Multi-Language Streaming FAQ

Broadcasting

How many languages are possible per stream ?

Clevercast has no restrictions. So, it depends on the broadcast protocol and encoder you use.

Which broadcast protocol should I use ?

That depends on your location, your encoder and the number of languages.

  • Location: our ingest servers are located in Europe. If you are broadcasting from another continent, you should broadcast using SRT (which is reliable over ultra long distances). Preferably your translators should be located in Europe, or at least have a short Round Trip Time (RTT) to our ingest servers.
  • Encoder, Languages: If you’re not using Translate at Home, you’re limited by the number of languages supported by your encoder.  OBS Studio supports both RTMP (up to 7 audio channels) and SRT (up to 6 audio tracks). Other SRT encoders support more languages (see the Encoder Support section).

Should I use Translate at Home (T@H) ?

If your interpreters can be present at the event location or in your studio, you can choose whether or not to use Translate at Home. There are a number of things that may determine your decision:

  • Ease of use: If you do not know how to add multiple audio channels / tracks to a video broadcast, or do not have the necessary input equipment, you should use T@H.
  • Costs, health & safety: T@H doesn’t require interpreters to travel.
  • Deployment: T@H doesn’t require translator booths or lots of time to set up.
  • Production requirements: Don’t expect T@H to be on par with a multilingual production on site. If you need audio of the highest quality or a dynamic mix, you should choose an on-site production with an SRT multi-track or RTMP multi-channel broadcast.
  • Backup recording: T@H allows you to make a server-side recording of all video and audio streams, but no backup of the simultaneous translations. If you broadcast all languages from the event location, you can make a backup recording at the event location.
  • Number of languages: T@H supports any number of languages. With a multilingual broadcast you are limited by the number of tracks or channels that your encoder supports.
  • Location, bandwidth, equipment: T@H has some requirements for interpreters (see below). If they can not be fulfilled, you should either hire different interpreters or not use T@H.

Live Streaming

How does multilingual live streaming work ?

The incoming streams are transmuxed and transcoded in realtime by Clevercast to streams that can be delivered using HLS. We use Amazon CloudFront for global delivery, so viewers anywhere in the world can request the stream from a local CloudFront server.

Note: since Amazon CloudFront has substantial price differences per region, we also offer the option to only deliver the stream through their Europe/US/Canada server regions (to offer lower prices for high traffic volumes).

How do viewers choose their language ?

You embed Clevercast player on your website(s). The player on your site will automatically show all available languages through a dropdown menu (headphone button). Your viewers can use it to select their preferred language.

This works on all (modern) browsers and devices (Android, iOS). Since we use adaptive streaming, each viewer will also get an optimal video stream (depending on screen size, connection, CPU).

How many concurrent viewers can watch the live stream ?

Since we use Amazon CloudFront for worldwide delivery, the number of concurrent viewers is more or less unlimited. If you expect 15.000 concurrent viewers or more, please let us know in advance (so we can make sure sufficient bandwidth is available).

Can I have a fully redundant setup ?

Yes. Clevercast has a main and backup ingest server, to which you can broadcast at the same time. If the broadcast to the main server is interrupted, Clevercast Player will detect this and automatically switch to the backup stream.

Can Clevercast simulcast separate languages ?

Not yet. Clevercast Multilingual has been designed to deliver a single live stream that contains multiple languages. It is currently not possible to separate the languages and send them as live streams to third party services.

Do you support pseudo-live scheduling ?

Currently not out of the box. But if you have a pre-recorded video, you can broadcast it yourself at the time it needs to be live. Or you can pay us to do it manually from our servers.

T@H requirements

What are the requirements for translators?

Basically, they must be able to sent the audio stream to Clevercast without distortion or packet loss.
This can roughly be translated into the following requirements:

  • Using a recent version of Mozilla Firefox
  • A minimal bandwidth of at least 5 Mbps up and down.
  • A wired connection to the internet! Even a good wireless connection with plenty of bandwidth may still cause audio distortion.
  • Headset with noise cancelling for audio output and input.
  • No excessive packet round-trip time. If packets arrive too late, the audio will be dropped or distorted. Our ingest servers are located in Europe, so translators in Europe will mostly be fine.
  • A recent computer with sufficient CPU and memory.

The most important requirement is sufficient testing! Each translator should test in a situation that matches the live event as much as possible.

Caveats

Below are some possible causes of issues during the live translation:

  1. Network congestion: if translators are in an intranet with much more traffic than during the test (eg. people viewing the live stream, multiple translators at the same location) this could cause problems (eg. dropped packets, audio distortion) that did not arise during testing.
  2. Wifi: don’t use Wifi if there is any way to avoid it. Even if it works during testing, it may still cause problems during the real live stream.
  3. Make sure that the sound from the microphone AND from the video stream goes through your headset. If the sound of the video stream goes through your speakers, this will certainly lead to interference.
  4. Clevercast allows viewers to hear a faded version of the original audio in the background of the translated audio streams. Don’t set this too loud: some speakers may sound louder in the original audio.

Encoder Support

Translate at Home

A broadcast for Translate at Home can be sent with any encoder (= video + mono or stereo audio). You can add any number of languages in Clevercast.

SRT multi-track broadcast

OBS Studio has support for 6 audio tracks.

vMix supports SRT broadcasts but currently does not support multiple audio tracks.

Other SRT encoders support 8 or more tracks. For example, the Intinor Direct Link and Makito X both support 8 stereo tracks, the Makito X4 supports 16 stereo tracks. You can use stereo to pan two different languages L+R (if you do this, change the Languages per Track setting in Clevercast to 2). This way, you can stream 16 languages using 8 stereo tracks.

If you have an SRT encoder and want to test interoperability with Clevercast, please contact us.

RTMP multi-channel broadcast

Currently only supported by OBS Studio through their surround sound feature, for up to 7 languages.

RTMP stereo panning for 2 languages

If you only need 2 languages, you can send a stereo broadcast over RTMP with both languages panned left and right. This can be done with any encoder.

How do I test with OBS Studio ?

You can test Translate at Home by simply sending a video stream with mono or stereo audio.

If you want to broadcast multiple audio tracks or channels, you need an external device that maps the audio input to tracks or channels (NOT both).

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