This FAQ concerns multilingual live streaming in general. For questions regarding live streams with remote simultaneous interpretation, see the FAQ on the Translate at Home overview.
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.
- 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) ?
This depends on a number of things:
- Costs, health & safety: T@H doesn’t require interpreters to travel.
- Ease of use, deployment: T@H doesn’t require translator booths and in depth technical knowledge. It can be set up quickly.
- 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 audio mix, you should choose an on-site production with an SRT multi-track or RTMP multi-channel broadcast.
- Audio quality: With T@H, the translated audio quality depends on the connection and equipment of your interpreters (see our requirements and best practices for interpreters).
- 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.
Are there broadcast guidelines or restrictions ?
The Clevercast Broadcasting Guidelines help you choose the right broadcasting settings. You may deviate from them to a certain extent. If this would result in problems, please contact us.
Additional guidelines are available for broadcasting multiple audio tracks with SRT and broadcasting multiple audio channels with OBS Studio.
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). Note: with this option, viewers on other continents are still able to watch the live stream, but their experience may be suboptimal.
How do viewers choose their language ?
You embed our video 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, 20.000 concurrent viewers or more is possible. If you expect more than 5.000 concurrent viewers, we’d appreciate some notice in advance.
Can I limit the number of viewers ?
Clevercast player doesn’t limit the number of viewers. If our player is embedded, your website could do this instead.
We also have a webinar solution, where our player is hosted on a (branded) webinar page. This supports viewer registration or invitation and thus can limit the number of viewers.
Can Chinese viewers watch the live stream ?
Amazon CloudFront’s network in mainland China is completely separate from their global network. Only companies with a valid Chinese business license have access to it. We don’t.
Amazon CloudFront does have other edge servers which are sufficiently close (eg. Hongkong). But the Chinese government requires all traffic to pass through their Great Firewall, which may cause traffic congestion. So we can’t guarantee the quality of experience of Chinese viewers.
Recording and Hosting
Can Clevercast record the multilingual live stream ?
Yes. The live stream can be recorded and downloaded as a single mp4 file containing the video stream and all audio streams (= languages).
This features is optional. If enabled, recording is automatically started when you start an event. When you set the event status to ended, the recording becomes available under the Live -> Recording menu.
Can Clevercast turn a recording into video on-demand ?
Yes. Clevercast lets you publish recordings to on-demand items. The on-demand video player can also be embedded on your website. Language selection works the same way as for the live stream.
This is also an optional feature.
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
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.
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 we can do it manually from our servers.
Testing & trial accounts
What are the limitations for trial accounts ?
By default, trial accounts are limited to 720p video, 4 languages and 5 hours of live streaming. If you need more hours, send an email to support@clevercast.com. In most cases, this won’t be a problem.
Don’t forget to turn off your encoder when you’re 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 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).
My live stream is not working ?
Make sure to follow our general broadcasting guidelines and our protocol-specific guidelines for Translate at Home, SRT multi-track and RTMP multi-channel. If you want to try out T@H, read our guide for interpreters.
Don’t forget to set the event status to Preview or Started. If you don’t do this, the live stream won’t work and T@H language rooms are not available.
For multi-track or multi-channel broadcast, make sure not to make these mistakes:
- Don’t mix tracks and channels. For RTMP multi-channel, your broadcast must contain multiple audio channels in a single track. For SRT multi-track, your broadcast must contain multiple audio tracks (with channels set to mono or stereo).
- For SRT multi-track, your broadcast must contain the same number of tracks as the number of languages in Clevercast. If you use SRT with OBS Studio, make sure to press the ‘Start Recording‘ button (instead of ‘Start Streaming‘).
- For RTMP multi-channel, your audio channel selection must be the same (eg 4.0) in your Clevercast event, input device settings (eg Blackmagic DeckLink) and OBS Studio Channels setting.
See our Troubleshooting page for more help. If nothing works, send us an email.
Encoder Support
Translate at Home
A broadcast for Translate at Home can be sent with any encoder (= video + mono or stereo audio) or third-party solution that can send an RTMP or SRT broadcast (eg. vMix, Zoom). You can add any number of languages in Clevercast.
SRT multi-track broadcast
OBS Studio has support for 6 audio tracks. Although there is a separate OBS Studio – Music Edition fork that supports up to 16 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. Although there is a separate OBS Studio – Music Edition fork that supports up to 16 audio channels.
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.
vMix
vMix supports RTMP and SRT broadcasts to Clevercast. But it doesn’t allow you to send multiple audio tracks. So you can only use it for stereo panning for 2 languages, or for Translate at Home.
Pricing
What are your prices based on ?
Clevercast Multilingual plans are based on the number of languages, the number of processing hours and the data traffic consumed by your viewers. For live streams with a large number of viewers, data traffic is usually the determining factor. We allow adding extra TBs of traffic to your plan in advance (= prepaid, at a lower price). This way, you avoid paying overuse afterwards (at a higher price).
Extra options include server-side recording, on-demand hosting and advanced support contracts (eg. event supervision).
For multilingual webinars, the required number of participants (registration) and interactive features (Q&A, chat and audience polling) are also taken into account.
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.
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 mbps, lasts 2 hours and has 100 concurrent viewers, you can use the following formula:
300 (viewers) x 5 (mbps) x 2 (hours) x 3600 (to seconds) / 8 (bits) = 1.350.000 MB (or 1350 GB)
Note that the bitrate also depends on the kind of content that you’re streaming. For highly dynamic content you will be using a higher bitrate while broadcast, but Clevercast will also transcode the different resolutions to a relatively high bitrate. For less dynamic content (eg. conference, talking heads) Clevercast will also transcode the resolutions to a lower bitrate. Here are some bitrates to go (= for usage in the formula):
- Highly dynamic content (eg. a sports game, live concert) in 1080p: 5.5-6 mbps
- Dynamic content (eg. talkshow, virtual event with people on different locations) in 1080p: 4,5-5 mbps
- Relatively static content (eg. talking heads, conference) in 1080p: 3,5-4 mbps
- Relatively static content (eg. talking heads, conference) in 720p: 3-3,5 mbps
Do you have event pricing ?
For small events, we will use our regular plans (single month license). For events with data traffic estimated to exceed 4 TB, we’ll make a custom price based on the duration of the live stream, estimated number of concurrent viewers, number of languages and required features.
Advanced
Is it possible to ingest streams from third parties (eg Zoom) ?
Clevercast has no integrations with third party services. 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 simulcast separate language streams (eg YouTube, Facebook) ?
Not yet. Clevercast multilingual streaming 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. However, this features is on our roadmap.
Can I simulcast the video and floor audio ?
That depends on the broadcast protocol. Contact us if you need this.
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 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.
This will work without any manual intervention for multi-channel and multi-track broadcasts. For T@H however, it will require interpreters to switch from the main language room to the backup language room (only the video and floor audio will failover automatically).
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.