Using Wowza for Closed Captions on Twitch

Wowza Streaming Engine
1

I am using Wowza to livestream a pre-recorded, pre-captioned local file to Twitch.tv. Twitch specify that Wowza can be used to format a livestream in the correct way such that Twitch recognises a caption file and shows it as closed captions on the stream. The video file is an mp4, and I have captions as EIA-608 in a separate sidecar file (as both .scc and .srt). Twitch specify that:

Captions may be transmitted using one of the following methods:1. CEA-708/EIA-608 embedded in the video elementary stream as described in ATSC A/72 (SEI user_data). This format is common among television broadcast encoders.

  1. CEA-708/EIA-608 transmitted via RTMP onCaptionInfo script/AMF0 tag. This format is common among Internet broadcast encoders and media servers such as Elemental Technologies and Wowza.

I have been able to use Wowza to stream to Twitch, but have been unable to get captions to show up on the stream.

I wanted to ask how I can use Wowza to either embed CEA708/EIA608 captions within a video file for streaming, or how to use Wowza to transmit CEA-708/EIA-608 via RTMP onCaptionInfo script/AMF0 tag? I have read multiple articles on using Wowza with closed captions but I have been unable to use them to do either of these tasks specifically.

Thank you so much

2

Hello Henry,

To clarify, I will assume you are using the method in this article to re-stream the vod file. So, to get the captions into the “live stream” you will need to inject the captions.

You can use the Wowza Streaming Engine Java API to inject onTextData events into live streams using the IMediaStream.sendDirect() call (see Example module for publishing onTextData captions to download the PublishOnTextData package, which uses this API). This enables a publisher that passes closed-caption data in the form of timed text events or SMPTE events to use the Wowza Streaming Engine Java API to inject onTextData into a live stream. The onTextData is intercepted and injected into the stream as CEA-608 events.

This is a bit advanced to configure, but if you need to clarify or ask questions on your workflow, please send those to the Wowza Support team to work with you directly.

Regards,

Mac