DASH: Support cross-AdaptationSet seamless switching

[kqyang]

http://dashif.org/wp-content/uploads/2016/12/DASH-IF-IOP-v4.0-clean.pdf

3.8. Switching across Adaptation Sets
 ...
 A content author may signal such seamless switching property across Adaptation Sets by providing
 a Supplemental Descriptor along with an Adaptation Set with @schemeIdUri set to
 urn:mpeg:dash:adaptation-set-switching:2016 and the @value is a comma-
 separated list of Adaptation Set IDs that may be seamlessly switched to from this Adaptation Set.
 ...
 As an example, a content author may signal that seamless switching across an H.264/AVC Adap-
 tation Set with AdaptationSet@id=”h264” and an HEVC Adaptation Set with Adapta-
 tionSet@id=”h265” is possible by adding a Supplemental Descriptor to the H.264/AVC Ad-
 aptation Set with @schemeIdUri set to urn:mpeg:dash:adaptation-set-switch-
 ing:2016 and the @value=”h265” and by adding a Supplemental Descriptor to the HEVC
 Adaptation Set with @schemeIdUri set to urn:mpeg:dash:adaptation-set-switching:2016
 and the @value=”h264”

This technology is expected to be available in ISO/IEC 23009-1:2014/Amd.4:2016, section 5.3.3.5.

Here is a sample content you can use for testing:

 "uri": "https://storage.googleapis.com/wvtemp/kylealexander/packager_test/iop_compliant_mpd_test/llama.mpd",
 "drm_scheme": "widevine",
 "drm_license_url": "https://proxy.uat.widevine.com/proxy?provider=widevine_test"

[ojw28]

Sanity check: Am I right in thinking the DASH IOP example is actually in violation of the DASH spec, because it uses string AdaptationSet@id values where-as the DASH spec says the type should be xs:unsignedInt? The example should use integers, I think?

[kqyang]

Good catch. I filed a bug to DASH-IF-IOP: Dash-Industry-Forum/DASH-IF-IOP#136.

Not sure why DASH uses xs:unsignedInt for AdaptationSet but uses StringNoWhitespaceType for Representation.

Anyway, the sample content referenced in the issue description should be compliant to both DASH spec and DASH-IF-IOP.

[ojw28]

Heh, I filed one through the form on the DASH-IF website. I had no idea it got mirrored to GitHub. I'll file any future issues on that tracker directly! Thanks for confirming.

[ojw28]

This is now supported in dev-v2.