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    Adding Audio Tracks to Videos using the Media Module

    In this topic you will learn how to add audio tracks to videos using the Media module.

    Videos can be configured with multiple audio tracks. Multiple audio tracks can be used to:

    • Play back the same video in different languages 
    • Provide audio with descriptions for the visually challenged
    • Provide stereo vs. multi-channel (surround sound) audio

    Multiple audio tracks are supported for HLS V4+ and DASH - with and without DRM protection. Videos with multiple audio tracks will display a headphone icon () in the controlbar. When the icon is clicked, the viewer can select between audio tracks.

    Below is an example of a video that has been configured with multiple audio tracks.

    Configuring the audio track properties

    Audio track files can be uploaded and hosted by Brightcove or reside at an internet accessible URL. To view and edit the audio track properties for a video, follow these steps:

    1. Open the Media module.
    2. Click the video title link and locate the Audio Tracks section. The audio track for the source video will appear.
    3. Click Edit or double-click in the section.
    4. Click Add Audio Track.
    5. Select if the audio track file will be uploaded from the local file system or from an external URL.
      • File Upload - Click Browse and select the audio track file from the local file system. The file will be uploaded to Video Cloud.
      • URL Upload - Enter the public URL where the audio track file resides and then click Upload. The file will be uploaded to Video Cloud.
    6. The Language field should contain the language code that specifies the language of the track text data.
    7. Select the Variant of text track. The Variant describes the kind of audio track. Options include:
      • main - The main track, usually the one muxed into the video file
      • alternate - An alternate audio track
      • commentary - An audio track that provides commentary on the video track
      • dub - A track containing a dubbed version of spoken words in a different language
      • descriptive - The track is descriptive of the video content in some way
    8. Click Add Audio Track to save the audio track information.
    9. Click Add Audio Track to add another audio track or Save to save the audio tracks. The newly added audio tracks will appear in the list when processing is finished.

    To delete an audio track, click the delete icon () next to the audio track. Note that there may be a delay before the UI is updated and the audio track no longer appears.

    When a video with multiple audio tracks is published, a headphone button () will appear on the player chrome. Click the button to select an audio track.

    Setting a default audio track

    When a video is uploaded, the source audio will be set as the main (default) track. To set an audio track to be the default track, follow these steps:

    1. Click Edit or double-click in the Audio Tracks section.
    2. Click on the track that is currently the default audio track.
    3. Uncheck the Default option.
    4. Click on the track that will be set as the default audio track.
    5. Check the Default option.
    6. Click Update Audio Track.

    Limitations

    The following limitations apply when using multiple audio tracks

    Audio masters not stored
    If you retranscode the video from the video master, the additional audio tracks will be lost, and must be re-added
    Audio-only files must be used
    Audio tracks must be audio-only files without video tracks
    HLSv3, HLS with audio and video in the same segment
    • The playback API will not return HLSv3 manifests
    • All HLS manifests will include de-muxed video/audio
    Smooth Streaming
    Smooth Streaming URLs will not be available.
    Social Distribution
    It is not possible to select which audio track will be used for distribution. The track included in the video source (the muxed in audio) will be used, always.
    Ordering of audio tracks beyond the one "default" track
    • You can pick a default audio track with CMS API per title by setting the is_default field to true
    • There is also an account default, which can be set by Support
    • This will only affect the "default" track in HLS manifests
    • No other ordering is possible
    Ingesting more than one audio track from a single source
    We support one audio track from the source supplied in ".master", and one for each source under ".audio_tracks.masters".
    DRM protection on videos that include only audio
    As soon as a video track is added, DRM protection will be enabled.
    End-user friendly labels
    We do not support custom labels for audio tracks. If you require that, you will need to make the change on the client side via the Player API.
    In some instances, switching tracks may cause the Brightcove Player to become unstable
    • Track switching before all audio segments have been downloaded
    • When the video is played back using the Silverlight plugin (in versions of IE less than 10, or any version of IE in versions of Window less than 8) - multiple audio tracks are not supported in Silverlight.
    • If the audio and video are different durations, the player will may stop whenever the shorter one runs out.
    Video "duration"
    The video duration reported by the catalog/Playback API may be incorrect if the audio tracks have different durations.

    Page last updated on 30 Jul 2020