Coded Picture Buffer Parameter Interpolation for Multi-Rate Stability
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Solution Overview
Problem
Existing video coding standards require a high bit consumption for transmitting HRD parameters for a dense selection of bitrates to ensure correct CPB operation, leading to potential buffer overflows or underflows, and lack flexibility in adjusting HRD parameters for various bit rates.
Innovation Solution
The solution involves interpolating between explicitly signaled CPB parameters at selected bit rates to achieve a balance between parameter transmission capacity and effective CPB operation, using interpolated temporal offsets and removal delays to manage the feeding and emptying of the coded picture buffer without causing underflows or overflows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high number of HRD parameters are transmitted for a dense selection of bitrates, then correct CPB operation for many bit rates is ensured, but bit consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing CPB parameters (such as cpb_size, initial_cpb_removal_delay, au_cpb_removal_delay) for multiple operation points during encoding. These pre-computed parameters are then transmitted to the decoder, eliminating the need for the decoder to perform complex real-time calculations and reducing the bit consumption required for parameter transmission while ensuring correct CPB operation across multiple bitrates.
Solution Approach 2:
The patent utilizes parameter changes by representing CPB parameters in different forms (e.g., using logarithmic scaling for cpb_size, using delta encoding for removal delays). This allows the same amount of information to be transmitted with fewer bits while maintaining the precision needed for correct CPB operation. The encoder transforms the parameters into a more compact representation that reduces transmission overhead.
2Productivity
If CPB parameters are optimized for one bitrate, then efficient decoding is achieved, but buffer overflows or underflows occur at other bit rates
Solution Approach 1:
The patent implements universality by designing the CPB parameter structure to serve multiple bitrates simultaneously. Instead of optimizing parameters for a single bitrate, the encoder provides a set of parameters that can be used across a range of bitrates. The decoder can select appropriate parameters from this set based on the actual bitrate being used, ensuring both efficient decoding and stable buffer operation at various bitrates.
Solution Approach 2:
The patent applies dynamics by allowing the CPB parameters to be adaptively selected based on the actual operating conditions. The bitstream contains multiple sets of CPB parameters corresponding to different operation points, and the decoder dynamically selects the appropriate parameter set based on the actual bitrate and buffering conditions. This dynamic adaptation prevents buffer overflows and underflows while maintaining decoding efficiency.
3Ease of operation
If detailed HRD parameters are transmitted for every bitrate, then precise control is achieved, but transmission overhead increases
Solution Approach 1:
The patent applies segmentation by dividing the HRD parameter information into multiple operation points, each with its own set of parameters. Instead of transmitting one comprehensive set of parameters for all bitrates, the bitstream is segmented into discrete operation points (e.g., Op0, Op1, Op2), each containing parameters optimized for specific bitrate ranges. This segmentation reduces the total transmission overhead while maintaining precise control where needed.
Solution Approach 2:
The patent uses partial action by transmitting only the essential CPB parameters needed for correct buffer operation, rather than all possible HRD parameters. The patent selectively transmits parameters such as cpb_size, initial_cpb_removal_delay, and au_cpb_removal_delay, which are the critical parameters for preventing buffer overflows and underflows, while omitting less critical parameters. This partial transmission approach reduces overhead while maintaining sufficient control precision.
Data Source
AI summary
Interpolation between explicitly signaled CPB (or HRD) parameters at selected bit rates is used to achieve a good compromise between CPB parameter transmission capacity and CPB parametrization effectiveness and may be, particularly, made in an effective manner.