Macroblock Shuffling for Rate Control in Image Encoding

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Solution Overview

Problem

MPEG-2 image encoding systems face challenges in performing rate control through macroblock shuffling due to dependencies within slices, leading to inefficient coding and increased overhead, particularly in I-frame-only encoding, which affects image quality and compression efficiency.

Innovation Solution

An image encoding apparatus that shuffles macroblocks from pseudo-random positions, performs space-frequency transforms, and adjusts rates based on predictive quantities, allowing for independent rate control of macroblocks without altering the slice structure, thereby ensuring fair bit allocation and maintaining high encoding efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If macroblock shuffling is performed in MPEG-2 encoding, then rate control efficiency is improved, but slice structure dependencies cause coding inefficiency and increased overhead

Engineering Contradiction:

Improverate control efficiencyVSAvoidcoding efficiency

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent divides the image into multiple slices, where each slice is independently encodable. This segmentation allows macroblocks to be shuffled within slice boundaries while maintaining independence, resolving the contradiction between rate control efficiency and coding efficiency by enabling parallel processing without inter-slice dependencies

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different encoding treatments to different regions: intra-slice macroblocks can be shuffled and independently encoded, while inter-slice dependencies are managed separately. This local differentiation allows rate control to operate efficiently on individual slices without compromising overall coding efficiency

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If I-frame-only encoding is used to maintain image quality, then image quality is preserved, but compression ratio deteriorates

Engineering Contradiction:

Improveimage qualityVSAvoidcompression ratio

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent changes the encoding parameters by allowing selective use of inter-frame prediction within slices while maintaining I-frame structure. This enables better compression ratios without sacrificing image quality, as the encoder can adaptively choose between intra and inter prediction modes on a slice-by-slice basis

Inventive Principle:

Principle #35Parameter changes

3Productivity

If predictive encoding is applied to shuffled macroblocks, then encoding efficiency is improved, but buffer management becomes constrained

Engineering Contradiction:

Improveencoding efficiencyVSAvoidbuffer management

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary rate control calculations before actual encoding by estimating the bit requirements of predictive-coded macroblocks. This preliminary action allows the buffer management system to allocate resources in advance, preventing buffer constraints while maintaining encoding efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback mechanisms where the encoder monitors buffer status and adjusts predictive encoding parameters accordingly. When buffer constraints are detected, the system reduces predictive encoding usage or adjusts quantization parameters to maintain reliable buffer management

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables high-speed rate control, reduces circuit scale, and homogenizes image quality, preventing buffer constraints and allowing for simultaneous encoding of multiple frames, while maintaining predictive encoding efficiency and supporting various applications including inter-frame coding.

Implementation Method 1

A shuffling portion collects and shuffles a plurality of macroblocks constituting the image data from respective positions within the image

Methodology Applied

Scientific EffectPseudo-random shuffling:

Implementation Method 2

an encoding portion which performs space-frequency transform and entropy encoding on the plurality of macroblocks collected and shuffled by the shuffling portion

Methodology Applied

Scientific EffectSpace-frequency transform:

Implementation Method 3

a rate control portion which controls the encoding portion to adjust, with the plurality of macroblocks as the base unit, a rate of the plurality of macroblocks after the encoding

Methodology Applied

Scientific EffectRate control with predictive correction:

Data Source

PatentUS8731056B2Image encoding apparatus, image encoding method, and image encoding program

Publication Date: 2014.05.20 GRASS VALLEY CANADA

AI summary

It is an object of the present invention to provide an image encoding apparatus, an image encoding method, and an image encoding program, which can homogenize image quality of an image as a whole without lowering encoding efficiency, being operable at high speed, and reduce the size of circuit scale by performing macroblock shuffling without changing slice structure. Provided is an image encoding apparatus, including: a shuffling portion which collects and shuffles a plurality of macroblocks constituting image data from respective positions within an image; an encoding portion which performs space-frequency transform and entropy encoding on the plurality of macroblocks collected and shuffled by the shuffling portion, as a base unit; and a rate control portion which controls the encoding portion to adjust the rate of the plurality of macroblocks after the encoding.