Configure closed captioning for Wowza Streaming Engine live streams

Updated on 01/15/2025 11:10 am PST

Wowza Streaming Engine™ media server software can take any captioning data embedded in a source stream and pass it through in a live stream output. It can also ingest caption data and convert it to the appropriate captioning format for live streaming using the HTTP Live Streaming (HLS) and Real-Time Messaging Protocol (RTMP) protocols.

Many player technologies, set-top boxes, and over-the-top (OTT) players can display CEA-608/708 closed captioning data embedded in live streams. Other player technologies can only display AMF onTextData captioning data.

Notes:
  • Please check with your player first to confirm support for CEA-708 embedded captions for live streams. Not all web-based HTML5 players fully support CEA-708 embedded captions currently.
  • Wowza Flowplayer doesn't support output for embedded CEA-708 captions in live streams. With web-based players, we recommend using WebVTT captions instead of embedded captions. For more, see Configure CEA-608/708 captions for WebVTT output and Configure onTextData captions for WebVTT output.

Before you start

Before you start working with caption configurations for live streams in Wowza Streaming Engine, follow these steps to create a live application in Wowza Streaming Engine. It may be helpful to also review the following resources:

We found this test media with embedded CEA-608 and CEA-708 captions helpful during testing.

Supported caption types

Various closed caption sources are available, and each streaming standard may use a different format for embedding captions on the output. Wowza Streaming Engine supports the following input sources and output formats for closed captions in live streams.

Supported input sources

The following input sources are supported for closed captioning with live streams in Wowza Streaming Engine:

  • CEA-608/708 captions embedded in live streams.
     
  • Action Message Format (AMF) onTextData captions embedded in input streams.
  • AMF onCaption and onCaptionInfo captions embedded in input streams.

We provide an example module that uses the Wowza Streaming Engine Java API to insert onTextData into a stream.

Supported outputs

The following output formats can be translated from any of the supported input sources for live streams in Wowza Streaming Engine:

  • onTextData events in RTMP live streams.
     
  • CEA-608/708 formatted SEI data in the video track of any live stream. This page focuses on CEA-608/708 captioning output in HLS and RTMP live streams.
     
  • WebVTT text tracks in HLS live streams.

Supported caption translations

The following table summarizes the input-to-output caption translations that are supported by Wowza Streaming Engine:
 
Outputs →

Inputs ↓		 RTMP
(onTextData)		 HLS and RTMP
(CEA-608/708 in video)		 HLS
(WebVTT)
AMF onTextData Yes Yes Yes
AMF onCaption Yes Yes Yes
CEA-608/708 Yes Yes Yes
via Java API Yes Yes Yes

Ingest and configure CEA-608/708 captions for live streams

This section explains how to set up your live application to monitor live streams with embedded CEA-608/708 captions, decode the captions, and pass them through or convert them to WebVTT captions in the output of an HLS live stream.

Due to the differing nature of CEA-608/708 captions versus captions in a streaming server, some caption modes are decoded more efficiently than others. Pop-on captions that appear anywhere on the screen as a whole, followed by another caption or no captions, are generally best. Other caption modes, such as scroll-up captions that draw directly to the screen, may exhibit some delay. This is because CEA-608/708 captions are drawn directly to the device, while Wowza Streaming Engine must detect the end of each caption to capture it and send it with the outgoing stream.

When considering how to send captions to Wowza Streaming Engine in live streams:

  • Use pop-on captions where possible.
  • If using other caption modes, minimize the amount of time between the start of the caption drawing and the end of the caption.
Note: A SMIL file is recommended to define media playback details for your CEA-608/708 captions. This allows the captions to be clearly identified in the player UI and captions menu. For more, see Understanding SMIL file syntax.

Configure CEA-608/708 captions for output in HLS live streams

Wowza Streaming Engine provides passthrough support for CEA-608/708 captions embedded in live streams. You can use these steps to additionally configure a live stream with:

  • Embedded CEA-608 captions and add language labels for Track 1 (CC1) and Track 3 (CC3) in your HLS output.
  • Embedded CEA-708 captions and add language labels for multiple caption tracks in your HLS output.
Note: Access to the Properties tab is limited to administrators with advanced permissions. For more information, see Manage credentials.
  1. In Wowza Streaming Engine Manager, click the Applications tab.
  2. Select your live application from the list.
  3. On the Setup tab, make sure Apple HLS is selected from the Playback Types.
  4. Click Edit on the Setup tab.
  5. Scroll to the Closed Captions section.
  6. Select the Ingest embedded CEA-608/708 captions in live streams radio button to enable the ModuleCEAToOnTextData module.
  7. Click Save and restart the application.
  8. (Required for CEA-708 output) On the Properties tab for your application, go to the Closed Captions properties section. Click Edit, and add this closed captioning property. Then Save.
Name Type Value Description
closedCaptionLive708LanguageMapping String 1:eng,2:spa,3:fra Creates comma-separated mapping for CEA-708 service numbers to convert them to three-character ISO-639 language codes during live stream ingest. For example, to accommodate the SMIL file in step 11, add 1:eng, 2:spa, 3:fra. Default value is 1:eng.
  1. (Optional) On the Properties tab for your application, go to the Closed Captions properties section. Click Edit, and add these closed captioning properties when applicable. Then Save.
Name
 Type
Description
captionLiveIngestLanguages String Specifies, in ISO-639, what subtitle languages are expected to be delivered. For example, eng, spa, fra with the SMIL file in step 11. If not specified, the language is based on the Wowza Streaming Engine server locale. This property is optional when using a SMIL file with textstream tags.
captionUndefinedLanguageId String The language code for the caption if the language ID provided isn't recognized. For example, eng. If not specified, this value defaults to the server's three-letter locale.
ccIngestCEA608EnableField1 Boolean Specifies if CEA-608 field 1 is enabled. The default value is true (enabled). Typically, either field 1 or field 2 is enabled, not both.
ccIngestCEA608EnableField2 Boolean Specifies if CEA-608 field 2 is enabled. The default value is false (disabled).
ccIngestCEALogCaptions Boolean Specifies if the parsed CEA-608/708 captions are logged. The default value is false (disabled).
ccIngestCEAVerboseLogging Boolean Enables verbose logging of the CEA-608/708 parser. The default value is false (disabled).
  1. After adding all properties, restart your application.
  2. To configure the player for CEA-608/708 output, create a myStream_608_708.smil file:
<smil>
  <head>
  </head>
    <body>
      <switch>
	<video src="mp4:myStream" system-bitrate="450000">
	  <param name="cupertinoTag.CLOSED-CAPTIONS" value="captions" valuetype="data"/>
	</video>
	<textstream src="mp4:myStream" system-language="eng">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="SERVICE1" valuetype="data"/>
	</textstream>
        <textstream src="mp4:myStream" system-language="spa">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="SERVICE2" valuetype="data"/>
	</textstream>
	<textstream src="mp4:myStream" system-language="fra">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="SERVICE3" valuetype="data"/>
	</textstream>
      </switch>
    </body>
</smil>
  1. Add the myStream_608_708.smil file to the [install-dir]/content folder for your Wowza Streaming Engine installation.
  2. Start a stream and send it to your Wowza Streaming Engine server. For more about publishing live streams, see Connect a live source to Wowza Streaming Engine.
  3. To test playback for CEA-608 captions, use Wowza Test Player and add this playback URL:

http://[ip-address]:1935/[application-name]/myStream_608_708.smil/playlist.m3u8

  1. To test playback for CEA-708 captions, use this test player and add this playback URL:

http://[ip-address]:1935/[application-name]/myStream_608_708.smil/playlist.m3u8

Note: Wowza Flowplayer doesn't currently support output for embedded CEA-708 captions in live streams.

Configure CEA-608/708 captions for WebVTT output in HLS live streams

With Wowza Streaming Engine, you can ingest a live stream with embedded CEA-608/708 captions and output WebVTT captions in your HLS live streams. For a cleaner display of the WebVTT captions in the generated HLS live stream, we recommend removing the embedded CEA-608/708 captions.

For more information about using a SMIL file with this workflow, see Override live caption ingest behavior using a SMIL file.

Note: Access to the Properties tab is limited to administrators with advanced permissions. For more information, see Manage credentials.
  1. In Wowza Streaming Engine Manager, click the Applications tab.
  2. Select your live application from the list.
  3. On the Setup tab, make sure Apple HLS is selected from the Playback Types.
  4. Click Edit on the Setup tab.
  5. Scroll to the Closed Captions section.
  6. Select the Ingest embedded CEA-608/708 captions in live streams radio button to enable the ModuleCEAToOnTextData module.
  7. Click Save and restart the application.
  8. Go to the Properties tab for your application.
  9. In the Closed Captions properties section, click Edit.
  10. Enable the properties in the following table and set their values as suggested. Then Save.
Name Type Value Description
captionLiveIngestLanguages String eng,spa,fra Specifies, in ISO-639, what subtitle languages are expected to be delivered. For example, eng, spa, fra. If not specified, the language is based on the Wowza Streaming Engine server locale. This property is optional when using a SMIL file with textstream tags.
ccIngestEnableCEA708 Boolean true Manages parsing for CEA-708 captions when ingesting a live stream and converting captions to onTextData events in live stream outputs. Default value is false.
cupertinoLiveCaptionsUseWebVTT Boolean true Specifies if live AMF onTextData events are converted to WebVTT subtitle format. If enabled (true), WebVTT subtitles are created. If disabled (false), CEA-608 captions are created.
closedCaptionLive708LanguageMapping String 1:eng,2:spa,3:fra Creates comma-separated mapping for CEA-708 service numbers to convert them to three-character ISO-639 language codes during live stream ingest. Default value is 1:eng.
  1. Go to the Custom properties section and click Edit.
  2. Enable the property in the following table and set its value as suggested. We recommend setting this property to avoid duplicate captions in the player UI. Set the path to /Root/Application/TimedText. Then Save.
Name Type Value Description
ccIngestCEARemoveExistingCEA Boolean true Works with the ModuleCEAToOnTextData module to remove ingested CEA-608/708 captions when generating onTextData events. This prevents captions from being duplicated in the player's output. The default value (false) preserves the ingested CEA-608/708 captions in the transcoded output. To remove the existing CEA-608/708 captions, set to true.
  1. (Optional) On the Properties tab for your application, go to the Closed Captions property section. Click Edit, and add this closed captioning property when applicable. Then Save.
Name Type Description
webVTTPreferredSource String Determines CEA-608/708 subtitle preferences in WebVTT outputs when ingested live streams contain embedded CEA-608 and CEA-708 subtitles for the same language. Possible values are CEA608 or CEA708.
  1. After setting all properties, restart your application.
  2. Start a stream and send it to your Wowza Streaming Engine server. For more about publishing live streams, see Connect a live source to Wowza Streaming Engine.
  3. To test playback, open Wowza Test Player and add the following playback URL:

http://[ip-address]:1935/[application-name]/myStream/playlist.m3u8

Note: You can confirm the presence of the generated WebVTT sidecar files in your browser's Network panel.

Ingest and configure AMF onTextData captions for live streams

This section explains how to set up your live application to monitor live streams with embedded AMF onTextData captions, decode the captions, and either convert them to CEA-608/708 captions or WebVTT captions in the output of an HLS live stream.

AMF onTextData events are commonly associated with RTMP and used to carry closed caption or subtitle information. An onTextData event usually includes the following fields:

  • text – Carries the UTF-8 encoded text for the event.
  • lang – The three-letter language ID for the event, for example, eng.
  • trackid – (Optional) For on-demand streaming, this is the ID of the text track in the video file. For live streaming, this field is either omitted or set to 99.

The live application in Wowza Streaming Engine monitors a live stream for onTextData events, extracts the text field, formats it as CEA-608/708 closed-caption data, and injects it into the video stream as SEI NAL units. Many player technologies, set-top boxes, and OTT players can then display the embedded closed-captioning data.

Note: A SMIL file is recommended to define media playback details for your CEA-608/708 workflows. This allows the captions to be clearly identified in the player UI and captions menu. For more, see Understanding SMIL file syntax.

Example module for publishing onTextData captions

Usually, onTextData events are published by an external source. But you can use the Wowza Streaming Engine Java API to inject onTextData events into live streams using the IMediaStream.sendDirect() call.

We provide an example module that 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-608/708 events.

You can download this PublishOnTextData.zip package with the example ModulePublishOnTextData module and use it to insert onTextData events into your Iive streams. The module takes caption data from a flat text file and injects an onTextData event into the live stream every 6.5 seconds. 

This module is only for testing purposes and is an example of injecting onTextData events into a live stream. It only supports sending onTextData events for a single language. If you use multiple languages in your onTextData workflows, modify this module and add several ontextdata.txt files to match your output in the [install-dir]/content folder. For example, ontextdata_eng.txt, ontextdata_fra.txt, and ontextdata_spa.txt​.

Configure onTextData captions for CEA-608 output in HLS live streams

With Wowza Streaming Engine, you can ingest a live stream with embedded onTextData events and output CEA-608 captions in your HLS live streams. The inbound live stream must contain proper Action Message Format (AMF) onTextData events for specified languages. If you need to inject onTextData events into your live streams, check this example module.

Note: Access to the Properties tab is limited to administrators with advanced permissions. For more information, see Manage credentials.
  1. In Wowza Streaming Engine Manager, click the Applications tab.
  2. Select your live application from the list.
  3. On the Setup tab, make sure Apple HLS is selected from the Playback Types.
  4. Click Edit on the Setup tab.
  5. Scroll to the Closed Captions section.
  6. Select the Ingest onTextData events in live streams radio button.
  7. Enable the ModuleOnTextDataToCEA module by selecting the Output to CEA-608 checkbox.
  8. Click Save and restart the application.
  9. (Optional) On the Properties tab for your application, go to the Closed Captions properties section. Click Edit, and add these closed captioning properties when applicable. Then Save.
Name
 Type
Description
cea608CaptionConverterColor Integer Changes the text color in the default CEA-608
caption converter. Valid values are 0 (white), 2 (green), 4 (blue), 6 (cyan), 8 (red),
 10 (yellow), and 12 (magenta).
closedCaptionLiveMaxDisplayTime Integer Maximum time, in milliseconds, that a CEA-608/708 closed caption is displayed on the screen. The default value is 10000 milliseconds.
  1. (Optional) On the Properties tab for your application, go to the Custom properties section. Click Edit, and add these custom properties when application. Set the path for each property to /Root/Application/TimedText. Then Save.
Name Type Value
closedCaptionLiveChannel Integer Specify the close captioning channel for
CEA-608 captions. Valid values are 0 (CC1)
and 1 (CC2). (Note: Only CC1 seems to work
with Apple iOS devices).
closedCaptionLiveCharacterSet String Set the closed caption character set to use when
converting onTextData text data to CEA-608
caption data. For example, UTF-8.
closedCaptionLiveCommandsPerFrame Integer Specifies the maximum number of closed caption commands to send per frame for CEA-608 captions (maximum is 31).
closedCaptionLiveEnableTranscoderResults Boolean Controls whether CEA-608/708 captions are passed through the Transcoder. If true, all CEA-608 captions are passed through.
closedCaptionLiveLogOnTextDataEvents Boolean Controls logging of individual onTextData events. Applies to both CEA-608 and CEA-708 caption configurations. If true, all onTextData events are logged.
closedCaptionLiveRemoveExistingCEACaptions Boolean Works with the ModuleOnTextDataToCEA module to remove existing embedded CEA-608/708 captions before generating new captions from onTextData events. This prevents captions from being duplicated in the player's output. The default value (true) removes the embedded captions. To preserve embedded captions, set to false.
  1. After adding all properties, restart your application.
  2. To configure the player for CEA-608 output, create a myStream_ontextdata_608.smil file:
<smil>
  <head>
  </head>
    <body>
      <switch>
	<video src="mp4:myStream" system-bitrate="450000">
	  <param name="cupertinoTag.CLOSED-CAPTIONS" value="captions" valuetype="data"/>
	</video>
	<textstream src="mp4:myStream" system-language="eng">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="CC1" valuetype="data"/>
	</textstream>
      </switch>
    </body>
</smil>
  1. Add the myStream_ontextdata_608.smil file to the [install-dir]/content folder for your Wowza Streaming Engine installation.
  2. Start a stream and send it to your Wowza Streaming Engine Server. If you need to inject onTextData events into your stream, see our example module. For more about publishing live streams, see Connect a live source to Wowza Streaming Engine.
  3. To test playback for CEA-608 captions, use Wowza Test Player and add this playback URL:

http://[ip-address]:1935/[application-name]/myStream_ontextdata_608.smil/playlist.m3u8

Configure onTextData captions for CEA-708 output in HLS live streams

With Wowza Streaming Engine, you can ingest a live stream with embedded onTextData events and output CEA-708 captions in your HLS live streams. The inbound live stream must contain proper Action Message Format (AMF) onTextData events for specified languages.

If you need to inject onTextData events into your live streams, check this example module, which only supports sending onTextData events for a single language. The SMIL file in this section defines three different language tracks in the player. When using multiple languages in your onTextData workflows, modify our example module and add several ontextdata.txt files to match your output in the [install-dir]/content folder. For example, to accommodate the SMIL file, add ontextdata_eng.txt, ontextdata_fra.txt, and ontextdata_spa.txt.

Note: Access to the Properties tab is limited to administrators with advanced permissions. For more information, see Manage credentials.
  1. In Wowza Streaming Engine Manager, click the Applications tab.
  2. Select your live application from the list.
  3. On the Setup tab, make sure Apple HLS is selected from the Playback Types.
  4. Click Edit on the Setup tab.
  5. Scroll to the Closed Captions section.
  6. Select the Ingest onTextData events in live streams radio button.
  7. Enable the ModuleOnTextDataToCEA module by selecting the Output to CEA-708 checkbox.
  8. Click Save and restart the application.
  9. This step is required for multiple languages or if the default language is not English. On the Properties tab for your application, go to the Closed Captions properties section. Click Edit, and add this closed captioning property and suggested value. Then Save.
Name Type Value Description
closedCaptionLive708LanguageMapping String 1:eng,2:spa,3:fra Creates comma-separated mapping for CEA-708 service numbers to convert them to three-character ISO-639 language codes during live stream ingest. For example, to accommodate the SMIL file in step 12, add 1:eng, 2:spa, 3:fra. Default value is 1:eng.
  1. (Optional) On the Properties tab for your application, go to the Closed Captions properties section. Click Edit, and add these closed captioning properties when applicable. Then Save.
Name Type Description
closedCaptionLive708AnchorPoint String Defines an anchor point for the initial position of the CEA-708 caption window. Valid values are top_left, top_center, top_right, middle_left, middle_center, middle_right, bottom_left, bottom_center, and bottom_right. Default value is bottom_center.
closedCaptionLive708CaptionType String Specifies POP_ON, ROLL_UP, or PAINT_ON caption types for the CEA-708 captions in the live stream output. Currently, only POP_ON is supported, and it serves as the default value.
closedCaptionLive708DebugLog Boolean Enables extra debug logging for CEA-708 captions during live stream output. Default value is false.
closedCaptionLive708HorizontalPosition Integer Adjusts the CEA-708 caption window horizontally from the initial anchor point for display during live stream output. Relative percentage or absolute pixel values may be used. The absolute range depends on the aspect ratio and is 0-209 for 16:9 or 0-159 for 4:3. Default value is 50.
closedCaptionLive708PenStyle Integer Corresponds to a predefined pen style ID from the ANSI/CTA-708-E standard. During live stream output for CEA-708 captions, determines pen size, default font, offset, edge type, foreground characteristics, etc. Valid values are 1 through 7. For more, Pen style ID properties. Default value is 1.
closedCaptionLive708PositionRelative Boolean Specifies if the CEA-708 caption positions for the live stream output are relative or absolute.
closedCaptionLive708VerticalPosition Integer Adjusts the CEA-708 caption window vertically from the initial anchor point for display during live stream output. Relative percentage or absolute pixel values may be used. The absolute range is 0-74 for all aspect ratios. Default value is 100.
closedCaptionLive708WindowStyle Integer Corresponds to a predefined window style ID from the ANSI/CTA-708-E standard. During live stream output for CEA-708 captions, determines window justification, print direction, scroll direction, word-wrap behavior, etc. Valid values are 1 through 7. For more, see Window style ID properties. Default value is 1.
closedCaptionLiveMaxDisplayTime Integer Maximum time, in milliseconds, that a CEA-608/708 closed caption is displayed on the screen. The default value is 10000 milliseconds.
  1. (Optional) On the Properties tab for your application, go to the Custom properties section. Click Edit, and add these custom properties when applicable. Set the path for each property to /Root/Application/TimedText. Then Save.
Name Type Value
closedCaptionLiveEnableTranscoderResults Boolean Controls whether CEA-608/708 captions are passed through the Transcoder. If true, all CEA-608/708 captions are passed through.
closedCaptionLiveLogOnTextDataEvents Boolean Controls logging of individual onTextData events. Applies to both CEA-608 and CEA-708 caption configurations. If true, all onTextData events are logged.
closedCaptionLiveRemoveExistingCEACaptions Boolean Works with the ModuleOnTextDataToCEA module to remove existing embedded CEA-608/708 captions before generating new captions from onTextData events. This prevents captions from being duplicated in the player's output. The default value (true) removes the embedded captions. To preserve embedded captions, set to false.
  1. After adding all properties, restart your application.
  2. To configure the player for CEA-708 output, create a myStream_708.smil file:
<smil>
  <head>
  </head>
    <body>
      <switch>
	<video src="mp4:myStream" system-bitrate="450000">
	  <param name="cupertinoTag.CLOSED-CAPTIONS" value="captions" valuetype="data"/>
	</video>
	<textstream src="mp4:myStream" system-language="eng">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="SERVICE1" valuetype="data"/>
	</textstream>
        <textstream src="mp4:myStream" system-language="spa">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="SERVICE2" valuetype="data"/>
	</textstream>
	<textstream src="mp4:myStream" system-language="fra">
	  <param name="iswowzacaptionstream" value="true" valuetype="data"/>
	  <param name="cupertinoTag.TYPE" value="CLOSED-CAPTIONS" valuetype="data"/>
	  <param name="cupertinoTag.GROUP-ID" value="captions" valuetype="data"/>
	  <param name="cupertinoTag.DEFAULT" value="YES" valuetype="data"/>
	  <param name="cupertinoTag.FORCED" value="NO" valuetype="data"/>
	  <param name="cupertinoTag.INSTREAM-ID" value="SERVICE3" valuetype="data"/>
	</textstream>
      </switch>
    </body>
</smil>
  1. Add the myStream_708.smil file to the [install-dir]/content folder for your Wowza Streaming Engine installation.
  2. Start a stream and send it to your Wowza Streaming Engine Server. If you need to inject onTextData events into your stream, see our example module. For more about publishing live streams, see Connect a live source to Wowza Streaming Engine.
  3. To test playback for CEA-708 captions, use this test player and add this playback URL:

http://[ip-address]:1935/[application-name]/myStream_708.smil/playlist.m3u8

Note: Wowza Flowplayer doesn't currently support output for embedded CEA-708 captions in live streams.

Pen style ID properties

The following table displays pen style ID properties described by the ANSI/CTA-708-E standard (Table 27). You can use these values for the closedCaptionLive708PenStyle closed captioning property when ingesting onTextData events and converting them to CEA-708 captions.

Window style ID properties

The following table displays window style ID properties described by the ANSI/CTA-708-E standard (Table 26). You can use these values for the closedCaptionLive708WindowStyle closed captioning property when ingesting onTextData events and converting them to CEA-708 captions.

Configure onTextData captions for WebVTT output in HLS live streams

With Wowza Streaming Engine, you can ingest a live stream with embedded onTextData events and output WebVTT captions in your HLS live streams. The inbound live stream must contain proper Action Message Format (AMF) onTextData events for specified languages.

If you need to inject onTextData events into your live streams, check this example module, which only supports sending onTextData events for a single language. When using multiple languages in your onTextData workflows, modify our example module and add several ontextdata.txt files to match your output in the [install-dir]/content folder. For example, to accommodate the SMIL file, add ontextdata_eng.txt, ontextdata_fra.txt, and ontextdata_spa.txt.

For more information about using a SMIL file with this workflow, see Override live caption ingest behavior using a SMIL file.

Note: Access to the Properties tab is limited to administrators with advanced permissions. For more information, see Manage credentials.
  1. In Wowza Streaming Engine Manager, click the Applications tab.
  2. Select your live application from the list.
  3. On the Setup tab, make sure Apple HLS is selected from the Playback Types.
  4. Click Edit on the Setup tab.
  5. Scroll to the Closed Captions section.
  6. Select the None checkbox.
  7. Click Save and restart the application.
  8. Go to the Properties tab for your application.
  9. Click Closed Captions in the Quick Links section.
  10. In the Closed Captions properties section, click Edit.
  11. Enable the properties in the following table and set their values as suggested based on your use case.
Name Type Value Description
captionLiveIngestLanguages String eng,spa,fra Specifies, in ISO-639, what subtitle languages are expected to be delivered. For example, eng, spa, fra. If not specified, the language is based on the Wowza Streaming Engine server locale. This property is optional when using a SMIL file with textstream tags.
cupertinoLiveCaptionsUseWebVTT Boolean true Specifies if live AMF onTextData events are converted to WebVTT subtitle format. If enabled (true), WebVTT subtitles are created. If disabled (false), CEA-608 captions are created.
  1. Click Save
     and restart the application.
  2. Start a stream and send it to your Wowza Streaming Engine Server. If you need to inject onTextData events into your stream, see our example module. For more about publishing live streams, see Connect a live source to Wowza Streaming Engine.
  3. To test playback for CEA-708 captions, use Wowza Test Player and add this playback URL:

http://[ip-address]:1935/[application-name]/myStream/playlist.m3u8

Note: You can confirm the presence of the generated WebVTT sidecar files in your browser's Network panel.

Ingest and configure AMF onCaption captions for live streams

This section describes setting up your live application to ingest AMF onCaption captions. Wowza Streaming Engine supports two kinds of AMF onCaption events. The first contains:

  • An onCaptionInfo event that defines the speakers and tracks caption information. This information may contain an array of speakers and an array of tracks.
  • onCaption events that have the actual captions. This includes an array of captions and an optional speaker index, which refers to the onCaptionInfo speaker array.

The second contains an onCaptionInfo event with a 708 caption type. This caption type contains Base64-encoded CEA-608 or CEA-708 caption data. Wowza Streaming Engine ingests only the CEA-608 caption data (in paint-on, roll-up, or pop-on styles).

  1. In Wowza Streaming Engine Manager, click the Applications tab.
  2. Select your live application from the list.
  3. Go to the Setup tab for your live application.
  4. On the application Setup page, click Edit.
  5. Scroll down to the Closed Captions section.
  6. Select onCaptionInfo events in live streams.
  7. Click Save.
  8. Restart the application.

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