CRA Picture Constraints for Flexible Video Random Access

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Solution Overview

Problem

Existing video codec standards limit the flexibility of random access points in video bitstreams, making operations like fast forwarding, rewinding, and switching between streams cumbersome due to constraints on decodable leading pictures.

Innovation Solution

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

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional video codec standards are used with strict constraints on random access points, then decoding reliability is maintained, but operational flexibility and adaptability deteriorate

Engineering Contradiction:

Improveflexibility of random access pointsVSAvoiddecoding reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The video bitstream is segmented into multiple access units, each containing a CRA picture that can serve as an independent random access point. This segmentation allows the video stream to be divided into manageable sections that can be accessed independently, improving flexibility without compromising the reliability of each segment's decoding

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

CRA pictures serve as intermediary elements between traditional I pictures and B pictures. These intermediary pictures provide reference frames that enable random access while maintaining decoding reliability through controlled use of bidirectional prediction, acting as a mediator that balances flexibility and reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If non-decodable leading pictures are allowed after CRA pictures, then adaptability and ease of operation improve, but device complexity increases

Engineering Contradiction:

Improveease of fast forwarding and rewindingVSAvoidcomplexity of managing non-decodable pictures

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The decoder is prepared in advance for the possibility of encountering non-decodable leading pictures by implementing preliminary checks and handling mechanisms. When a CRA picture is encountered, the decoder预先 (in advance) determines whether subsequent leading pictures are decodable, and if not, gracefully handles them by skipping or discarding them, making fast forwarding and rewinding easier without requiring complex real-time decision-making

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The bitstream structure itself carries information about the decodability of leading pictures through syntax elements and flags. This self-service mechanism allows the decoder to automatically determine whether to attempt decoding or skip pictures without external control, reducing the complexity of managing non-decodable pictures while improving ease of operation

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12501072B2Constraints and unit types to simplify video random access

Publication Date: 2025.12.16 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.