 , G 5 , B 0 , B 1 , B 4 , B 5  acquired by replacing the intermediate-order bits of R 2 , R 3 , G 2 , G 3 , B 2 , B 3  with the low-order bits. 
         [0059]    Similarly, the pixels ranging from the sixteenth frame to the twenty ninth frame are transmitted as the thinned-out data, the pixels of the thirtieth frame are transmitted as the replaced data, the pixels from the thirty first frame to the forty fourth frame are transmitted as the thinned-out data, the pixels of the forty fifth frame are transmitted as the replaced data, the pixels from the forth sixth frame to the fifty ninth frame are transmitted as the thinned-out data, and the pixels of the sixtieth frame are transmitted as the replaced data. In this example, a frame rate is set to 60 fps, and the processes of the first through sixtieth frames are repeated per second. 
         [0060]    Thus, the image control unit  40 , when transmitting the data at a predetermined frame rate, repeats the thinning-out process and the replacing process at a predetermined cycle. 
         [0061]    On the other hand, the liquid crystal panel sided interface  20  stores the low-order bits of R 0 , R 1 , G 0 , G 1 , B 0 , B 1  of the pixels of the sixtieth frame, and supplements these low-order bits to the image information (12 bits) ranging from the first frame down to the fourteenth frame, thereby restoring the image information (12 bits) back to the 18-bit data of R 0 -R 5 , G 0 -G 5 , B 0 -B 5  (which will hereinafter be also referred to as a supplementing process). 
         [0062]    Further, the interface  20  adds the intermediate-order bits of the just-anterior frame (the fourteenth frame) to the image information (12 bits) of the fifteenth frame, and replaces the intermediate-order bits with the low-order bits, thereby restoring the data back to the 18-bit data of R 0 -R 5 , G 0 -G 5 , B 0 -B 5  (which will hereinafter be also termed a re-replacing process). 
         [0063]    Similarly, the interface  20  repeats the supplementing process and the re-replacing process at a predetermined cycle (for every 15 frames in this example). Namely, the interface  20  restores the 18-bit image information from the 12-bit image information and displays the restored image information on the liquid crystal panel. 
         [0064]    As described above, the image control unit  40  in this example thins out the 18-bit data into 12-bit data and thus transmits the data, and hence a data signal transmission load becomes 12/18. 
         [0065]    As a matter of fact, the data are transmitted while adding  3 -bit timing signals to the 12-bit data signals per pixel.  FIG. 7  is a schematic diagram showing a case of transmitting the data signals via the three pairs of lines L 1 , L 2 , L 3 . As illustrated in  FIG. 7 , the respective bits are transmitted at timings (clocks) determined by clock signals of line L 4 . Namely, image control unit  40  transmits, with five clocks, the 12-bit data signals and the 3-bit timing signals (at the fifth clock). 
         [0066]    Accordingly, in the example in  FIG. 7 , the image control unit  40 , through the lines L 1 -L 3 , transmits R 5 , G 5 , B 5  at the first clock, and transmits R 4 , G 4 , B 4  at the second clock. Then, in the case of the image information of the frame thinned out by deleting the low-order bits, the image control unit  40  transmits R 3 , G 3 , B 3  at the third clock, then transmits R 2 , G 2 , B 2  at the fourth clock, and transmits the timing signals H, V, DE at the fifth clock. 
         [0067]    Then, in the case of transmitting the image information of the frame with the low-order bits replaced, the image control unit  40 , through the lines L 1 -L 3 , transmits R 5 , G 5 , B 5  at the first clock, transmits R 4 , G 4 , B 4  at the second clock, transmits R 1 , G 1 , B 1  at the third clock, transmits R 0 , G 0 , B 0  at the fourth clock, and transmits the timing signals H, V, DE at the fifth clock. Namely, the image control unit  40  replaces the data to be transmitted at the third through fourth clocks with the low-order bits from the intermediate-order bits (which are indicated by a range delimited by a dot dashed line in  FIG. 7 ). 
         [0068]    It is to be noted that though explained for convenience by arranging the bits in the sequence from the high-order to the low-order for every color such as R 5 , R 4 , R 3 , R 2 , the transmission is not limited to this sequence. The actual transmission sequence is set by taking into consideration a frequency at which each bit switched over to High or Low, an influence of noise, etc. 
         [0069]    Further, “H” of the timing signal represents a signal (Hsync) for taking synchronization in the horizontal direction, wherein as shown in  FIG. 8 , “High” is kept for a period during which the data for  1  line in the horizontal direction of frame are transmitted, and “Low” is kept for a predetermined period till the transmission of the data of a next line is started since the transmission of the data for 1 line has been finished. 
         [0070]    “V” of the timing signal represents a signal (Vsync) for taking the synchronization in the vertical direction (FIG.  3 ), wherein “High” is kept for a period during which the data for  1  frame are transmitted, and “Low” is kept for a predetermined period till the transmission the data of a next frame is started since the transmission of the data for 1 frame has been finished. 
         [0071]    Then, “DE” of the timing signal represents a signal (Data Enable) showing an existence or non-existence of the data signal. Namely, the signal DE becomes “High” for a period during which the display is conducted and becomes “Low” for a period (non-display period) during which the display is not conducted. 
         [0072]    Next, the image control unit  40  and the liquid crystal panel sided interface  20  in the first embodiment will be specifically described with reference to  FIGS. 9 and 10 . 
         [0073]    The image control unit  40  in the first embodiment includes, as illustrated in  FIG. 9 , an image information generating unit  41 , a replacing unit  42 , an identification signal generating unit  43 , a thinning-out unit  44  and an output unit  45 . 
         [0074]    The image information generating unit  41  generates the image information on the basis of a display command of a processing result of the CPU  31  etc. The configuration for generating the image information, i.e., the data signals and the timing signals, is widely known, and hence its detailed explanation is omitted. 
         [0075]    The replacing unit  42  executes a replacing process of replacing, in the data with the plurality of gradations that form the image information, at least part of the high-order data with the low-order data. 
         [0076]    The identification signal generating unit  43  generates pieces of identifying information for identifying the image information after the replacement and the image information just before the replacement. 
         [0077]    The thinning-out unit  44  executes the thinning-out process of thinning out the data with the plurality of gradations that form the image information by deleting the low-order data. 
         [0078]    The output unit  45  consecutively outputs the image information after being thinned out (which is also referred to as the post-thinning-out image information or the post-thinning-out frame) or the image information after being replaced (which is also termed the post-replacing image information or the post-replacing frame). 
         [0079]    Then, the image control unit  40 , when the image information generating unit  41  generates the image information on the basis of the display command, judges whether or not the information is the image information (frame) undergoing the replacing process by the replacing unit  42  on the basis of the timing signal of the image information. Further, the replacing unit  42  also judges whether or not the frame is the frame just anterior to the frame subjected to the replacing process. For example, the replacing unit  42  counts the V-signals and, if this count value is a predetermined count value ( 15 ,  30 ,  45 ,  60  in this example), judges that the frame is the frame subjected to the replacing process. Similarly, the replacing unit  42 , if the result of counting (count value) is a value just anterior ( 14 ,  29 ,  44 ,  59  in this example) to the predetermined count value, judges that it is the frame just anterior to the frame undergoing the replacing process. 
         [0080]    When judging that it is the frame just anterior to the frame undergoing the replacing process, for example, when detecting the V-signal serving as a delimiter between the thirteenth frame and the fourteenth frame, the replacing unit  42  notifies the identification signal generating unit  43  of this purport. Similarly, when judging that it is the frame undergoing the replacing process, for example, when detecting the V-signal serving as the delimiter between the fourteenth frame and the fifteenth frame, the replacing unit  42  notifies the identification signal generating unit  43  of this purport. 
         [0081]    The identification signal generating unit  43  notified of the purport that it is the frame just anterior to the frame undergoing the replacing process, sends the identifying information specifying the frame concerned in a way that embeds this identifying information into the non-display period timing signal. Similarly, the identification signal generating unit  43  notified of the purport that it is the frame undergoing the replacing process, sends the identifying information specifying the frame concerned in a way that embeds this identifying information into the non-display period timing signal. For instance, the timing signal is, as shown in  FIG. 8 , such that when the V-signal is “Low”, the H-signal and the DE-signal also become “Low”. Such being the case, in the case of embedding the identifying information purporting that it is the frame just anterior to the frame undergoing the replacing process, both of the DE-signal and the H-signal are set “High” during the “Low” period of the V-signal. Likewise, in the case of embedding the identifying information purporting that it is the frame subjected to the replacing process, only the DE-signal is set “High” during the “Low” period of the V-signal. It is to be noted that without being limited to this scheme, it is sufficient if capable of transmitting the information specifying the frame just anterior to the frame undergoing the replacing process or specifying the frame subjected to the replacing process by use of the non-display period timing signal. For example, at the delimiter of the line in the horizontal direction, during the “Low” period of the H-signal, the DE-signal becomes also “Low”, i.e., becomes a status where “0” continues. During the “Low” period of the H-signal, the identifying information may also be transmitted by changing the DE-signal such as  01 ,  11 . Note that the identification signal generating unit  43  transmits to the output unit  45  the timing signal during the display period and the timing signal during the non-display period of the non-notified frame without any change. 
         [0082]    Then, the replacing unit  42 , if the result of counting (count value) is not the predetermined count, transmits the data signals to the thinning-out unit  44  without executing the replacing process. 
         [0083]    The thinning-out unit  44  thins out, as described above, the 18-bit image information by deleting the low-order 2 bits for every color into the 12-bit image information. 
         [0084]    The output unit  45  outputs the data signals after undergoing this thinning-out process and the timing signals via the lines L 1 -L 3  at the timings determined by the clock signals. 
         [0085]    On the other hand, the liquid crystal panel sided interface  20  includes a receiving unit  21 , a re-replacing unit  22 , an identifying information extracting unit  23 , a memory  24 , a supplementing unit  25 , a data extracting unit  26  and an output unit  27 . 
         [0086]    The receiving unit  21  consecutively receives the image information from the image control unit  40 , then transmits the data signals to the re-replacing unit  22 , and at the same time transmits the timing signals to the identifying information extracting unit  23 . 
         [0087]    The re-replacing unit  22  replaces part (the intermediate-order bits) of the high-order data of the post-thinning-out frame received just before the post-replacing frame with the low-order information (low-order bits) by attaching these pieces of data to the post-replacing frame. 
         [0088]    The identifying information extracting unit  23  extracts the identifying information from the timing signals and supplies the identifying information to the re-replacing unit  22  and to the data extracting unit  26 . Namely, the identifying information extracting unit  23  monitors the non-display period timing signal and, if the timing signal being originally kept at “Low” becomes “High”, extracts this signal as the identifying information. The identifying information specifying the post-replacing frame and the identifying information specifying the frame just before the replacement, are thereby supplied. 
         [0089]    The memory  24  is stored with the low-order data (low-order bits) or at least part (intermediate-order bits) of the high-order data, which are extracted by the data extracting unit  26 . 
         [0090]    The supplementing unit  25  supplements the low-order data extracted from the post-replacing image information to the post-thinning-out image information received subsequently to the post-replacing image information. 
         [0091]    The data extracting unit  26  extracts the low-order data of the data signals or at least part of the high-order data of the data signals, and stores the extracted data in the memory  24 . In the first embodiment, the low-order 2 bits are extracted for every color. Specifically, in the case of the post-thinning-out frame, the intermediate-order bits of R 3 , R 2 , G 3 , G 2 , B 3 , B 2  are stored, and, in the case of the post-replacing frame, the low-order bits of R 1 , R 0 , G 1 , G 0 , B 1 , B 0  are stored. 
         [0092]    The output unit  27  outputs the post-supplementing image information and the post-replacing image information to the liquid crystal panel  2 , wherein these pieces of image information are displayed on the liquid crystal panel  2 . 
         [0093]      FIG. 10  is a flowchart showing a processing flow when the liquid crystal panel sided interface  20  restores and outputs the image information. 
         [0094]    As shown in  FIG. 10 , in the interface  20 , when receiving the image information through the receiving unit  21 , at first the re-replacing unit  22  judges based on the identifying information given from the identifying information extracting unit  23  whether the frame is the post-replacing frame or not (step  1 , which will hereinafter be abbreviated such as S 1 ). If judged to be post-replacing frame, the re-replacing unit  22  reads the data stored in the memory  24 , and replaces the bits with the low-order bits, thus adding these bits as the intermediate-order bits (S 2 ). 
         [0095]    Further, if the re-replacing unit  22  judges in step  1  that the frame is not the post-replacing frame, the supplementing unit  25  reads the data from the memory  24  and supplements the bits as the low-order bits to the data signals (S 4 ). 
         [0096]    Then, the data extracting unit  26  extracts the intermediate-order bits or the low-order bits of the data signals on the basis of the identifying information, and stores the extracted bits in the memory  24 . Namely, the data extracting unit  26  saves the low-order bits in the memory  24  in the case of the post-replacing frame (S 3 ), then saves the intermediate-order bits in the memory  24  in the case of the frame just before the replacement (S 6 ), and saves the low-order bits in the memory  24  in the case of the frame other than these categories of frames (S 7 ). It is to be noted that if step  3  is surely executed, step  7  may be omitted. 
         [0097]    The output unit  27  outputs and displays the post-supplementing frame and the post-replacing frame line by line to and on the liquid crystal panel  2  on the basis of the timing signals (S 8 ). 
         [0098]    Thus, according to the first embodiment, it is possible to attain the speedup and the stability by thinning out the image information. 
       Second Embodiment  
       [0099]      FIG. 11  is a schematic view of the image information transmitting device and the image information receiving device in a second embodiment. The second embodiment is different from the first embodiment discussed above in terms of transmitting the data signals in a way that embeds the identifying information into the data signals. Note that other configurations are the same, and the repetitive explanations are omitted by marking the same components with the same numerals and symbols. 
         [0100]    An identifying information generating unit  43 A of the image information control unit  40  in the second embodiment, when receiving from the replacing unit  42  notification purporting that the frame is the replacement frame or the frame just before the replacement, generates the identifying information showing this purport and embeds this identifying information into the non-display period data signals, thus transmitting the data signals. For instance, when the DE-signal is at “Low”, the data signals originally become “Low”. Then, when the DE signal is in the non-display period, i.e., the “Low” period, the identifying information is transmitted by setting at “High” the data signals being originally kept in “Low”. For example, in the case of embedding the identifying information showing a purport of being the frame just anterior to the frame undergoing the replacing process, the data signals are set to “1” (High) at the timings of R 5  and G 5 , and, in the case of embedding the identifying information showing a purport of being the frame undergoing the replacing process, the data signals are set to “1” (High) at the timings of B 5  and G 4 . Note that the data signals during the non-display period are changed into a predetermined pattern, whereby the frame just anterior to the frame undergoing the replacing process and the frame undergoing the replacing process, it is sufficient, can be identified. 
         [0101]    On the other hand, an identifying information extracting unit  23 A of the liquid crystal panel sided interface  20  according to the second embodiment detects based on the timing signal (DE signal) whether the period is the non-display period or not, then monitors the data signals during the non-display period, and, when the data signals being originally kept at “Low” become “High”, extracts this information as the identifying information. The re-replacing unit  22  and the data extracting unit  26  are thereby supplied with the identifying information specifying the post-replacing frame and the identifying information specifying the frame just before the replacement. 
         [0102]    The processes of the re-replacing unit  22  and the data extracting unit  26 , which have received the identifying information from the identifying information extracting unit  23 A, are the same as in the first embodiment discussed above. 
         [0103]    Accordingly, even configured to transmit the data signals while embedding the identifying information into the data signals, it is feasible to attain the speedup and the stability on the occasion of transmitting the image information as in the first embodiment discussed above even with the configuration of transmitting the data signals in a way that embeds the identifying information into the data signals. 
       Third Embodiment  
       [0104]      FIG. 12  is a schematic view of the image information transmitting device and the image information receiving device in a third embodiment. The third embodiment is different from the first embodiment discussed above in terms of executing the re-replacing process not based on the identifying information but at a predetermined cycle. Note that other configurations are the same, and the repetitive explanations are omitted by marking the same components with the same numerals and symbols. 
         [0105]    The image control unit  40  and the interface  20  in the third embodiment, it is settled, execute the replacing process at a predetermined cycle, e.g., at an interval of 15 frames. 
         [0106]    A replacing unit  42 B of the image control unit  40  counts the number of frames (frame count) on the basis of the timing signal (e.g., the V-signal), then judges, if the count value is a predetermined count value ( 15 ,  30 ,  45 ,  60  in this example), that it is the frame subjected to the replacing process, and executes the replacing process. 
         [0107]    It is to be noted that the thinning-out process by the thinning-out unit  44  and the output process by the output unit  45  are the same as those in the embodiments discussed above. 
         [0108]    Then, the re-replacing unit  22 B and a data supplementing unit  26 B of the interface  20  each count the frame count on the basis of the data signals, and judge whether the frame is the post-replacing frame or the frame just before the replacement. 
         [0109]    In the interface  20  in the third embodiment, as illustrated in  FIG. 10 , when receiving the image information from the image control unit  40 , to start with, the re-replacing unit  22  judges based on the count value of the frame count whether the frame is the post-replacing frame or not (step  1 , which will hereinafter be abbreviated such as S 1 ). If judged to be post-replacing frame, the re-replacing unit  22  reads the data stored in the memory  24 , and replaces the bits with the low-order bits, thus adding these bits as the intermediate-order bits (S 2 ). 
         [0110]    Further, if the re-replacing unit  22  judges in step  1  that the frame is not the post-replacing frame, the supplementing unit  25  reads the data from the memory  24  and supplements the bits as the low-order bits to the data signals (S 4 ). 
         [0111]    Then, the data extracting unit  26  extracts the intermediate-order bits or the low-order bits of the data signals on the basis of the count value of the frame count, and stores the extracted bits in the memory  24 . Namely, the data extracting unit  26  saves the low-order bits in the memory  24  in the case of the post-replacing frame (S 3 ), then saves the intermediate-order bits in the memory  24  in the case of the frame just before the replacement (S 6 ), and saves the low-order bits in the memory  24  in the case of the frame other than these categories of frames (S 7 ). 
         [0112]    The output unit  27  outputs and displays the post-supplementing frame and the post-replacing frame line by line to and on the liquid crystal panel  2  on the basis of the timing signals (S 8 ). 
         [0113]    Thus, according to the third embodiment, it is possible to attain the speedup and the stability by thinning out the image information. 
       Fourth Embodiment  
       [0114]      FIG. 13  shows an example where the image information transmitting method of the present invention is applied to communications via a network between computers. 
         [0115]    Computers  1 A,  1 B shown in  FIG. 13  are, similarly to the computer illustrated in  FIG. 1 , computers of a general purpose that have the main body including an arithmetic processing unit constructed of a CPU (Central Processing Unit)  31 , a main memory  32 , etc, the storage unit (hard disk)  33  stored with data and software for an arithmetic process, input/output ports  34 , the network control unit (NCU)  35 , the image control unit  40  and so on. 
         [0116]    Input devices such as the keyboard, the mouse and a CR-R 0 M drive, and output devices such as the display device  2  and a printer are properly connected to the input/output ports  34 . 
         [0117]    The NCU  35  controls the communications with other computers via the network. 
         [0118]    The storage unit  33  is preinstalled with operating system (OS) and application software (an image information transmission program). 
         [0119]    The arithmetic processing unit properly reads the OS and the application program from the storage unit  33  and executes the OS and the application program, and executes an arithmetic process of information inputted from the input/output ports  34  and from the NCU  35  and of the information read from the storage unit  33 , thereby functioning as a replacing unit  31 A, a thinning-out unit  31 B, a re-replacing unit  31 C, a supplementing unit  31 D and a data extracting unit  31 E. 
         [0120]    This replacing unit  31 A executes the replacing process of replacing, in the data with the plurality of gradations that form the image information, at least part of the high-order data with the low-order data. 
         [0121]    The thinning-out unit  31 B executes the thinning-out process of thinning out the data with the plurality of gradations that form the image information by deleting the low-order data. 
         [0122]    The re-replacing unit  31 C executes the re-replacing process of replacing part (the intermediate-order bits) of the high-order data of the post-thinning-out frame received just before the post-replacing frame with the low-order information (low-order bits) by attaching these pieces of data to the post-replacing frame. 
         [0123]    The supplementing unit  31 D executes the supplementing process of supplementing the low-order data extracted from the post-replacing image information to the post-thinning-out image information received subsequently to the post-replacing image information. 
         [0124]    The data extracting unit  31 E extracts the low-order data of the data signals or at least part of the high-order data of the data signals, and stores the extracted data in the memory  32 . In the fourth embodiment, the low- or intermediate-order 2 bits are extracted for every color. Specifically, in the case of the post-thinning-out frame, the intermediate-order bits of R 3 , R 2 , G 3 , G 2 , B 3 , B 2  are stored, and, in the case of the post-replacing frame, the low-order bits of R 1 , R 0 , G 1 , G 0 , B 1 , B 0  are stored. 
         [0125]    The output unit  27  outputs the post-supplementing image information and the post-replacing image information to the liquid crystal panel  2 , wherein these pieces of image information are displayed on the liquid crystal panel  2 . 
         [0126]    The computers  1 A,  1 B in the fourth embodiment have both of the components of the image information transmitting device and the components of the image information receiving device and have the configuration capable of transmitting and receiving, however, in  FIG. 13 , for the convenience&#39;s sake, the computer  1 A used herein is exemplified as the image information transmitting device while the computer  1 B employed herein is exemplified as the image information receiving device. 
         [0127]    Next, the image information transmitting method between these computers  1 A and  1 B will be explained. 
         [0128]    The computer  1 A captures the image information generated by the image information generating unit  41  etc, for example, the information on a desktop image, and the replacing unit  31 A counts a frame count of the image information and judges whether or not it is the frame undergoing the replacing process. The count value of this frame count may involve using the timing signal as in the case of the embodiments discussed above, and may also involve counting arbitrary type of information representing delimiters of the frames. For instance, the replacing unit  31 A counts the frame count and, if the count value is the predetermined count value ( 15 ,  30 ,  45 ,  60  in this example), judges that the frame is the frame undergoing the replacing process. 
         [0129]    Further, if the result of counting (count value) is not the predetermined count value, the replacing process is not executed, while the thinning-out unit  31 B, as illustrated in  FIG. 4 , thins out the 18-bit image information by deleting the low-order 2 bits for every color into the 12-bit image information. 
         [0130]    Then, the NCU  35  transmits the post-replacing process frame and the post-thinning-out process frame to the computer  1 B via the network such as the Internet. 
         [0131]    In the computer  1 B receiving this image information, to begin with, the re-replacing unit  31 C counts the frame count, and judges based on the result of counting whether the frame is the post-replacing frame or not (S 1 ). Note that the same processes as those in  FIG. 10  are marked with the same step numbers. If being the post-replacing frame, If judged to be post-replacing frame, the re-replacing unit  31 C reads the data stored in the memory  32 , and replaces the bits with the low-order bits, thus adding these bits as the intermediate-order bits (S 2 ). 
         [0132]    Further, if the re-replacing unit  31 C judges in step  1  that the frame is not the post-replacing frame, the supplementing unit  31 D reads the data from the memory  32  and supplements the bits as the low-order bits to the data signals (S 4 ). 
         [0133]    Then, the data extracting unit  26  counts the frame count and extracts the intermediate-order bits or the low-order bits of the data signals on the basis of the result of counting, and stores the extracted bits in the memory  32 . Namely, the data extracting unit  26  saves the low-order bits in the memory  32  in the case of the post-replacing frame (S 3 ), then saves the intermediate-order bits in the memory  32  in the case of the frame just before the replacement (S 6 ), and saves the low-order bits in the memory  32  in the case of the frame other than these categories of frames (S 7 ). 
         [0134]    The image control unit  40  outputs and displays the post-supplementing frame and the post-replacing frame to and on the liquid crystal panel  2  (S 8 ). 
         [0135]    Thus, according to the fourth embodiment, it is possible to reduce the data signals transmitted via the network down to  12 / 18  and to attain the speedup and the stability. 
         [0136]    &lt;Others&gt; 
         [0137]    The present invention is not limited to only the illustrated examples given above and can be, as a matter of course, changed in a variety of forms in the range that does not deviate from the gist of the present invention. 
         [0138]    &lt;Incorporation by Reference&gt; 
         [0139]    The disclosures of Japanese patent application No. JP2006-094118 filed on Mar. 30, 2006 including the specification, drawings and abstract are incorporated herein by reference.