BD-ROM Entry Map for High-Speed Slide Show Random Access
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Solution Overview
Problem
Current random access techniques for slide shows, which require high accuracy in accessing specific pictures, are inefficient due to the need for frequent stream analysis and long processing times, making it difficult to implement features like displaying previous or next pictures quickly.
Innovation Solution
A recording medium with a video stream and stream management information that includes an entry map and a flag indicating the application type, allowing for high-speed random access by pointing all picture data to entry addresses, enabling access to next or distant pictures without analyzing the stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stream analysis is performed to achieve high-accuracy random access in slide shows, then picture access precision is improved, but access time increases significantly
Solution Approach 1:
The patent pre-calculates and stores the mapping relationship between picture numbers and byte offsets in the video stream within the entry map during the encoding phase. This preliminary action eliminates the need for runtime stream analysis, allowing direct access to any picture by simply looking up the pre-computed offset, thus achieving both high precision and fast access speed.
Solution Approach 2:
The entry map serves as a pre-prepared cushion that stores all necessary positioning information before runtime. By having this information ready in advance, the system avoids the time-consuming process of analyzing the variable-length encoded stream during random access operations, effectively cushioning against the time loss that would otherwise occur.
2Productivity
If entry map with one-second time accuracy is used for video streams, then random access efficiency is improved, but picture-level access accuracy deteriorates
Solution Approach 1:
The patent changes the parameter granularity of the entry map from one-second intervals to picture-level intervals. By storing the byte offset for each individual picture in the entry map, the system maintains high random access efficiency while achieving precise picture-level access accuracy, resolving the contradiction between efficiency and precision.
3Loss of information
If frequent stream accesses are performed for picture analysis, then picture location information is obtained, but access speed deteriorates
Solution Approach 1:
The patent creates a copy of the essential positioning information (byte offsets) from the variable-length encoded video stream and stores it in the entry map in advance. This copying eliminates the need for frequent accesses to the original stream during runtime, as all necessary location information is already available in the entry map, thus maintaining information completeness while dramatically improving access speed.
Data Source
AI summary
Video streams and an entry map are recorded on a BD-ROM in association with each other. The video stream constituting a slide show includes a plurality of IDR pictures. The entry map (EP_map) associated with the IDR pictures indicates an entry time (PTS_EP_start) of each IDR picture included in the video stream in association with an entry point (SPN_EP_start). Application_type indicates that entry information of each of pieces of picture data constituting the video stream exists in the EP_map and each piece of picture data is to be decoded independently.