Parallel Image Encoding Without Slice Boundaries or Skip Macroblocks
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Solution Overview
Problem
In parallel image encoding, the issue arises when encoding macroblocks across processing area boundaries, where the quantization parameter of the last macroblock of a previous area cannot be used for the top macroblock of the next area due to parallel processing, leading to decoding errors and image quality deterioration, as existing methods either require forming slices or fixing quantization parameters, which compromise encoding efficiency or image quality.
Innovation Solution
The solution involves adding a non-zero coefficient to the top macroblock's orthogonally-transformed coefficients or changing the coded block pattern to indicate the existence of a non-zero coefficient, allowing the use of the last macroblock's quantization parameter for the top macroblock, thereby avoiding the need for slice formation and enabling efficient prediction across processing area boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel processing is used to improve processing capability, then productivity is improved, but decoding errors occur due to quantization parameter inconsistency across processing area boundaries
Solution Approach 1:
The patent applies preliminary action by forcing the top macroblock of each parallel processing area to have non-zero coefficients before encoding. This is achieved by adding a non-zero coefficient to the top macroblock's transformed coefficients or by setting the coded block pattern to indicate non-zero coefficients exist. This preliminary modification ensures that the top macroblock cannot be encoded as a skip macroblock, thereby preventing the decoding error that would otherwise occur due to quantization parameter inconsistency between parallel processing areas.
2Reliability
If slices are formed to prevent quantization parameter reference across boundaries, then decoding accuracy is improved, but encoding efficiency deteriorates due to loss of prediction
Solution Approach 1:
Instead of forming slices to prevent quantization parameter reference, the patent applies preliminary action by modifying the top macroblock's coefficients to ensure they are non-zero. This allows the system to maintain continuous prediction across processing area boundaries without forming slices, thereby preserving encoding efficiency while still preventing the decoding errors that would occur with skip macroblocks.
3Reliability
If quantization parameter is fixed to ensure consistency, then decoding accuracy is improved, but image quality deteriorates due to loss of adaptive control
Solution Approach 1:
The patent applies preliminary action by selectively forcing only the top macroblock of each parallel processing area to have non-zero coefficients, while allowing all other macroblocks to use adaptive quantization parameters. This selective approach prevents decoding errors at processing area boundaries without sacrificing the adaptive quantization control that maintains high image quality in the rest of the image.
Data Source
AI summary
The present invention provides an image encoding device which does not necessitate reference of a quantization parameter between consecutive macroblocks across a parallel processing area boundary without forming slices. The image encoding device encodes a macroblock of an encoding target image by parallel processing sequentially from the top of a parallel processing area, and possesses an encoding element for every parallel processing area. When all the quantized orthogonally-transformed coefficients of a top macroblock of the parallel processing area are zero, the encoding element adds a non-zero coefficient to a part of the coefficients, making the coefficients non-zero. Accordingly, generation of a skip macroblock in the top macroblock of each parallel processing area is suppressed. Since slice formation is not necessary, the prediction over a parallel processing area boundary is applied, and encoding efficiency improves. Errors are not generated in decoding and the decoded image quality does not deteriorate.