Chapter Markers
Chapter markers give named navigation points within a media presentation without splitting it into separate files.
A concert recording can remain one continuous video while offering a menu of songs. Chapter markers attach names to positions in its timeline.
| Illustrative chapter | Stored position in seconds |
|---|---|
| Opening — 00:00 | 0 |
| The journey — 12:40 | 760 |
| Finale — 48:15 | 2,895 |
Choosing The journey asks the player to seek to 760 seconds. The ordinary chapter entry does not create a separate clip or make that picture independently decodable; normal index lookup and decoder restart still apply.
The name, start time, and any end time are chapter information. A preview image is another object. A player can generate it from the picture near a chapter position or obtain navigation previews through a separate process. Storing a chapter title does not store the corresponding image.
An edit moves the landmarks
If a new version removes the first 30 seconds before The journey, its new position becomes 730 seconds, or 12:10. Copying the old 12:40 marker unchanged would land 30 seconds late. Chapter preservation after an edit therefore involves mapping positions to the new timeline, not just copying chapter names.
A simple remux that preserves the timeline can retain those positions more directly. Inspecting the chapter list establishes which entries the output actually contains.
Matroska can also define ordered editions that choose ranges and alter the sequence being played. That is a different use of chapter structures. For an ordinary scene or song list, the useful model is a named position in one fixed presentation.