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Which broadcast protocol should I choose?

When creating an event, you must decide how your broadcast to Clevercast will be sent. Clevercast supports both the RTMP and SRT broadcast protocols:

  • SRT was introduced in 2017 and is an improvement over RTMP in many ways. The Secure Reliable Transport (SRT) protocol is a new open source broadcast protocol, promoted by the SRT Alliance of which Clevercast is a member. It includes mechanisms for packet recovery while maintaining low latency between encoder and ingest server. It is therefore particularly suited for long-distance and high-quality broadcasting across unreliable and unpredictable networks like the public internet. Unlike RTMP, it has built-in mechanisms for authentication and encryption.
  • RTMP is a well established protocol that works fine if the distance between encoder and ingest server is not too big, but it hasn't been designed for intercontinental broadcasts over unreliable networks.

We recommend using SRT for all multilingual live streams, especially those with AI closed captions and speech translations. Using SRT significantly reduces the chance of interruptions.

Our ingest servers are located in Europe - our streaming servers are worldwide - but it is perfectly possible to send a reliable full HD SRT broadcast to Clevercast from anywhere in the world.

If you are using an in-browser studio (eg Streamyard, Restream.io) or meeting solution (eg Zoom or Webex) an RTMP broadcast will be sent from their application servers in North America. For those cases, Clevercast has an ingest hub in North America. This way, you can also send an RTMP broadcast with an encoder from the US, Canada or Mexico.

If you need to use RTMP from a continent other than Europe and North America, add a custom RTMP ingest hub to your plan.

Single-language streams

For single-language streams (without extra audio languages or closed captions) choose one of the following broadcast protocols:

  • SRT Broadcast (Clevercast as listener): SRT broadcast, using your encoder as the caller and Clevercast as listener. For most SRT encoders, you should choose this option.
  • RTMP from Europe: single language RTMP broadcast from Europe
  • RTMP from North America, Streamyard, Zoom...: RTMP broadcast that originates from the US, Canada or Mexico, or from an application with servers in North America like Streamyard, Zoom and WebEx.
  • RTMP using custom ingest hub: RTMP broadcast with an encoder in a continent other than Europe and North America. This must be requested in advance.
  • Clevercast as SRT Caller (uncommon): SRT broadcast, using your encoder as the listener and Clevercast as the caller. This is a more uncommon option, only supported by some SRT encoders.

Multilingual streams

If your stream contains multiple audio languages, the available broadcast protocols depend on how simultaneous interpretation is done.

  • If your interpreters are not present at the (virtual) event, they can use Translate at Home (T@H). In this case, you need to broadcast a regular stream with single audio.
  • If your interpreters are present at the event location and you are sending their audio streams along with the video stream, you'll need an SRT multi-track or RTMP multi-channel broadcast.

Single-language broadcast for T@H and captions

If you broadcast a regular stream, to which additional audio languages and/or closed captions are added through Clevercast, you can choose from the following protocols:

  • SRT for T@H and Captions: single language SRT broadcast, to which audio languages and/or closed captions are added through Clevercast. In this case, your encoder is the SRT caller and Clevercast is the SRT listener.
  • RTMP from Europe for AI & T@H languages: single language RTMP broadcast from Europe, to which audio languages and/or closed captions are added through Clevercast.
  • RTMP from North America, Streamyard, Zoom... for AI & T@H languages: single language RTMP broadcast from the US, Canada or Mexico, or from an application with servers in the US like Streamyard, Zoom, WebEx..., to which audio languages and/or closed captions are added through Clevercast.
  • RTMP using custom ingest hub for AI & T@H languages: RTMP broadcast with an encoder in a continent other than Europe and North America (if you cannot or don't want to use SRT), to which audio languages and/or closed captions are added through Clevercast. This must be requested in advance.
  • Clevercast as SRT Caller (uncommon) for AI & T@H languages: single language SRT broadcast, using your encoder as the listener and Clevercast as the caller.

Multilingual broadcasts

If you broadcast a stream with multiple audio tracks or channels, you can choose from the following protocols:

  • SRT broadcast with extra audio tracks (Clevercast as listener): SRT broadcast, containing multiple audio tracks and/or channels. In this case, your encoder is the SRT caller and Clevercast is the SRT listener. This can be combined with adding closed captions through Clevercast.
  • RTMP stereo broadcast with 2 languages (L+R): RTMP broadcast of a video with a single audio track. The audio track contains a stereo channel with the 2 languages panned L+R. This is possible with any encoder.
  • RTMP 4.0 surround broadcast: RTMP broadcast of a video with a single audio track. The audio track contains a 4.0 surround sound channel with 4 languages. This is currently only possible with OBS Studio.
  • RTMP 7.1 surround broadcast: RTMP broadcast of a video with a single audio track. The audio track contains a 7.1 surround sound channel with 7 languages. This is currently only possible with OBS Studio.
  • Clevercast as SRT Caller (uncommon): SRT broadcast, using your encoder as the listener and Clevercast as the caller, containing multiple audio tracks and/or channels.

Separate RTMP stream per language

On a project basis, it is possible to create a multilingual live stream by broadcasting a separate RTMP stream (video+audio) for each language. Unless you need this for a specific purpose (e.g. if one of the languages is sign-language), broadcasting multiple audio tracks/channels is generally a better idea.

Simulive streams

Simulive streaming allows you to let Clevercast broadcast a pre-recorded video as if it were a live stream. Viewers will not see any difference between a simulive stream and a real live stream. For a multilingual simulive stream, viewers will also be able to select their preferred language and/or closed captions in Clevercast player.

If your plan includes it, you can select one of the following broadcast protocols:

  • Simulive streaming with single audio: the broadcast will be done by Clevercast, based on a VoD item with a single audio language
  • Simulive streaming with multilingual audio: the broadcast will be done by Clevercast, based on a VoD item with multiple audio languages
  • Simulive using multiple videos: the broadcast will be done by Clevercast, based on multiple VoD items (each with a different language). This is only available on a project basis.