feat: Preserve cdata on manifest parsing and expose on dash event messageData

[vodlogic]

In order to parse Content Programme Metadata as specified in DVB DASH spec in section 9.1.2, the XML parser and Dash Events need to support CDATA in the payload.

This PR preserves CDATA when the manifest is parsed and assigns the CDATA to the event.messageData if the attribute exists.

Would welcome feedback on whether preserving CDATA should be driven from a player settings configuration.

There doesn't seem to be any specific existing test coverage in these areas, but the whole suite continues to pass and I have tested access to the CDATA within a player event using scheme urn:dvb:iptv:cpm:2014.

As this is my first dash.js contribution, I've also uploaded a feedback agreement to the mailing list.

[dsilhavy]

@vodlogic Thanks for this, is there any teststream you used for testing?

[dsilhavy]

@vodlogic As you suggested please add a settings flag in order to enable/disable the keepCData attribute in DashParser

[vodlogic]

When testing config settings, it turns out that X2JS is ignoring the keepCData property as no matter whether I set the value to true, false or undefined, we always have the currentMpdEvent.__cdata property available containing the CData.

Looking at the current dash.js and latest versions of the X2JS code, I can see that keepCData is assigned to false if it is undefined:

dash.js/externals/xml2json.js

Line 68 in 7567702

if(config.keepCData === undefined) {

But then it gets assigned anyway if config.keepCData is false

dash.js/externals/xml2json.js

Line 325 in 7567702

if( result.__cnt == 1 && result.__cdata!=null && !config.keepCData ) {

As x2js is third party code that dash.js has forked some time ago I suggest that we keep the existing behaviour and just use currentMpdEvent.__cdata if it is available.

[dsilhavy]

Thanks for investigating this, sounds good to me