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Dynamic Media videos do not play in Firefox due to audio codec incompatibility

Last update: October 26, 2026

This article explains why Dynamic Media videos using out-of-the-box video presets don’t play in Mozilla Firefox, even though they work in other browsers, and provides steps to resolve the issue.

Description description

Environment

  • Adobe Experience Manager (AEM) Dynamic Media (all versions)

Symptoms

  • Videos encoded with out-of-the-box Dynamic Media video presets don’t load or play in Mozilla Firefox.

  • The same video assets, URLs, and embed codes function normally in Google Chrome and Microsoft Edge.

  • In Firefox, the video player displays a spinner or fails to start playback.

  • Browser console show errors such as:

    • Unhandled promise error occured. Error: AbortError: The fetching process for the media resource was aborted by the user agent at the user's request.
    • Firefox-specific error codes, such as NS_BINDING_ABORTED or NS_ERROR_DOM_MEDIA_FATAL_ERR (0x806e0005).

  • Network logs indicate successful asset delivery (HTTP 200/206), but playback doesn’t start.

Steps to reproduce

  1. Embed a Dynamic Media Video component with any out-of-the-box video preset (For example: Adaptive Video Preset).
  2. Publish the page.
  3. Test playback in Firefox.

Cause

Dynamic Media out-of-the-box video presets could encode audio as HE-AAC (mp4a.40.5), which isn’t supported by Firefox’s Media Source Extensions (MSE) pipeline. Using AAC-LC (mp4a.40.2) ensures compatibility and restores playback in Firefox.

Resolution resolution

Follow the steps below to resolve the issue:

  1. In AEM, navigate to Tools → Assets → Video Profiles (or Dynamic Media video profiles in AEM 6.5).

  2. Locate the video profile applied to the folder containing the affected assets. This profile will have one or more MP4 presets.

  3. Copy the out-of-the-box Adaptive Video Encoding profile. Don’t edit the shipped profile directly.

  4. Edit all MP4 presets in the copied profile:

    • Set Audio Codec to Dolby AAC-LC (maps to dolby_aac → mp4a.40.2).
    • Remove or avoid any HE-AAC / HE-AACv2 options (dolby_heaac, dolby_heaacv2).

  5. In the profile, set Applied to folders to the DAM folders where the problematic videos reside.

  6. Trigger re-encoding (DM Encode Video workflow) on the affected videos.

  7. Confirm in the .mpd manifest that the DASH audio codec string is now mp4a.40.2.

  8. For Multi-Audio / Adaptive Video Sets (AVS):

    • Open the AVS asset in AEM Assets → Properties → Captions & Audio Tracks.
    • Select the AAC-LC audio track and click Set as default (accept Replace, if prompted).
    • Save & Close, then republish the video.

  9. After a few minutes, clear the browser cache, and re-test in Firefox to verify playback.

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