Video Coding Drift Compensation via DC Coefficient Prediction

Solution Overview

Problem

Transcoding devices suffer from a temporal or spatial drift effect due to imperfect estimation of requantization errors, leading to progressive deterioration of picture quality, especially in INTRA type pictures during the transcoding of a sequence of pictures.

Innovation Solution

A method for coding a block of a picture that involves determining a prediction coefficient from a previously reconstructed reference block, calculating residual values, transforming these values, and replacing the DC coefficient with the difference between the product of the proportionality coefficient and the average picture data, thereby improving the quality by avoiding drift during transcoding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional transcoding is performed using FPDT method, then bitrate adaptation is achieved, but temporal or spatial drift effect occurs leading to progressive deterioration of picture quality

Engineering Contradiction:

ImprovebitrateVSAvoidpicture quality

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by determining a prediction coefficient from previously reconstructed reference blocks before performing the main transcoding operation. This prediction coefficient is used to guide the quantization process, ensuring that the transcoding maintains reference consistency and prevents drift accumulation from the outset, rather than correcting drift after it occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by using previously reconstructed reference blocks to determine prediction coefficients that guide the current block's quantization. This creates a feedback loop where past reconstruction quality informs future quantization decisions, ensuring consistent reference maintenance and preventing drift accumulation across the picture sequence.

Inventive Principle:

Principle #23Feedback

2Quantity of substance

If quantization is performed with a second quantization step determined according to required bitrate, then bitrate adaptation is achieved, but requantization errors accumulate causing drift

Engineering Contradiction:

ImprovebitrateVSAvoidreference consistency

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the quantization process based on the prediction coefficient derived from reference blocks. Instead of using a fixed quantization step, the method modifies quantization parameters adaptively to maintain reference consistency, thereby preventing drift while still achieving the required bitrate adaptation.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If DC coefficient prediction is performed from reference blocks, then compression efficiency is improved, but drift effect occurs due to imperfect estimation

Engineering Contradiction:

Improvecompression efficiencyVSAvoidprediction accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by determining a prediction coefficient from previously reconstructed reference blocks before performing the main transcoding operation. This prediction coefficient is used to guide the quantization process, ensuring that the transcoding maintains reference consistency and prevents drift accumulation from the outset, rather than correcting drift after it occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by using previously reconstructed reference blocks to determine prediction coefficients that guide the current block's quantization. This creates a feedback loop where past reconstruction quality informs future quantization decisions, ensuring consistent reference maintenance and preventing drift accumulation across the picture sequence.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9094716B2Methods for coding and decoding a block of picture data, devices for coding and decoding implementing said methods

Publication Date: 2015.07.28 INTERDIGITAL MADISON PATENT HLDG

AI summary

A method for coding a block of picture data is disclosed. The method comprises the following steps:determining a prediction coefficient of a DC coefficient of a block from a DC coefficient of at least one previously reconstructed reference block,determining, for each pixel of the block, a prediction value such that the average of prediction values is proportional to the prediction coefficient to a proportionality coefficient close,calculating, for each pixel of the block, a residual value by subtracting from the picture data of the pixel the prediction value of the pixel,transforming the block of residual values by a first transform into a first block of coefficients,replacing, in the first block of coefficients, the DC coefficient by the difference between the product of the proportionality coefficient and the average of picture data of the block and the prediction coefficient, andquantizing and coding the first block of coefficients.