What Is Caption Encoding?
Usually captions are output as a separate “side car” file and added to a video player, which renders the captions in sync with the video. However, in certain cases it is necessary to embed the captions in the video itself. Caption encoding ensures that your captions will be viewable if you don’t have a video platform, if you want an offline option, or if you need captioned videos for kiosks. Another reason is to create a self-contained captioned video that can be distributed as a single asset. Caption-encoded videos also work across mobile devices.
Another major use case for caption encoding is social video. Many social media platforms, like Twitter and Instagram, don’t support uploading a separate caption file. In order to have your video play with captions on these platforms, you must encode them into the video.
Note that captions must be encoded in order be accepted in iTunes.
How Does It Work?
You begin by uploading your video file for captioning and transcription processing. If you already have a transcript, you can use the automated transcript alignment service.
Once your file has been captioned, you can order the caption encoding service and choose the appropriate encoding profile (see below). Upon completion you will receive an email notification and be able to download a M4V video with encoded captions.
The video will work with any player or device that supports M4V videos, including QuickTime, iPad, iPhone, iPod, iTunes, JW Player, and Flowplayer.
Because the captions are soft-encoded in the video, users will be able to turn them on or off using the video player controls. In addition to the caption-encoded video, you will have full access to all the other captions formats that we produce, as well as our interactive transcript and other video plugins.
Input / Output Formats
The source video that you upload can be in almost any web format that doesn’t use a proprietary codec. When ordering caption encoding you will have the option to select an encoding profile to optimize video playback for a certain device.
For example, the iPhone5 profile transcodes your video for a target width of 1136 pixels, 30 frames per second, and a frame rate of 3 Mb/sec. You can also use your original source video as long as the video encoding is H.264 and audio is AAC. The closed captions track will be added to the video and put in a M4V container.
Download a demo video with encoded closed captions–you’ll need to play it in a QuickTime or VLC player and make sure to enable the captions (subtitles). Please note that some versions of Windows Media Player do not support caption-encoded videos.
Note: For social media video, you’ll need to upload your video in a format supported by the social platform (for example, Twitter takes MP4 videos). Then, order caption encoding > source with open captions.
The encoding time depends on duration and other factors. Most encoding requests are completed within 8 hours.
Caption encoding incurs a fee for each video produced. The fee is in addition to the captioning/transcription fees. See the complete pricing details.