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Guide to Closed Captions

Last Updated: Mar 25, 2017 11:21PM PDT

Guide to Closed Captions

This article explains what closed captions are, and how to use them on Twitch.

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Twitch users are now able to follow the conversation on stream thanks to a Live Closed Captions service on Twitch-produced content. Whether you have a hearing impairment or just want to squeeze a little Twitch into your library study session, you will not miss out on Twitch-produced content when listening to the audio is not an option.

Live Closed Captions on Twitch are typed live (very quickly!) by a professional stenographer hired to cover Twitch events such as Twitch Weekly and some stage events at TwitchCon. Captions are written as they are said so that nothing is missed. You can also adjust caption size, color, placement, and other settings to improve visibility for each user and each stream. Your settings will be saved and used to display captions any time they are available on a stream or if you re-watch a Past Broadcast from a stream that was captioned.

Captions elsewhere on Twitch can be provided by broadcasters who are able to transmit caption files embedded in their streams or via their broadcast encoders.

Index (click to jump):
How to Use Live Closed Captions: for Viewers
How to Use Live Closed Captions: for Broadcasters
Frequently Asked Questions

 

Turn on Closed Captions by clicking the “CC” button on the video player. The “CC” button is only present when captions are available on a live stream or video:
 

 


Change your caption display setting by clicking the Gear Icon on the video player and selecting “Closed Captioning” from the Player Options menu:
 

 


You will see a selection of preset display options and tabs where you can adjust each setting individually:


 

 

 

 

 

 

 

 

 
As a broadcaster, if you want to offer captions to your audience, you will need to transmit caption files in an accepted format embedded in your stream, or alongside your stream, through your broadcast encoder.

The Live Closed Captions system on Twitch accepts captions in line 21 CEA-708/EIA-608 format and in CC1 NTSC field 1.

Keep in mind: you are responsible for all content that appears on your broadcast, including captioned content. Using the Closed Captions system in a manner that violates Twitch’s Community Guidelines or Terms of Service may result in a suspension of your Twitch account.

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.
     
  2. 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.
When transmitting via RTMP, the payload must contain an ECMA Array with two element pairs:
  • A string named "type" containing the characters "708"
  • A string named "data" that contains a base64 encoded CEA-708/EIA-608 payload

Example:
00000000  12 00 00 69 00 00 00 00  00 00 00 02 00 0d 6f 6e  |...i..........on|
00000010  43 61 70 74 69 6f 6e 49  6e 66 6f 08 00 00 00 02  |CaptionInfo.....|
00000020  00 04 74 79 70 65 02 00  03 37 30 38 00 04 64 61  |..type...708..da|
00000030  74 61 02 00 3c 74 51 41  78 52 30 45 35 4e 41 4e  |ta..<tQAxR0E5NAN|
00000040  4c 41 50 79 55 72 76 79  55 49 50 79 52 51 50 7a  |LAPyUrvyUIPyRQPz|
00000050  49 35 66 7a 73 37 50 7a  76 4c 50 77 67 56 50 7a  |I5fzs7PzvLPwgVPz|
00000060  33 36 66 7a 30 34 2f 78  6f 67 50 79 55 4c 2f 38  |36fz04/xogPyUL/8|
00000070  3d 00 00 09 00 00 00 74                           |=......t|
 
  • Q: How do I know if a stream or video has captions?
    • A: When captions are available on a live stream or video, you will see a “CC” button that lets you turn captions on or off.
       
  • Q: What channels will be sure to have Closed Captioning?
    • A: As of September 9, 2016, ‘Twitch Weekly’, a show about all things Twitch, will air with live captions every Friday at 1 PM PT / 4PM ET on an ongoing basis. As well, the live stream from the Kappa Theater at TwitchCon 2016, September 30 - October 2, will also air with live captions.
       
  • Q: Do I have to update my settings every time a stream has captions?
    • A: No. Once you turn captions on or off or adjust the display settings, your preference will be saved for the next time you watch content that supports captions.
       
  • Q: Why do you call them “Closed Captions” are there “Open Captions”?
    • A: Yes! In short, Open Captions are always visible to viewers, but Closed Captions can be turned on or off. We want to give viewers the choice to use captions or turn them off whenever they are available.