Image Signal Processor Line Buffer Management for In-Stream Stabilization
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Solution Overview
Problem
Small, mobile devices with high-resolution cameras face limitations in processing image data due to limited availability of image data at any given time, which hinders effective image stabilization and other processing operations.
Innovation Solution
An image signal processor (ISP) is configured to apply transformations, such as image stabilization, by using a transformation module that estimates the center of a vertical support window and adjusts line buffers to handle finite-length sliding windows of image data, enabling operations like image resampling and perspective transforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If image processing operations are performed in-stream with limited image data availability, then processing efficiency is improved, but the ability to properly process image data deteriorates
Solution Approach 1:
The system performs preliminary actions by estimating the center of the vertical support window and pre-calculating the required line buffers before processing each output pixel line. This allows the ISP to prepare the necessary image data in advance, ensuring that when data is needed for processing, it is already available in the correct position, thus maintaining both efficiency and quality.
Solution Approach 2:
The system dynamically adjusts the vertical support window center based on the transformation being applied. By calculating the center position for each output pixel line and adjusting the support window accordingly, the system adapts to different processing requirements in real-time, maintaining processing quality while operating with limited data availability.
2Device complexity
If a finite-length sliding window of image lines is used for processing, then device complexity is reduced, but the quantity of available image data deteriorates
Solution Approach 1:
The system performs preliminary calculation of the vertical support window center and pre-positions the required line buffers before processing begins. This preliminary preparation allows the finite sliding window to contain sufficient data for accurate processing without requiring larger buffers, thus maintaining both low complexity and adequate data quantity.
Solution Approach 2:
The system changes the parameter of the vertical support window center position based on the transformation characteristics. By dynamically adjusting this parameter for different output pixel lines, the system optimizes the use of the finite buffer space, ensuring that the limited data available in the sliding window is positioned correctly for accurate processing.
3Object-affected harmful factors
If image stabilization transformations are applied in-stream, then motion artifacts are reduced, but the availability of sufficient image data for accurate processing deteriorates
Solution Approach 1:
The system performs preliminary estimation of the transformation parameters and pre-calculates the vertical support window center for image stabilization. By preparing the necessary data and transformation information in advance, the system can apply stabilization transformations accurately even with limited data availability in the sliding window, reducing motion artifacts while maintaining transformation precision.
Solution Approach 2:
The system uses feedback from processing previous output pixel lines to estimate the center of the vertical support window for subsequent lines. This feedback mechanism allows the system to continuously refine its understanding of the transformation requirements, improving transformation accuracy while operating with the limited data available in the finite sliding window.
Data Source
AI summary
An output rescale module may determine an estimated set of lines to hold in vertical support for use when performing image transformations. For example, an output rescale module may monitor input Y coordinates (in terms of input pixel lines) computed over previous lines and compute a set of lines to hold in a set of line buffers. As each output pixel line is generated, the output rescale module may compute the minimum and maximum values of Y generated by the transform across that line. The minimum and maximum input Y coordinates may then be averaged to determine the center value (the centermost input line) for that output line. The difference (in terms of input pixel lines) between centerlines for two adjacent output lines may be added to the centerline value for the current output line to estimate a center line for the next (not yet generated) output pixel line.