Caption Encoding Service: Best Practices

Before ordering a captions-encoded video, it is important to adhere to the following best practices to ensure the best results.

IMPORTANT NOTE FOR BROADCAST DELIVERABLES: Please note that the encoding service is intended for use cases like offline file sharing, kiosk video displays etc and not intended for broadcast deliverables. For broadcast deliverables, please download a closed caption file from your 3Play Media account and encode the captions outside of the account system using encoding software like Handbrake, Apple Compressor, or Adobe Media Encoder.

Requirements for Encoded Captions

  • The source file must exist within your 3Play account.
    The order must be placed within 60 days after the transcription or alignment process is complete as this is how long 3Play Media stores the source video.
  • The media file must be finished (i.e., complete or delivered).
    Note that his implies that an English transcript must exist.
  • The source file (the media file that was originally uploaded to your 3Play account) must have a video track.
  • If USE SOURCE or Source w/ Open Captions* is selected (i.e., requesting to have captions encoded into the original video that was uploaded to your 3Play account), the source video must be encoded as an MP4. It can be in another container (e.g., .flv, m4v), as long as the video track is H.264 and the audio track is AAC.


Before ordering a captions-encoded video, proofread your transcript or preview your video with the captions to ensure it is to your satisfaction.

NOTE: If you notice text you would like to change, make the necessary edits and save your changes before ordering your caption encoded video as all existing text at the time of ordering will be reflected in the encoded version you will later download. Edits made AFTER your order is placed for a caption encoded video will NOT propagate to your video when it is ready to be downloaded- edits must be made and saved before your order is placed.

See more information on previewing a transcript.
See more information on reviewing a video with captions.
See more information on editing transcripts.

Turnaround Time

Most encoding requests are completed within 8 hours subject to available computer resources. This time can also vary depending on the duration of the content, and number of files and settings requested.

Order and Download Timeline

After your file has been transcribed or aligned by 3Play Media, you have 60 days to order a caption-encoded video.

After the caption-encoded video has been created and is download-ready, you have 60 days to download the new video from your account.

.M4V Container and Playback

A closed captions track will be added to the source video (possibly transcoded, per customer specification) and put in an .m4v container. For example, if the file you uploaded to your 3Play account was named myvideo.mp4, the video you download with the soft-encoded captions will be named myvideo.m4v. The specs will remain the same unless specified otherwise, the only difference is the media file extension is now .m4v

For most video players, the closed captions will need to be explicitly turned on by the viewer.

*Open Captions

If you choose Source w/ Open Captions, the captions are "burned in" to the video frames.  
They become part of the image and therefore will always be visible.  
Some transcoding takes place for this, but the system tries to maintain the quality of the source video.  
The output is still saved to a ".m4v" file, with the same specifications as for any closed caption format.

Vertical Caption Placement

Open Caption Encodings can support Vertical Caption Placement except Bottom Bar Open Captions. Please contact your account manager to enable this option.




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