#333 DASH: Wrong location of the ContentProtection element in the MPD.

[Vladimir Kazakov]

When creating CENC encrypted DASH media using MP4Box (using GPAC.Framework.Setup-0.5.1-DEV-rev5413-x64.exe; latest, at the moment), the resulting MPD has ContentProtection elements placed inside Representation elements. This is wrong, since according to the "DASH-AVC/264 Interoperability Points" document (http://dashif.org/white-papers/), ContentProtection elements must be in AdaptationSet elements.

So, when using dash.js, if ContentProtection elements are in Representation elements, the playback doesn't work. Manually moving ContentProtection elements to AdaptationSet elements solves the issue, and the playback starts to work as expected.

[Cyril Concolato]

Hi Vladimir,

According to the latest DASH spec (ISO/IEC 23009-1:2013), ContentProtection is allowed in AdaptationSet, Representation and SubRepresentation. The content generated by MP4Box ar DASH-conformant. You can try it with the DASH Validator and let us know if this is not the case. Now, we'll look into the restrictions imposed by the DASH-if and see what we can do about it. You might want to ask dash.js about being more tolerant here.

[Romain Bouqueau]

@Vladimir, thanks for reporting.
@Cyril Since we have the '-profile dashavc264' supported in GPAC, I think we should restrict it in this case.
I'll have a look later and let you know here.

[Greg Rutz]

I have attached a proposed fix for this. It relies on the existing "first_in_set" parameter passed to the dasher_segment_file() media-specific function. This seems to be the existing way that MPD elements are inserted at the AdaptationSet level even though they require media-specific information.

I'd be happy to make additional modifications to the patch to conform to the GPAC maintainers suggestions.

G

[Romain Bouqueau]

Thank you Greg. Patch applied as https://sourceforge.net/p/gpac/code/5469/