Video Encoder Skipped Macroblock Quantization Control

Solution Overview

Problem

In video compression, especially in block-based motion-compensated methods like MPEG-1, MPEG-2, and H.264/AVC, skipped macroblocks with coarse quantization lead to long-lived distortion, particularly in scenes with static backgrounds, resulting in suboptimal image quality due to inconsistent quantization across frames.

Innovation Solution

Implement a method to limit the number of consecutive times a block is coded as skipped without re-setting the quantization level to a finer level, thereby re-selecting the mode and re-setting the quantization level for blocks that have been skipped for a predefined amount of time, ensuring that the quantization level is adjusted to a relatively fine level to improve image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If skipped macroblocks are coded with coarse quantization to maintain efficient compression, then compression efficiency is improved, but image quality deteriorates due to long-lived distortion

Engineering Contradiction:

Improvecompression efficiencyVSAvoidimage quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by making the quantization level adaptive rather than fixed. The system dynamically adjusts the quantization level based on the skip count of macroblocks, transitioning from coarse quantization during prolonged skip sequences to fine quantization when skips are detected. This dynamic adjustment resolves the contradiction by allowing the system to optimize for compression efficiency during stable periods while switching to fine quantization to correct distortion accumulation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the quantization parameter (QP) based on the skip count of macroblocks. When a macroblock is skipped for a certain number of consecutive frames, the system changes the QP parameter to a finer level. This parameter change allows the system to maintain compression efficiency during normal operation while improving image quality when distortion becomes problematic, thus resolving the contradiction between compression efficiency and image quality.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If quantization level is set to coarse level for skipped blocks to reduce bitrate, then bitrate is reduced, but distortion accumulates over time

Engineering Contradiction:

ImprovebitrateVSAvoiddistortion accumulation

Core Design Contradiction:

Quantity of substanceVSLoss of information

Solution Approach 1:

The patent implements feedback by monitoring the skip count of macroblocks and using this information to adjust the quantization level. The system continuously tracks how many consecutive frames a macroblock has been skipped and provides feedback to the quantization decision. When the skip count exceeds a threshold, the feedback mechanism triggers a switch to finer quantization, preventing unbounded distortion accumulation while maintaining low bitrate operation during normal skip sequences.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies periodic action by implementing a threshold-based review mechanism that periodically checks the skip count and adjusts quantization accordingly. Rather than continuously adjusting, the system performs periodic evaluations at defined skip thresholds, creating a rhythm of coarse quantization interrupted by periodic fine quantization corrections. This periodic action prevents distortion accumulation while maintaining efficient compression during most frames.

Inventive Principle:

Principle #19Periodic action

3Stability of the object's composition

If skipped macroblocks are not re-quantized to maintain consistent compression, then compression consistency is maintained, but image quality deteriorates due to persistent distortion

Engineering Contradiction:

Improvecompression consistencyVSAvoidimage quality

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by making the quantization level adaptive rather than fixed. The system dynamically adjusts the quantization level based on the skip count of macroblocks, transitioning from coarse quantization during prolonged skip sequences to fine quantization when skips are detected. This dynamic adjustment resolves the contradiction by allowing the system to optimize for compression efficiency during stable periods while switching to fine quantization to correct distortion accumulation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the quantization parameter (QP) based on the skip count of macroblocks. When a macroblock is skipped for a certain number of consecutive frames, the system changes the QP parameter to a finer level. This parameter change allows the system to maintain compression efficiency during normal operation while improving image quality when distortion becomes problematic, thus resolving the contradiction between compression efficiency and image quality.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8077772B2Coding background blocks in video coding that includes coding as skipped

Publication Date: 2011.12.13 CISCO TECHNOLOGY INC

AI summary

A method, an apparatus, and a method to encode a block in a picture of a time sequence of pictures such as video. The method includes selecting the mode for coding the block, one of the modes being to code the block as skipped. The method further includes limiting the number of consecutive times a particular block is coded as skipped without re-setting the quantization level to a relatively fine level of quantization and re-selecting the mode.