Hybrid DPCM-PCM Image Encoding for Fast High-Quality Decoding
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Solution Overview
Problem
Existing image encoding methods face challenges in achieving high compression ratios without degrading image quality, particularly due to limitations in fixed-length compression techniques that hinder real-time decoding and parallel processing.
Innovation Solution
An image encoding device that dynamically determines the compression mode for each pixel between DPCM and PCM based on predicted data, adjusts PCM code lengths within predetermined limits, and uses tags to facilitate efficient decoding, allowing for high-quality image restoration with reduced processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed-length compression is used for each pixel, then encoding simplicity is maintained, but compression ratio cannot be enhanced above a certain level
Solution Approach 1:
The patent applies dynamics by making the code length variable rather than fixed. The encoding device dynamically determines the code length for each pixel based on the absolute difference value, transitioning from a static fixed-length approach to a dynamic variable-length approach that adapts to local image characteristics.
Solution Approach 2:
The patent changes the parameter of code length from a fixed value to a variable value determined by the absolute difference. By modifying this key parameter based on local image complexity, the system achieves higher compression ratios while maintaining encoding simplicity through the use of lookup tables.
2Quantity of substance
If short fixed length encoding is used, then compression ratio is enhanced, but accuracy of post-decoding image is degraded
Solution Approach 1:
The patent applies local quality by using different code lengths for different pixels based on their local characteristics. Pixels with small absolute differences use shorter codes, while pixels with large differences use longer codes, optimizing the balance between compression ratio and image accuracy locally rather than applying a uniform approach.
Solution Approach 2:
The patent changes the code length parameter dynamically based on the absolute difference value. This parameter change allows the system to use shorter codes where appropriate (enhancing compression) while using longer codes where needed (maintaining accuracy), thus resolving the contradiction between compression ratio and image quality.
3Quantity of substance
If variable code length encoding is used, then compression ratio is enhanced, but decoding processing time is increased
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correspondence between absolute difference values and code lengths in lookup tables during the encoding phase. This preliminary preparation allows the decoding device to quickly determine code lengths without complex calculations, significantly reducing decoding processing time while maintaining high compression ratios.
Solution Approach 2:
The patent uses copying by storing pre-computed code length information in lookup tables that can be efficiently copied or referenced during decoding. Instead of performing complex variable-length calculations in real-time, the system copies or references pre-prepared data structures, accelerating the decoding process.
4Quantity of substance
If variable code length encoding is used, then compression ratio is enhanced, but parallel processing becomes difficult
Solution Approach 1:
The patent applies segmentation by dividing the image data processing into independent pixel-level operations. Each pixel's encoding can be performed independently using the same variable-length logic with lookup tables, allowing results to be processed in parallel. The segmentation of processing tasks enables both variable-length compression and parallel execution.
Solution Approach 2:
The patent uses preliminary action by pre-computing the variable-length code mappings in lookup tables before parallel processing begins. This preliminary preparation eliminates the need for complex inter-processor communication or synchronization during parallel decoding, as each processing unit can independently reference the pre-computed tables.
Data Source
AI summary
The present invention provides an image encoding device that can balance encoding at a high compression ratio and restoration of a high-quality image by decoding in a short processing time. Compression mode determination means 3 determines a compression mode to be one of DPCM and PCM based on target pixel data inputted from a terminal 21 and predicted data calculated by a predetermined method. For the DPCM, DPCM compression means 5 compresses a difference value between the target pixel data and the predicted data to DPCM encoded data having a predetermined DPCM code length. For the PCM, PCM compression means 7 compresses the target pixel data to PCM encoded data having a PCM code length determined by PCM code length determination means 9. The PCM code length determination means 9 calculates the PCM code length for each piece of target pixel data such that a total of post-encoding code lengths becomes an allowable value or less in a unit of predetermined pixel group among the plurality of pixels. Tag/code output means 13 outputs the encoded data by adding a tag indicating whether the compression mode is the DPCM or the PCM to the encoded data.