DocumentationAnalyticsStreaming media services guide

Chapter offset

Last update: May 28, 2026

CREATED FOR:

  • Developer

This page covers data collection for the Chapter offset variable. See Chapter offset for the corresponding reporting dimension.

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The chapter offset variable is the offset of the chapter inside the content, measured in seconds from the start. The first chapter typically has offset 0; subsequent chapters have offsets matching their playhead start time.

Property
Value
Context data variable
a.media.chapter.offset
XDM collection field
xdm.mediaCollection.chapterDetails.offset
Audience Manager trait
c_contextdata.a.media.chapter.offset
Required
No (Mobile SDK); Yes (Edge, Media Collection API)
Sent with
Chapter start, chapter close
Web SDK

Set offset inside xdm.mediaCollection.chapterDetails when calling sendEvent:

code language-javascript 
alloy("sendEvent", {
  xdm: {
    eventType: "media.chapterStart",
    mediaCollection: {
      chapterDetails: {
        friendlyName: "Act II",
        index: 2,
        offset: 240,
        length: 360
      },
      sessionID: "{sid}",
      playhead: 240
    }
  }
});
iOS

Pass the offset in seconds as the fourth argument (startTime) to createChapterObject.

code language-swift 
let chapterObject = Media.createChapterObjectWith(name: "Act II",
                                              position: 2,
                                                length: 360,
                                             startTime: 240)

tracker.trackEvent(event: MediaEvent.ChapterStart, info: chapterObject, metadata: nil)
Android

Pass the offset in seconds as the fourth argument (startTime) to createChapterObject.

code language-kotlin 
val chapterObject = Media.createChapterObject("Act II",
                                              2L,
                                              360.0,
                                              240.0)

tracker.trackEvent(Media.Event.ChapterStart, chapterObject, null)
Roku

Set offset inside xdm.mediaCollection.chapterDetails when calling sendMediaEvent for media.chapterStart:

code language-brightscript 
m.aepSdk.sendMediaEvent({
    "xdm": {
        "eventType": "media.chapterStart",
        "mediaCollection": {
            "chapterDetails": {
                "friendlyName": "Act II",
                "index": 2,
                "offset": 240,
                "length": 360
            },
            "playhead": 240
        }
    }
})
Media Edge API

Call the chapterStart endpoint with offset inside xdm.mediaCollection.chapterDetails:

code language-json 
{
  "events": [{
    "xdm": {
      "eventType": "media.chapterStart",
      "mediaCollection": {
        "chapterDetails": {
          "index": 2,
          "offset": 240,
          "length": 360
        },
        "sessionID": "{sid}",
        "playhead": 240
      }
    }
  }]
}

Legacy implementation types (Analytics-only)

Media SDK JS 3.x

Pass the offset as the fourth argument to ADB.Media.createChapterObject:

code language-javascript 
var chapterInfo = ADB.Media.createChapterObject(
  "Act II",
  2,
  360,
  240
);

tracker.trackEvent(ADB.Media.Event.ChapterStart, chapterInfo, contextData);
Chromecast

Pass the chapter offset in seconds as the fourth argument (startTime) to ADBMobile.media.createChapterObject:

code language-javascript 
var chapterInfo = ADBMobile.media.createChapterObject(
  "Pilot Episode - Opening",  // name
  1,                          // position
  240,                        // length
  0                           // startTime (seconds from content start)
);
ADBMobile.media.trackEvent(ADBMobile.media.Event.ChapterStart, chapterInfo, null);
Media Collection API

Include media.chapter.offset in the params object of your chapterStart POST request:

code language-json 
{
  "playerTime": { "playhead": 240, "ts": 1699523820000 },
  "eventType": "chapterStart",
  "params": {
    "media.chapter.offset": 240
  }
}

See the Media Collection API events reference for the full request structure.

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