Graphics display system with anti-aliased text and graphics feature

• US 6,927,783 B1
• Filed: 11/09/1999
• Issued: 08/09/2005
• Est. Priority Date: 11/09/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: MacInnis, Alexander G., Tang, Chengfuh Jeffrey, Kranawetter, Greg A., Patterson, James T., Xie, Xiaodong
• Primary Examiner(s): Brier, Jeffery A.
• Assistant Examiner(s): YANG, RYAN R
• Application Number:
  US09/437,205
• Time in Patent Office: 2,100 Days
• Field of Search: 345/581, 345/582, 345/592, 345/611, 345/615, 382/264, 382/269
• US Class Current: 345/629
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0653 Monitoring storage devices or systems
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0683 Plurality of storage devices
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 1/60 Memory management
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform
• CPC Class Codes: G09G 2310/0224 Details of interlacing
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2340/02 Handling of images in compressed format, e.g. JPEG, MPEG
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 2340/10 Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels
• CPC Class Codes: G09G 2340/125 wherein one of the images is motion video
• CPC Class Codes: G09G 2360/02 Graphics controller able to handle multiple formats, e.g. input or output formats
• CPC Class Codes: G09G 2360/121 using a cache memory
• CPC Class Codes: G09G 2360/125 using unified memory architecture [UMA]
• CPC Class Codes: G09G 2360/126 The frame memory having additional data ports, not inclusive of standard details of the output serial port of a VRAM
• CPC Class Codes: G09G 2360/128 Frame memory using a Synchronous Dynamic RAM [SDRAM]
• CPC Class Codes: G09G 5/001 Arbitration of resources in a display system, e.g. control of access to frame buffer by video controller and/or main processor
• CPC Class Codes: G09G 5/02 : characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/024 : using colour registers, e.g. to control background, foreground, surface filling G09G5/06 takes precedence
• CPC Class Codes: G09G 5/026 : Control of mixing and/or overlay of colours in general G09G5/022 and G09G5/024 take precedence
• CPC Class Codes: G09G 5/06 : using colour palettes, e.g. look-up tables
• CPC Class Codes: G09G 5/12 : Synchronisation between the display unit and other units, e.g. other display units, video-disc players
• CPC Class Codes: G09G 5/14 : Display of multiple viewports
• CPC Class Codes: G09G 5/28 : for enhancement of character form, e.g. smoothing
• CPC Class Codes: G09G 5/346 : for systems having a bit-mapped display memory
• CPC Class Codes: G09G 5/36 : characterised by the display of a graphic pattern, e.g. using an all-points-addressable [APA] memory
• CPC Class Codes: G09G 5/363 : Graphics controllers
• CPC Class Codes: H04N 11/143 : Encoding means therefor H04N11/16 takes precedence
• CPC Class Codes: H04N 11/20 : Conversion of the manner in which the individual colour picture signal components are combined, e.g. conversion of colour television standards
• CPC Class Codes: H04N 19/42 : characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/423 : characterised by memory arrangements H04N19/433 takes precedence
• CPC Class Codes: H04N 19/436 : using parallelised computational arrangements
• CPC Class Codes: H04N 19/44 : Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/59 : involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/61 : in combination with predictive coding
• CPC Class Codes: H04N 21/42204 : User interfaces specially adapted for controlling a client device through a remote control device; Remote control devices therefor constructive details of casings for the remote control device H01H9/0235; user interfaces for controlling a tuning device of a television receiver through a remote control H03J9/00; remote control of peripheral devices connected to a television receiver through the remote control device of the television receiver H04B1/205
• CPC Class Codes: H04N 21/426 : Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/42653 : for processing graphics
• CPC Class Codes: H04N 21/4305 : Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/4316 : for displaying supplemental content in a region of the screen, e.g. an advertisement in a separate window
• CPC Class Codes: H04N 21/434 : Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/440263 : by altering the spatial resolution, e.g. for displaying on a connected PDA
• CPC Class Codes: H04N 21/4438 : Window management, e.g. event handling following interaction with the user interface
• CPC Class Codes: H04N 21/47 : End-user applications
• CPC Class Codes: H04N 5/04 : Synchronising for television systems using pulse code modulation H04N7/56
• CPC Class Codes: H04N 5/126 : whereby the synchronisation signal indirectly commands a frequency generator
• CPC Class Codes: H04N 5/14 : Picture signal circuitry for video frequency region cameras or camera modules comprising electronic image sensors, or control thereof H04N23/00
• CPC Class Codes: H04N 5/44504 : Circuit details of the additional information generator, e.g. details of the character or graphics signal generator, overlay mixing circuits
• CPC Class Codes: H04N 5/45 : Picture in picture , e.g. displaying simultaneously another television channel in a region of the screen
• CPC Class Codes: H04N 5/46 : for receiving on more than one standard at will deflecting circuits of multi-standard receivers H04N3/27
• CPC Class Codes: H04N 7/0122 : the input and the output signals having different aspect ratios
• CPC Class Codes: H04N 7/0135 : involving interpolation processes interpolation-based image scaling G06T3/4007; interpolation for video coding H04N19/587, H04N19/59
• CPC Class Codes: H04N 9/45 : Generation or recovery of colour sub-carriers
• CPC Class Codes: H04N 9/641 : Multi-purpose receivers, e.g. for auxiliary information H04N9/642 takes precedence
• CPC Class Codes: H04N 9/642 : Multi-standard receivers

Abstract

A graphics integrated circuit chip is used in a set-top box for controlling a television display. The graphics chip processes analog video input, digital video input, a graphics input and an audio input simultaneously. The system may use anti-aliased text and graphics to provide high quality display of graphical elements, or glyphs, which represent an image of a character of text or graphics, on television and other displays. The graphical elements may be superimposed over live video or arbitrary graphics imagery.

Claims

1. A method of displaying a graphical element comprising the steps of:

filtering the graphical element with a low pass filter to generate a multi-level value per pixel at an intended final display resolution;

reducing a gray level of the multi-level values by at least one bit to generate reduced multi-level values for use as alpha blend values; and

using the reduced multi-level values as the alpha blend values for the graphical element in a subsequent compositing stage,

wherein generation of the multi-level values do not depend on alpha blend values that existed prior to filtering.

2. The method of displaying a graphical element of claim 1 wherein the reduced multi-level values are written into a display buffer where the reduced multi-level values are used as the alpha blend values when contents of the display buffer are composited with other graphics and video images.

3. The method of displaying a graphical element of claim 1 wherein the graphical element is initially rendered at a higher resolution than the intended final display resolution.

4. The method of displaying a graphical element of claim 3 wherein the graphical element is initially rendered at four times the resolution of the intended final display resolution in at least a horizontal direction.

5. The method of displaying a graphical element of claim 3 wherein the graphical element is initially rendered at four times the resolution of the intended final display resolution in at least a vertical direction.

6. The method of displaying a graphical element of claim 1 wherein the low pass filter is a box filter.

9. The method of displaying a graphical element of claim 1 wherein the alpha blend values include CLUT indexes, each CLUT index is associated with a CLUT entry, and each CLUT entry contains a CLUT alpha blend value.

10. The method of displaying a graphical element of claim 1 wherein the alpha blend values are used to form alpha portions of pixels having a color portion and an alpha portion.

11. The method of displaying a graphical element of claim 10 wherein the pixels having color portions and alpha portions are in an alphaRGB (4,4,4,4) format.

12. The method of displaying a graphical element of claim 1 wherein the graphical element has a plurality of foreground colors, which are filtered using the low pass filter.

13. The method of displaying a graphical element of claim 12 wherein the filtered plurality of foreground colors are used as color portions of pixels having a color portion and an alpha portion.

14. The method of displaying a graphical element of claim 13 wherein the pixels having a color portion and an alpha portion are in an alphaRGB format.

15. The method of displaying a graphical element of claim 13 wherein the pixels having a color portion and an alpha portion are in an alphaYUV format.

16. The method of displaying a graphical element of claim 12 wherein the filtered plurality of foreground colors are used as color choices in a CLUT format.

17. The method of displaying a graphical element of claim 1 wherein an outline of the graphical element, including all colors other than background color, is filtered using the low pass filter, wherein the graphical element has a plurality of foreground colors.

18. The method of displaying a graphical element of claim 17 wherein the filtered outline is used as an alpha per pixel value.

19. The method of displaying a graphical element of claim 18 wherein the filtered outline is used as the alpha per pixel value in a direct color format, the direct color format including an alphaRGB format.

20. The method of displaying a graphical element of claim 18 wherein the filtered outline is used as a choice of an alpha value per CLUT entry in a CLUT format.

7. A method of displaying a graphical element comprising the steps of:

filtering the graphical element with a low pass filter to generate a multi-level value per pixel at an intended final display resolution;

reducing a gray level of the multi-level values by at least one bit to generate reduced multi-level values;

storing the reduced multi-level values in a display buffer; and

using the reduced multi-level values as alpha blend values for the graphical element in a subsequent compositing stage,

wherein the graphical element includes text, and the display buffer is defined to have a constant foreground color that is consistent with a desired foreground color of the text.

8. A method of displaying a graphical element comprising the steps of:

filtering the graphical element with a low pass filter to generate a multi-level value per pixel at an intended final display resolution;

reducing a gray level of the multi-level values by at least one bit to generate reduced multi-level values;

storing the reduced multi-level values in a display buffer; and

using the reduced multi-level values as alpha blend values for the graphical element in a subsequent compositing stage,

wherein the graphical element includes graphics, and the display buffer is defined to have a constant foreground color that is consistent with a desired foreground color of the graphics.

21. A method of displaying a graphical element comprising the steps of:

filtering the graphical element with a low pass filter to generate a multi-level value per pixel at an intended final display resolution;

reducing a gray level of the multi-level values by at least one bit to generate reduced multi-level values for use as alpha blend values; and

using the reduced multi-level values as the alpha blend values for the graphical element in a subsequent compositing stage,

wherein the reduced multi-level values are written into a display buffer where the reduced multi-level values are used as alpha blend values when contents of the display buffer are composited with other graphics and video images, and

wherein the step of using the reduced multi-level values as the alpha blend values for the graphical element in a subsequent compositing stage comprises compositing the display buffer with other graphics and video contents while blending the display buffer with all layers behind it using alpha per pixel values.

22. A method of displaying a graphical element comprising the steps of:

filtering the graphical element with a low pass filter to generate a multi-level value per pixel at an intended final display resolution;

reducing a gray level of the multi-level values by at least one bit to generate reduced multi-level values; and

using the reduced multi-level values as alpha blend values for the graphical element in a subsequent compositing stage,

wherein the reduced multi-level values are written into a display buffer where the reduced multi-level values are used as the alpha blend values when contents of the display buffer are composited with other graphics and video images, and

wherein opacity of the graphical element may be varied by specifying an alpha value of the display buffer.

23. A graphics display system for displaying a graphical element comprising:

a low pass filter for filtering the graphical element to generate multi-level values, one multi-level value per each pixel, at an intended final display resolution;

a display buffer for storing the multi-level values; and

a display engine for compositing the graphical element with at least one graphics image using the multi-level values as alpha blend values,

wherein generation of the multi-level values do not depend on alpha blend values that existed prior to filtering, and

wherein a gray level of the multi-level values is reduced by at least one bit prior to using them as the alpha blend values.

24. The graphics display system for displaying a graphical element of claim 23 wherein the graphical element is initially rendered at a higher resolution than the intended final display resolution.

25. The graphics display system of claim 23 wherein the low pass filter is a box filter.

28. The graphics display system of claim 23 wherein the alpha blend values include CLUT indexes, each CLUT index is associated with a CLUT entry, and each CLUT entry contains a CLUT alpha blend value.

29. The graphics display system of claim 23 wherein the alpha blend values are used to form alpha portions of pixels having a color portion and an alpha portion.

30. The graphics display system of claim 29 wherein the pixels having a color portion and an alpha portion are in an alphaRGB (4,4,4,4) format.

31. The graphics display system of claim 23 wherein the graphical element has a plurality of foreground colors, which are filtered using the low pass filter.

32. The graphics display system of claim 31 wherein the filtered plurality of foreground colors are used as color portions of pixels having a color portion and an alpha portion.

33. The graphics display system of claim 32 wherein the pixels having a color portion and an alpha portion are in an alphaRGB format.

34. The graphics display system of claim 32 wherein the pixels having a color portion and an alpha portion are in an alphaYUV format.

35. The graphics display system of claim 31 wherein the filtered plurality of foreground colors are used as color choices in a CLUT format.

36. The graphics display system of claim 23 wherein an outline of the graphical element, including all colors other than background color, is filtered using the low pass filter, wherein the graphical element has a plurality of foreground colors.

37. The graphics display system of claim 36 wherein the filtered outline is used as an alpha per pixel value.

38. The graphics display system of claim 37 wherein the filtered outline is used as the alpha per pixel value in a direct color format, the direct color format including an alphaRGB format.

26. A graphics display system for displaying a graphical element comprising:

a low pass filter for filtering the graphical element to generate multi-level values, one multi-level value per each pixel, at an intended final display resolution;

a display buffer for storing the multi-level values; and

a display engine for compositing the graphical element with graphics images using the multi-level values as alpha blend values,

wherein the graphical element includes text, and the display buffer is defined to have a constant foreground color that is consistent with a desired foreground color of the text, and

wherein a gray level of the multi-level values is reduced by at least one bit prior to using them as the alpha blend values.

27. A graphics display system for displaying a graphical element comprising:

a low pass filter for filtering the graphical element to generate multi-level values, one multi-level value per each pixel, at an intended final display resolution;

a display buffer for storing the multi-level values; and

a display engine for compositing the graphical element with graphics images using the multi-level values as alpha blend values,

wherein the graphical element includes graphics, and the display buffer is defined to have a constant foreground color that is consistent with a desired foreground color of the graphics, and

wherein a gray level of the multi-level values is reduced by at least one bit prior to using them as the alpha blend values.

39. A graphics display system for displaying a graphical element comprising:

a low pass filter for filtering the graphical element to generate multi-level values, one multi-level value per each pixel, at an intended final display resolution;

a display buffer for storing the multi-level values; and

a display engine for compositing the graphical element with graphics images using the multi-level values as alpha blend values, wherein a gray level of the multi-level values is reduced by at least one bit prior to using them as the alpha blend values,

wherein an outline of the graphical element, including all colors other than background color, is filtered using the low pass filter, wherein the graphical element has a plurality of foreground colors

wherein the filtered outline is used as an alpha per pixel value, and

wherein the filtered outline is used as a choice of an alpha value per CLUT entry in a CLUT format.

40. A graphics display system for displaying a graphical element comprising:

a low pass filter for filtering the graphical element to generate multi-level values, one multi-level value per each pixel, at an intended final display resolution;

a display buffer for storing the multi-level values; and

a display engine for compositing the graphical element with graphics images,

wherein translucency of the graphical element is varied by specifying the alpha value of the display buffer, and

wherein a gray level of the multi-level values is reduced by at least one bit prior to using them as the alpha blend values.