[EME] Specification Question, do we really need canPlayType("codecs","Key System")?

Does the UA decide Key System based on initialization data of media content?

If the needKey event have not reported Key System to app, it means UA cannot recognize the initData's encrypted mechanism, this may mean that the UA does not support this Key System.

When we touch the UA with canPlayType("codecs" , "key system"), I think we are just trying to find what key systems are supported for certain media formats or containers, but if the UA does not recognize the content's key system, how can it support the key system we embedded in canPlayType.

If we choose a different key system to test the UA, and the UA support, does it mean we need to abort the media resource fetch algorithm and change to a different content format encrypted by supported key system?

So I doubt the real sense of canPlayType extension for key system detection, why not let needKey event report the codesc+key system pairs list to app when the UA cannot recognize the key system from the initialization data? Even if we report this information, the app will change to anther encrypted media source supported by the UA?



Yang
Huawei