Adaptive Reconstruction Levels for Video Quantization

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Solution Overview

Problem

Current video encoding standards, such as H.264/AVC, face challenges in achieving optimal rate-distortion performance due to the use of uniform quantization step sizes, which can lead to inefficiencies in data compression, especially for video data that requires precise reconstruction levels.

Innovation Solution

The implementation of adaptive reconstruction levels within the quantization process, where the encoder computes and transmits these levels to achieve better rate-distortion coding performance without significantly increasing coding complexity, by using a method that involves solving a quadratic optimization problem on the encoder side and adjusting reconstruction levels based on actual data distributions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If uniform quantization step sizes are used, then device complexity is reduced, but rate-distortion performance deteriorates

Engineering Contradiction:
Improvequantization process complexityVSAvoidrate-distortion performance
Core Design Contradiction:
Device complexityVSLoss of information

Solution Approach 1:

The patent applies local quality by using different quantization step sizes for different sub-parts of the data space. Instead of a uniform quantization step size across all data, the method partitions the data space into multiple sub-parts, each with its own optimized quantization step size. This allows the quantization process to adapt to local characteristics of the data distribution, improving rate-distortion performance while maintaining reasonable device complexity through the structured approach to determining these step sizes.

Inventive Principle:
Principle #3Local quality

2Loss of information

If adaptive reconstruction levels are computed and transmitted, then rate-distortion performance is improved, but loss of time increases due to additional computation

Engineering Contradiction:
Improverate-distortion performanceVSAvoidcoding time
Core Design Contradiction:
Loss of informationVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-determining a set of candidate quantization step sizes before the actual quantization process. These candidate step sizes are established in advance based on statistical analysis or optimization criteria, so that during encoding, the system only needs to select from this pre-computed set rather than performing complex real-time optimization. This reduces coding time while still achieving improved rate-distortion performance through the use of adaptive step sizes selected from the pre-determined candidates.

Inventive Principle:
Principle #10Preliminary action

3Manufacturing precision

If quantization step sizes are optimized for data distribution, then manufacturing precision is improved, but device complexity increases

Engineering Contradiction:
Improvereconstruction accuracyVSAvoidquantization process complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the data space into multiple sub-parts, each characterized by its own data distribution statistics. For each sub-part, a specific quantization step size is determined based on its local characteristics. This segmentation approach allows the system to achieve high reconstruction accuracy by adapting to local data patterns while managing device complexity through the modular structure of processing different sub-parts separately with predetermined step sizes.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP2678944B1Methods and devices for data compression using offset-based adaptive reconstruction levels
Publication Date: 2019.11.06 BLACKBERRY LTD
  • EP2678944B1 patent drawingFigure 1
  • EP2678944B1 patent drawingFigure 2
  • EP2678944B1 patent drawingFigure 3~4

AI summary

Encoding and decoding methods are presented that used offset-based adaptive reconstruction levels. The offset data is inserted in the bitstream with the encoded video data. The offset data may be differential data and may be an index to an array of offset values from which the differential offset is calculated by the decoder. The offset to an adaptive reconstruction level may be adjusted for each slice. The offsets may be specific to a particular level/index and data type. In some cases, offsets may only be sent for a subset of the levels. Higher levels may apply no offset, may apply an average offset, or may apply the offset used for the highest level having a level- specific offset.