Chrominance Prediction From Luminance With Bounded Coefficients
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Solution Overview
Problem
The next-generation moving picture encoding method VVC faces high calculation complexity due to large bit requirements for lookup tables and potential prediction coefficient values exceeding input pixel ranges, with unnecessary smoothing operations on all pixels.
Innovation Solution
A moving picture decoding device and method that specifies minimum and maximum luminance pixel values without smoothing, reduces lookup table precision, and sets an upper limit for prediction coefficients, aligning calculation precision with interpolation filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision lookup tables are used for deriving prediction coefficients, then prediction accuracy is improved, but calculation complexity and number of bits required for operations increase
Solution Approach 1:
The patent changes the precision parameter of lookup tables from high precision to reduced precision, and sets an upper limit on prediction coefficient values. This parameter change resolves the contradiction by achieving acceptable prediction accuracy while significantly reducing calculation complexity and bit requirements for operations.
2Reliability
If smoothing operations are applied to all pixels for deriving prediction coefficients, then prediction robustness is improved, but unnecessary calculations increase processing time
Solution Approach 1:
The patent extracts only the necessary pixels (those needed for linear modeling) from the set of all pixels, eliminating unnecessary smoothing operations on irrelevant pixels. This extraction approach maintains prediction robustness for the essential pixels while removing redundant calculations that slow down processing.
Solution Approach 2:
Instead of applying smoothing to all pixels (excessive action), the patent applies smoothing only to the specific pixels required for accurate prediction (partial action). This partial application maintains necessary prediction robustness while avoiding the processing overhead of unnecessary operations.
3Adaptability or versatility
If prediction coefficients are allowed to have large absolute values, then prediction range is improved, but output values may exceed input pixel value range causing overflow
Solution Approach 1:
The patent applies preliminary anti-action by setting an upper limit on the absolute value of prediction coefficients before they are used in prediction calculations. This preventive measure ensures that prediction results remain within the valid pixel value range, preventing overflow while maintaining sufficient prediction range through the use of linear models and gradient calculations.
Data Source
AI summary
A decoding device includes a transformer sets a decoded luminance component of a prediction target block to the same number of samples as that of the chrominance component corresponding to the decoded luminance component of the prediction target block and generates a luminance reference signal. A specificator specifies luminance pixels having minimum and maximum pixel values of the decoded luminance component adjacent to the decoded luminance component of the prediction target block, respectively, outputs luminance pixel values obtained from specified luminance pixels, and outputs chrominance pixel values from pigment pixels corresponding to the luminance pixels. A derivator derives a linear prediction parameter from the two pixel values and a linear prediction model. A chrominance linear predictor obtains chrominance prediction signal applying the linear prediction model based on the linear prediction parameter to the luminance reference signal. The chrominance prediction and residual signals are summed to generate a reconstructed chrominance signal.