---
title: Media agent for Video JS v4.2.0
source: https://docs.newrelic.com/docs/release-notes/streaming-browser-release-notes/streaming-browser-agent-videojs-26-06-19
---

## Highlights

-   Explicit opt-in for **AWS MediaTailor**, with full support for **custom CDN domains**.
-   New `config.ad.type` API to choose between **CSAI** and **SSAI** (`DAI`, `MT`) ad tracking — no more URL-based guessing for SSAI.
-   End-to-end logging through `nrvideo.Log`, with active detection mode logged at startup.

## Features

### MediaTailor custom CDN support

Replaced URL-based auto-detection with explicit opt-in.

-   Enabled the tracker via `mediatailor: true` (or `mediatailor: { trackingUrl, adSegmentPrefix }`), supporting both default AWS hostnames and custom CDN domains.
-   Added `MT_DEFAULT_AD_SEGMENT_PATH` (`/tm/`) constant for AWS-recommended CDN ad-segment path; ad segments rewritten to a custom CDN domain under `/tm/` are detected automatically.
-   Updated `isMediaTailorSegment()` to check the default AWS segments hostname, the `/tm/` path, and an optional customer-supplied `adSegmentPrefix`.
-   Threaded `adSegmentPrefix` through HLS (VHS) and DASH manifest parsing.
-   Added explicit session initialization via `mediatailor: { trackingUrl }` for `POST /v1/session/` flows.

### Ad tracking configuration

Introduced `config.ad.type` to control ad tracker selection.

-   Exposed `AD_TRACKING` constant with **CSAI** (flat value covering IMA / Brightcove IMA / Freewheel / generic) and **SSAI** sub-types (`DAI`, `MT`).
-   Required an explicit sub-type for SSAI — each platform needs its own SDK and cannot be auto-detected.
-   Mapped `SSAI.MT` to imply `mediatailor: true`.
-   Added a fallback to CSAI auto-detection with a warning when `config.ad.type` is unset (backward compatible for v4.1.2 users).
-   Co-located `segmentPrefix` and `trackingUrl` under `config.ad`.
-   Added `DaiAdsTracker` to static exports.

### Logging improvements

-   Exposed `VideojsTracker.Log` as a static so UMD callers can set log level.
-   Added logging of the active ad segment detection mode at tracker startup.
-   Added logging of the matched ad segment detection path on the first ad break (once per session).
-   Added logging of which CSAI framework was auto-detected (BrightcoveIma / IMA / Freewheel / generic).
-   Replaced `console.log/warn/error` with `nrvideo.Log` across MediaTailor files.

## Bug fixes

-   Fixed buffer end handling in tracker.
-   Fixed `register-plugin.js` silently dropping the options object and not forwarding it to the `TrackerJS` constructor.

## Documentation

-   Updated the README and SSAI docs for custom CDN support, clarified when `trackingUrl` and `adSegmentPrefix` overrides are needed, and cleaned up `sessionId` references.
-   Corrected `adSegmentPrefix` references to `config.ad.segmentPrefix` in the SSAI troubleshooting docs.

## Upgrade from 4.1.x

-   **No breaking changes for CSAI users.** If `config.ad.type` is unset, the tracker still auto-detects CSAI frameworks (with a one-time warning).
-   **MediaTailor users must opt in explicitly.** Replace any URL-pattern reliance with one of:
    -   `mediatailor: true` (default AWS hostnames + `/tm/` path)
    -   `mediatailor: { trackingUrl, adSegmentPrefix }` (custom CDN / explicit session init)
    -   `config.ad.type: AD_TRACKING.SSAI.MT`
-   If you previously passed `adSegmentPrefix` at the top level, move it to `config.ad.segmentPrefix`.