Two-pass image decoding for progressive display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The decoding of images during web page loading is time-consuming and resource-intensive, leading to slower loading times and user experience issues like white areas and flickering in browsers.
Innovation Solution
A two-pass decoding mechanism that first decodes images using only direct current (DC) coefficients to generate a low-resolution image, which is then processed for display, followed by a secondary decoding using both DC and alternating current (AC) coefficients to produce a high-resolution image when conditions are met, minimizing resource usage and improving user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard JPEG decoding is used to maintain high image quality, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The decoding process is segmented into two distinct passes: a first pass that decodes only DC coefficients to produce a low-resolution preview image, and a second pass that decodes AC coefficients to produce the final high-resolution image. This segmentation allows the system to display content progressively rather than waiting for complete decoding, thereby reducing perceived loss of time while maintaining final image quality.
Solution Approach 2:
The first decoding pass performs preliminary action by decoding only the DC coefficients before the AC coefficients are fully processed. This preliminary decoded image using only DC coefficients can be displayed immediately to provide visual feedback to users, while the second pass completes the decoding with AC coefficients to achieve the final high-quality image, thus overlapping processing with display operations.
2Manufacturing precision
If image decoding is performed completely before display, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The system performs preliminary decoding of DC coefficients and displays this intermediate result before the complete decoding process finishes. This allows the browser to show content to users progressively, improving perceived loading time while the second pass completes the full decoding for final image quality.
Solution Approach 2:
The decoding process continues in the background while the first decoded image is being displayed and processed. The second decoding pass using AC coefficients runs concurrently or in overlapping time periods with the display operations, ensuring that useful action (both decoding and display) continues without interruption rather than waiting for complete decoding.
3Productivity
If two-pass decoding is implemented to reduce processing time, then productivity is improved, but device complexity increases
Solution Approach 1:
The complex decoding task is segmented into two manageable passes with clearly defined responsibilities: the first pass handles DC coefficients for quick preview generation, and the second pass handles AC coefficients for final quality enhancement. This segmentation makes the overall complex process more manageable and implementable without requiring fundamentally new hardware or algorithms.
Solution Approach 2:
The patent reuses the existing JPEG decoding infrastructure and algorithms for both passes, copying the proven decoding logic rather than creating entirely new decoding mechanisms. The first pass copies the standard decoding process but stops early after DC coefficients, and the second pass copies the same process to complete the decoding with AC coefficients, thereby improving productivity without significantly increasing device complexity.
Data Source
AI summary
An image decoder includes a processor and a memory. The memory includes instructions configured to cause the processor to perform operations. The operations receive an encoded image, perform a first decoding of the encoded image to generate a first decoded image, store the first decoded image in the memory, process the first decoded image for displaying, perform a second decoding of the first decoded image and generate a second decoded image, and process the second decoded image for displaying.