Live Captioning with in-player (608 encoded) caption delivery for your Event(s)

Providing captions for your event is a key part of ensuring your event is accessible, and 3Play is here to help! Below is a guide to ensuring the 3Play Live Captions delivered via 608 caption encoding for your event are a success. This document applies to the following live captioning delivery workflows. Please refer to the below documents for how to schedule captions in 3Play. 


Please ensure you test the workflow you intend to use for your event in advance of your event! This will ensure you have enough time to address any issues, and that things run smoothly for your real event. 


Captioning Delivery

3Play will  receive your stream from your video source / encoder, and will then generate and encode captions into the video stream via a 608 standard. From there we will pass the video stream with encoded captions to your specified destination (ex Brightcove). While 3play encodes the captions into the video stream, the process of decoding the captions and the settings for how they appear within the video are controlled through the end video player (ex Brightcove).

3Play will start delivering captions as soon as speech is detected (which is indicated within 3Play on the Live Captioning homepage in your account). For this reason, the caption label in the end video player will likely not appear until speech has started (and thus captions generated) in your stream. 


Stream Start vs Event Start Times

3Play provides the ability to specify both a Stream Start Time as well as an Event Start Time. The Stream Start Time represents the time at which 3Play will initiate a service to listen for your stream. Do not attempt to stream to 3Play before the stream start time, as the stream connection will fail to connect from your encoder to 3Play and your encoder will display an error message. 

The Event Start Time is intended to represent your audience-facing start time in 3Play. 


Supported event lengths

We currently have limitations on event length, related to streams with higher bitrates. Please see the below chart of event length maximum recommendations at different bitrate ranges:

<1mbps - 600+ minutes
1-2mbps - 330 minutes
2-3mbps - 220 minutes
3-4mbps - 160 minutes
4-5mbps - 135 minutes
5-6mbps - 110 minutes


Stream redundancy 

If your captioning delivery method is via 608 caption encoding (such as with our Brightcove In Player, and our RTMP In Player workflows), 3Play is streaming both video and captions to the end video player - if you choose to End Event through the 3Play interface, this will also end the video stream. Do not select this unless you want to stop streaming your video. 


Additionally, if your stream to 3Play, or the 3Play stream to your specified restream URL is compromised, both captions and video will be impacted. As such we recommend that customers using this workflow have a secondary stream directly between their encoder and the end video player as a fall back.


Stream Recovery

If there is a disconnection between your encoder and 3Play, this will cause the event in 3Play to end. In order to begin the stream again, you will need to schedule a new event in 3Play. 

If you are using a 3Play-provisioned reserved transcoder: please ensure the recovery event is scheduled at least 5 minutes in the future to ensure the transcoder has enough time to reset prior to re-initiating your stream. 

If you do not have 3Play-provisioned reserved infrastructure: The new event will have a unique RTMP URL and Key, which must be updated in your encoder.


Support Pathways:

We're here to help! 3Play’s support team business hours are Monday through Friday 8am to 8pm ET.

  • Online: navigate to and select “Submit a request” in upper right hand corner.
  • Phone: (617) 764-5189 - select support in menu. It requires a voice mail and routes that to our support queue



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