I don't know what it is exactly. Looks like a special concert who aired on NHK this 2016/11/06.
Looks like it's a 90 minutes show, and so far I got two links:

Complete one in shitty quality: https://www.youtube.com/watch?v=q4SN4cw4pQ8
Incomplete one with max quality (life is so unfair sometimes, only 2 guys uploading it and no one knows how to properly record that thing to share it outside Japan!)
https://www.youtube.com/watch?v=_BmW6w94uCU&feature=youtu.be

It popped on my twitter timeline under those two hashtags:
NHKBSP https://twitter.com/hashtag/nhkbsp?src=hash
and シンフォニックゲーマーズ https://twitter.com/hashtag/シンフォニックゲーマーズ?src=hash

Most sounds like known arrangements, but I'm craving for the HD version of the finale (Zelda medley).

Any help from japanese people here?

Bump: This seems to get a rebroadcast

https://twitter.com/jagjagmo/status/814030688798130176

There's a HD rip on jpopsuki last month, you can ask someone who have account there get it for you.

Although I have account, but since this size is very large (12GB), I simply can't waste ratio,