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.

Translate at Home (T@H): unlimited
SRT multi-track broadcast: 6 languages with OBS Studio, more audio tracks supported by other encoders (tested with 16 languages, see the Encoder Support section below)
RTMP multi-channel broadcast (only supported by OBS Studio): 7 languages via 7.1 channels.

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.

Recording and Hosting

Can Clevercast record the multilingual live stream ?

Yes. The live stream is recorded as a single m4v file containing all audio (= languages) and video (= resolutions) streams. You can download it afterwards from Clevercast.

How do I record an event ?

When you start an event, recording is automatically started. When you set the event status to ended, the recording becomes available under the Live -> Recording menu (for download or conversion to on-demand, see below).

Can Clevercast host a recording as on-demand video ?

Yes, but only if this feature is enabled for your account. It lets you publish your recording to an on-demand video item. The on-demand video player can also be embedded on your site. Language selection will work in the same way as the live stream.

Can I upload multilingual videos to Clevercast for on-demand hosting ?

You can upload videos with different languages and turn them into a multilingual video that is available for on-demand viewing.

If you have a separate video and audio streams, you can send them to us. We can manually turn them into a multilingual on-demand video (= on a project basis).

Can Clevercast also host the page on which the video is embedded ?

Yes, you can use our Webinar solution if you don’t want to host the video on your own site. In that case, you can limit the number of viewers by requiring them to register or by inviting them.

Platform

Does T@H allow multiple translators for the same language ?

Yes, they can translate sequentially or even simultaneously in the same room. They can also communicate with the other translators in the room via text chat.

Can I customize the player’s look and feel ?

Yes. You can create your own branded player (via the Media -> Players menu) and select this as the player for your event. You can also use our player API.

Can I limit accessibility of my live stream ?

Yes. You create a viewing profile (via the Media -> Viewing Profiles menu) and select this as the viewing profile for your event. This lets you create white- and blacklists for countries, domains and IP addresses.

Do you have statistics?

Yes, we have both realtime and post-event statistics. They include standard data like number of viewers, concurrent viewers over time, location of viewers, used devices, referrers… but all data refer to the live or on-demand video as a whole. There are no per-language statistics.

Can I limit the number of viewers ?

Our player doesn’t limit the number of viewers. Since the player is embedded, your website could do this instead.

We also have a webinar solution, where our player is hosted on our branded webinar page which allows for registration/invitation and thus can limit the number of viewers.

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:

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.
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.
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.
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).

Testing & Pricing

What are processing hours ?

When receiving a multilingual broadcast, Clevercast needs to do realtime transmuxing and transcoding so the video can be watched in the player. This happens when you are broadcasting to an event with status preview, started or paused.

My trial account doesn’t have enough processing hours ?

If you need more processing hours for your trial account, please send an email to support@clevercast.com. In most cases, this won’t be a problem.

Don’t forget to turn off your broadcaster when you are not testing. Preferably also set the event status to waiting or ended. If you don’t, it will be reset by Clevercast after 4 hours (= for trial accounts).

How do I calculate the traffic I need ?

The amount of traffic is the total amount of bytes (GB) delivered to your viewers. To estimate it, you need:

The duration of your live stream(s).
The average viewer’s bitrate of your video (in mbps). This will be lower than the bitrate of your broadcast: since Clevercast uses adaptive streaming, some viewers (small screen size, slow connection) will not see the video in 1080p. Typically, it will be somewhere halfway between 1080p and 720p. For example, if you are broadcasting 1080p at 6 mbps, the average viewer’s bitrate will be closer to 5 mbps.
The estimated number of concurrent viewers, for the whole duration of your live stream.

For example, if your live stream is broadcasted at 6.8 mbps, lasts 2 hours and has 300 concurrent viewers, you can use the following formula:
300 (viewers) x 6 (mbps) x 2 (hours) x 3600 (to seconds) / 8 (bits) = 1620.000 MB (or 1620 GB)

Your plans do not include enough traffic?

Our Plus plans allows you to include any number of TBs in your plan (prepaid). This way, you avoid paying overuse (at a higher price).
For example, if you estimate you will need more than 10TB anyway, you could add 8TB of traffic to your Plus plan. Your plan will then include 10.5 TB of traffic.

Advanced

Is it possible to ingest streams from third parties (Zoom, Teams, etc …) ?

Clevercast has no integrations with third parties. But if the third party service allows re-streaming an RTMP (eg. Zoom) or SRT stream, it can be used as input for Translate at Home.

Is it possible to lower the streaming latency ?

To an extent. By default, our HLS segments are set to 6 seconds. Together with player buffering this will result in a minimal latency of 18 seconds (which can go up to half a minute on some connections or devices).

To lower your latency, we can configure your account to use HLS segments of 3 seconds (important: in that case the keyframe interval of your broadcast should be 3 seconds). When Clevercast player is configured not to do buffering, you will reach a latency of 12-16 seconds.

However, this may cause clients with a slow internet connection to see more spinners or not be able to watch the video altogether. In theory, HLS segments could be lowered to 2 seconds, but this will have even more consequences for slow clients.

NOTE: the new LHLS protocol from Apple can’t be used. It isn’t yet supported by any player framework and remains a work in progress.

Can I simulcast the video and floor audio to YouTube, Facebook… ?

That depends on the broadcast protocol. Contact us if you need this.

Most of my viewers are in Europe, US and Canada?

We can limit delivery to the Amazon CloudFront servers in Europe, US and Canada. This will result in cheaper traffic prices (both extra and overuse).

Note: this doesn’t mean that viewers on other continents won’t be able to watch the live stream, but their experience may be suboptimal.

More info

T@H overview: multilingual livestreams with remote simultaneous interpretation

How to: simultaneous interpretation with Translate at Home (T@H)

How to: broadcast multiple audio tracks with SRT

How to: broadcast RTMP audio channels with OBS Studio

Clevercast Broadcasting Guidelines

Troubleshooting live streaming