Method for dynamically adjusting video brightness

• US 7,110,046 B2
• Filed: 11/04/2003
• Issued: 09/19/2006
• Est. Priority Date: 11/04/2003
• Status: Active Grant

• Current Assignee: Cyberlink Corporation
• Original Assignee: Cyberlink Corporation
• Inventors: Lin, Pin-Ting, Huang, Hochao
• Primary Examiner(s): Yenke, Brian P.
• Application Number:
  US10/700,843
• Publication Number:
  US 20050093795A1
• Time in Patent Office: 1,050 Days
• Field of Search: 348/254, 348/678, 348/679, 348672-675, 345/589, 345/684, 382168-172
• US Class Current: 348/679
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response

Abstract

A method for dynamically adjusting video brightness performs histogram equalization on a video YUV brightness/color signal to generate an equalization brightness curve. The brightness of each pixel is compared with every pixel of the video frame before and after histogram equalization to generate a comparison difference value. The brightness of the pixel is adjusted so that the brightness difference after adjustment won'"'"'t be larger than three times of the comparison difference value and won'"'"'t be smaller than a fourth of the comparison difference value. The brightness of each pixel before and after histogram equalization is compared, one by one, to generate a brightness difference value. The brightness difference value is adjusted so that the brightness difference after adjustment won'"'"'t be larger than a largest brightness value and won'"'"'t be smaller than a smallest brightness value. The brightness of each video frame can be properly adjusted to accomplish clearer displaying effect.

Claims

1. A method for dynamically adjusting video brightness, the method comprising at least the steps of:

(a). performing histogram equalization to a video brightness/color signal to generate an equalization brightness curve;

(b). comparing the brightness of each pixel before and after histogram equalization with the brightness of every pixel one by one to generate a comparison difference value, adjusting the brightness of said pixel to be not larger than three times of said comparison difference value and not smaller than a fourth of said comparison difference value; and

(c). comparing the brightness of each pixel, one by one, before and after histogram equalization to generate a brightness difference value, adjusting the brightness of said pixel to be not larger than a largest brightness value and not smaller than a smallest brightness value.

2. The method for dynamically adjusting video brightness as claimed in claim 1, further comprising the following step before said Step (a):

inputting a video signal having a plurality of said video frames, each said video frame being composed of a plurality of pixels, and each said pixel using red, green and blue color signals to generate said subpixels.

3. The method for dynamically adjusting video brightness as claimed in claim 1, wherein said video brightness/color signal in said Step (a) is a YUV brightness/color signal.

4. The method for dynamically adjusting video brightness as claimed in claim 1, further comprising the following step before said Step (a):

converting red, green and blue color signals of a plurality of video frames into said video brightness/color signal.

5. The method for dynamically adjusting video brightness as claimed in claim 4, wherein formulae for converting said red, green and blue color signals into a YUV brightness/color signal.

6. The method for dynamically adjusting video brightness as claimed in claim 1, further comprising the following steps before said Step (a):

recording the brightness/color signal of each said video frame to generate an original brightness curve of each said video frame; and

comparing said original brightness curve with a basic brightness curve to determine whether said video frame is too bright or too dark.

7. The method for dynamically adjusting video brightness as claimed in claim 6, wherein said original brightness curve is obtained by gathering statistics of a number of each brightness value of all pixels in said video frame.

8. The method for dynamically adjusting video brightness as claimed in claim 1, wherein said equalization brightness curve in said Step (a) is obtained by gathering statistics of the brightness difference value of all pixels in said video frame before and after histogram equalization.

9. The method for dynamically adjusting video brightness as claimed in claim 1, wherein adjustment of each pixel brightness in said Step (C) is accomplished by making every brightness difference values larger than said largest brightness value equal to said largest brightness value and every brightness difference values smaller than said smallest brightness value equal to said smallest brightness value.

10. The method for dynamically adjusting video brightness as claimed in claim 9, wherein said largest brightness value and said smallest brightness value are constant values.

11. The method for dynamically adjusting video brightness as claimed in claim 9, wherein said largest brightness value and said smallest brightness value are values that can be varied according to the brightness value.

12. The method for dynamically adjusting video brightness as claimed in claim 1, wherein adjustment of each pixel brightness in said Step (C) is accomplished by multiplying each pixel brightness value before and after histogram equalization by a scale and making said brightness difference value of said pixel not exceed a largest brightness difference value.

13. The method for dynamically adjusting video brightness as claimed in claim 1, further comprising the following step after said Step (c):

comparing said equalization brightness curve of said video frame and that of at least a video frame before and making each said pixel brightness of each said video frame be not larger than a largest brightness difference value after at least one adjustment.

14. The method for dynamically adjusting video brightness as claimed in claim 1, further comprising the following step after said Step (c):

adjusting the color intensity of each said pixel, and increasing or decreasing a magnitude of the red or blue color according to the distribution of the red or blue colors in each video frame.

15. The method for dynamically adjusting video brightness as claimed in claim 14, wherein the red color is given extra weight to increase vividness of color.

16. The method for dynamically adjusting video brightness as claimed in claim 1, further comprising the following step after said Step (c):

converting said video brightness/color signal after adjustment into red, green and blue color signals of said video frame.

17. The method for dynamically adjusting video brightness as claimed in claim 16, wherein said brightness/color signal is a YUV brightness/color signal, and formulae for converting said brightness/color signal into red, green and blue color signals.