I posted about this on the google group, but didn't get a response, so I'm posting here for a larger audience.
So far, the design for fast-forward is to simply remove any delays between screen refreshes in the emulator. Although this works, on systems such as mine, my CPU can't handle rendering much faster than at 100% speed so fast-forward
doesn't have much of an effect. I think it would be nice for people with slower machines, if fast forward looked more like when you fast-forward when watching a DVD, i.e. instead of showing smooth motion very quickly, it skips through the frames at a certain rate.
Basically, in fast-forward mode, the core would still process all ROM instructions, but it would not issue requests to the rendering/audio plugins for every single frame. It would only call out to the plugins every nth frame (depending on the fast-forward speed). This would result in slower systems being able to support fast-forward since the system would not be processing the same amount of graphics/audio as it does during normal gameplay.
Before looking into if this is even possible, I want to get feedback on whether people would like this behavior or not. I think fast-forward is mainly used to skip through cut scenes in games, but are there other uses of fast-forward that wouldn't work well with the new fast-forward behavior?