Video Random Access Unit Types for Flexible Stream Switching

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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 '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 and constraints to simplify mapping to container formats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If video codec standards enforce strict constraints on decodable leading pictures after random access points, then decoding reliability is improved, but flexibility for random access operations deteriorates

Engineering Contradiction:

Improvedecoding reliabilityVSAvoidflexibility for random access operations

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the bitstream into multiple access units, each containing a random access picture and associated leading pictures. This segmentation allows the decoder to independently process each access unit, enabling reliable random access at multiple points while maintaining flexibility for different access operations like fast forward, rewind, and stream switching.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic flags (e.g., broken link access picture flag, random access skipped leading picture flag) that allow the encoder to dynamically indicate the decodability status of leading pictures. This dynamic signaling mechanism enables the system to adapt between strict constraints and relaxed constraints based on the specific random access requirements, resolving the contradiction between reliability and flexibility.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If video codec standards allow multiple types of random access pictures with different constraints, then adaptability for different access operations is improved, but device complexity deteriorates

Engineering Contradiction:

Improveadaptability for different access operationsVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent creates a universal random access picture structure that can serve multiple functions: clean random access (CRA), broken link access (BLA), and intermediate random access pictures. This multi-functional design allows a single picture type to support various access operations (fast forward, rewind, stream switching) without requiring entirely separate structures, thereby improving adaptability while controlling complexity through unified processing logic.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12513336B2Constraints and unit types to simplify video random access

Publication Date: 2025.12.30 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.