Video signal processing method for improving the picture of dim area

• US 6,433,838 B1
• Filed: 01/31/2000
• Issued: 08/13/2002
• Est. Priority Date: 04/09/1999
• Status: Expired due to Term

• Current Assignee: Winbond Electronics Corporation
• Original Assignee: Winbond Electronics Corporation
• Inventors: Chen, An-Tung
• Primary Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US09/494,909
• Time in Patent Office: 925 Days
• Field of Search: H04/N.5202, H04/N.521, H04/N.969, H04/N.977, H04/N.964, 348/674, 348/675, 348/686, 348/630, 348/631, 348/708, 348/712, 348/713, 348/642, 348/254, 348/255, 348/256
• US Class Current: 348/674
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82
• CPC Class Codes: H04N 9/69 for modifying the colour signals by gamma correction controlling camera response for colour signals H04N23/83

Abstract

A method of video signal processing that reduces computational and circuit costs. The method of processing a video signal of the present invention comprises the following steps: First, receiving a video input signal including an input luminance signal and input chrominance signals from a signal source. Next, correcting the input luminance signal of the video input signal to generate a corrected luminance signal. And finally outputting the corrected luminance signal and the input chrominance signals as the enhanced video signal to the subsequent video processor, such as a TV encoder, for converting the corrected signal from digital into analog. The correction of the luminance signal is accomplished by first normalizing the luminance signal by a predetermined value of a full-scale luminance. If the normalized luminance signal is greater than a first predetermined percentage, the corrected luminance signal is equal to the input luminance signal. If the normalized luminance signal is less than the first predetermined percentage and greater than a second predetermined percentage, the input luminance signal is corrected by non-linear correction to generate the corrected signal. If the normalized luminance signal is less than the second predetermined percentage, the input luminance signal is corrected by linear correction to generate the corrected luminance signal.

Claims

1. A video signal processing method for improving the picture of a dim area, comprising the following steps:

receiving a video input signal including an input luminance signal and input chrominance signals from a signal source;

normalizing the luminance signal by a predetermined value of a full-scale luminance;

using the input luminance signal as a corrected luminance signal when the normalized luminance signal is greater than a first predetermined percentage;

nonlinearly correcting the luminance signal to generate the corrected luminance signal when the normalized luminance signal is less than the first predetermined percentage and greater than a second predetermined percentage;

linearly correcting the luminance signal to generate the corrected luminance signal when the normalized luminance signal is less than the second predetermined percentage; and

outputting the corrected luminance signal and the input chrominance signals as the enhanced video signal to a subsequent video processor.

2. The method as claimed in claim 1, wherein the first predetermined percentage is 50%.

3. The method as claimed in claim 1, wherein the second predetermined percentage is 13.5%.

4. The method as claimed in claim 1, wherein the nonlinear correcting step is implemented by the formula:

5. The method as claimed in claim 4, wherein the real number t1 is 0.6.

6. The method as claimed in claim 1, wherein the linear correcting step is implemented by the formula:

7. The method as claimed in claim 6, wherein the real number t2 is 1.7.

8. The method as claimed in claim 1, wherein the subsequent video processor is a TV encoder.