AC Decoder Bypassing for JPEG Image Decoding Efficiency
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Solution Overview
Problem
Conventional JPEG decoding processes are inefficient, particularly during the Huffman decoding process, due to the need to fully decode all AC coefficients for an 8 by 8 block, which is time-consuming and impractical for low display resolutions where only a limited number of AC coefficients are required.
Innovation Solution
An image decoding apparatus and method that bypasses unnecessary AC coefficients by determining if the number of generated AC coefficients exceeds a predetermined parameter, allowing for an AC bypassing process to skip further decoding and reduce processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full AC coefficient decoding is performed for an 8x8 block, then complete image fidelity is maintained, but decoding time increases significantly
Solution Approach 1:
The patent extracts only the necessary AC coefficients required for the target display resolution from the full set of 63 AC coefficients in an 8x8 block. By identifying and processing only the relevant coefficients (those that will contribute to pixels within the display resolution), the system eliminates redundant decoding operations while maintaining acceptable image fidelity for the intended display device.
Solution Approach 2:
The patent applies partial action by decoding only the required number of AC coefficients rather than all 63 coefficients in an 8x8 block. The system determines the exact number of coefficients needed based on the display resolution and decodes only that portion, avoiding the excessive action of fully decoding all coefficients when many would be discarded anyway due to downscaling.
2Loss of information
If all AC coefficients are decoded for high resolution images, then complete detail information is preserved, but processing efficiency decreases for low display resolutions
Solution Approach 1:
The patent applies local quality by adapting the decoding process to the specific requirements of the target display resolution. Instead of uniformly decoding all coefficients regardless of output needs, the system adjusts the number of coefficients decoded based on the local requirements of each block relative to the display resolution, optimizing the balance between information preservation and processing efficiency for each specific case.
3Measurement precision
If conventional Huffman decoding process is used for all blocks, then complete decoding accuracy is achieved, but time consumption increases for low resolutions
Solution Approach 1:
The patent introduces dynamics by making the decoding process adaptive to the target display resolution. The system dynamically determines the number of AC coefficients to decode based on the relationship between the original image resolution and the display resolution. This dynamic adjustment allows the system to maintain decoding accuracy for the required coefficients while reducing time consumption by avoiding decoding of unnecessary coefficients that would be discarded during downscaling.
Data Source
AI summary
An image decoding apparatus is provided, including a parser and an AC decoder. The parser is provided for parsing a bit stream to acquire a first unit. The first unit includes a DC code and a plurality of AC codes respectively corresponding to a DC coefficient and AC coefficients for a first block of the image. The AC decoder generates a plurality of first AC coefficients for the first block by decoding the plurality of AC codes of the first unit, and determines whether the number of the plurality of first AC coefficients exceeds a predetermined parameter. If so, the AC decoder obtains a second unit of the bit stream corresponding to a second block following the first block by performing an AC bypassing process on the first unit. Each AC code comprises a Huffman code and a VLI code.