Bitstream Start Code Navigation Without Index Tables
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Solution Overview
Problem
Conventional techniques for navigating audio-visual digital content are limited, especially when index tables are unavailable or do not provide sufficient flexibility, making it difficult for users to navigate content with variable data sizes, frame rates, or non-uniform bitrates.
Innovation Solution
A system that uses a start code navigator and a bitstream navigator to allow users to navigate desired durations within bitstreams, even without indexing, by employing a navigation scheme selector, navigation time correlator, target locator, and start code locator to determine target locations and decode data sequences efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional navigation techniques using index tables are used, then navigation to pre-designated locations is enabled, but flexibility in navigating arbitrary durations is limited
Solution Approach 1:
The system uses the bitstream's own timing information and data structure to perform navigation, eliminating the need for external index tables. The navigator extracts timing data directly from the bitstream packets and uses this self-contained information to calculate byte offsets for seeking to desired presentation times.
Solution Approach 2:
The system dynamically adjusts navigation parameters based on the variable bitrate and packet structure of the bitstream. By calculating byte offsets using actual timing information from the stream rather than fixed index table entries, the system adapts to changing data rates and achieves flexible navigation without pre-defined indices.
2Ease of operation
If index tables are constructed for navigation, then navigation capability is provided, but processing time and resources are excessively consumed
Solution Approach 1:
The system performs preliminary extraction of timing information from bitstream packets during the initial scan, storing this metadata for rapid navigation calculations. This preliminary action avoids the need to construct full index tables while still enabling efficient seeking by having timing data ready before navigation operations.
Solution Approach 2:
The system extracts only the essential timing information needed for navigation from the bitstream packets, rather than constructing complete index tables with all possible navigation points. This selective extraction of critical data enables navigation functionality while minimizing processing overhead and memory requirements.
3Ease of operation
If sequential navigation from one start code to the next is used, then navigation is possible, but navigation speed is slow for large durations
Solution Approach 1:
The system pre-calculates byte offsets for target locations based on timing information extracted from the bitstream. By performing this calculation in advance using the formula involving DTS values and byte counts, the system can jump directly to desired locations rather than sequentially traversing through intermediate data, dramatically improving navigation speed for large time durations.
4Device complexity
If navigation is implemented without timing information, then device complexity is reduced, but navigation precision to desired durations is lost
Solution Approach 1:
The system uses timing information (DTS values) that is already embedded within the bitstream packets themselves. By leveraging this self-contained timing data, the system achieves precise navigation to desired presentation times without requiring external timing sources or complex synchronization mechanisms, thus maintaining low device complexity while ensuring high navigation precision.
Data Source
AI summary
A request may be received to navigate through a bitstream by a navigation time, the bitstream having a plurality of data sequences, each of the plurality being associated with a different presentation time of the bitstream. The navigation time may be correlated with a number of bytes from a current location of the bitstream to a target location of the bitstream. The bitstream may be navigated to reach the target location within the bitstream, based on the number of bytes. Navigation may then occur from an initial start code proximate to the target location within the bitstream to a further start code until a final start code is reached that has a timestamp which, compared to a timestamp of the current location, indicates a presentation time that corresponds to the navigation time and thereby satisfies the request.