keepProtectionMediaKeys should not keep unsuccessful license requests

[squapp]

Environment

• The MPD passes the DASH-IF Conformance Tool on https://conformance.dashif.org/
• The stream has correct Access-Control-Allow-Origin headers (CORS)
• [] There are no network errors such as 404s in the browser console when trying to play the stream
• The issue observed is not mentioned on https://github.com/Dash-Industry-Forum/dash.js/wiki/FAQ
• The issue occurs in the latest reference client on http://reference.dashif.org/dash.js/ and not just on my page

• Link to playable MPD file: any DRM-protected stream
• Dash.js version: 4.7.1
• Browser name/version: any browser
• OS name/version: any OS

Steps to reproduce

Enable keepProtectionMediaKeys, then attachSource with wrong LA-URL (video does not play back), then attachSource with correct LA-URL (video still does not play back)

Observed behavior

It seems as if keepProtectionMediaKeys also "remembers" unsuccessful license requests (e.g. 404, 503) and does not trigger new license requests for the same KID. For unsuccessful license requests dash.js fires error code 114.

Expected behavior

Check for unsuccessful license requests (e.g. with HTTP response code 404 or 503) or watch for Dashjs error code 114. If this is the case, do not "keepProtectionMediaKeys"

[bbert]

If keepProtectionMediaKeys is enabled, then only "usable" sessions are retained.
I've done some tests on chrome and it seems there is an issue when closing a MediaKeySession that is not usable, the promise seems not to resolved. That explains why the session is not removed.

@dsilhavy I suggest not waiting for close()'s promise to be resolved/catched in ProtectionModel_21Jan2015.stop() and ProtectionModel_21Jan2015.reset().

BTW in ProtectionModel_21Jan2015.reset(), videoElement has previously been set to null, thus code is done() callback is not more useful. Don't remember if it has always beed tne case

[dsilhavy]

Addressed in #4239