Image Coding Sub-band Overflow Control
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Solution Overview
Problem
Conventional methods for compressing RAW images, such as JPEG 2000's EBCOT, have a high processing load and are not suitable for real-time processing in embedded devices, leading to data corruption and reproduction issues due to excessive data amounts.
Innovation Solution
A coding method that performs wavelet transformation on image data components, codes sub-bands, and adjusts the total code amount by replacing or discarding data in units of sub-bands to meet a threshold, using simple processing that does not require a special decoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If EBCOT (embedded coding) is used for compressing RAW images, then the data amount can be reduced after coding, but the processing load becomes extremely heavy and real-time processing becomes difficult
Solution Approach 1:
The image data is divided into multiple sub-bands through wavelet transformation, and each sub-band is coded independently. This segmentation allows the system to process and compress data in manageable units, reducing the overall processing load while maintaining compression effectiveness. The patent applies this by dividing the image into frequency sub-bands and coding them separately rather than using the complex EBCOT embedded coding approach.
2Ease of manufacture
If conventional compression methods are used without proper code amount control, then the processing is simpler, but the data amount exceeds the transfer rate causing data corruption
Solution Approach 1:
The patent implements dynamic code amount control by monitoring the total code amount during the coding process and adjusting the compression parameters accordingly. When the code amount approaches the threshold, the system dynamically truncates less important sub-bands to ensure the total data amount remains within the transfer rate limits, preventing data corruption while maintaining processing simplicity.
3Quantity of substance
If multiple sub-bands are truncated to reduce data amount, then the code amount control is achieved, but the truncated sub-bands cannot be comprehended without retrieving the end code
Solution Approach 1:
The patent performs preliminary organization of coded data by arranging sub-bands in a specific order and inserting end codes at predetermined positions before the actual decoding process. This preliminary structuring allows the decoding device to easily identify which sub-bands are present and which are truncated without needing to search through the entire data stream, significantly simplifying the decoding operation.
4Quantity of substance
If a layer structure is adopted for compression, then data amount can be reduced, but overheads occur making it not always suitable
Solution Approach 1:
The patent extracts only the essential compression functionality needed for RAW image data by using wavelet transformation and sub-band coding without adopting the complex layered structure of JPEG 2000. The system takes out the core compression mechanism (wavelet-based sub-band decomposition) and implements it in a simplified manner that avoids the overhead associated with multiple layers and embedded coding structures.
Data Source
AI summary
A frequency transformation unit executes discrete wavelet transformation processing on image data, quantizes the output of sub-bands of each component using a quantization unit, and performs entropy coding using a coding unit. If a total code amount of the image data that has been coded exceeds a maximum value that has been set, an overflow control unit replaces the coded data with copy data obtained by coding 0 in order from sub-bands having the lowest priority, until the total code amount is less than or equal to the maximum value.