Image Compressor Fixed Bit Length Predicted Difference
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Solution Overview
Problem
Conventional electronic cameras face limitations in high-speed continuous shooting due to the large amount of uncompressed raw data, leading to interrupted shooting sessions and reduced frame rates, as existing compression techniques either result in variable data sizes or degrade image quality when attempting to increase compression efficiency.
Innovation Solution
An image compressor that calculates predicted differences and applies coarser quantization steps when the difference exceeds a threshold, setting a fixed bit length for each pixel, combined with gradation compression and variable length encoding to manage data size and maintain image quality, ensuring a consistent number of frames can be captured during high-speed shooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If variable length encoding is used to compress raw data, then compression efficiency is improved, but the amount of compressed data becomes variable and unpredictable
Solution Approach 1:
The patent changes the parameter of bit length from variable to fixed. By allocating a predetermined fixed bit length for each pixel's predicted difference, the system ensures that the total compressed data size is predictable (number of pixels × fixed bit length per pixel), while still achieving compression through quantization of the predicted differences.
2Reliability
If fixed bit length encoding is used to ensure predictable data size, then data size predictability is improved, but compression efficiency deteriorates
Solution Approach 1:
The patent applies local quality by using predicted difference encoding where each pixel is processed individually based on its local characteristics. The predicted difference (actual pixel value - predicted pixel value) is quantized and encoded with a fixed bit length. This local processing approach maintains compression efficiency while ensuring fixed output size, as each pixel's contribution to the total data size is predetermined.
3Productivity
If compression efficiency is increased to store more frames in buffer memory, then the number of storable frames is improved, but image quality degradation increases
Solution Approach 1:
The patent employs dynamic predicted difference encoding where the quantization process adapts to the local image characteristics through prediction. By calculating predicted differences based on neighboring pixels or temporal information, the encoding dynamically adjusts to preserve important image features while compressing redundant information, thus maintaining image quality while increasing compression ratio.
Data Source
AI summary
An image compressor of the present invention includes a difference calculating unit and a difference requantizing unit. The difference calculating unit calculates a predicted difference between a pixel value of image data and a predicted value (a calculated value of the pixel value predicted from known data). When a magnitude of the predicted difference exceeds a predefined threshold value, the difference requantizing unit applies the coarse quantization steps to requantize the predicted difference to keep a bit range to predetermined size. In this manner, compressed data, in which a bit length of the predicted difference for one pixel is adjusted to a fixed bit length, is generated.