Dependent Random Access Points for Video Bitstream Efficiency
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Solution Overview
Problem
Existing video coding technologies, such as HEVC, are inefficient in handling screen content due to the high cost of periodic intra random access points (IRAPs) and the propagation of errors in videos with motion, especially in scenarios where parts of the video are not updated for long periods.
Innovation Solution
The introduction of dependent random access points (DRAPs), which are temporal predictive pictures that use a previous IRAP or DRAP as a sole reference picture, reducing bit cost and enabling efficient random access operations while maintaining error robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic intra random access points (IRAPs) are used to provide random access and error robustness, then reliability is improved, but bitrate increases due to high encoding cost
Solution Approach 1:
The patent segments the random access point functionality into two types: IRAP pictures for error robustness and DRAP pictures for frequent random access. This segmentation allows the system to use intra-coded IRAPs sparingly (every 1-2 seconds) while using inter-coded DRAPs more frequently (every 0.5-1 second), thereby maintaining reliability while reducing overall bitrate compared to using only IRAPs
Solution Approach 2:
The patent changes the coding parameter of random access points from always intra-coded (IRAP) to allowing inter-coded variants (DRAP). By changing the prediction mode parameter from intra-prediction to inter-prediction for DRAP pictures, the encoding cost is significantly reduced while maintaining random access capability through restricted reference picture sets
2Reliability
If intra prediction is used for random access points, then error robustness is improved, but compression efficiency deteriorates
Solution Approach 1:
The patent introduces dynamics by allowing the prediction mode to change based on the picture type. IRAP pictures use static intra-prediction for error robustness, while DRAP pictures use dynamic inter-prediction for better compression efficiency. The system dynamically switches between prediction modes depending on whether error robustness or compression efficiency is the priority
Solution Approach 2:
The patent changes the prediction mode parameter from intra-prediction to inter-prediction for DRAP pictures, significantly improving compression efficiency. Additionally, the reference picture set parameter is changed to include only IRAP and previous DRAP pictures, maintaining error robustness while enabling more efficient temporal prediction
3Productivity
If inter prediction is used to reduce bit cost, then compression efficiency is improved, but error propagation increases in videos with motion
Solution Approach 1:
The patent introduces DRAP pictures as intermediary elements between IRAP pictures. These DRAP pictures use inter-prediction for compression efficiency but are constrained to reference only IRAP and previous DRAP pictures, preventing error propagation from unrelated picture sequences. The DRAP acts as a mediator that enables efficient compression while maintaining error boundaries
Solution Approach 2:
The patent changes the reference picture set parameter for DRAP pictures to include only IRAP and previous DRAP pictures, creating a controlled dependency chain. This parameter change allows inter-prediction for compression efficiency while limiting error propagation scope to only the immediate predecessor pictures in the restricted reference set
Data Source
AI summary
The present embodiments introduce a new type of random access point in video bitstreams that can be used for random access operations but can be represented in encoded form at a lower bit cost as compared to IRAP pictures. The random access point is a dependent random access point (DRAP) picture that is encoded and decoded as a temporal predictive picture using an IRAP picture and/or a previous, according to a decoding order, DRAP picture as sole reference picture(s) for the DRAP picture. The DRAP picture constitutes a random access point in a video bitstream.