Reference Picture List Constraints in Video Coding

The patent introduces an intermediary mechanism that determines additional information about unavailable reference pictures through a series of checks involving picture type identification, reference picture list analysis, and constraint evaluation. This intermediary process resolves the complexity by systematically determining what information can be inferred about no reference picture entries without requiring actual reference picture data.

The patent performs preliminary actions by checking whether a picture is an instantaneous decoder refresh (IDR) picture and determining additional information about reference pictures before the actual constraint checking process. This preliminary analysis prevents complexity during the main constraint verification by pre-establishing the status of reference picture availability and applicable constraints.

The patent applies local quality by determining additional information selectively based on the specific conditions of each reference picture entry. Instead of uniformly processing all entries, the system only performs additional determination steps when necessary (e.g., when identifying IDR pictures or when reference picture lists indicate unavailable references), thereby maintaining adaptability while minimizing processing overhead.

The patent employs partial action by implementing constraint checking and additional information determination only for the extent necessary to ensure bitstream conformance. The system performs minimal required processing - checking picture types, analyzing reference picture lists, and determining constraints only when unavailable reference pictures are detected - avoiding excessive processing for normal cases where reference pictures are available.