Video Decoder DPB Output Delay Reduction via Reorder Threshold
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Solution Overview
Problem
The existing video coding standards, such as H.264/AVC and HEVC, face delays in picture output due to the need to wait for slice headers and the complexity of managing the decoded picture buffer (DPB), which affects the efficiency of decoding and encoding processes.
Innovation Solution
A method is introduced where a decoder determines the number of pictures marked as needed for output in the DPB and compares it against a value derived from syntax elements, allowing for the early output of pictures by marking them as not needed for output if the number exceeds a certain threshold, thereby reducing output delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pictures are stored in the decoded picture buffer (DPB) to maintain correct output order, then output order accuracy is improved, but output delay increases
Solution Approach 1:
The patent applies preliminary action by performing picture output before the traditional picture output process would allow. The decoder determines that a picture can be output by checking if the number of pictures marked as needed for output exceeds the maximum reorder pictures value, enabling early output without waiting for all reference pictures to be decoded. This reduces output delay while maintaining correct output order through the buffer management mechanism.
2Measurement precision
If the decoder waits for all reference pictures to be decoded before outputting pictures, then decoding accuracy is improved, but processing speed decreases
Solution Approach 1:
The patent enables preliminary output of pictures by introducing a new condition for picture output: when the number of pictures marked as needed for output in the DPB exceeds the maximum reorder pictures value. This allows the decoder to output pictures before the traditional picture output process would permit, as long as the buffer management rules are satisfied. This improves processing speed while maintaining decoding accuracy through proper reference picture management.
3Reliability
If the decoded picture buffer (DPB) size is increased to store more reference pictures, then reference picture availability is improved, but memory usage increases
Solution Approach 1:
The patent introduces a new parameter 'maximum reorder pictures' that controls the DPB management behavior. By comparing the number of pictures marked as needed for output against this parameter, the system can dynamically determine when to output pictures and when to mark them as unused for reference. This parameter-based control optimizes the balance between reference picture availability and memory usage without requiring a fixed increase in DPB size.
Data Source
AI summary
The embodiments reduce output delay for pictures by determining after a current picture has been decoded and stored in a decoded picture buffer, DPB, a number of pictures in the DPB that are marked as needed for output. This number is compared, after a current picture has been decoded and stored in the DPB, against a value derived form at least one syntax element present or to be present in a bitstream representing pictures of a video sequence. If this number is greater than the value a picture, which is the first picture in output order, of the pictures in the DPB that are marked as needed for output is preferably output and marked as not needed for output.