Fixed-Length Image Compression for LCD DCC Bit Rate Control
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Solution Overview
Problem
Conventional image compression techniques for LCD DCC devices suffer from subjective picture quality deterioration, increased decoder complexity, and inability to achieve exact bit rate control, particularly due to transform coding and entropy coding methods.
Innovation Solution
A data compression system that selectively uses Differential Pulse Code Modulation (DPCM) and Pulse Code Modulation (PCM) methods to compress and reconstruct image data in 2×2 blocks, allowing for exact bit rate control and minimizing picture quality deterioration by representing compressed data with predetermined fixed lengths of bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If transform coding compression is applied to compress image data for LCD DCC devices, then the data compression ratio is improved, but the subjective picture quality deteriorates due to edge portion crushing and block artifacts
Solution Approach 1:
The image data is divided into 2×2 pixel blocks for processing. Each block is compressed independently using DPCM or PCM methods, allowing precise control over the compression process while maintaining edge integrity. This segmentation approach prevents the block artifacts and edge crushing problems associated with traditional transform coding that processes larger blocks.
Solution Approach 2:
The patent changes the fundamental compression parameter from transform coding to predictive coding (DPCM/PCM). By using differential encoding that references neighboring pixels rather than frequency transformation, the method preserves edge sharpness and subjective picture quality while achieving the required compression ratios for LCD DCC applications.
2Productivity
If entropy coding is used for image compression in LCD DCC devices, then the compression efficiency is improved, but the decoder complexity increases significantly
Solution Approach 1:
The patent extracts and removes the complex entropy coding stage from the compression system. By using fixed-length or simple variable-length DPCM/PCM encoding directly on the predictive differences, the method eliminates the need for complex entropy decoding operations, significantly simplifying the decoder while maintaining compression efficiency suitable for LCD DCC devices.
3Quantity of substance
If conventional image compression standards are applied to LCD DCC devices, then the data storage requirement is reduced, but the ability to achieve exact bit rate control is lost
Solution Approach 1:
The patent implements a dynamic mode selection mechanism that adaptively chooses between DPCM and PCM methods for each 2×2 block based on local image characteristics. This dynamic approach allows precise control over the bit rate by adjusting the compression mode and quantization parameters, ensuring exact bit rate control while reducing data storage requirements to fit LCD DCC memory constraints.
Data Source
AI summary
A method, medium, and system compressing and/or reconstructing image data. The data compression method includes compressing current data according to a plurality of modes for compressing current data, determining whether the current data compressed according to the plurality of modes can be represented by a fixed length of bits, selecting a mode from among modes in which the compressed current data can be represented by the fixed length of bits, and outputting the compressed current data according to the selected mode. Accordingly, it is possible to significantly lower the complexity of an image encoder/decoder system, and exactly meet a picture-based Control Bit Rate (CBR) suitable for a Liquid Crystal Display Dynamic Capacitance Compensation (LCD DCC) device/system.