Moving Picture Encoder Scene Change Detection
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Solution Overview
Problem
Existing moving picture encoding technologies face challenges in accurately detecting scene changes, leading to potential image quality degradation due to excessive information allocation during frequent scene changes and misdetection of static images, especially when the time axis is not even.
Innovation Solution
The solution involves dynamically adjusting the scene change detection threshold based on the VBV buffer's remainder, canceling scene change detection when necessary, and initializing the rate control parameter using a database of moving average absolute differences to optimize information allocation and prevent misdetected scene changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scene change detection is performed using fixed threshold based on SAD time change, then scene changes can be detected, but image quality degrades when scene changes occur frequently due to excessive information allocation
Solution Approach 1:
The patent implements dynamic threshold adjustment by making the scene change detection threshold variable based on VBV buffer remainder. When buffer remainder is large, the threshold is lowered to enable sensitive scene change detection. When buffer remainder is small, the threshold is raised to prevent excessive scene change detection that would consume too much information allocation, thus preventing image quality degradation.
Solution Approach 2:
The patent changes the detection parameter (threshold value) based on buffer status. The threshold is dynamically adjusted according to the VBV buffer remainder, transforming a fixed parameter into a variable one that adapts to different encoding conditions, resolving the contradiction between detection sensitivity and image quality maintenance.
2Reliability
If I frame is inserted every time scene change is detected, then scene change correlation is handled, but information allocation is insufficient for other coding when scene changes occur frequently
Solution Approach 1:
The patent dynamically controls I-frame insertion by adjusting the scene change detection threshold based on buffer remainder. When information allocation is sufficient (large buffer remainder), I-frames are inserted upon scene change detection. When information allocation is constrained (small buffer remainder), the raised threshold prevents false scene change detection, thereby reducing unnecessary I-frame insertions and preserving information for other coding purposes.
3Ease of operation
If static image screen is processed with scene change detection, then detection process is uniform, but misdetection occurs due to large SAD time change without actual scene change
Solution Approach 1:
The patent adjusts the detection threshold parameter based on buffer remainder to differentiate between actual scene changes and static image variations. By raising the threshold when buffer remainder is small, the system becomes more selective, preventing misdetection of static screens as scene changes while maintaining simple uniform processing logic.
4Device complexity
If scene change detection threshold is fixed, then detection process is simple, but detection accuracy varies with buffer status and scene frequency
Solution Approach 1:
The patent introduces dynamic threshold adjustment based on VBV buffer remainder, making the detection process adaptive to different encoding conditions. This adds some complexity but significantly improves detection accuracy by preventing both missed detections and false detections, balancing the trade-off between process complexity and detection precision.
Data Source
AI summary
In encoding of moving pictures, I-frame is inserted when a scene change occurs. If scene changes frequently occur in the range of a predetermined amount-of-information allocation, the amount of information allocated to an encoding process on I-frame becomes enlarged. Therefore, the amount of information cannot be sufficiently reserved for another coding, thereby considerably degrading the quality of an image. Thus, a scene change detection threshold is obtained depending on the remainder in the VBV buffer, the scene change detection threshold is compared with a scene change detection value for determination of the occurrence of a scene change, and it is determined whether or not a scene change has occurred based on the comparison result.