Multiple Reference Line Intra Prediction for Lower Bit Usage
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in representing less likely intra prediction directions, leading to increased bit usage and reduced compression efficiency.
Innovation Solution
The proposed solution involves decoding prediction information to select a reference line and intra prediction mode, with a reduced set of potential modes for even indexes and a default reference line for odd indexes or non-probable modes, optimizing the bit representation of intra prediction directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional intra prediction with single reference line is used, then all intra prediction modes are available for all blocks, but the number of bits required to represent less likely prediction directions increases
Solution Approach 1:
The patent segments the intra prediction modes into two distinct groups: a first group of intra prediction modes associated with a first reference line, and a second group of intra prediction modes associated with a second reference line. This segmentation allows the encoder to selectively apply different mode sets based on the prediction direction, reducing the bit representation overhead for less likely directions while maintaining support for all prediction modes through reference line switching.
Solution Approach 2:
The patent implements dynamic selection of intra prediction mode groups based on the actual prediction direction and content characteristics. The encoder dynamically determines whether to use the first group or second group of modes, and dynamically selects between first and second reference lines, allowing adaptability to different block types and prediction scenarios while optimizing bit usage.
2Productivity
If multiple reference lines are introduced for intra prediction, then compression efficiency improves, but the complexity of decoding and reference line selection increases
Solution Approach 1:
The patent segments reference lines into a first reference line and a second reference line, each associated with specific groups of intra prediction modes. This segmentation simplifies the decoding process by providing clear rules for when to use each reference line, reducing the complexity of reference line selection while enabling multiple reference line support for improved compression efficiency.
Solution Approach 2:
The patent changes the parameter of reference line indexing by introducing an explicit reference line index that can take values of 0 or 1. This parameter change provides a simple, standardized mechanism for selecting between multiple reference lines, making the decoding process more manageable while enabling the flexibility needed for improved compression performance.
3Loss of information
If a reduced set of intra prediction modes is used for even indexes, then bit representation is optimized, but the flexibility for certain prediction directions is reduced
Solution Approach 1:
The patent segments intra prediction modes into those with even indexes (forming a first group) and those with odd indexes (forming a second group), associating each group with a specific reference line. This segmentation optimizes bit representation by using a reduced mode set for each reference line while maintaining overall flexibility through reference line switching, as the union of both groups covers all prediction directions.
Data Source
AI summary
In a method for video decoding, prediction information of a current block is decoded from a coded video bitstream. The prediction information is indicative of a reference line selected from multiple reference lines and an intra prediction mode selected from a set of potential intra prediction modes that is associated with the reference line. At least one sample of the current block is reconstructed based on the intra prediction mode and at least one reference sample in the reference line. When the reference line is a non-zero reference line, a first set of potential intra prediction modes associated with the non-zero reference line includes a smaller number of potential intra prediction modes compared to a second set of potential intra prediction modes associated with a zero reference line. The first set of potential intra prediction modes only includes most probable modes.