Video Coding Consistency Huawei’s Conformance Window Rules for Reference Picture Resampling

Huawei Technologies Co., Ltd. has filed a patent for a method that enforces consistency rules for conformance windows when multiple picture parameter sets with the same picture dimensions are used in video coding – a technical standard contribution that prevents decoding errors in complex video streams that employ reference picture resampling.

The Problem

Modern video coding standards – including H.264, HEVC and the latest Versatile Video Coding (VVC) standard – are extraordinarily complex specifications that must handle an enormous range of video content, delivery scenarios and device capabilities. The standards define multiple levels of parameter sets: sequence parameter sets that apply to an entire video sequence, picture parameter sets that can apply different settings to individual pictures or groups of pictures, and other structures that allow fine-grained control over how video is encoded and decoded.

Reference picture resampling (RPR) is a feature introduced in VVC that allows different pictures within the same video sequence to have different spatial resolutions – enabling dynamic resolution changes in the bitstream without requiring a full sequence parameter set change. This is valuable for scenarios such as adaptive bitrate streaming, spatial scalability and video with mixed content requiring different quality levels for different sections.

The interaction between multiple picture parameter sets and conformance windows creates a potential ambiguity in decoders. A conformance window defines the active display area of a picture – it specifies which portion of the coded picture area actually contains the displayable image, accounting for padding and alignment constraints in the coded domain. When two picture parameter sets refer to the same sequence parameter set and have the same picture width and height values, a question arises: should their conformance windows also be required to be the same? If different conformance windows are permitted for the same picture dimensions, decoders may produce incorrect output – displaying wrong portions of pictures or producing visual artefacts.

What This Invention Does

Huawei’s invention addresses this ambiguity by establishing a clear rule: when a first picture parameter set and a second picture parameter set both refer to the same sequence parameter set and have the same values for picture width and picture height, they must also have the same values for the conformance window. This constraint ensures that wherever the same picture dimensions appear within a sequence, the same display area definition applies consistently.

The decoder method described in the patent receives picture parameter sets and checks this conformance constraint – if two parameter sets with the same dimensions are found to have different conformance windows, this represents a non-conformant bitstream. Valid bitstreams that satisfy the constraint enable the decoder to apply the conformance window reliably and consistently to all current pictures corresponding to those parameter sets, regardless of which specific parameter set is in effect for any given picture.

By mandating this consistency rule at the codec specification level, the invention prevents a class of potential decoding errors before they occur – rather than requiring decoders to implement complex error recovery logic for ambiguous bitstream conditions. This kind of normative constraint is a standard tool in video coding standards development for eliminating sources of implementation variation and ensuring interoperability across different encoder and decoder implementations.

Key Features

Conformance window consistency rule. When two picture parameter sets reference the same sequence parameter set and have identical picture width and height values, they are required to have identical conformance window values, eliminating ambiguity in how the display area is defined.

Reference picture resampling context. The invention specifically addresses the interaction between conformance windows and reference picture resampling – a VVC feature enabling dynamic resolution changes within a video sequence.

Decoder method specification. The invention is expressed as a decoding method, providing clear rules that decoder implementations must follow when receiving and processing picture parameter sets in compliant bitstreams.

Interoperability assurance. By defining a normative constraint that applies to both encoders and decoders, the invention ensures that different implementations will handle conformance windows consistently, supporting interoperability across the video ecosystem.

VVC/H.266 standards relevance. The technical scope of the invention places it squarely within the VVC (Versatile Video Coding / H.266) standards context, the latest generation international video coding standard in which Huawei has been a major contributor.

Who Is Behind It?

Huawei Technologies Co., Ltd. is one of China’s largest technology companies and a major contributor to international video coding standards through its active participation in the Joint Video Experts Team (JVET) that developed VVC. The inventors Jianle Chen and Fnu Hendry are video coding researchers with extensive contributions to the VVC standardisation process. The application is filed through Phillips Ormonde Fitzpatrick and is a divisional of an earlier filing (AU 2024266970), tracing back to a US provisional application from July 2019 coinciding with the VVC standards development period.

Why It Matters

Video streaming now accounts for a majority of global internet traffic, and the efficiency of video compression directly affects the bandwidth, storage and energy costs of delivering video content to billions of devices. The VVC standard represents a major advance in compression efficiency – roughly halving the bandwidth required compared to its predecessor HEVC – and features like reference picture resampling are important tools for making VVC deployments flexible and bandwidth-efficient in real-world streaming scenarios.

The technical quality of the VVC standard depends on rigorous resolution of exactly the kinds of parameter interaction questions addressed by this patent. Ambiguities in how parameter sets interact can cause interoperability failures between devices from different manufacturers – a serious problem in a market where users expect video to play correctly across all their devices regardless of who made the encoder or decoder. Huawei’s contribution to clarifying the conformance window consistency rules reflects the detailed, painstaking standards work that underlies the smooth operation of the global video streaming ecosystem.

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AU 2026201614 was published in the Australian Official Journal of Patents on 19 March 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.