Castr + Subtitles

Castr streams everything.
It translates nothing.

Castr is a powerful cloud multistreaming platform — it sends your stream to Twitch, YouTube, Facebook, and dozens more simultaneously. But it has zero speech recognition, zero live captions, and zero translation. StreamTranslate fills that gap at the source, before the signal ever reaches Castr.

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No downloads. No API keys. Works with any browser source compatible software.

The Short Answer
StreamTranslate works upstream of Castr — in your local streaming software (OBS, Streamlabs, etc.). Add the overlay URL as a browser source, and your captions are baked into the video signal before it reaches Castr. Every platform Castr distributes to gets the subtitled version automatically.
ℹ What Castr Does (and Doesn't Do)
Castr is a cloud encoding and multistreaming service. You push one RTMP stream to Castr, and it rebroadcasts to Twitch, YouTube, Facebook, LinkedIn, and 30+ other destinations simultaneously. That's its entire job — distribution. Speech recognition, captions, and translation are out of scope by design. StreamTranslate handles those before the stream reaches Castr.

How to Add Subtitles to a Castr Stream

Setup — 60 seconds

  1. Go to streamtranslate.live and create your overlay. Pick language, translation target, font, and colors.
  2. Copy your unique overlay URL.
  3. In OBS or Streamlabs, add a Browser Source layer. Paste your StreamTranslate URL. Set to 1920×1080.
  4. Configure OBS/Streamlabs to push to your Castr RTMP endpoint as normal.
  5. Go live. Captions are baked into the stream that Castr receives and distributes to all your destinations.

What StreamTranslate Adds to Castr

FeatureCastr (native)Castr + StreamTranslate
Live subtitles / captionsNone✓ Real-time, word-by-word
Real-time translationNone✓ 65 languages
Multistream with subtitlesSubtitles not included✓ All Castr destinations get captions
API key management—None required
Setup complexity—Paste URL → done

Common Questions

Will captions appear on Twitch AND YouTube when multistreaming via Castr?
Yes. Because StreamTranslate renders captions into your video source before the stream reaches Castr, every destination Castr distributes to receives the captioned video — Twitch, YouTube, Facebook, and all others simultaneously.
Do I need to do anything inside Castr to make this work?
No. StreamTranslate integrates at the local streaming software level. Castr sees a normal RTMP stream and distributes it as usual — it doesn't need to know about StreamTranslate at all.
What streaming software works between StreamTranslate and Castr?
Any software that supports browser sources and RTMP output: OBS Studio, Streamlabs, XSplit, or any other local encoder. Add StreamTranslate as a browser source layer, then push to Castr via RTMP as normal.
Does this work with Castr's cloud encoder?
StreamTranslate works with local streaming software that pushes to Castr. If you use Castr's hosted encoder or pull-stream features, you would need a local encode stage to inject the overlay first.

Ready to Caption Your Castr Streams?

Takes 60 seconds. No downloads, no API keys, no configuration beyond pasting a URL.

Start Free Trial See how it works →

Also stream IRL

Also supports IRL with Moblin and the OBS audio plugin, including home and cloud OBS setups such as IRL Toolkit.

Use an OBS receiver for IRL Pro, Larix Broadcaster, PRISM Live Mobile or TVU Go. Cloud providers may need to install the plugin on your server.

Moblin · Moblin Browser Source · Cloud OBS · IRL Toolkit · OBS Studio · IRL Pro · Larix Broadcaster · PRISM Live Mobile · TVU Go · MediaMTX

IRL setup guide · Desktop setup guide