# Caption Encoding

Closed captions encoded into your live video and simulcast to the platforms your audience watches, from YouTube to Twitch.

- **Standard**: CEA-608
- **Input**: RTMP / SRT
- **Output**: RTMP / SRT / HLS

## What it does

### Captions inside the stream

Your video is re-encoded with a caption track that the platform shows as closed captions, ready for viewers to switch on.

### Synchronised captions

The stream is held back about 10 seconds so each caption lands on the picture at the moment its words were spoken, instead of trailing behind the speaker as live captions usually do.

### Simulcast to every platform

YouTube, Facebook, X, Twitch, Vimeo, Dailymotion, Kaltura, Brightcove, Microsoft Teams, Wowza, Akamai and custom RTMP endpoints.

### Encoded in the cloud

No encoder hardware to rent or run: Line 21 handles the encoding as a cloud service.

### Good to know

Platforms accept one caption track, the stream reaches viewers about 10 seconds later than the live feed, and Latin-based scripts are the most reliable. For several languages, use HLS streaming.

[HLS streaming](https://line-21.com/features/hls-streaming)

## Learn more

- [RTMP streaming docs](https://line-21.com/docs/destinations/rtmp-streaming)
- [Video feeds](https://line-21.com/docs/feeds/video)

Talk to us: [contact page](https://line-21.com/contact) or hello@line-21.com.