Patent Publication Number: US-9418631-B2

Title: Display control apparatus and method and image processing method

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
     This patent application is based on Taiwan, R.O.C. patent application No. 100118243 filed on May 25, 2011. 
     FIELD OF THE INVENTION 
     The present invention relates to a display technology field, and more particularly, to a display control apparatus for reducing image scaling and method thereof. 
     BACKGROUND OF THE INVENTION 
     In the display technology field, a scaler, widely applied to a display control apparatus, e.g., a television (TV) or a display, is capable of appropriately scaling images and displayed contents having different resolutions from image sources and displaying the image contents on the display apparatus completely. When a resolution of image content from an image source becomes higher and higher, the resolution needs to be reduced to conform to a display panel having a lower resolution, i.e., the image frame needs to be scaled to conform to the display panel having the lower resolution; however, the resolution of the image content may be undesirably affected, especially content having a high degree of detail, including small characters, may become blurred after having been scaled in this manner. 
     As multimedia developed, in addition to a personal computer (PC), other types of multimedia devices also serve as image sources of the display apparatus, e.g., a DVD player or video game system. Most players can define output resolutions according to support ability of a transmission interface, but most users are unlikely to adjust the resolutions according to different contents. Therefore, when a resolution of content is different from an output resolution of a player (e.g., the output resolution of the player is 1920×1080 pixels, and the resolution of the content is 1366×768 pixels), the player needs to first scale the content to the output resolution, and then transmit the content to a display end via a transmission interface supporting the output resolution as shown in  FIG. 1 . However, when the resolution of a panel at the display end is different from the output resolution of the player, the content needs to be scaled again to conform to the resolution of the panel before it is displayed at the display end. Image quality displayed on the resultant panel may be damaged, for example, images may exhibit pixel loss or degradation when the content is scaled multiple times in this manner. 
     In addition, in applications having three-dimensional (3D) display, a pair of active 3D glasses are turned on and turned off to conform to left and right frames of the display control apparatus to achieve the desired 3D display effect. Since each image frame comprises a data enable (DE) region and a blanking region, in the prior art, the pair of 3D glasses is only turned on during a scan interval corresponding to the blanking region of the image frame after the DE region (i.e., to-be-displayed content) of an image frame is completely displayed in order to properly display the complete display content. When the turn-on time of the pair of 3D glasses is increased, the frame luminance perceived by a user is typically increased. In addition, since a liquid crystal display (LCD) apparatus has a long response time of liquid crystal elements, a long turn-on time of the pair of 3D glasses can stabilize the liquid crystal elements to avoid liquid crystal elements not responding in order to achieve an accurate status before the pair of 3D glasses is turned off. Therefore, the turn-on time of the pair of 3D glasses influences the 3D display effect. However, when the scaler of the display control apparatus downscales an image from a high-resolution image source to the lower resolution of the panel, the blanking region of the image is correspondingly scaled down, so that the turn-on time of the pair of 3D glasses is reduced, which is unbeneficial to the 3D display effect of the display. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing issues, one object of the present invention is to provide a display control apparatus and method thereof capable of reducing image scaling times while maintaining image quality. 
     Another object of the present invention is to provide a display control apparatus and method thereof capable of selecting a display region in a source image without performing scaling by conforming to a resolution of a display panel so as to maintain a definition of image content. 
     Yet another object of the present invention is to provide a display control apparatus and method thereof capable of performing display according to a predetermined display timing signal to extend a turn-on time of a pair of 3D glasses thereby improving 3D display effect. 
     According to an embodiment of the present invention, a method for displaying an image frame on a display panel comprises providing the image frame comprising a valid data region that is larger than a visual region of the display panel; generating an output timing signal according to a relative position of the visual region corresponding to the valid data region, so that a partial region of the valid data region corresponds to the visual region of the display panel; and outputting the image frame and the output timing signal to the display panel, so as to display the partial region of the valid data region in the visual region of the display panel according to the output timing signal. 
     According to another embodiment of the present invention, a display control apparatus for controlling a display panel to display an image frame comprises a data processing unit, for providing the image frame comprising a valid data region that is larger than a visual region of the display panel; and a timing generating unit, for generating an output timing signal according to a relative position of the visual region corresponding to the valid data region, so that a partial region of the valid data region corresponds to the visual region of the display panel; wherein the partial region of the valid data region is displayed in the visual region of the display panel according to the output timing signal. 
     According to yet another embodiment of the present invention, a method comprises providing a source image frame comprising a source valid data region; generating an output image frame according to an output resolution and the source image frame, so that the source valid data region forms a part of the an output valid data region of the output image frame, with the output resolution being larger than that of the source valid data region; generating selection information for indicating a position of the source valid data region in the output valid data region; and outputting the output image frame and the selection information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of image scaling performed on a player end and a display end. 
         FIG. 2A  is a block diagram of a display control apparatus in accordance with an embodiment of the present invention. 
         FIG. 2B  is a block diagram of a display control apparatus in accordance with another embodiment of the present invention. 
         FIG. 3A  and  FIG. 3B  are schematic diagrams of the display manner as illustrated in  FIG. 2A  and a conventional display manner, respectively. 
         FIG. 4A  and  FIG. 4B  are schematic diagrams of the display manner as illustrated in  FIG. 2B  and a conventional display manner, respectively. 
         FIG. 5  is a schematic diagram of different selection parts in a valid data region as illustrated in  FIG. 2B  in accordance with an embodiment of the present invention. 
         FIG. 6  is a schematic diagram of a first manner for a timing generating unit illustrated in  FIG. 2A  and  FIG. 2B  to generate an output timing signal in accordance with an embodiment of the present invention. 
         FIG. 7  is a schematic diagram of a second manner for a timing generating unit illustrated in  FIG. 2A  and  FIG. 2B  to generate an output timing signal in accordance with an embodiment of the present invention. 
         FIG. 8  is a block diagram of a display control apparatus in accordance with another embodiment of the present invention. 
         FIG. 9  is a schematic diagram of a display manner applied to the display control apparatus illustrated in  FIG. 8 . 
         FIG. 10  is a flow chart of a display method in accordance with an embodiment of the present invention. 
         FIG. 11  is a flow chart of a display method in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 2A  is a block diagram of a display control apparatus in accordance with an embodiment of the present invention. A display control apparatus  20  comprises a data processing unit  21  and a timing generating unit  22 . The data processing unit  21  receives an image frame that is temporarily stored in a buffer. The image frame comprises a valid data region and an invalid data region, and the valid data region is larger than a visual region (i.e., a region practically visible to a user) of a display panel  23 . The valid data region can be a DE region, and the invalid data region can be a blanking region. The timing generating unit  22  generates an output timing signal to the display panel  23 , so that a partial region (referred to as a first partial region in the following description) of the valid data region corresponds to the visual region of the display panel  23 . Therefore, when the data processing unit  21  outputs the image frame to the display panel  23  for display, the display panel  23  displays the first partial region in the visual region according to the output timing signal.  FIG. 3A  is a schematic diagram of an H tt1 ×V tt1  frame (including V tt1  scan lines each having H tt1  pixels) displayed in the foregoing display manner. The frame comprises an H 1 ×V DE1  valid data region (i.e., the data enable region), and the remaining part is an invalid data region (i.e., the blanking region). The panel can only display an H 1 ×V 1  region (i.e., the first partial region represented by diagonal lines) in the visual region. As observed in  FIG. 3A , the number of scan lines in the first partial region is smaller than that of the scan lines in the valid data region (i.e., V 1  is smaller than V DE1 ).  FIG. 3B  shows a schematic diagram of an H tt2 ×V tt2  frame in a conventional display manner. An H 2 ×V 2  region (H 2 =H 1 , V 2 =V 11 ) is displayed in the visual region of the panel, and is the valid data region of the H tt2 ×V tt2  frame (i.e., V DE2 =V 2 ). By comparing  FIG. 3A  with  FIG. 3B , a vertical resolution V DE1  of the valid data region in  FIG. 3A  is larger than a vertical resolution V DE2  of the valid data region in  FIG. 3B . It is to be noted that, although a horizontal resolution of the valid data region in  FIG. 3A  is equal to that of the valid data region in  FIG. 3B  (i.e., H 2 =H 1 ), H 1  may also be defined as being larger than H 2  in other embodiments. In order to let the display panel  23  perform the display manner shown in  FIG. 3A , the timing generating unit  22  needs to generate a specific output timing signal, e.g., a specific data enable signal corresponding to the valid data region in  FIG. 3A , and the number of scan lines corresponding to the specific data enable signal is larger than that of scan lines of the visual region of the panel. For example, when the visual region of the panel has a resolution of 1366×768, the display control unit  21  generates an output timing signal conforming to the valid data region having a resolution of 1366×900 or 1920×1080. 
     Preferably, when the display panel  23  supports 3D display, the timing generating unit  22  further generates a glasses control signal, so that a pair of 3D glasses is turned on during a scan interval corresponding to a remaining region of the valid data region excluding the first partial region. Compared to the prior art, a turn-on time of the pair of 3D glasses can be extended via the approach in this embodiment. The pair of 3D glasses can be turned only on during a scan interval of the blanking region in the conventional display manner, and must be turned off during a scan interval of the entire valid data region as shown in  FIG. 3B . However, according to  FIG. 3A , in this embodiment, the pair of 3D glasses can be still turned-on during a scan interval of the remaining region of the valid data region excluding the first partial region. Therefore, as far as a proportion that the turn-on time of the pair of 3D glasses occupies a total scan interval of the frame is concerned, the proportion (i.e., (V tt1 −V 1 )/V tt1 ) in  FIG. 3A  is larger than the proportion (i.e., (V tt2 −V 2 )/V tt2  in  FIG. 3B , where V tt2  is smaller than V tt1 , V 2 =V 1 ), so that the turn-on time of the pair of 3D glasses is longer in  FIG. 3A  than that in  FIG. 3B  with the same length of scan interval of the frame. 
       FIG. 2B  is a block diagram of a display control apparatus in accordance with another embodiment of the present invention. Compared to  FIG. 2A , the display control apparatus  30  in  FIG. 2B  further comprises a determining unit  31 , for determining a relative position of the first partial region in the valid data region of the frame according to selection information, and generating corresponding position information to the timing generating unit  22 . The timing generating unit  22  generates the corresponding output timing signal according to the position information, so that the first partial region can be accurately displayed in the visual region of the display panel  23 . Generation of the corresponding output timing signal according to the position information is described in detail below. When the resolution of the valid data region of the frame is larger than that of the visual region of the display panel  23  (e.g., a maximum resolution supported by the visual region, or a user-defined resolution), the display control apparatus  30  achieves an effect of reducing image scaling times. For example, in  FIG. 4A , since the resolution of the valid data region of the frame received by the data processing unit  21  is larger than that of the visual region of the panel, after the determining unit  31  selects the relative position (e.g., marked by diagonal lines) of the first partial region according to the selection information, the data processing unit  21  directly outputs the frame that is not scaled to the display panel  23 , so that the first partial region is directly displayed in the visual region of the panel to maintain a definition of original source content. The prior art (e.g.,  FIG. 4B ) requires that the received frame needs to be scaled, so that a down-scaled valid data region is displayed in the visual region of the panel, undesirably affecting the resultant definition of the display content. 
     In this embodiment, when the display panel  23  supports 3D display, as observed in  FIG. 4A  and  FIG. 4B , the turn-on time of the pair of 3D glasses is longer than in the prior art. Referring to  FIG. 4A , according to a glasses control signal generated by the timing generating unit  22 , the turn-on time of the pair of 3D glasses is defined as being within in a scan interval of the remaining region of the valid data region excluding the visual region of the panel. Referring to  FIG. 4B , since the valid data region and the invalid data region are proportionally changed when image scaling is performed in the prior art, the proportion that the turn-on time of the pair of 3D glasses occupies the total scan interval of the frame is equal to that of the originally received frame. Therefore, the proportion that the turn-on time of the pair of 3D glasses occupies the total scan interval of the frame in  FIG. 4A  is larger than in  FIG. 4B . In other words, compared to  FIG. 4B , the turn-on time of the pair of 3D glasses is increased in  FIG. 4A . 
     More specifically, the foregoing selection information is user-inputted. For example, when the display panel  23  has a touch function or provides a user interface (e.g., on screen display (OSD)), the user can input the selection information via a touch manner or by operating the user interface to select a to-be-displayed region. Accordingly, when image content having a lot of details and small characters is observed, the user directly selects a favorite part to display without undesirably affect the definition due to image scaling. For example, referring to  FIG. 5 , the user can accurately display (without scaling) source images of different parts (e.g., the upper left part or lower right part) of the valid data region. When the display panel  23  supports a 90-degree rotation function, a horizontal display may be rotated to a vertical display as shown in  FIG. 5  (it is to be noted that, the horizontal display and the vertical display may be performed in different valid data regions). 
     Two approaches for generating the output timing signal by the timing generating unit  22  are described below. The first approach is to generate a predetermined horizontal data enable (HDE) signal, and the number of scan lines corresponding to the HDE signal is determined according to the number of scan lines in the first partial region to achieve an effect that only a part (i.e., the first partial region) of the valid data region of the frame is displayed in the visual region of the panel. For example, the number of scan lines corresponding to the HDE signal is directly equal to that of the scan liens in the first partial region as shown in  FIG. 6 . The data processing unit  21  receives data of the frame according to a receiving timing signal, which comprises the HDE signal having each pulse corresponding to a scan line of the valid data region, a horizontal synchronization (H-sync) signal and a vertical synchronization (V-sync) signal. When the timing generating unit  22  generates the output timing signal, in addition to the H-sync signal and the V-sync signal, the timing generating unit  22  further shields a part of the HDE signal that originally corresponds to the valid data region of the whole frame, and only remains a part of the HDE signal corresponding to the first partial region as the HDE signal for display on the panel. Accordingly, the display panel  23  can display the first partial region in its visual region according to the modified HDE signal. 
     The second approach is to remain the received HDE signal without performing shielding, and to set a relative position of a start scan line of the visual region of the panel in the valid data region by adjusting timing between a vertical reference signal and the HDE signal. It is to be noted that, when the originally received timing signal received by the data processing unit  21  comprises a vertical data enable (VDE) signal (having each pulse corresponding to a whole valid data region), since a pulse start position of the VDE signal corresponds to a first pulse of the HDE signal, the relative position of the start scan line of the visual region of the panel in the valid data region is set by adjusting the timing between the vertical reference signal and the VDE signal. The vertical reference signal may be the V-sync signal or a vertical start pulse signal, which is a reference time point for displaying the frame. The second approach is applicable to a situation that there is a fixed timing difference between the start scan line position of the visual region of the panel and the vertical reference signal. In practical applications, the fixed timing difference is represented by the number of scan lines. Since the position information generated by the determining unit  31  records the relative position of the first partial region in the valid data region, i.e., it is determined in advance the relative position of the start scan line of the visual region of the panel in the valid data region, the timing generating unit  22  adjusts the relative timing between the vertical reference signal and the HDE signal (or the VDE signal) when the output timing signal is generated according to the position information, so that the fixed timing difference between the vertical reference signal and the predetermined start scan line position of the visual region of the panel is maintained, and thus the start scan line of the visual region of the panel can be indirectly set at the accurate relative position to accurately display the first partial region on the visual region of the panel. Referring to  FIG. 7 , the relative position of the visual region of the panel in the valid data region is changed for the reason that the user inputs different selection information, for example. Therefore, the timing generating unit  22  adjusts timing of the V-sync signal without shielding the HDE signal to maintain the fixed timing difference (a duration of two scan lines as shown in  FIG. 7 ) between the V-sync signal and the predetermined start scan line position of the visual region of the panel, and thus accurately display the selected region in the visual region of the panel. The overmuch HDE signal is omitted by the display panel  23 . 
     In an embodiment, the frame received by the display control apparatus  30  and the selection information are provided by an image source as shown in  FIG. 8 . An image source  81  provides a frame to the data processing unit  21 , and provides the selection information corresponding to the frame to the determining unit  31 . The image source  81  can be a multimedia player, e.g., a DVD player. The image source  81  generates the frame and the corresponding selection information according to a source frame and an output resolution. The image source  81  comprises a transmission interface for transmitting the frame to the data processing unit  21 , e.g., the transmission interface can be a Video Graphics Array (VGA) interface, a DisplayPort interface, an High-Definition Multimedia Interface (HDMI), a Digital Visual Interface (DVI), or a wireless interface. The output resolution is adopted by the image source  81  when transmitting the frame, and the transmission interface supports the output resolution. The source frame comprises a source valid data region (i.e., source image content) corresponding to the foregoing first partial region, and the resolution of the valid data region of the frame (i.e., the output frame of the image source  81 , i.e., the frame received by the data processing unit  21 ) is equal to the output resolution and is larger than the resolution of the source valid data region as shown in  FIG. 9 . In other words, the embodiment illustrated in  FIG. 8  is applied to a situation that the output resolution of the image source  81  is larger than that of the source image. It is to be noted that, as shown in  FIG. 9 , image data only exists in the first partial (represented by diagonal lines) in the valid data region of the frame, the remaining part of the valid data region of the frame presenting in conjunction with the output resolution contains no image data at all. When the frame is received at a display end (comprising the display control apparatus  30  and the display panel  23 ), the determining unit  31  determines the relative position of the first partial region in the valid data region according to the selection information provided by the image source  81 , and the timing generating unit  22  generates the corresponding output timing signal to display the first partial region in the visual region of the panel as shown in  FIG. 9 . 
     More specifically, the image source  81  receives support mode information from the determining unit  31  to obtain a resolution supported by the visual region of the display panel  23 . The support mode information and the foregoing selection information can be transmitted and received via a predetermined communication mechanism between the image source  81  and the display control apparatus  30 , e.g., the predetermined communication mechanism is a display data channel (DDC), a DisplayPort auxiliary channel, and the like. Referring to  FIG. 9 , when the image source  81  determines that the resolution of the visual region of the display panel  23  is equal to that of the source valid data region of the source frame according to the support mode information, the image source  81  directly regards the source valid data region as the first partial region without performing scaling when the frame to be outputted to the data processing unit  21  is generated according to the source frame. Since the resolution of the first partial region of the frame received at the display end is equal to that of the visual region of the panel, scaling need not be performed to directly display the frame. In the prior art, the source image is scaled to conform to the output resolution of the image source  81 , and is again scaled to conform to the resolution of the visual region of the panel at the display end. Therefore, compared to the prior art, the embodiment provided in  FIG. 8  is capable of avoiding image scaling to improve resultant image display quality. 
     When the image source  81  determines that the resolution of the visual region of the display panel  23  is different from that of the source valid data region according to the support mode information, two approaches are introduced below. 
     The first approach is to perform scaling via the image source  81 . When the frame to be outputted to the data processing unit  21  is generated according to the source frame, the image source  81  performs image scaling on the source valid data region to generate the first partial region, so that the resolution of the first partial region is equal to that of the visual region of the panel. Accordingly, the received frame is directly displayed at the display end without performing scaling. 
     The second approach is to perform scaling at the display end. When the frame to be outputted to the data processing unit  21  is generated according to the source frame, the image source  81  directly regards the source valid data region as the first partial region. When the data processing unit  21  receives the frame, image scaling is performed on the first partial region to convert the resolution of the first partial region to the resolution of the visual region of the panel to display. 
     Image scaling is only performed once via either the first approach or the second approach, so that the method provided by the embodiment is capable of achieving the effect of reducing image scaling at a lower computational cost, since image scaling is performed twice in the prior art. 
       FIG. 10  is a flow chart of a display method in accordance with an embodiment of the present invention. The display method is applied to a display control apparatus  30  in  FIG. 2B . In Step  101 , a frame and selection information are received. The frame comprises a valid data region comprising a partial region (i.e., the foregoing first partial region), and the selection information is for determining a relative position of the first partial region in the valid data region. The selection information is user-inputted or is provided by an image source. 
     In Step  102 , an output timing signal is generated according to the relative position of the first partial region in the valid data region. For example, two generating approaches are described below. 
     According to the first approach, the output timing signal comprises an HDE signal, and the number of scan lines corresponding to the HDE signal is determined according to the number of scan lines in the first partial region, which is described in detail in the previous description and shall not be described for brevity. 
     According to the second approach, the output timing signal comprises a vertical reference signal and an HDE signal (or a VDE signal). Relative timing between the vertical reference signal and the HDE signal (or the VDE signal) is determined according to the foregoing relative position. The vertical reference signal can be a V-sync signal or a vertical start pulse signal, which is described in detail in the previous description and shall not be described for brevity. 
     In Step  103 , the frame is displayed on a display panel according to the output timing signal. The first partial region is displayed in a visual region of the display panel, and the number of scan lines in the first partial region is smaller than that of the scan lines in the valid data region. 
     Preferably, when the display panel supports 3D display, the display method in  FIG. 10  further comprises a step (not shown) of providing a glasses control signal, so that a pair of 3D glasses is turned on during a scan interval corresponding to the remaining region of the valid data region excluding the first partial region. Accordingly, compared to the prior art, a turn-on time of the pair of 3D glasses is extended, which is described in detail in the previous description and shall not be described for brevity. 
       FIG. 11  shows a flow chart of a display method in accordance with another embodiment of the present invention, and the display method is applied to the display control apparatus illustrated in  FIG. 8 . In this embodiment, a frame and selection information received at the display end are provided by an image source. In Step  111 , the image source generates the frame and the selection information according to a source frame and an output resolution. The source frame comprises a source valid data region corresponding to the foregoing first partial region, and a resolution of the valid data region of the frame is equal to the output resolution and is larger than the resolution of the source valid data region. In Step  112 , the image source outputs the frame and the selection information, and the frame is outputted according to the output resolution. The following processes, Step  113  to Step  115 , are equivalent to Step  101  to Step  103  in  FIG. 10 . In this embodiment, when the resolution of the visual region of the panel is equal to that of the source valid data region, in Step  111 , when the image source generates the frame, the source valid data region is regarded as the first partial region to avoid image scaling, which is described in detail in the previous description and shall not be described for brevity. When the resolution of the visual region of the panel is not equal to that of the source valid data region, in Step  111 , when the image source generates the frame, image scaling is performed on the source valid data region to generate the first partial region, so that the resolution of the first partial region is equal to that of the visual region of the panel. Accordingly, the number of image scaling is reduced in this embodiment than in the prior art, which is described in detail in the previous description and shall not be described for brevity. 
     Another situation exists when the resolution of the visual region of the panel is not equal to that of the source valid data region. In Step  111 , when the image source generates the frame, the source valid data region is regarded as the first partial region, and between Step  113  and Step  114 , the flow further comprises a step (not shown) of performing image scaling on the first partial region to convert the resolution of the first partial region to that of the visual region of the panel, so that the number of image scaling is reduced compared to the prior art, which is described in detail in the previous description and shall not be described for brevity. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not to be limited to the above embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.