Abstract:
There is provided a signal processing apparatus including a first image generating unit, a second image generating unit, a first selecting unit selects at least one of the first image generating unit and the second image generating unit and outputs an image, an image signal processing unit that performs signal processing on the image and outputs the processed image, a second selecting unit that selects one of the first selecting unit and the image signal processing unit and outputs an image, a storing unit that stores information on operations of the second image generating unit and the image signal processing unit, and a third selecting unit that selects at least one of the second image generating unit and the image signal processing unit and connects the selected one to the storing unit, whereby the storing unit is shared between the second image generating unit and the image signal processing unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. JP 2008-212129 filed in the Japanese Patent Office on Aug. 20, 2008, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a signal processing apparatus and a signal processing method. 
     2. Description of the Related Art 
     In a moving image display apparatus in related art that displays a moving image such as a movie at high quality and at a high refresh rate and displays high-definition computer graphics, generally, memory bandwidth is used mainly by a frame rate conversion mechanism that converts a frame rate and a graphics computation mechanism that performs graphics processing. 
     In the moving image display apparatus in related art, since semiconductor memory apparatuses are used separately by the frame rate conversion mechanism and the graphics computation mechanism, there is an issue that the number of semiconductor memory apparatuses increases, increasing circuit size. To solve such an issue, moving image display apparatuses that aim to reduce the number of memories are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2002-125200 and 2002-359819. 
     SUMMARY OF THE INVENTION 
     The techniques disclosed in Japanese Patent Application Laid-Open Nos. 2002-125200 and 2002-359819, however, do not mention a reduction in the number of memories by switching images to be inputted or display refresh rates and thus there is an issue that the number of memories may not also be reduced when a moving image is displayed by switching display refresh rates. 
     The present invention addresses the above-identified and other issues associated with methods and apparatuses in related art. There is a need for a novel and improved signal processing apparatus and signal processing method that enable reduction of the number of memories by sharing memories around the time of switching images to be inputted or display refresh rates. 
     According to an embodiment of the present invention, there is provided a signal processing apparatus including: a first image generating unit that generates an image; a second image generating unit that generates an image different from the image generated by the first image generating unit; a first selecting unit that selects at least one of the first image generating unit and the second image generating unit and outputs an image from the selected one; an image signal processing unit that performs signal processing on the image outputted from the first selecting unit and outputs the processed image; a second selecting unit that selects one of the first selecting unit and the image signal processing unit and outputs an image from the selected one; a storing unit that stores information on operations of the second image generating unit and the image signal processing unit; and a third selecting unit that selects at least one of the second image generating unit and the image signal processing unit and connects the selected one to the storing unit, whereby the storing unit is shared between the second image generating unit and the image signal processing unit. 
     According to such a configuration, the first image generating unit generates an image, the second image generating unit generates an image different from the image generated by the first image generating unit, and the first selecting unit selects at least one of the first image generating unit and the second image generating unit and outputs an image from the selected one. The image signal processing unit performs signal processing on the image outputted from the first selecting unit and outputs the processed image. The second selecting unit selects one of the first selecting unit and the image signal processing unit and outputs an image from the selected one. The storing unit stores information on operations of the second image generating unit and the image signal processing unit. The third selecting unit selects at least one of the second image generating unit and the image signal processing unit and connects the selected one to the storing unit, whereby the storing unit is shared between the second image generating unit and the image signal processing unit. As a result, by switching input images, the number of memories can be reduced. 
     The signal processing apparatus according to an embodiment of the present invention may further include a selection control unit that controls selections made by the second selecting unit and the third selecting unit. 
     When the first selecting unit selects the first image generating unit, the second selecting unit and the third selecting unit may select the image signal processing unit. 
     When the first selecting unit selects the second image generating unit, the second selecting unit may select the first selecting unit and the third selecting unit may select the second image generating unit. 
     When the first selecting unit selects the first image generating unit and the second image generating unit, the second selecting unit may select the image signal processing unit and the third selecting unit may select the second image generating unit and the image signal processing unit. 
     The image signal processing unit may perform a process of converting a frame rate. 
     According to another embodiment of the present invention, there is provided a signal processing method including: a first image generation step of generating an image in a first image generating unit; a second image generation step of generating an image in a second image generating unit that is different from the image generated in the first image generation step; a first selection step of selecting at least one of the image generated in the first image generation step and the image generated in the second image generation step and outputting the selected image; an image signal processing step of performing, in an image signal processing unit, signal processing on the image outputted in the first selection step and outputting the processed image; a second selection step of selecting one of the image outputted in the first selection step and the image outputted in the image signal processing step and outputting the selected image; and a third selection step of selecting at least one of the second image generating unit and the image signal processing unit and connecting the selected one to a storing unit that stores information on operations of the second image generating unit and the image signal processing unit, whereby the storing unit is shared between the second image generating unit and the image signal processing unit. 
     As described above, according to the present invention, a novel and improved signal processing apparatus and signal processing method can be provided that enable reduction of the number of memories by switching input images. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustrative view showing the external appearance of a moving image display apparatus  100  according to an embodiment of the present invention; 
         FIG. 2  is an illustrative view showing a configuration of the moving image display apparatus  100  according to the embodiment of the present invention; 
         FIG. 3  is an illustrative view showing the operation of the moving image display apparatus  100  for when a moving image is displayed in a high-speed display mode; 
         FIG. 4  is an illustrative view showing the operation of the moving image display apparatus  100  for when a moving image is displayed in a low-speed display mode; 
         FIG. 5  is an illustrative view showing the operation of the moving image display apparatus  100  for when a moving image is displayed in a composite display mode; 
         FIG. 6  is an illustrative view showing an example of moving images displayed on the display unit  111  in the composite display mode in the moving image display apparatus  100  according to the embodiment of the present invention; and 
         FIG. 7  is an illustrative view showing a configuration of a moving image display apparatus  10  in related art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
     A preferred embodiment of the present invention will be described in detail in the following order. 
     (1) Configuration of a moving image display apparatus in related art 
     (2) Configuration of a moving image display apparatus according to an embodiment of the present invention 
     (3) Operation of the moving image display apparatus according to the embodiment of the present invention 
     (4) Conclusions 
     (1) CONFIGURATION OF A MOVING IMAGE DISPLAY APPARATUS IN RELATED ART 
     First, prior to describing in detail a preferred embodiment of the present invention, a configuration of a moving image display apparatus in related art will be described.  FIG. 7  is an illustrative view showing a configuration of a moving image display apparatus  10  in related art. The configuration of the moving image display apparatus  10  in related art will be described below with reference to  FIG. 7 . 
     As shown in  FIG. 7 , the moving image display apparatus  10  in related art includes a video input unit  11 , a graphics computing unit  12 , a video input switching unit  13 , a frame rate converting unit  14 , a display unit  15 , a first memory  16 , and a second memory  17 . 
     The video input unit  11  generates moving images from moving image sources such as television broadcasts, hard disk recorders, optical disk recorders, and other video media. The video input unit  11  generates, for example, a 60 Hz moving image. The graphics computing unit  12  generates computer graphics moving images and generates, for example, high-definition moving images such as three-dimensional computer graphics. The graphics computing unit  12  is connected to the first memory  16 . 
     The video input switching unit  13  selects one of moving images respectively supplied from the video input unit  11  and the graphics computing unit  12 , according to a moving image to be displayed on the display unit  15 . The moving image selected by the video input switching unit  13  passes through the frame rate converting unit  14  and is then displayed on the subsequent display unit  15 . 
     Note that the video input switching unit  13  may output a composite moving image formed from a moving image supplied from the video input unit  11  and a moving image supplied from the graphics computing unit  12 . In the configuration shown in  FIG. 7 , the video input switching unit  13  can generally generate a composite moving image as changing a composite ratio according to a coefficient value supplied from the graphics computing unit  12 . 
     The frame rate converting unit  14  converts the frame rate of the moving image outputted from the video input switching unit  13  and outputs the resulting moving image. The frame rate converting unit  14  is connected to the second memory  17 . The frame rate converting unit  14 , for example, accepts as input a moving image with 60 Hz which is a refresh rate for general broadcasts, etc., and generates and outputs a moving image with 120 Hz which is a high-quality refresh rate. The display unit  15  displays the moving image whose frame rate is converted by the frame rate converting unit  14 . 
     The first memory  16  is a semiconductor memory connected to the graphics computing unit  12 . The first memory  16  requires, for example, a bandwidth of 51.2 Gbps (Giga bits per second) and a capacity of 128 MB (Mega Bytes) when the graphics computing unit  12  operates. 
     The second memory  17  is a semiconductor memory connected to the frame rate converting unit  14 . The second memory  17  requires, for example, a bandwidth of 22.5 Gbps and a capacity of 64 MB when the frame rate converting unit  14  operates. 
     When the first memory  16  and the second memory  17  are implemented using a plurality of semiconductor memory apparatuses, each, for example, providing a bandwidth of 12.8 Gbps and a capacity of 32 MB, operating at a data rate of 800 MHz, and having a 16-bit width, the first memory  16  and the second memory  17  can be implemented using six semiconductor memory apparatuses in total, i.e., four for the first memory  16  and two for the second memory  17 . 
     The configuration of the moving image display apparatus  10  in related art has been described above. As such, in the moving image display apparatus  10  in related art, semiconductor memories are respectively connected to the graphics computing unit  12  and the frame rate converting unit  14 . However, since the semiconductor memories are respectively connected to the graphics computing unit  12  and the frame rate converting unit  14 , for example, even when the graphics computing unit  12  is not in operation, the first memory  16  connected to the graphics computing unit  12  may not be used by the frame rate converting unit  14 , and even when the frame rate converting unit  14  is not in operation, the second memory  17  connected to the frame rate converting unit  14  may not be used by the graphics computing unit  12 . Hence, a memory may not be shared between the graphics computing unit  12  and the frame rate converting unit  14 , causing an issue of an increase in circuit size and cost. 
     In view of this, the present invention provides a signal processing apparatus and a signal processing method that enable reduction of a circuit size and cost by allowing a semiconductor memory to be shared between a graphics computation process and a frame rate conversion process. In the following, a preferred embodiment of the present invention will be described in detail. 
     (2) CONFIGURATION OF A MOVING IMAGE DISPLAY APPARATUS ACCORDING TO AN EMBODIMENT OF THE PRESENT INVENTION 
     First, a moving image display apparatus according to an embodiment of the present invention will be described.  FIG. 1  is an illustrative view showing the external appearance of a moving image display apparatus  100  according to an embodiment of the present invention.  FIG. 2  is an illustrative view showing a configuration of the moving image display apparatus  100  according to the embodiment of the present invention. The configuration of the moving image display apparatus  100  according to the embodiment of the present invention will be described below with reference to  FIGS. 1 and 2 . 
     The moving image display apparatus  100  according to the embodiment of the present invention shown in  FIGS. 1 and 2  is an example of a signal processing apparatus according to an embodiment of the present invention. As shown in  FIG. 1 , the moving image display apparatus  100  according to the embodiment of the present invention is provided with a display unit  111  for displaying a moving image. 
     As shown in  FIG. 2 , the moving image display apparatus  100  according to the embodiment of the present invention includes a video input unit  102 , a graphics computing unit  104 , a video input switching unit  106 , a frame rate converting unit  108 , a display mode switching unit  110 , a display unit  111 , a memory sharing unit  112 , a memory  114 , and a switching control unit  116 . 
     The video input unit  102  is an example of a first image generating unit according to an embodiment of the present invention. The video input unit  102  generates moving image signals to be displayed on the display unit  111  as moving images, from moving image sources such as television broadcasts, hard disk recorders, optical disk recorders, and other video media. The video input unit  102  generates a moving image signal with a frequency (fv) of, for example, 60 Hz. The moving image signal generated by the video input unit  102  is sent to the video input switching unit  106 . 
     The graphics computing unit  104  is an example of a second image generating unit according to an embodiment of the present invention. The graphics computing unit  104  generates moving image signals to be displayed on the display unit  111  as computer graphics moving images and generates, for example, an image displayed by an Internet WWW (World Wide Web) browser and a high-definition moving image such as three-dimensional computer graphics. In the present embodiment, the graphics computing unit  104  generates and outputs an image with higher definition than that of an image generated by the video input unit  102 . The graphics computing unit  104  generates a computer graphics moving image with a frequency (fv) of, for example, 60 Hz. The graphics computing unit  104  is connected to the memory  114  through the memory sharing unit  112 . 
     The video input switching unit  106  is an example of a first selecting unit according to an embodiment of the present invention. The video input switching unit  106  selects a moving image signal(s) supplied from the video input unit  102  and/or the graphics computing unit  104 , according to a moving image to be displayed on the display unit  111 . The moving image signal(s) selected by the video input switching unit  106  passes through the frame rate converting unit  108  and the display mode switching unit  110  and is then outputted to the subsequent display unit  111  where the moving image signal(s) is displayed as a moving image(s). 
     Note that the video input switching unit  106  may combine a moving image signal supplied from the video input unit  102  and a moving image signal supplied from the graphics computing unit  104  and output the resulting composite moving image signal. In the configuration shown in  FIG. 2 , the video input switching unit  106  may combine moving image signals as changing a combination ratio according to a coefficient value supplied from the graphics computing unit  104 . When a moving image signal supplied from the video input unit  102  and a moving image signal supplied from the graphics computing unit  104  are combined, the moving image signals are displayed on the display unit  111  as a moving image in which the moving image signals are combined. 
     The frame rate converting unit  108  is an example of an image signal processing unit according to an embodiment of the present invention. The frame rate converting unit  108  performs a frame rate conversion process for converting a frame rate, on the moving image signal outputted from the video input switching unit  106  and outputs the moving image signal whose frame rate has been converted. The frame rate converting unit  108  is connected to the memory  114  through the memory sharing unit  112 . The frame rate converting unit  108 , for example, accepts as input a moving image signal with 60 Hz which is a refresh rate for general broadcasts, etc., and generates and outputs a moving image signal with 120 Hz which is a high-quality refresh rate. The moving image signal outputted from the frame rate converting unit  108  passes through the display mode switching unit  110  and is supplied to the subsequent display unit  111  where the moving image signal is displayed as a moving image. Note that although in the present embodiment a frame rate conversion process is performed on a moving image signal, needless to say, the present invention is not limited thereto and image signal processing other than a frame rate conversion process may be performed on a moving image signal. 
     The display mode switching unit  110  is an example of a second selecting unit according to an embodiment of the present invention. The display mode switching unit  110  switches between display modes of a moving image to be displayed on the display unit  111 . The display mode switching unit  110  selects one of a moving image based on the moving image signal whose frame rate is converted by the frame rate converting unit  108  and a moving image based on the moving image signal whose frame rate is not converted and which is outputted from the video input switching unit  106  and can thereby display the selected moving image on the display unit  111 . 
     The moving image display apparatus  100  according to the present embodiment has two display modes, i.e., a high-speed display mode which is a display mode for when a moving image such as a movie is displayed at high quality and at a high refresh rate and a low-speed display mode which is a display mode for when video is displayed at a low refresh rate other than when the high-speed display mode is used, such as when high-definition computer graphics is displayed. The display mode can be switched and used by a user of the moving image display apparatus  100  according to a desired mode. 
     In the present embodiment, the timing at which the display mode is switched may be, for example, one at which the user performs an operation on a remote controller or one at which a video signal is inputted to the video input unit  102 . Examples of the operation on the remote controller by the user include switching of a video input to an external input and explicit display mode switching. 
     The display unit  111  is to display a moving image and displays a moving image based on the moving image signal outputted from the display mode switching unit  110 . For the display unit  111 , a liquid crystal display apparatus, a plasma display apparatus, an organic EL display apparatus, and other video display devices can be used. Though not shown in  FIG. 2 , the display unit  111  includes a signal processing circuit for analyzing a moving image signal supplied from the display mode switching unit  110  and displaying a moving image based on a result of the analysis. 
     The memory sharing unit  112  is an example of a third selecting unit according to an embodiment of the present invention. The memory sharing unit  112  couples connections of the graphics computing unit  104  and the frame rate converting unit  108  to a storage apparatus (memory  114 ) in the respective display modes and thereby allows a bandwidth and a capacity of the storage apparatus (memory  114 ) to be shared between the graphics computing unit  104  and the frame rate converting unit  108 . The memory sharing unit  112  may be implemented by, for example, a memory bus implemented by a semiconductor circuit. 
     The memory  114  is a semiconductor memory connected to the graphics computing unit  104  and the frame rate converting unit  108  through the memory sharing unit  112 . A bandwidth required for the memory  114  is the maximum value of the sum of a bandwidth requested to the memory sharing unit  112  by the graphics computing unit  104  and a bandwidth requested to the memory sharing unit  112  by the frame rate converting unit  108  in the respective display modes. Similarly, a capacity required for the memory  114  is the maximum value of the sum of a capacity requested to the memory sharing unit  112  by the graphics computing unit  104  and a capacity requested to the memory sharing unit  112  by the frame rate converting unit  108  in the respective display modes. 
     For example, in the high-speed display mode of the moving image display apparatus  100  according to the present embodiment, though described later, the operation of the graphics computing unit  104  is stopped. Hence, the bandwidth and capacity of the graphics computing unit  104  are not requested to the memory sharing unit  112 . Meanwhile, in the high-speed display mode, since the frame rate converting unit  108  is in operation in order to convert the refresh rate of a moving image, a bandwidth of 22.5 Gbps and a capacity of 64 MB, for example, are requested to the memory sharing unit  112 . Accordingly, in the high-speed display mode, the memory  114  requires, for example, a bandwidth of 22.5 Gbps and a capacity of 64 MB. 
     In the low-speed display mode of the moving image display apparatus  100  according to the present embodiment, the graphics computing unit  104  is in operation and thus a bandwidth of 51.2 Gbps and a capacity of 128 MB, for example, are requested to the memory sharing unit  112 . Meanwhile, in the low-speed display mode, since there is no need to convert a frame rate, the operation of the frame rate converting unit  108  is stopped and thus does not request the memory sharing unit  112  for its bandwidth and capacity. Accordingly, in the low-speed display mode, the memory  114  requires, for example, a bandwidth of 51.2 Gbps and a capacity of 128 MB. 
     Hence, in such a case, the bandwidth and capacity required for the memory  114  are a bandwidth of 51.2 Gbps and a capacity of 128 MB which are maximum values and required for the graphics computing unit  104 . When the memory  114  is implemented using a plurality of semiconductor memory apparatuses, each, for example, providing a bandwidth of 12.8 Gbps and a capacity of 32 MB, operating at a data rate of 800 MHz, and having a 16-bit width, the memory  114  can be implemented using four of such semiconductor memory apparatuses. Thus, comparing with the above-described moving image display apparatus  10  in related art, the number of semiconductor memory apparatuses of the same type can be reduced by two. 
     The switching control unit  116  controls switching operations of the display mode switching unit  110  and the memory sharing unit  112 . For example, when the user of the moving image display apparatus  100  makes a setting to display a moving image on the display unit  111  in the high-speed display mode, the switching control unit  116  controls the display mode switching unit  110  to be connected to the frame rate converting unit  108  and controls the memory sharing unit  112  to connect the frame rate converting unit  108  to the memory  114 . When the user of the moving image display apparatus  100  makes a setting to display a moving image on the display unit  111  in the low-speed display mode, the switching control unit  116  controls the display mode switching unit  110  to be connected to the video input switching unit  106  and controls the memory sharing unit  112  to connect the graphics computing unit  104  to the memory  114 . 
     The configuration of the moving image display apparatus  100  according to the embodiment of the present invention has been described above. Next, the operation of the moving image display apparatus  100  according to the embodiment of the present invention will be described. 
     (3) OPERATION OF THE MOVING IMAGE DISPLAY APPARATUS ACCORDING TO THE EMBODIMENT OF THE PRESENT INVENTION 
     The operation of the moving image display apparatus  100  according to the embodiment of the present invention will be described for each display mode. First, the operation of the moving image display apparatus  100  for when a moving image is displayed in the high-speed display mode will be described. 
       FIG. 3  is an illustrative view showing the operation of the moving image display apparatus  100  for when a moving image is displayed in the high-speed display mode. In the moving image display apparatus  100  according to the embodiment of the present invention, in the high-speed display mode, the operation of the graphics computing unit  104  is stopped and the frame rate converting unit  108  is in operation. Thus, in  FIG. 3 , for convenience sake, the graphics computing unit  104  whose operation is stopped, lines connected to the graphics computing unit  104 , and a line connected directly to the display mode switching unit  110  from the video input switching unit  106  are indicated by dashed lines to show that the operation is stopped. 
     To allow the moving image display apparatus  100  according to the embodiment of the present invention to operate in the high-speed display mode, for example, a CPU or any other control unit (not shown) sends out an activation instruction to the video input unit  102  and sends out a pause instruction to the graphics computing unit  104 . Also, the video input switching unit  106  is instructed to select an output from the video input unit  102  and an activation instruction is sent out to the frame rate converting unit  108 . The display mode switching unit  110  is instructed to select an output from the frame rate converting unit  108  and the display unit  111  is instructed for high-speed display to display a moving image whose refresh rate is 120 Hz. Note that the order in which the instructions are sent out to the respective units may be any order. 
     In the high-speed display mode, when a moving image signal having a 60 Hz refresh rate is inputted from the video input unit  102 , the moving image signal passes through the video input switching unit  106  and is sent to the frame rate converting unit  108 . The frame rate converting unit  108  performs a process of converting the refresh rate from 60 Hz to 120 Hz. As regards the refresh rate conversion process performed by the frame rate converting unit  108 , which is not directly related to the present invention, a detailed description is omitted. 
     When the refresh rate of the moving image signal is converted from 60 Hz to 120 Hz by the frame rate converting unit  108 , the frame rate converting unit  108  outputs the converted moving image signal to the display unit  111  through the display mode switching unit  110 . The display unit  111  displays a moving image with a 120 Hz refresh rate which is outputted from the frame rate converting unit  108 . 
     As described above, in the high-speed display mode, the operation of the graphics computing unit  104  is stopped. Thus, in the high-speed display mode, the bandwidth and capacity of the graphics computing unit  104  are not requested to the memory sharing unit  112 . In contrast, in the high-speed display mode, since the frame rate converting unit  108  is in operation in order to convert the refresh rate of a moving image signal, a bandwidth of 22.5 Gbps and a capacity of 64 MB, for example, are requested to the memory sharing unit  112 . Accordingly, in the high-speed display mode, the memory  114  requires, for example, a bandwidth of 22.5 Gbps and a capacity of 64 MB. 
     Next, the operation of the moving image display apparatus  100  for when a moving image is displayed in the low-speed display mode will be described.  FIG. 4  is an illustrative view showing the operation of the moving image display apparatus  100  for when a moving image is displayed on the display unit  111  in the low-speed display mode. 
     In the moving image display apparatus  100  according to the embodiment of the present invention, in the high-speed display mode, the graphics computing unit  104  is in operation and the operation of the frame rate converting unit  108  is stopped. Thus, in  FIG. 4 , for convenience sake, the frame rate converting unit  108  whose operation is stopped, lines connected to the frame rate converting unit  108 , and a line connected directly to the display mode switching unit  110  from the video input switching unit  106  are indicated by dashed lines to show that the operation is stopped. 
     To allow the moving image display apparatus  100  according to the embodiment of the present invention to operate in the low-speed display mode, for example, a CPU or any other control unit (not shown) sends out a pause instruction to the video input unit  102  and sends out an activation instruction to the graphics computing unit  104 . Also, the video input switching unit  106  is instructed to select an output from the graphics computing unit  104  and a pause instruction is sent out to the frame rate converting unit  108 . The display mode switching unit  110  is instructed to select an output from the video input switching unit  106  and the display unit  111  is instructed for low-speed display to display a moving image whose refresh rate is 60 Hz. Note that the order in which the instructions are sent out to the respective units may be any order. 
     According to  FIG. 4 , a moving image signal is supplied from the graphics computing unit  104 . On the other hand, in the low-speed display mode, a moving image signal may be supplied from the video input unit  102 .  FIG. 4  shows the case of using the memory  114  to supply a moving image signal from the graphics computing unit  104 . 
     In the example shown in  FIG. 4 , in the low-speed display mode, when a moving image signal having a 60 Hz refresh rate is inputted from the graphics computing unit  104 , the moving image signal passes through the video input switching unit  106  and the display mode switching unit  110  without passing through the frame rate converting unit  108  and is then outputted to the display unit  111 . The display unit  111  displays a moving image with a 60 Hz refresh rate which is supplied from the graphics computing unit  104 . 
     As described above, in the low-speed display mode of the moving image display apparatus  100  according to the present embodiment, the graphics computing unit  104  is in operation and thus a bandwidth of 51.2 Gbps and a capacity of 128 MB, for example, are requested to the memory sharing unit  112 . Meanwhile, in the low-speed display mode, since there is no need to convert a frame rate, the operation of the frame rate converting unit  108  is stopped and thus does not request the memory sharing unit  112  for its bandwidth and capacity. Accordingly, in the low-speed display mode, the memory  114  requires, for example, a bandwidth of 51.2 Gbps and a capacity of 128 MB. 
     As such, the portions operating in the moving image display apparatus  100  vary depending on the display mode of a moving image to be displayed on the display unit  111 . Hence, by using semiconductor memories in a shared manner between the operating portions that vary depending on the display mode, the number of semiconductor memories to be used can be reduced, contributing to a reduction in circuit area and cost. 
     Note that although in the above description two types of display modes for a moving image to be displayed on the display unit  111  are exemplified, i.e., the high-sped display mode and the low-speed display mode, other display modes may be present. For example, as a display mode for a moving image to be displayed on the display unit  111 , a composite display mode in which the high-speed display mode and the low-speed display mode are combined may be present. 
       FIG. 5  is an illustrative view showing the operation of the moving image display apparatus  100  for when a moving image is displayed on the display unit  111  in a composite display mode in which the high-speed display mode and the low-speed display mode are combined. In the composite display mode according to the present embodiment, the graphics computing unit  104  generates a moving image signal by three-dimensional computer graphics with lower definition than that in the low-speed display mode, and at the same time, the frame rate converting unit  108 , for example, accepts as input a moving image signal with 60 Hz which is a normal refresh rate and generates an intermediate-quality moving image signal with a 120 Hz refresh rate. Then, in the composite display mode according to the present embodiment, the display mode switching unit  110  outputs a composite moving image signal formed from the moving image signal supplied from the video input unit  102  and the moving image signal supplied from the graphics computing unit  104 . 
     To allow the moving image display apparatus  100  according to the embodiment of the present invention to operate in the composite display mode, for example, a CPU or any other control unit (not shown) sends out an activation instruction to the video input unit  102  and also sends out an activation instruction to the graphics computing unit  104 . The video input switching unit  106  is instructed to combine an output from the video input unit  102  and an output from the graphics computing unit  104  at any combination ratio and output the combined signal. An activation instruction is sent out to the frame rate converting unit  108 . The display mode switching unit  110  is instructed to select an output from the frame rate converting unit  108  and the display unit  111  is instructed for high-speed display to display a moving image whose refresh rate is 120 Hz. Note that the order in which the instructions are sent out to the respective units may be any order. 
     Accordingly,  FIG. 5  shows a state in which the memory  114  is shared between the graphics computing unit  104  and the frame rate converting unit  108 . In the composite display mode, the graphics computing unit  104  requests the memory sharing unit  112  for, for example, a bandwidth of 24.9 Gbps and a capacity of 64 MB. Also, in the composite display mode, the frame rate converting unit  108  requests the memory sharing unit  112  for, for example, a bandwidth of 13.5 Gbps and a capacity of 32 MB. Thus, in the composite display mode, the memory  114  requires a bandwidth of 38.4 Gbps and a capacity of 96 MB. Note that when the memory  114  is shared between the graphics computing unit  104  and the frame rate converting unit  108 , the memory sharing unit  112  may control a connection destination such that access to the memory  114  is performed in a time division manner. 
     When the moving image display apparatus  100  has two modes, i.e., the low-speed display mode and the composite display mode, with an operation in the low-speed display mode requiring a bandwidth of 51.2 Gbps and a capacity of 128 MB in the memory  114 , the bandwidth and capacity required for the memory  114  are a bandwidth of 51.2 Gbps and a capacity of 128 MB which are maximum values of the two display modes. When the memory  114  is implemented using a plurality of semiconductor memory apparatuses, each, for example, providing a bandwidth of 12.8 Gbps and a capacity of 32 MB, operating at a data rate of 800 MHz, and having a 16-bit width, the memory  114  can be implemented using four of such semiconductor memory apparatuses. 
       FIG. 6  is an illustrative view showing an example of moving images displayed on the display unit  111  in the composite display mode in the moving image display apparatus  100  according to the embodiment of the present invention.  FIG. 6  shows a data broadcasting screen  150  in terrestrial digital broadcasting or BS digital broadcasting, as an example of moving images displayed on the display unit  111  in the composite display mode in the moving image display apparatus  100  according to the embodiment of the present invention. On the data broadcasting screen shown in  FIG. 6 , a moving image from the video input unit  102  is displayed on an upper right portion of the screen denoted by reference numeral  152  and moving images generated by the graphics computing unit  104  are displayed in other areas. 
     Even when moving images are thus displayed by a combination of the high-speed display mode and the low-speed display mode, by using semiconductor memories in a shared manner between the graphics computing unit  104  and the frame rate converting unit  108 , the number of semiconductor memories to be used can be reduced, contributing to a reduction in circuit area and cost. 
     The operation of the moving image display apparatus  100  according to the embodiment of the present invention has been described above for each display mode. In addition, the above-described operations of the moving image display apparatus  100  may be performed in a manner such that a control means such as a CPU provided in the moving image display apparatus  100  sequentially reads a computer program stored in a storing means in the moving image display apparatus  100  and executes the computer program. 
     (4) CONCLUSIONS 
     As described above, according to the embodiment of the present invention, the moving image display apparatus  100  includes the memory sharing unit  112  and the display mode switching unit  110 . By the memory sharing unit  112  and the display mode switching unit  110 , when a moving image such as a movie is displayed at high quality and at a high refresh rate the high-speed display mode is used, and when a mode other than the high-speed display mode is used, such as when high-definition computer graphics is displayed, the low-speed display mode in which video is displayed at a low refresh rate is used. By using these two modes by switching them, high-quality display of a moving image such as a movie at a high refresh rate and display of high-definition computer graphics can be implemented with a smaller circuit area and at lower hardware cost, without impairing user&#39;s substantial convenience, as compared with moving image display apparatuses in related art. 
     By controlling a selection of a connection destination made by the memory sharing unit  112  such that the memory  114  is shared between the graphics computing unit  104  and the frame rate converting unit  108 , display mode switching can be implemented at lower hardware cost as compared with moving image display apparatuses in related art. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
     Although the above embodiment describes, as an example, the moving image display apparatus  100  that generates and displays moving image signals, needless to say, the present invention is not limited thereto and not only moving images but also still images may be generated and displayed.