Video Bitstream Random Access with CRA and BLA Picture Types

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Solution Overview

Problem

Existing video codec standards limit the flexibility of random access points in video bitstreams, restricting the ability to perform operations like fast forward, rewind, and seamless switching between video streams, due to constraints on decodable leading pictures.

Innovation Solution

Introduce 'broken link access' (BLA) pictures that allow non-decodable leading pictures after CRA pictures in the bitstream, using flags or indicators to manage these leading pictures, and redefine unit types and constraints for random access point pictures to simplify mapping to container formats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If constraints on decodable leading pictures are maintained in existing video codec standards, then decoding reliability is ensured, but flexibility of random access points is restricted

Engineering Contradiction:

Improveflexibility of random access pointsVSAvoiddecoding reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the bitstream into multiple CRA (Clean Random Access) pictures, each serving as an independent random access point. By dividing the video stream into segments that can be independently decoded, the system enables flexible random access at multiple points while maintaining decoding reliability within each segment. The segmentation allows leading pictures to be associated with specific CRA pictures without compromising overall decoding stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic management of leading pictures through flags and indicators that allow the decoder to adaptively handle non-decodable leading pictures. The system dynamically adjusts decoding behavior based on the presence of CRA pictures and associated leading pictures, enabling flexible random access while maintaining reliability through adaptive control mechanisms.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If CRA pictures are allowed only at the beginning of the bitstream, then decoding simplicity is maintained, but operational flexibility for fast forward and rewind is limited

Engineering Contradiction:

Improveoperational flexibility for fast forward and rewindVSAvoidbitstream structure complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent divides the bitstream into multiple segments, each beginning with a CRA picture that can serve as an independent random access point. This segmentation enables fast forward and rewind operations to jump to any CRA picture rather than being restricted to the beginning of the bitstream, significantly improving operational flexibility while managing complexity through structured segmentation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces leading pictures as intermediary elements that bridge CRA pictures in the bitstream. These leading pictures, which may be non-decodable, serve as placeholders or markers that enable random access functionality without requiring complex restructure of the entire bitstream, thus easing operational flexibility while controlling device complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If non-decodable leading pictures are allowed after CRA pictures in the middle of the bitstream, then random access flexibility is improved, but mapping to container format becomes more complex

Engineering Contradiction:

Improvenumber of access pointsVSAvoidmapping complexity to container format

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the bitstream at CRA picture boundaries, creating independent units that can be mapped to container formats. Each segment begins with a CRA picture and may include associated leading pictures. This segmentation simplifies mapping to container formats by creating clear boundaries and units, while still allowing non-decodable leading pictures to enhance random access flexibility within each segment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different handling rules locally to different parts of the bitstream. CRA pictures and their associated leading pictures are treated as a local unit with specific properties, allowing non-decodable leading pictures to exist without requiring changes to the overall container format mapping strategy. This local quality approach enables increased access points while managing mapping complexity through localized handling.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12413782B2Constraints and unit types to simplify video random access

Publication Date: 2025.09.09 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Disclosed herein are innovations for bitstreams having clean random access (CRA) pictures and/or other types of random access point (RAP) pictures. New type definitions and strategic constraints on types of RAP pictures can simplify mapping of units of elementary video stream data to a container format. Such innovations can help improve the ability for video coding systems to more flexibly perform adaptive video delivery, production editing, commercial insertion, and the like.