How to simulcast translated live streams to external platforms

If you use Clevercast to broadcast a multilingual live stream, you can also configure it to simulcast the separate language streams to external platforms like YouTube, Facebook, Twitter … Clevercast will use the highest video resolution set for your event and merge it with the audio stream of a particular language. The resulting live stream is broadcasted to the RTMP address for the given platform.

Every RTMP address (identified by a server URL and stream key) to which you send a simultaneously translated live stream is called a simulcast target in Clevercast. This guide explains how you can configure these simulcast targets for your live events.


Adding simulcast targets to your account

Per-language simulcast targets are an optional add-on to your Multilingual Live Streaming plan. They must be ordered before you can use them in your event(s). You can add any number of per-language simulcast targets to your plan.

This is possible no matter which method you use for multilingual live streaming: SRT with multiple audio tracks, RTMP with multiple audio channel and Clevercast Translate@Home (T@H). In each case, the separate languages can be simulcasted to third party platforms and solutions.


Configuring simulcast targets for your multilingual event

Once your account supports per-language simulcast targets, you can start adding them to your multilingual live event. On the event page, you will see a ‘Simulcast Streams’ button at the bottom of the ‘Broadcast’ panel. Press this button to go to the ‘Simulcast Targets’ management page.

The Simulcast Streams button on an event page

On the management page, you add a simulcast target for a particular language by filling in the form and pressing the ‘Add simulcast target’ button. For each simulcast target, you need to provide the following settings:

  • Name of the Simulcast target : this is only for informational purposes
  • Simulcast Server URL : the external RTMP server URL to which the stream must be broadcasted
  • Simulcast Stream Key/Name : the stream key (aka stream name) provided by the external platform
  • Simulcast from Clevercast main or backup origin : the Clevercast streaming server from which to broadcast. In most cases this should be set to ‘Main’. You can only use ‘Backup‘ if you are actually broadcasting to our backup streaming server.

‘Add simulcast target’ form

The Simulcast Server URL and Stream Key should be provided by the external platform. See this blog page on where to find them in YouTube, Facebook and Twitter.

You can add multiple simulcast targets for the same language. If you have a redundant setup and the external platform provides a backup server URL, you can choose to create two simulcast targets for the same stream key (= Clevercast main to external main + Clevercast backup to external backup). Note that if you use T@H, interpreters will also have to move to a language room on our backup streaming server.

Existing simulcast targets can be updated at any time, and new simulcast targets can be added. You should preferably do this while your event status is set to Waiting or Ended.


Broadcasting to the simulcast targets

The broadcast is automatically sent to your simulcast targets when both these conditions are fulfilled:

  • your event status is set to Preview, Started or Paused
  • your broadcast is being received by Clevercast

Clevercast always broadcasts your event’s highest resolution to all simulcast targets (usually 1080p or 720p). On the event page, you can determine which streaming resolutions are used. Please note that some third external platforms don’t accept 1080p.

Clevercast currently transmuxes all multilingual streams to an outgoing stream with a frame rate of 25 frames per second and a keyframe interval of 2 seconds. Therefore, the external platform should support a frame rate of 25 frames per second. Note: we strongly recommend that you also use 25 frames per second and a key frame interval of 2 seconds when broadcasting to Clevercast.

When your event status is set to Ended or Waiting, the broadcast to the external platforms stops. This also happens if your broadcast to Clevercast is interrupted. However, in the latter case, it should automatically restart when Clevercast receives your broadcast again.