POC Recalculation in Scalable Video Decoding
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Solution Overview
Problem
The existing High Efficiency Video Coding (HEVC) standard faces challenges in efficiently managing picture order count (POC) values, particularly with non-aligned random access point pictures, leading to issues like error resilience, non-existing picture problems, and increased bit cost due to mandatory signaling of poc_reset_flag in each slice header.
Innovation Solution
A method and system for efficiently determining and managing POC values by retrieving a POC recalculation value from a random access point picture in the base layer, recalculating POC values of reference pictures in the decoded picture buffer, and signaling this recalculation value in the slice header, specifically for IDR pictures, to maintain correct output order and comply with POC alignment rules without increasing bit cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If poc_reset_flag is signaled in each slice header to maintain POC alignment, then POC alignment compliance is improved, but bit cost increases
Solution Approach 1:
The patent extracts the POC recalculation information from the slice header and places it in the access unit level (in the trailing picture header of the last slice). This allows the same POC recalculation to be applied to multiple slices without repeating the flag in each slice header, thereby reducing bit cost while maintaining POC alignment compliance.
Solution Approach 2:
The patent makes the POC recalculation value applicable to all slices within an access unit by positioning it at the access unit level. A single poc_decrement value can recalculate POC for multiple slices, giving it universal application across the access unit and eliminating the need for redundant signaling in each slice header.
2Reliability
If POC values are recalculated for all reference pictures to maintain error resilience, then error resilience is improved, but device complexity increases
Solution Approach 1:
The patent performs POC recalculation at the access unit level before slice decoding begins. By calculating the poc_decrement value early and making it available to all slices, the decoder avoids complex per-slice POC calculations and can straightforwardly apply the pre-computed recalculation to all reference pictures, reducing overall device complexity.
Solution Approach 2:
The patent introduces an intermediary poc_decrement value that mediates between the access unit POC structure and individual slice POC values. This intermediary carries the recalculation information efficiently through the bitstream and enables simplified POC management in the decoder without requiring complex error handling logic in each slice.
Data Source
AI summary
A POC recalculation value is retrieved by a decoder from an encoded representation of a RAP picture in a base layer of a video stream comprising pictures in multiple layers. POC values of reference pictures in a DPB of the decoder are recalculated using the POC recalculation value. By signaling the POC recalculation value in the RAP picture, which enables the decoder to correctly handle video streams with non-aligned RAP pictures.