Letter Box Detection in MPEG Decoding via Multi-Stage Filtering
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Solution Overview
Problem
Existing MPEG decoding technologies fail to accurately detect the size of letter boxes inserted during encoding, leading to aspect ratio mismatches and unnatural image patterns when displaying images on screens with different aspect ratios, causing wasted space and potential screen damage in CRT monitors.
Innovation Solution
A method and apparatus for detecting letter boxes using a six-step filtering process, including processing area filtering, intra-macroblock filtering, impulse data filtering, inter-macroblock filtering, inter-line filtering, and inter-picture filtering, to determine the size of letter boxes inserted in images, allowing for correct aspect ratio matching during MPEG decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If letter box regions are inserted during MPEG encoding to match aspect ratios, then compatibility with 4:3 displays is improved, but aspect ratio mismatch occurs when displaying on 16:9 screens
Solution Approach 1:
The patent replaces manual or simple display adjustment methods with an automated image processing system that analyzes pixel data to detect letter box regions. The system uses filtering algorithms (intra-macroblock, inter-macroblock, inter-line, inter-picture) to automatically identify and remove letter box regions, substituting mechanical display adjustments with intelligent image analysis and processing.
Solution Approach 2:
The system performs self-service by automatically detecting and removing letter box regions without requiring user intervention. The image processing apparatus analyzes the decoded image data, identifies letter box regions through multi-stage filtering, and automatically adjusts the display image to match the correct aspect ratio, eliminating the need for manual configuration or user reference to predetermined sizes.
2Measurement precision
If letter box regions are removed and original 16:9 image is displayed on 16:9 screen, then aspect ratio accuracy is improved, but incorrect numerical values result in ineffective image reproduction
Solution Approach 1:
The patent implements feedback mechanisms through multi-stage filtering processes that iteratively refine the detection of letter box regions. The system uses intra-macroblock filtering, inter-macroblock filtering, inter-line filtering, and inter-picture filtering to progressively improve detection accuracy. This feedback loop ensures that only accurate letter box detection results are used for final image reconstruction, maintaining both aspect ratio accuracy and image reproduction reliability.
Solution Approach 2:
The patent segments the image processing into multiple independent filtering stages, each handling a specific aspect of letter box detection. The intra-macroblock filtering handles local pixel variations, inter-macroblock filtering handles block-level changes, inter-line filtering handles horizontal boundaries, and inter-picture filtering handles temporal consistency. This segmentation allows each stage to specialize in specific detection tasks, improving overall reliability of image reproduction.
3Productivity
If letter box detection is performed using simple methods, then processing speed is improved, but detection precision is insufficient leading to wasted screen space
Solution Approach 1:
The patent segments the detection process into four distinct filtering stages: intra-macroblock filtering, inter-macroblock filtering, inter-line filtering, and inter-picture filtering. Each stage processes specific aspects of the image data independently, allowing parallel processing and optimizing for both speed and precision. The segmentation enables the system to perform complex detection through coordinated simple operations rather than a single complex operation.
Solution Approach 2:
The patent performs preliminary filtering actions in the early stages (intra-macroblock and inter-macroblock filtering) to pre-identify and remove obvious letter box regions before performing more computationally intensive analysis. This preliminary action reduces the amount of data that needs to be processed in subsequent stages, improving overall processing speed while maintaining high detection precision through the cumulative effect of all filtering stages.
Data Source
AI summary
In a device and a method for detecting a letter box for an MPEG decoder, the method includes performing processing area filtering for selecting a processing area of an image used to detect the letter box; performing intra-macroblock filtering for determining the letter box area based on a change level of pixels in macroblocks in one line of the image from the processing area; performing impulse data filtering for excluding the line being detected a high frequency component from the determined letter box area; performing inter-macroblock filtering for determining the letter box area based on a change level of lines between macroblocks of the image; performing inter-line filtering for determining a boundary of the letter box based on an average of the pixel values of the lines; and performing inter-picture filtering for outputting a boundary value of the letter box that has the highest frequency number as the boundary of the letter box in successive images.