CABAC Renormalization Using Non-Iterative Interval Updates
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Solution Overview
Problem
The iterative renormalization step in CABAC encoding methods for video compression is slow due to its long execution time, forming a bottleneck in the encoding process.
Innovation Solution
Replacing the iterative renormalization method with a non-iterative process that directly calculates and updates the interval parameters, including determining the upper limit of the interval, identifying common high-order bits, and adjusting the number of bits to be inserted, allowing for faster processing without iterations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the iterative renormalization method is used in CABAC encoding, then the encoding accuracy is maintained, but the processing speed deteriorates due to long execution time
Solution Approach 1:
The patent replaces the iterative renormalization process with a direct calculation method that skips multiple intermediate iterations. By computing the number of iterations N in advance using the formula N = log2(CIR/V1/4) and directly calculating the final interval values, the method rushes through what would otherwise require multiple sequential iteration steps, thereby significantly improving processing speed while maintaining encoding accuracy.
Solution Approach 2:
The patent performs preliminary calculations to determine the number of iterations N required before actually executing the renormalization. By pre-calculating N based on the initial interval size CIR and threshold V1/4, the system prepares the exact number of steps needed in advance, avoiding the overhead of iterative checking and condition evaluation during the actual renormalization process, thus improving processing speed.
2Reliability
If the iterative renormalization method is used in CABAC encoding, then the correct probability interval is calculated, but the execution time increases forming a bottleneck
Solution Approach 1:
The patent skips the iterative execution by directly calculating the final interval values using closed-form mathematical expressions. Instead of repeatedly applying the renormalization formula N times where N is determined through iteration, the method computes the result in a single step using the pre-determined N, thereby eliminating the time loss associated with iterative execution while preserving calculation correctness.
Solution Approach 2:
The patent changes the parameter representation by working with the logarithmic form of the interval size and using bit-length calculations instead of floating-point iterative multiplication. By transforming the renormalization operation into bit manipulation and integer arithmetic based on pre-calculated parameters, the method maintains mathematical correctness while dramatically reducing execution time.
Data Source
AI summary
An encoding device and method, of CABAC type, for an initial stream of binary digital information intended to generate an outgoing stream to form video images, after decoding, the method included the following steps: bit-by-bit analysis of the successive series of bits of the initial binary stream so as to deduce therefrom, for each bit, an interval representing the probability of occurrence associated with this bit, this interval being defined by its size CIR and its lower bound CIL, analysis of this interval so as to ensure, if necessary, a renormalization thereof. The renormalization is non-iterative and for each bit of the initial stream is compliant with the appended figure in which: M is the length of the sequence S of high-order bits common to CIL and CIR, N is the integer number such that CIR.2N-1<0.25≦CIR.2N, BO is the number of bits waiting to be inserted.