Patent Publication Number: US-2010123822-A1

Title: Method for Converting Between Display Information Scales

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to display information, such as video information and graphics information. More particularly, the invention relates to methods for converting between different display information scales. 
     2. Description of the Related Art 
     The aspect ratio and other scale formats used to format display information typically is a numerical expression of the width to height of the display information. Display information includes, e.g., video information and graphics information displayed on a device, such as a television (monitor) or other suitable display device. For standard television graphics, e.g., National Television System Committee (NTSC) graphics, the aspect ratio is 4:3, i.e., a “4” unit width corresponding to a “3” unit height, proportionally, regardless of the actual size of the screen. For wide screen digital television (DTV) formats for high definition television (HDTV) and some standard definition television (SDTV) formats, the aspect ratio is wider: 16:9, i.e., a “16” unit width corresponding to a “9” unit height, proportionally, regardless of the actual size of the screen. 
     Since there exists display information meant for display on devices with a 4:3 aspect ratio and display information meant for display on devices with a 16:9 aspect ratio, content providers, service providers and others responsible for delivering and/or displaying display information often are faced with the task of providing display information in both (and sometimes additional) aspect ratio formats or converting display information between different aspect ratios or between other different scale formats. Conventional methods for converting display information typically require that a portion of the converted display information be removed or cut off when displayed, or that edges be added to either the top and bottom or to one or both sides of the display. Some conventional conversion methods use linear conversion techniques to fill out the final display window or screen, however such methods introduce linear distortion to the display information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a device for use in converting display information between display formats; 
         FIG. 2  is a simplified diagram showing conversion of display information between an arcuate format and a chordal or subtense format; and 
         FIG. 3  is another simplified diagram showing conversion of display information between an arcuate format and a chordal or subtense format. 
         FIG. 4  illustrates an exemplary operation for performing a conversion in accordance with the principles of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, like reference numerals indicate like components to enhance the understanding of the display information scaling device and method through the description of the drawings. Also, although specific features, configurations and arrangements are discussed hereinbelow, it should be understood that such specificity is for illustrative purposes only. A person skilled in the relevant art will recognize that other steps, configurations and arrangements are useful without departing from the spirit and scope of the invention. 
     Referring now to  FIG. 1 , shown is a block diagram of a display information processing apparatus or device  10  for use in converting display information between various display formats, e.g., from a first display format to one or more other display formats. For purposes of discussion herein, display information includes, e.g., video information and/or graphics information. Also, for purposes of discussion herein, a display format includes any suitable format for displaying display information, e.g., various aspect ratios, such as 4:3 and 16:9 aspect ratios and other aspect ratios. 
     The processing device  10  can be completely or partially any suitable device or subsystem (or portion thereof) for receiving and/or processing video/graphic signal display information. Such devices include any signal converter or decoder (set-top) box or other suitable computing device or video device, including a residential gateway, an internet protocol (IP), satellite or cable digital video recorder, a computer, or a home media server system. All or a portion of the processing device  10  can be comprised of any suitable structure or arrangement, e.g., one or more integrated circuits. 
     The processing device  10  includes an input buffer  12 , a processor or scaler/converter processing unit  14  coupled to the output of the buffer  12 , and a memory or memory unit  15  coupled to the processor  14 . Also, the processing device  10  may include an output buffer or memory unit  16  coupled to the output of the processor  14 . It should be understood that the processing device  10  includes other components, hardware and software (not shown) that are used for the normal operation of features and functions of the processing device  10  not specifically described herein. Examples of other components include decoders, decrypters and tuners. 
     The processing device  10  receives display information from an appropriate source (not shown) of display information, e.g., video information and/or graphics information generated locally from a device, such as a set-top box, or remotely from a service provider of video content that includes graphics and/or graphics information. The service provider can be a television service provider (e.g., a national or local television network), a cable television service provider, an Internet content service provider, a satellite broadcast system service provider, or other suitable service provider. The processing device  10  outputs information to an end-user display, which can be any suitable display device, such as a television or computer monitor. 
     The processor  14  can be completely or partially configured in the form of hardware circuitry and/or other hardware components within a larger device or group of components. Alternatively, the processor  14  can be completely or partially configured in the form of software, e.g., as processing instructions or one or more sets of logic or computer code. In such configuration, the logic or processing instructions typically are stored in a data storage device (e.g., the memory  15 ), which typically is coupled to the processor  14 . Alternatively, the memory  15  can be included as part of the processor  14 , although such is not necessary. The processor accesses the necessary instructions from the data storage device and executes the instructions or transfers the instructions to the appropriate location within the processing device  10 . 
     In operation, the processing device  10  receives display information generated or transmitted from the source. The input buffer  12  stores, at least temporarily, all or a portion of the received display information, which has a first scale format. For example, the display information can be display information having a 4:3 aspect ratio or other suitable scale format. The input buffer  12  provides the stored display information to the processor  14  at a rate that allows the processor  14  to suitably process the display information, i.e., convert the display information from the first scale format to a second scale format, e.g., to a 16:9 aspect ratio. The scale format conversion will be discussed in greater detail hereinbelow. The processor  14  outputs the converted display information to the end-user device either directly or, alternatively, via the output buffer  16 , at a rate suitable for the end-user display device to receive the display information. 
     In general, the processor  14  determines or is otherwise made aware of the scale format of the display information it receives. For example, the scale format of the display information can be encoded or otherwise contained in the display information, e.g., in accordance with any suitable transmission standard that is used to transmit display information. As discussed hereinabove, the scale format can be any suitable display information aspect ratio, e.g., a 4:3 aspect ratio, a 16:9 aspect ratio or other aspect ratio. 
     As will be discussed in greater detail hereinbelow, the processor  14  then arcuately converts the display information from its current (first) scale format to a desired (second) scale format. The amount of arcuate conversion is based on the first or initial scale format of the display information. The amount of arcuate conversion also is based on whether the initial scale format of the display information is being expanded or compressed, and the shape of the curve or arc being used as the basis for the arcuate conversion. Both the shape of the curve being used in the arcuate conversion and whether the display information is being expanded or compressed can be at least partially determined or selected by the end user or, alternatively, can be determined automatically by the processor  14 . 
     The accuracy of the arcuate conversion generally is proportional to the number of defined segments or format zones used by one or more scaling algorithms in converting the display information in the defined format zones from the first scale format to the second scale format, as will be discussed in greater detail hereinbelow. Accuracy associated with arcuate conversion generally refers to the closeness of the arcuate conversion to the theoretically ideal arcuate conversion. The resolution of the arcuate conversion depends greatly on the capability of the hardware and/or software used to perform the arcuate conversion. Such capabilities also will relate to the number of format zones used in the arcuate conversion. 
     For purposes of discussion herein, the term “arcuate conversion” or “arcuately converting” is understood to represent any process in which format conversion of display information involves converting at least one dimension, e.g., the horizontal dimension, of display information between an arc length of a curve having a first endpoint and a second endpoint and a linear line segment of the arc length of the curve from the first endpoint to the second endpoint. Thus, for a dimension of display information that would fit along, e.g., an arc of a circle from a first endpoint to a second endpoint, arcuate conversion refers to converting the length of that dimension of the display information to the length of the chord or subtense of the arc from the same first endpoint to the same second endpoint. Such arcuate conversion generally involves compressing at least a portion of the display information, as the length of a linear line segment of the arc length of a curve is less than the length of the arc length of the curve. 
     Similarly, for a dimension of display information that would fit along a linear line segment of the arc length of a curve from a first endpoint to a second endpoint, arcuate conversion refers to converting the length of that dimension of the display information to the length of the n arc length of the curve from the same first endpoint to the same second endpoint. In such case, arcuate conversion generally involves extending or expanding at least a portion of the display information, as the arc length of a curve is greater than the length of a linear line segment of the arc length of a curve. Those of skill in the art will appreciate that the arc minimizes the conversion level at the center of the picture, hence, minimizing the distortion of images at the center. Images which extend outward from the center are scaled to a greater degree in the conversion, hence pushing the majority of any distortion from the conversion to the periphery of the displayed images. 
     Arcuate conversion also includes defining the dimension of the display information being converted into a number of segments or zones, with the scaling conversion of the zones being different from one another in each half of the dimension of the display information. Also, it should be understood that the curve of the arc length of the curve to which a dimension of the display information would fit does not have to be a circular curve, but can be any suitable curved shape. For example, the curve can be a parabola, an ellipse, or a curve defined by a plurality of linear segments. However, for purposes of explanation hereinbelow, the curve is shown as an arc and the line segment of the arc length of the curve (arc) is the chord or subtense of the arc. 
     Referring now to  FIG. 2 , shown is a simplified diagram  20  showing conversion of one dimension, e.g., the horizontal dimension, of display information between an arcuate format and a chordal or subtense format. For purposes of discussion herein, the term “arcuate format” is understood to be a display format of display information in which the length of a dimension of the display information would fit along an arc length of a curve (e.g., an arc) from a first endpoint to a second endpoint. Also, for purposes of discussion herein, the term “chordal format” or “subtense format” is understood to be a display format of display information in which the length of a dimension of the display information would fit along a line segment of an arc length of a curve (e.g., a chord or subtense of an arc) from a first endpoint to a second endpoint. 
     More specifically, in terms of a circular curve, for display information having an arcuate format, a dimension of the display information has a length that would fit along an arc from a first endpoint to a second endpoint that defines an angle θ subtended by the arc. The length of the arc is r×(θπ/180), where r is the radius of the arc. Similarly, for display information having a chordal or subtense format, a dimension of the display information has a length that would fit along a chord or subtense of an arc from a first endpoint to a second endpoint that defines an angle θ subtended by the arc. The length of the chord or subtense of the arc is 2r×sin(θ/2), where r is the radius of the arc. 
     In  FIG. 2 , shown is a circle  20  with an arc  22  having a first endpoint  24  (A) and a second endpoint  26  (C) that defines an angle θ subtended by the arc  22 . A chord or subtense  28 , i.e., the chord or subtense of the arc  22 , also has the first endpoint  24  (A) and the second endpoint  26  (C). The radius r of the arc  22  is defined from the center (E) of the circle  20  to any point on the arc  22 , and is shown generally as  29 . Although the arc  22  is shown as a circular arc, the arc  22  can be any suitable curved shape, e.g., an ellipse, as discussed hereinabove. 
     For display information that is to be arcuately converted between an arcuate format and a chordal or subtense format, the arc  22  represents the length of a dimension of the display information, e.g., the horizontal dimension, in the arcuate format. Similarly, the chordal or subtense  28  represents the length of the corresponding dimension of the display information in the chordal or subtense format. For example, for display information that has an x:y format, with x being the width and y being the height of the formatted display information, if the display information is in arcuate format, then the length of the arc  22  from points A to C is equal to x. If the display information is in chordal or subtense format, then the length of the chord or subtense  28  from points A to C is equal to x. 
     Thus, display information that begins in arcuate format and is arcuately converted to chordal or subtense format is compressed, e.g., horizontally compressed, from the length of the arc  22  to the length of the chord or subtense  28 , e.g., using an appropriate scaling algorithm, as the length of the arc  22  is greater than the length of the chord or subtense  28 . Similarly, display information that begins in chordal or subtense format and is arcuately converted to arcuate format is expanded or extended, e.g., horizontally, from the length of the chord or subtense  28  to the length of the arc  22 , e.g., using an appropriate scaling algorithm. 
     To convert display information from an arcuate form to a chordal or subtense format using a single or the same scaling algorithm effectively amounts to scaling using linear compression. For example, assume that display information having a plurality of horizontal video lines equal in width to the arc  22  is to be arcuately converted to display information having a plurality of horizontal video lines equal in width to the chord or subtense  28 . Using a single scaling algorithm to perform such conversion would involve horizontally compressing each portion of each horizontal video line of the display information by the same amount, i.e., linear compression. As discussed hereinabove, linear conversion methods typically introduce an undesirable amount of distortion. 
     However, using arcuate conversion, if the horizontal video line or other suitable dimension of the display information is divided into a plurality of format zones, with various format zones scaled differently from the other format zones, e.g., according to different scaling algorithms, the conversion is more accurate and results in less distortion than conventional linear conversion techniques. For example, format zones defined near the center of the display information are converted in a manner that introduces less distortion than conversion of display information in format zones defined near the edges of the display information. 
     Referring now to  FIG. 3 , shown is a circle  40  similar to the circle  20  shown in  FIG. 2 . The circle  40  has an arc  42  with endpoints  44  (A) and  46  (C) that define an angle  6 θ subtended by the arc  42 . The circle also has a chord or subtense  48 , i.e., the chord or subtense of the arc  42 , with endpoints  44  (A) and  46  (C). The circle  40  also has a radius r (shown as  49 ) of the arc  42  defined from the center (E) of the circle  40  to any point on the arc  42 . 
     The circle  40  is divided into a plurality of conversion zones, e.g., six zones: zones  51 - 56 , with each zone defining an angle θ, as shown. Using arcuate conversion, various zones are scaled by a different amount using one or more appropriate scaling algorithms. For example, due to the complementary nature of the arc  42  (and circles in general), zones  51  and  56  can be scaled by a first amount or in a first manner, e.g., using a first scaling algorithm, zones  52  and  55  can be scaled by a second amount or in a second manner, e.g., using a second scaling algorithm, and zones  53  and  54  can be scaled by a third amount or in a third manner, e.g., using a third scaling algorithm. In this manner, using a first scaling amount or algorithm, arcuate conversion in the zone  51  occurs between the portion of the arc  42  from points A to F and the portion of the chord or subtense  48  from points A to J. Similarly, arcuate conversion in the zone  56  occurs between the portion of the arc  42  from points I to C and the portion of the chord or subtense  48  from points M to C. 
     Similarly, arcuate conversion in the zone  52  occurs between the portion of the arc  42  from points F to G and the portion of the chord or subtense  48  from points J to K. Arcuate conversion in the zone  55  occurs between the portion of the arc  42  from points H to I and the portion of the chord or subtense  48  from points L to M. In keeping with the defined example, a second scaling amount or algorithm would be used to arcuately convert those portions of the arc  42  and the chord or subtense  48  in each of the zones  52  and  55 . 
     Similarly, for the zones  53  and  54 , a third scaling amount or algorithm would be used to arcuately convert between the portion of the arc  42  from points G to B and the portion of the chord or subtense  48  from points K to D. Also, the third scaling amount or algorithm would be used to arcuately convert between the portion of the arc  42  from points B to H and the portion of the chord or subtense  48  from points D to L. 
     Thus, if the display information is being arcuately converted from an arcuate format (arc  42 ) to a chordal or subtense format (chord or subtense  48 ), the length of the portion of the dimension of the display information that would fit along the portion of the arc  42  from points I to C is compressed, e.g., horizontally, to the length of the portion of the chord or subtense  48  from points M to C, using the first scaling amount or algorithm. Similarly, the length of the portion of the dimension of the display information that would fit along the portion of the arc  42  from points H to I is compressed, e.g., horizontally, to the length of the portion of the chord or subtense  48  from points L to M, using the second scaling amount or algorithm. In this manner, arcuate conversion occurs in each conversion zone using the appropriate respective scaling amount or algorithm. 
     Similarly, if the display information is being arcuately converted from a chordal or subtense format (chord or subtense  48 ) to an arcuate format (arc  42 ), the length of the portion of the dimension of the display information that would fit along the portion of the chord or subtense  48  from points A to J is expanded or extended, e.g., horizontally, to the length of the portion of the arc  42  from points A to F, using the first scaling amount or algorithm. Similarly, the length of the portion of the dimension of the display information that would fit along the portion of the chord or subtense  48  from points J to K is horizontally extended to the length of the portion of the arc  42  from points F to G, using the second scaling amount or algorithm. In this manner, the length of each chordal or subtense portion, as defined by its respective zone, is expanded to the length of its corresponding arcuate portion in that respective zone using the particular scaling amount or algorithm. 
     It should be understood that zones  51  and  56  are scaled differently than zones  52  and  55  and differently than zones  53  and  54 . Also, zones  52  and  55  are scaled differently than zones  53  and  54 . By using a plurality of format zones and different scaling amounts and/or algorithms for arcuately converting between the length of the arc  42  and the length of the chord or subtense  48 , the conversion is more accurate than, e.g., linear conversion processes and other conventional conversion processes, at least to the extent that less distortion is introduced. It should be understood that any suitable number of format zones can be defined for purposes of arcuate conversion and any suitable number of scaling algorithms can be used to arcuately convert the defined zones. 
     Nonetheless, regardless of the number of format zones that are created, in theory, any conversion, including arcuate conversion, will introduce at least some amount of distortion. However, the arcuate conversion as described herein tends to produce a three dimensional (3D) effect that tends to subtly distract the viewer from the distortion that is introduced. Thus, not only does arcuate conversion introduce less distribution than conventional conversion techniques, but also tends to produce an effect than reduces or obscures the effect of the distortion that is introduced. 
       FIG. 4  illustrates an exemplary operation for performing a conversion. As illustrated in  FIG. 4 , the size of the display is preferably determined (step S 1 ). The display size may be determined from user input in response to a prompt or by receipt of identifying information of the characteristics of the display, such as during an initial connection or set up stage between the display and processing device  10 . The arc size may be determined as discussed above in connection with  FIGS. 2 and 3  based on display size and the intended display aspect ratio of the received video information (step S 3 ). The intended display aspect ratio of the received video information may predetermined or preprogrammed into processing device, may be determined from information in the video information stream or network providing the video information stream (e.g. program information or a program map table), or may be programmed by a user or technician. The number of arc segments to be used may be determined based on established conversion accuracy levels or based on accuracy levels (or limited distortion levels) which are set according to a user&#39;s input (step S 5 ). For example, a conversion from a 4:3 aspect ratio to a 16:9 aspect ration may achieve an acceptable accuracy level using six segments, whereas a conversion to another aspect ratio may use a different number of segments. The process preferably ends with performance of the conversion (step S 7 ). 
     Although the conversion processes described herein have been described primarily with respect to the horizontal dimension of the display information, it should be understood that such conversion processes also can be performed with respect to the vertical dimension of the display information. Moreover, such conversion processes can be performed on both the horizontal and vertical dimensions of the same display information. 
     The methods described herein may be implemented in a general, multi-purpose or single purpose processor. Such a processor will execute instructions, either at the assembly, compiled or machine-level, to perform that process. Those instructions can be written by one of ordinary skill in the art following the description herein and stored or transmitted on a computer readable medium. The instructions may also be created using source code or any other known computer-aided design tool. A computer readable tangible medium may be any medium capable of carrying those instructions and may include random access memory (RAM), dynamic RAM (DRAM), flash memory, read-only memory (ROM), compact disk ROM (CD-ROM), digital video disks (DVDs), magnetic disks or tapes, optical disks or other disks, silicon memory (e.g., removable, non-removable, volatile or non-volatile). 
     It will be apparent to those skilled in the art that many changes and substitutions can be made to the display information scaling device and method herein described without departing from the spirit and scope of the invention as defined by the appended claims and their full scope of equivalents.