Recording/playback of gameplay sessions

[NovaSquirrel]

Record keypresses and let you watch gameplay again. Maybe offer to save a recording after a battle with someone.

[pinobatch]

This will absolutely be needed for online multiplayer, as each player's view of the other players' playfields is essentially a movie.

[NovaSquirrel]

I was thinking that a player would send updates to the playfield to the other player, since sending keys sounds like too big an opportunity to desync. Would take up a lot less bandwidth if I can just send keys though.

[pinobatch]

I fear that sending playfield updates could make cheating too easy. That's why I decided to tie it to this bug.

FCEUX movies are a saved state followed by a stream of keypresses. Thus desync shouldn't happen so long as

• The player and recorder use the same game physics. This means in multiplayer, all players are running the same version of the client.
• Game physics use data types whose behavior is well defined by applicable C or C++ standards, of which unsigned integers are most tightly defined and leave the least up to implementation.
• Keys are sent and received timely, in order, and without error.

If you can get movies to stay synced, multiplayer should also.