First up is this tweet by Kevin Franklin of 343.

https://twitter.com/kevin_franklin/status/532032058579636224

Next comes a post by Josh Holmes on the Team Beyond forums, giving us more info about Spectating in Halo 5 Guardians: 

“You can spectate your friends in matchmaking or customs, in Arena or Warzone. It’s a live Theater save film that streams directly from the server, with all of the Theater controls & camera options (1st person, 3rd person, Free cam). You can rewind, fast forward, adjust playback speed, etc. Player outlines can be toggled on or off (as they can in Theater now).

There is theoretically no limit to the number of clients that can spectate on any given session, so long as you are friends with one of the players. The is a delay of 15-30 seconds from the live gameplay because the server is writing out the save film as it simulates the session, streaming it out to attached clients which are then replaying the film from there. This delay is configurable to make it longer, but we figure that 15-30 seconds is sufficient to address concerns RE: cheating.

We’ll keep augmenting spectator mode over time based on feedback from casters & TOs. Just getting it to work as a streamed save film in the cloud without any impact to server perf was a big engineering effort.”

This really is great news for those who have wanted spectator mode. I can see jumping in on this during a friend’s game to watch them play, while waiting for them to finish that game, so you can join in with them after. Certainly, if you’re able to check out pro player’s games, you might be able to learn a lot from them with their gameplay.

-Sal