Encoders let a broadcaster simultaneously receive and encode live closed captions via Line 21 data, allowing them to be displayed alongside a television program or video in real-time.

Usually, captions are output as a separate “sidecar” 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.

Encoders can seem complex, but they’re designed to simplify how quality captions are delivered to your broadcast. While there are emerging virtual and alternative encoding methods, in this article, we’ll focus on the top three traditional encoder connections used in live captioning workflows: telco (analog/modem), telnet (digital/IP), and iCap (only if the encoder is manufactured by EEG).

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How Do Encoders Work?

The Top Three Live Encoder Workflows

Input / Output Formats


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.

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