segmentIndex

segmentIndex is a data construct used to describe and locate segments within a larger data set, typically a media file or a segmented data stream. It serves as a map from segment identifiers to information about where the segment is stored and when it occurs, enabling efficient access without scanning the entire file.

In practice, a segmentIndex records attributes such as the segment number, byte offset or file range, length in bytes, start time, end time, and duration. Some implementations also include timing scales, keyframe indicators, or versioning information. The result is a compact reference that supports quick seeking, parallel downloads, and streaming operations by allowing clients to retrieve a specific segment directly.

Segment indexes can be stored in different ways. They may be embedded within the surrounding container or file as metadata, or provided as a separate index file that accompanies the data. They can be static, created ahead of time for on-demand content, or dynamic, updated during live streaming as new segments become available.

Common use cases include adaptive media streaming, where a segmentIndex helps a player jump to a particular segment or quality level, and large-scale data storage systems that partition data into fixed or variable length segments. The index supports efficient random access, efficient bandwidth use, and smoother playback by reducing the need to read through unrelated data.

Limitations include overhead from maintaining the index and potential inconsistency between the index and the actual data if updates are not synchronized. Proper synchronization and update strategies are essential for reliable access.