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Is it possible to pass additional VTT information when using onTextData to WebVTT with live streams?


I am writing a module to inject onTextData events into a live stream that is then converted to WebVTT compatible closed captions using the instructions located here:

However, the VTT file has some additional formatting information contain on the same line as the time range. Here is an example of a single entry:

00:01:00.060 --> 00:01:23.016 align:start line:85% position:12% size:16%

Hello World

I am able to successfully pass the captions using the AMFDataObject and the onTextData event but cannot find a way to pass the additional formatting information. It appears Wowza writes the time range itself and I cannot modify or override it.

Here is the code being used to send the onTextData event:

public void sendTextDataMessage(String message) { 

	try {
		AMFDataObj amfData = new AMFDataObj();
		amfData.put("text", new AMFDataItem(message));
		amfData.put("language", new AMFDataItem(languageID));
		iStream.sendDirect("onTextData", amfData);
	} catch(Exception e) {

Is there any way to pass the formatting (or any other additional information defined in the VTT spec) to Wowza so it will display properly? Are there any other values used to configure the AMFDataObj for VTT captioning besides “text” and “language”?

Can anyone answer this question? I’m having trouble finding any answers to this, and it can be pretty important to control caption positions.