Video blending using time-averaged color keys

• US 9,024,966 B2
• Filed: 09/07/2007
• Issued: 05/05/2015
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Meulen, Pieter van der
• Primary Examiner(s): WANG, JIN CHENG
• Application Number:
  US11/852,187
• Publication Number:
  US 20090066716A1
• Time in Patent Office: 2,797 Days
• Field of Search: 345/629, 345/589, 345/597, 348/E9.056, 348/586, 358/3.13
• US Class Current: 345/597
• CPC Class Codes: G09G 2340/12 Overlay of images, i.e. displayed pixel being the result of switching between the corresponding input pixels
• CPC Class Codes: G09G 3/2044 using dithering
• CPC Class Codes: G09G 3/2051 with use of a spatial dither pattern
• CPC Class Codes: G09G 3/2055 the pattern being varied in time
• 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 5/026 Control of mixing and/or overlay of colours in general G09G5/022 and G09G5/024 take precedence
• CPC Class Codes: G09G 5/14 Display of multiple viewports
• CPC Class Codes: H04N 9/75 Chroma key

Abstract

A display system combines a graphic plane and a video overlay plane using color keys in the graphics plane. By time-averaging patterns of color keys in successive frames of the graphics plane, individual pixels of the graphics plane can be made to appear partially transparent. Using this technique, regions in the graphics plane (e.g., a menu) can be partially transparent with respect to the video overlay, and aliasing can be reduced by making selected pixels in the graphics plane partially transparent.

Claims

1. A method for video blending of graphics and video content for a display system, the method comprising:

rendering one or more graphics items for display with the video content;

generating a series of graphics frames containing the rendered one or more graphics items, the series of graphics frames comprising;

a first graphics frame with a first dither pattern of color keyed pixels applied to it, wherein the first dither pattern assigns a first set of pixels in the first graphics frame a color value equal to a color key; and

a second graphics frame with a second dither pattern of color keyed pixels applied to it, wherein the second dither pattern assigns a second set of pixels in the second graphics frame a color value equal to the color key, wherein the first set of pixels is different from the second set of pixels;

receiving the video content as a series of video overlay frames;

generating, with a hardware processor, a series of video frames comprising a time-averaged blending of the one or more graphics items and the video content by combining each video overlay frame of the series of video overlay frames with one of the first graphics frame and second graphics frame in alternating fashion between the first graphics frame and the second graphics frame to create a time-averaged partial transparency effect of the one or more graphics items with respect to the video content; and

outputting the series of video frames for display on the display system.

2. The method of claim 1, wherein each of the generated series of graphics frames includes an area containing the rendered one or more graphics items and at least one of the first dither pattern and second dither pattern, thereby producing a partial transparency of the one or more graphics items in the generated series of video frames.

3. The method of claim 1, wherein each of the first dither pattern and second dither pattern is a randomized Floyd-Steinberg dither pattern.

4. The method of claim 1, wherein a plurality of pixels near an edge of a graphics item have a color value equal to the color key in one or more of the graphics frames and a color value not equal to the color key in one or more of the graphics frames, thereby reducing aliasing around the graphics object.

5. The method of claim 1, wherein the series of graphics frames comprises a sequence of three or more graphics frames.

6. The method of claim 1, wherein the series of graphics frames comprises a sequence of graphics frames containing at least two instances of a particular graphics frame.

7. A method for rendering a video stream including graphics and a video overlay, the method comprising:

generating a plurality of dither patterns of color keyed pixels, the plurality of dither patterns comprising a first dither pattern and a second dither pattern;

assigning, with a hardware processor, the plurality of dither patterns to successive graphics frames in a repeating sequence so that the first dither pattern is assigned to a first graphics frame and the second dither pattern is assigned to a second graphics frame, wherein the plurality of dither patterns define locations of pixels that are assigned the color value of a color key on the graphics frames to which the plurality of dither patterns are assigned; and

drawing each video frame to comprise a time-averaged blending of one or more graphics items rendered in the successive graphics frames and the video overlay by combining a video overlay frame with a graphics frame from the successive graphics frames in alternating fashion between each of the successive graphics frames to create a time-averaged partial transparency effect of the one or more graphics items with respect to the video overlay.

8. A non-transitory computer-readable medium containing computer program code for performing the method comprising:

rendering one or more graphics items for display with the video content;

generating a series of graphics frames containing the rendered one or more graphics items, the series of graphics frames comprising;

a first graphics frame with a first dither pattern of color keyed pixels applied to it, wherein the first dither pattern assigns a first set of pixels in the first graphics frame a color value equal to a color key; and

a second graphics frame with a second dither pattern of color keyed pixels applied to it, wherein the second dither pattern assigns a second set of pixels in the second graphics frame a color value equal to the color key, wherein the first set of pixels is different from the second set of pixels;

receiving the video content as a series of video overlay frames;

generating, with a processor, a series of video frames comprising a time-averaged blending of the one or more graphics items and the video content by combining each video overlay frame of the series of video overlay frames with one of the first graphics frame and second graphics frame in alternating fashion between the first graphics frame and the second graphics frame to create a time-averaged partial transparency effect of the one or more graphics items with respect to the video content; and

outputting the series of video frames for display on a display system.

9. The computer-readable medium of claim 8, wherein each of the generated series of graphics frames includes an area containing the rendered one or more graphics items and at least one of the first dither pattern and second dither pattern, thereby producing a partial transparency of the one or more graphics items in the generated series of video frames.

10. The computer-readable medium of claim 8, wherein each of the first dither pattern and second dither pattern is a randomized Floyd-Steinberg dither pattern.

11. The computer-readable medium of claim 8, wherein a plurality of pixels near an edge of a graphics item have a color value equal to the color key in one or more of the graphics frames and a color value not equal to the color key in one or more of the graphics frames, thereby reducing aliasing around the graphics object.

12. The computer-readable medium of claim 8, wherein the series of graphics frames comprises a sequence of three or more graphics frames.

13. The computer-readable medium of claim 8, wherein the series of graphics frames comprises a sequence of graphics frames containing at least two instances of a particular graphics frame.

14. A display system comprising:

a display screen;

a memory;

a processor;

a display controller coupled to the display screen for controlling video frames reproduced on the display screen; and

a video blending module stored in the memory, the video blending module configured to cause the processor to;

render one or more graphics items for display with content from a video overlay,

generate a series of graphics frames containing the rendered one or more graphics items, the series of graphics frames comprising;

a first graphics frame with a first dither pattern of color keyed pixels applied to it, wherein the first dither pattern assigns a first set of pixels in the first graphics frame a color value equal to a color key; and

a second graphics frame with a second dither pattern of color keyed pixels applied to it, wherein the second dither pattern assigns a second set of pixels in the second graphics frame a color value equal to the color key, wherein the first set of pixels is different from the second set of pixels;

receive the video overlay content as a series of video overlay frames;

generate a series of video frames comprising a time-averaged blending of the one or more graphics items and the video content by combining each video overlay frame of the series of video overlay frames with one of the first graphics frame and second graphics frame in alternating fashion between the first graphics frame and the second graphics frame to create a time-averaged partial transparency effect of the one or more graphics items with respect to the video content;

output the series of video frames to the display controller for reproduction on the display screen.

15. The display system of claim 14, wherein the video blending module is configured to generate a series of graphics frames that include an area containing the rendered one or more graphics items and at least one of the first dither pattern and second dither pattern, thereby producing a partial transparency of the one or more graphics items in the generated series of video frames.

16. The display system of claim 14, wherein the video blending module is configured to generate graphics frames in which a plurality of pixels near an edge of a graphics item have a color value equal to the color key in one or more of the graphics frames and a color value not equal to the color key in one or more of the graphics frames, thereby reducing aliasing around the graphics object.