CAVLC Level Prefix Switching for High-Bitrate Video Encoding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
At high bit rates, the encoding efficiency of video data decreases due to increased values of quantized transform coefficients, leading to a higher amount of code bits generated during variable length encoding in video encoding applications.
Innovation Solution
A video image encoding device employs a variable length encoding unit that uses multiple encoding modes, including CAVLC, where levels equal to or greater than a threshold value are encoded using fixed length encoding, reducing the amount of code bits by distinguishing each level prefix and using variable and fixed length codes effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CAVLC is used at high bit rate, then computational cost is reduced, but encoding efficiency decreases due to increased values of quantized transform coefficients
Solution Approach 1:
The patent changes the encoding parameters for level_prefix by introducing a fixed length encoding mode that activates when level_prefix values are equal to or greater than a threshold. This parameter change allows the system to adapt the encoding strategy based on the actual data characteristics at high bit rates, thereby improving encoding efficiency while maintaining computational feasibility
Solution Approach 2:
The patent introduces dynamic switching between variable length encoding and fixed length encoding modes for level_prefix based on the threshold condition. This dynamic approach allows the encoding system to automatically adjust its behavior according to the bit rate and data characteristics, resolving the contradiction between computational cost and encoding efficiency
2Quantity of substance
If quantization step is increased to control bit rate, then values of quantized transform coefficients decrease, but amount of code bits increases leading to lower compression efficiency
Solution Approach 1:
The patent changes the encoding parameter strategy by introducing fixed length encoding for level_prefix values that meet certain conditions. This parameter change ensures that even when quantized transform coefficients have high values requiring more bits, the encoding remains efficient and predictable, thereby maintaining compression efficiency while controlling bit rate
Data Source
AI summary
In a variable length encoding for video data, the compression rate of video image encoding is increased by improving the level encoding method. A CAVLC encoding unit acquires coefficients obtained by orthogonally transforming and quantizing video image data in each block unit, determines an encoding mode of variable length encoding among those in a table_A and a table_B, or a mixture thereof by a level encoding mode controller and outputs the determination result to a level_prefix unit. In the table_B, a fixed_length bit string is allocated to a level_prefix which is at least a prescribed value. The level_prefix unit performs a level_prefix encoding in the determined encoding mode to output the result to an output control unit.