Brightness adjusting methods for video frames of video sequence by applying scene change detection and/or blinking detection and brightness adjusting devices thereof

• US 7,667,739 B2
• Filed: 12/15/2006
• Issued: 02/23/2010
• Est. Priority Date: 12/15/2006
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Hsuan, Chih-Lin
• Primary Examiner(s): Tran; Sinh
• Assistant Examiner(s): Bemben; Richard M
• Application Number:
  US11/611,140
• Publication Number:
  US 20080143883A1
• Time in Patent Office: 1,166 Days
• Field of Search: 348/207.99, 348/208.14, 348/222.1, 348/227.1, 348/687, 348/688, 348/701, 34833301-33313, 382168-172, 382/254, 382/274, 345/589
• US Class Current: 348/222.1
• CPC Class Codes: H04N 21/4318 by altering the content in the rendering process, e.g. blanking, blurring or masking an image region image enhancement or restoration in general G06T5/00
• CPC Class Codes: H04N 21/44008 involving operations for analysing video streams, e.g. detecting features or characteristics in the video stream arrangements characterised by components specially adapted for monitoring, identification or recognition of video in broadcast systems H04H60/59
• CPC Class Codes: H04N 5/147 Scene change detection
• CPC Class Codes: H04N 5/57 Control of contrast or brightness

Abstract

A brightness adjusting method for video frames of a video sequence includes receiving a current video frame of the video sequence and performing a scene change detection to determine if a scene change occurs between the current video frame and a previous video frame. Thereafter, one of a plurality of candidate brightness adjusting schemes is applied to the current video frame according to a scene change detection result.

Claims

1. A brightness adjusting method for video frames of a video sequence, the method comprising:

(a) receiving a current video frame of the video sequence;

(b) performing a scene change detection to determine if a scene change occurs between the current video frame and a previous video frame; and

(c) applying one of a plurality of candidate brightness adjusting schemes to the current video frame according to a scene change detection result;

wherein step (b) comprises;

(b1) performing a blinking detection check to determine if a blinking detection is required;

(b2) if a blinking detection check result indicates that the blinking detection is required, performing the scene change detection and the blinking detection; and

(b3) if the blinking detection check result indicates that the blinking detection is not required, performing the scene change detection;

step (c) comprises;

(c1) if the blinking detection check result indicates that the blinking detection is required, applying one of the candidate brightness adjusting schemes to the current video frame according to the scene change detection result and a blinking detection result; and

(c2) if the blinking detection check result indicates that the blinking detection is not required, applying one of the candidate brightness adjusting schemes to the current video frame according to the scene change detection result;

step (c2) comprises;

when the scene change detection result indicates that a scene change occurs between the current video frame and the previous video frame, a first brightness adjusting scheme of the candidate brightness adjusting schemes is applied to the current video frame; and

when the scene change detection result indicates that no scene change occurs between the current video frame and the previous video frame, a second brightness adjusting scheme of the candidate brightness adjusting schemes is applied to the current video frame; and

step (c1) comprises;

when the blinking detection result indicates that blinking occurs;

if the scene change detection result indicates that a scene change occurs between the current video frame and the previous video frame, applying a third brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

if the scene change detection result indicates that no scene change occurs between the current video frame and the previous video frame, applying a fourth brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

when the blinking detection result indicates that no blinking occurs;

if the scene change detection result indicates that a scene change occurs between the current video frame and the previous video frame, applying a fifth brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

if the scene change detection result indicates that no scene change occurs between the current video frame and the previous video frame, applying a sixth brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame.

2. The method of claim 1, wherein the second brightness adjusting scheme, the fourth brightness adjusting scheme, and the sixth brightness adjusting scheme are the same, and the first brightness adjusting scheme is identical to the fifth brightness adjusting scheme.

3. The method of claim 1, wherein the first brightness adjusting scheme is completed in M fields, the second brightness adjusting scheme is completed in N fields, the third brightness adjusting scheme is completed in K fields, and M<

K<

N.

4. The method of claim 1, wherein the first brightness adjusting scheme is completed in M fields, the second brightness adjusting scheme is completed in N fields, the third brightness adjusting scheme maintains brightness of the current video frame, and M<

N.

5. The method of claim 1, wherein the scene change detection is performed by:

comparing a difference between a luminance distribution of the current video frame and a luminance distribution of the previous video frame with a threshold value; and

detecting a scene change between the current video frame and the previous video frame when the difference is greater than the threshold value.

6. The method of claim 1, wherein the blinking detection is performed by:

utilizing a predetermined selection rule to identify target values from luminance statistics of at least three adjacent video frames; and

referencing a distribution of the target values to determine if blinking occurs.

7. The method of claim 6, wherein the predetermined selection rule is:

for each of the three adjacent video frames, selecting a target value according a predetermined percentile of a luminance distribution of a video frame.

8. The method of claim 6, wherein the predetermined selection rule is:

for each of the three adjacent video frames, sorting a plurality of pixels of a video frame according to gray levels, and selecting a k^th pixel from the sorted pixels to be a target value.

9. The method of claim 1, wherein the blinking detection check is performed by:

checking if the current video frame within a scene is preceded by a plurality of video frames of the scene; and

if the current video frame is preceded by the plurality of video frames, the blinking detection check result indicates that the blinking detection is required.

10. A brightness adjusting device for processing video frames of a video sequence, the brightness adjusting device comprising:

a video buffer, for receiving a current video frame of the video sequence;

a scene change detector, coupled to the video buffer, for generating a scene change detection result according to a scene change between the current video frame and a previous video frame;

a storage unit, for storing a plurality of candidate brightness adjusting schemes;

a video processor, coupled to the video buffer, the scene change detector, and the storage unit, for applying one of the plurality of stored candidate brightness adjusting schemes to the current video frame according to the scene change detection result; and

a blinking detector, coupled to the video buffer, for performing a blinking detection, and a blinking detection check to determine if the blinking detection is required;

wherein if a blinking detection check result indicates that the blinking detection is required, the scene change detector is enabled to perform the scene change detection and the blinking detector is enabled to perform the blinking detection;

if the blinking detection check result indicates that the blinking detection is not required, the scene change detector is enabled to perform the scene change detection;

if the blinking detection check result indicates that the blinking detection is required, the video processor applies one of the candidate brightness adjusting schemes to the current video frame according to the scene change detection result and a blinking detection result;

if the blinking detection check result indicates that the blinking detection is not required, the video processor applies one of the candidate brightness adjusting schemes to the current video frame according to the scene change detection result;

when the blinking detection check result generated by the blinking detector indicates that the blinking detection is not required and the scene change detection result generated by the scene change detector indicates that a scene change occurs between the current video frame and the previous video frame, the video processor applies a first brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

when the blinking detection check result indicates that the blinking detection is not required and the scene change detection result indicates that no scene change occurs between the current video frame and the previous video frame, the video processor applies a second brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame;

when the blinking detection check result indicates that the blinking detection is required and the blinking detection result indicates that blinking occurs;

if the scene change detection result indicates that a scene change occurs between the current video frame and the previous video frame, the video processor applies a third brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

if the scene change detection result indicates that no scene change occurs between the current video frame and the previous video frame, the video processor applies a fourth brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

when the blinking detection check result indicates that the blinking detection is required and the blinking detection result indicates that no blinking occurs;

if the scene change detection result indicates that a scene change occurs between the current video frame and the previous video frame, the video processor applies a fifth brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame; and

if the scene change detection result indicates that no scene change occurs between the current video frame and the previous video frame, the video processor applies a sixth brightness adjusting scheme of the candidate brightness adjusting schemes to the current video frame.

11. The brightness adjusting device of claim 10, wherein the second brightness adjusting scheme, the fourth brightness adjusting scheme, and the sixth brightness adjusting scheme are the same, and the first brightness adjusting scheme stored is identical to the fourth brightness adjusting scheme.

12. The brightness adjusting device of claim 10, wherein the video processor completes execution of the first brightness adjusting scheme in M fields, the video processor completes execution of the second brightness adjusting scheme in N fields, the video processor completes execution of the third brightness adjusting scheme in K fields, and M<

K<

N.

13. The brightness adjusting device of claim 10, wherein the video processor completes execution of the first brightness adjusting scheme in M fields, the video processor completes execution of the second brightness adjusting scheme in N fields, the video processor executes the third brightness adjusting scheme for maintaining brightness of the current video frame, and M<

N.

14. The brightness adjusting device of claim 10, wherein the scene change detection compares a difference between a luminance distribution of the current video frame and a luminance distribution of the previous video frame with a threshold value;

and detects a scene change between the current video frame and the previous video frame when the difference is greater than the threshold value.

15. The brightness adjusting device of claim 10, wherein the blinking detector utilizes a predetermined selection rule to identify target values from luminance statistics of at least three adjacent video frames including the current video frame;

and references a distribution of the target values to determine if blinking occurs.

16. The brightness adjusting device of claim 15, wherein the predetermined selection rule is:

for each of the three adjacent video frames, selecting a target value according a predetermined percentile of a luminance distribution of a video frame.

17. The brightness adjusting device of claim 15, wherein the predetermined selection rule is:

for each of the three adjacent video frames, sorting a plurality of pixels of a video frame according to gray levels, and selecting a k^th pixel from the sorted pixels to be a target value.

18. The brightness adjusting device of claim 10, wherein the blinking detector checks if the current video frame within a scene is preceded by a plurality of video frames of the scene and generates the blinking detection check result indicating that the blinking detection is required if the current video frame is preceded by the plurality of video frames.