Dynamic Bit Allocation for P-Pictures in CBR Video Coding
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Solution Overview
Problem
In constant bit rate (CBR) moving image coding systems, the allocation of coding bits to intra-coded (I) and inter-coded (P/B) pictures results in insufficient sharpness for P-pictures, leading to decreased subjective image quality due to error propagation and flicker noise, especially in scenes with motion.
Innovation Solution
A moving image coding apparatus that dynamically adjusts the number of coding bits for P-pictures within a Group Of Pictures (GOP) by increasing bits for P-pictures after a predetermined position, using a picture information amount control processor to maintain image quality and reduce error propagation, while keeping the bit rate constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of coding bits for P-pictures is reduced to maintain constant bit rate, then the bit rate is kept constant, but the image sharpness and quality of P-pictures deteriorate
Solution Approach 1:
The patent applies dynamics by making the number of coding bits for P-pictures variable rather than fixed. The bit allocation is dynamically adjusted based on the position of P-pictures within the GOP, with later P-pictures receiving more bits than earlier ones. This dynamic allocation allows the system to maintain constant average bit rate while ensuring sufficient bits are available for P-pictures that would otherwise suffer from bit starvation, thereby resolving the contradiction between constant bit rate and image sharpness.
Solution Approach 2:
The patent applies local quality by differentiating the bit allocation strategy for different P-pictures based on their position within the GOP. Instead of uniform bit allocation, the system allocates more coding bits to P-pictures located after a predetermined position in the GOP sequence. This localized differentiation ensures that P-pictures requiring higher quality (later ones) receive adequate bits, while maintaining the overall constant bit rate constraint.
2Reliability
If the number of coding bits for I-pictures is increased to reduce coding error, then the coding error is reduced, but the number of coding bits available for P-pictures is reduced
Solution Approach 1:
The patent applies local quality by differentiating bit allocation between I-pictures and P-pictures based on their specific roles and positions. I-pictures, which serve as reference pictures and are crucial for reducing coding error propagation, are allocated sufficient bits. Meanwhile, P-pictures are allocated variable bits based on their position in the GOP, ensuring that the overall bit distribution optimizes both error reduction and available bits for inter-coded pictures.
Solution Approach 2:
The patent applies preliminary action by ensuring that I-pictures are properly coded with adequate bits before P-pictures are coded. Since I-pictures serve as references for subsequent P-pictures, allocating sufficient bits to I-pictures beforehand prevents coding errors from propagating to P-pictures. This preliminary bit allocation to I-pictures ensures that the foundation is solid before building upon it with P-picture data.
3Quantity of substance
If uniform bit allocation is used for all P-pictures, then the bit rate is constant, but image quality degradation and flicker noise increase
Solution Approach 1:
The patent applies dynamics by replacing uniform static bit allocation with a dynamic variable allocation scheme. The number of coding bits for P-pictures changes based on their position within the GOP, with later P-pictures receiving more bits. This dynamic adjustment prevents the bit starvation that occurs with uniform allocation, thereby reducing flicker noise and image quality degradation while maintaining constant average bit rate.
Solution Approach 2:
The patent applies local quality by implementing position-dependent bit allocation for P-pictures. Different P-pictures receive different bit allocations based on their specific position in the GOP sequence. This localized differentiation addresses the specific needs of different P-pictures, preventing uniform allocation from causing flicker noise and image quality issues in later frames.
Data Source
AI summary
A moving image coding apparatus is provided. The moving image coding apparatus includes a processing unit having an information amount control processor determining a quantization parameter in such a manner that while a lead-in of the set of the pictures is set as a reference, upon a position of the inter-coded picture being after a predetermined position corresponds to a first position at a predetermined cycle shorter than the number of pictures included in the set of the pictures, the number of coding bits allocated to the inter-coded picture is a value obtained by adding a first predetermined amount to a predetermined reference value, and upon the position of the inter-coded picture being after the predetermined position and also at a second position different from the first position, the number of coding bits is a value obtained by subtracting a second predetermined amount from the reference value.