Patent Grant
9047800
This relates generally to displays, and more particularly, to techniques for selecting an appropriate display resolution when an electronic device is using an external display.
Electronic devices such as computers and cellular telephones often contain displays. Internal device displays may often be relatively small. Many electronic devices allow a user to display information on external display to take advantage of the potentially larger size and enhanced viewing position available when using an external display.
External displays may vary significantly in their capabilities. This can pose challenges in situations in which a user desires to use an external display. If care is not taken, the resolution that a device uses to supply output to an external display will not be well matched to the supported resolutions of the external display.
It would therefore be desirable to be able to provide improved techniques for selecting a resolution to be used in displaying information on an external display.
A user may couple an external display to an electronic device using a communications path. The communications path may be used in forming a communications link between the external display and the electronic device. The link may have an associated bandwidth.
Extended display identification data or other information on the capabilities of the external display may be provided to the electronic device over the communications path. The extended display identification data may include a list of timing elements (sometimes referred to as display resolutions). Each timing element may include display parameters such as a horizontal active pixel count, a vertical active pixel count, a pixel clock and other parameters associated with the operation of the external display.
The electronic device may tag timing elements with their type. For example, the device may tag timing elements as being established timings, standard timings, or detailed timings. The device may also tag Consumer Electronics Association (CEA) timing elements.
Certain timing elements may be more likely than others to be appropriate for displaying information on the external display. For example, the first-listed detailed timing element may be more likely than other timing elements to be associated with a native (preferred) display resolution. Accordingly, the electronic device may flag those timing elements as being preferred.
After tagging timing elements with their types and flagging preferred timing elements, the electronic device may use process the timing elements using a scoring function. The scoring function may be used to rate each timing element based on its appropriateness for use in displaying information on the external display.
A resulting scored list of timing elements may be sorted by score. The sorted scored list may be filtered to remove inappropriate timing elements. For example, timing elements having pixel clocks that exceed the bandwidth of the communications link and having frame buffer requirements that exceed the frame buffer capabilities of display driver circuitry in the electronic device may be removed from the sorted scored list of timing elements.
The electronic device may automatically use a selected one of the timing elements in the filtered list in displaying information on the external display or may provide a user with an interactive opportunity to select one of these timing elements.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.
Display 12 may be a television, a computer monitor, a projector, or any other suitable equipment for displaying visual information. Display 12 may include control circuitry 18 for displaying information on display module 14. Display 12 may use a display module of any suitable type. For example, display 12 may be a liquid crystal display, an organic light-emitting diode display, a plasma display, a cathode ray tube display, an electrowetting display, an electrophoretic display, or a display that uses other display technologies.
Control circuitry 18 may contain circuits such as memory, processors, application specific integrated circuits, and other storage and processing circuitry. Communications circuitry in control circuitry 18 may be used for communicating with communications circuitry in control circuitry 26 of electronic device 24 over path 22. Control circuitry 26 of electronic device 24 may contain memory, processors, application specific integrated circuits, and other storage and processing circuitry. Display driver circuitry within control circuitry 26 may be used to display information internally using display module or externally using display 12.
Path 22 may be, for example, a cable having opposing ends with connectors. The connectors may mate with corresponding connectors in display 12 and device 24. The cable may be a display cable such as a High-Definition Multimedia Interface (HDMI) cable, a DisplayPort® cable, a Digital Visual Interface (DVI) cable, Video Graphics Array (VGA) cable, or other display cable. If desired, communications path 22 may include an optical cable or a wireless path. Configurations in which cable 22 is an electrical cable may sometimes be described herein as an example.
Electronic device 10 may be a portable electronic device such as a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, or a media player. Device 10 may also be a television, a set-top box, a desktop computer, a computer monitor into which a computer has been integrated, or other suitable electronic equipment.
Device 10 may have an internal display such as display module 30. When it is desired to display information for a user of device 10 using display module 30, control circuitry 26 may produce output for display module 30. When it is desired to display information externally using external display 12, control circuitry 26 may transmit the information that is to be displayed to control circuitry 18 of display 12. Control circuitry 18 of display 12 may then use internal display driver circuitry to display the information on display module 14.
Different displays may have different capabilities. For example, one display may support a display timing (sometimes referred to as a display resolution) of 640 pixels×480 pixels at a 60 Hz refresh rate, whereas another display may support a display timing of 1024×768 at 60 Hz. If control circuitry 26 of device 24 does not use an appropriate display timing for display module 14 when transmitting output to display 12, display 12 will not operate properly and the desired information from device 24 will not be displayed on display module 14.
Control circuitry 18 may maintain information on the supported display timings for display 12 (i.e., supported resolutions) using stored information 20. With one suitable arrangement, which is sometimes described herein as an example, stored display capabilities information 20 may use a structure such as the extended display identification data (EDID) structure to maintain information on the capabilities of display 12. This is, however, merely illustrative. Other formats may be used to store information on the display timings supported by display 12, if desired.
When a user wishes to view information on external display 12, the user may couple display 12 to device 24 using path 22. Device 24 may, in response to being coupled to display 12, obtain information from display 12 on its capabilities. For example, device 24 may request that display 12 provide device 24 with information on the capabilities of display 12. Display 12 may respond to the request from the device by providing display capabilities information such as EDID information 20.
Control circuitry 26 in device 24 can receive and process the requested information on the capabilities of display 12. For example, control circuitry 26 may extract timing elements from EDID information 20. The timing elements identify which display timings (resolutions) display 12 should theoretically support.
In practice, not all of the timing elements that are provided by display 12 to device 24 will correspond to display resolutions that are actually supported by display 12. Some display resolutions will also be more appropriate than others in displaying typical content from device 24. Moreover, system limitations such as the bandwidth available in the communications link associated with path 22 and the hardware capabilities of device 24 (e.g., the size of the frame buffer in the display driver circuitry of control circuitry 26) may restrict which timing elements are appropriate to use in displaying information on display 12. To ensure that control circuitry 26 identifies appropriate settings to use in displaying information on display 12, control circuitry 26 can score each potential timing element that is received from display 12 (e.g., each timing element in the EDID data structure) using attributes of that timing element. The timing elements can then be filtered based on their scores to determine which timing elements are appropriate for use by electronic device 24.
In general, any type of data structure or data format may be used by display 12 to convey information about the capabilities of display 12 to other equipment. Illustrative scenarios in which display capability information is conveyed in the form of extended display identification data (EDID) information are sometimes described herein as an example. The use of EDID information to convey information on display capabilities is, however, merely illustrative.
Illustrative EDID information 20 that may be maintained by display 12 is shown in
The Consumer Electronics Association (CEA) has created an indexed list of common timing elements. In block 20-N, display 12 may maintain information on which of these CEA timing elements are supported by display 12. CEA timing elements may, for example, be listed using CEA timing element indices (CEA identifiers). In the example of
It can be cumbersome to present a user of device 26 with too many choices of available display timings. Accordingly, rather than displaying all available timing elements, device 24 may rank timing elements to assist the user in selecting a satisfactory timing element. If desired, device 24 may use the ranked timing elements to present a shortened list of available timings to a user from which the user may select a desired timing. Device 24 may also be configured to make an automatic display timing selection from the ranked timing elements. Device 24 may, for example, automatically use the highest-ranked timing element, thereby avoiding the need for user input.
Any suitable scoring scheme may be used when ranking the available timings from the EDID blocks. A flow chart of steps involved in implementing an illustrative scoring function using control circuitry 26 is shown in
The operations of
At step 32, the timing element scoring function may set the value of scoring parameter SCORE to the active pixel clock divided by a scaling factor (i.e., SCORE may be made equal to the product of HT, VT, and R divided by a scaling factor of 106). As an example, the value of SCORE for a timing element with horizontal, vertical, and refresh parameters of 1920, 1080, and 60 Hz, respectively, is 124 points.
Some types of timing elements are more likely than others to be appropriate for use in displaying information on display 14. For example, standard timings 20B are generally more likely to correspond to satisfactory actual supported timings than established timings 20A. In theory, established timings 20A should be fully supported by display 12, because established timings 20A are included in EDID information 20. In practice, however, a manufacturer of a given display may sometimes include a legacy timing in established timings 20A, even though the legacy timing is not supported by the given display. Detailed timings 20C, and, particularly, the first listed detailed timing in detailed timings 20C, may be more likely than standard timings 20B to correspond to a satisfactory supported timing for the display. CEA timings 20D are likewise more likely than standard timings 20B to correspond to an appropriate supported timing for the display.
During timing element processing operations, device 24 may use control circuitry 26 to identify which timing elements in EDID information 20 are most likely to actually be supported by display 12 and are most likely to exhibit optimum performance. These “preferred” (i.e., “native”) timing elements can be flagged. During the operations of step 34, control circuitry 26 may use the scoring function to identify whether the timing element that is being processed has been flagged as being preferred. In response to identifying that the timing element is a preferred timing element, the value of SCORE for the timing element may be incremented by a predetermined amount (e.g., 10000 points or other suitable value).
At step 36, control circuitry 26 may use the scoring function to determine whether the timing element has an aspect ratio (e.g., an HT/VT value) that is the same as that of a preferred timing element. If the timing element does have an aspect ratio that matches the aspect ratio of a preferred timing element, the value of SCORE for the timing element may be incremented by a predetermined amount (e.g., 5000 points or other suitable value).
At step 38, control circuitry 26 may use the scoring function to determine whether the timing element has a refresh rate R that is the same as that of a preferred timing element. If the timing element does have a refresh rate value that matches the refresh rate of a preferred timing element, the value of SCORE for the timing element may be incremented by a predetermined amount (e.g., 1000 points or other suitable value).
At step 40, control circuitry 26 may use the scoring function to determine whether the timing element is a CEA timing element (i.e., whether the timing element was contained within CEA block 20-N of EDID information 20). If the timing element is a CEA timing element, the value of SCORE for the timing element may be incremented by a predetermined amount (e.g., 500 points or other suitable value).
At step 42, control circuitry 26 may use the scoring function to determine the type of communications link that has been established by control circuitry 26 and 18 between device 24 and display 12 and may use this information to adjust the value of SCORE. Examples of link types that may be established over communications path 22 include a High-Definition Multimedia Interface (HDMI) link, a DisplayPort® link, a Digital Visual Interface (DVI) link, and a Video Graphics Array (VGA) link. Other types of link may be used if desired. Upon ascertaining the link type that is being used by device 24, control circuitry 26 may adjust SCORE accordingly. Because displays that use HDMI links are more likely to prefer CEA-based modes of operation than displays that use DisplayPort, DVI, or VGA, control circuitry 26 may, for example, increase the value of SCORE if the timing element is a CEA timing element and the detected link type is HDMI or may increase the value of SCORE if the timing element is a non-CEA timing element and the detected link type is a non-HDMI link type such as DisplayPort, DVI, or VGA.
Other scoring criteria may be used in scoring timing elements in display capability information 20 if desired. The illustrative scoring technique of
At step 44, a user may couple device 24 and external display 12 using communications path 22. Once coupled by path 22, a communications link such may be formed between control circuitry 26 of device 24 and control circuitry 18 of display 12. In some types of communications links such as a DisplayPort link, the bandwidth associated with communications over the link may be negotiated between control circuitry 26 and control circuitry 18. The bandwidth of the link over path 22 may vary depending on the quality of path 22. If, for example, path 22 is a cable with a low bandwidth, the negotiated bandwidth of the link between device 24 and display 12 will be low. If path 22 is a high bandwidth cable, the negotiated bandwidth of the link between device 24 and display 12 will be high. An example of a negotiated bandwidth for the link between device 24 and display 12 is 3.24 Gbps. This is merely illustrative. Any suitable communications link bandwidth may be negotiated between device 24 and display 12 if desired.
At step 46, device 24 may obtain information from display 12 on the capabilities (i.e., the purported capabilities) of display 12. For example, control circuitry 26 may use protocols such as Display Data Channel (DDC) protocols to request that control circuitry 18 provide information on the capabilities of display 12 such as EDID information 20 to control circuitry 26. Display 12 may maintain EDID information 20 in storage (e.g., non-volatile memory in control circuitry 18). In response to receiving an EDID request from device 24, display 12 may transmit the requested EDID information to device 24. Device 24 may use control circuitry 26 to receive and process the transmitted EDID information. For example, control circuitry 26 may be used to parse the EDID information that has been received by extracting information such as timing elements 20A, 20B, 20C and 20D of
At step 48, control circuitry 26 may categorize the timing elements in the list by tagging timing elements with their type and by flagging those timing elements that are preferred by the display (i.e., timing elements corresponding to the display's “native” resolution). For example, control circuitry 26 can label timing elements from EDID block 20-0 as being “established” timings 20A, as being “standard” timings 20B, or as being “detailed” timings 20C and may label timings from EDID block 20-N as being “CEA” timings 20D. Timing elements that may be flagged as being “preferred” include the first listed detailed timing element and all CEA timing elements in block 20-N that have an associated high native bit.
At step 50, each of the timing elements in the labeled list of timing elements may be processed using a scoring function such as the scoring function of
At step 54, control circuitry 26 may remove timing elements from the sorted list that are not appropriate to use because their bandwidth requirements exceed the available bandwidth of the link between display 12 and device 24. If, as an example, the negotiated bandwidth between device 24 and display 12 is 1 Gbps, control circuitry 26 may filter out all timing elements having pixel clocks greater than 1 GHz). The display driver circuitry of control circuitry 26 may have a frame buffer that is used in outputting information to be displayed on display 12. If the amount of information that is being displayed on display 12 when using a particular timing element would cause the display driver circuitry to overload the frame buffer, that timing element can be removed from the sorted list.
After filtering the timing element list to remove inappropriate timing elements based on the capabilities of the display driver circuitry in control circuitry 26 of device 24 and the capabilities of the communications link over path 22, device 24 can use an appropriate timing element to display information (e.g., text, images, and/or video) from device 24 on external display 12. For example, device 24 may use one of the remaining timing elements in the list to display information on display 12.
With one suitable arrangement, the control circuitry 26 of device 24 may perform this operation automatically, without need for input from a user. Control circuitry 26 may, for example, use the timing element at the top of the sorted list (i.e., the timing element with the highest value of SCORE). If only a single timing element remains following filtering, control circuitry 26 may use that timing element in displaying information on display 12.
With another suitable arrangement, some or all of the list of timing elements may be presented on display 30 as selectable display timing options. A user may select on an on-screen option or may otherwise interactively select which of the displayed timing elements to use in displaying information on display 12.
The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.
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