Video Bitstream Random Access Leading Picture Removal
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Solution Overview
Problem
In media playback using the MPEG media transport protocol, random access to bitstreams of SAP type 2 or SAP type 3 results in significant delays due to the need to decode and display leading pictures, which hinders fast access and synchronization during channel or bitstream switching.
Innovation Solution
A method and apparatus that determine the NAL unit type of subsequent pictures in a bitstream, remove leading pictures based on this type, and decode and display trail pictures immediately, allowing for fast random access playback by advancing the presentation time composition of the IRAP and trail pictures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal decodes all leading pictures related to the reconstructed IRAP picture to ensure proper video sequence, then the video playback reliability is improved, but the access delay increases significantly
Solution Approach 1:
The patent extracts and removes leading pictures from the bitstream before decoding, based on determining their NAL unit types. By identifying and eliminating specific picture types (such as non-random-accessible pictures) from the decoding queue, the system reduces the number of pictures that need to be decoded while maintaining playback reliability through selective removal of only those pictures that are not required for proper video sequence reconstruction.
2Speed
If the terminal removes leading pictures from the bitstream to reduce decoding delay, then the random access speed is improved, but the presentation time synchronization may be disrupted
Solution Approach 1:
The patent changes the presentation time parameters by advancing the composition PTs of the IRAP picture and trail picture by the number of leading pictures removed. This parameter adjustment compensates for the time that would have been spent decoding the removed leading pictures, thereby maintaining presentation time synchronization while achieving faster random access through selective picture removal.
3Productivity
If the terminal parses NAL unit headers to identify picture types for selective removal, then the decoding efficiency is improved, but the processing complexity increases
Solution Approach 1:
The patent performs preliminary parsing of NAL unit headers to identify picture types before the actual decoding process begins. By determining the NAL unit types of pictures in advance and identifying which pictures should be removed as leading pictures, the system prepares the bitstream for optimized decoding. This preliminary identification action reduces the overall decoding workload and improves decoding efficiency, as the decoder only needs to process the remaining necessary pictures.
Data Source
AI summary
The present invention relates to a method of playing back a bitstream for transferring a group of pictures, the method comprising the steps of: parsing, when a random access occurs in a first picture, a network abstraction layer (NAL) unit header of at least one second picture following the first picture and determining a NAL unit type of the at least one second picture; removing the at least one second picture from the bitstream on the basis of the determined NAL unit type; and decoding and displaying the bitstream from which the at least one second picture has been removed.