I was wondering about this, not for SMB but Friday the 13th on NES. I'm only making a post here because I take it SMB frame counting is very precise and done a specific way, like many NES games with very optimized speedruns.

Most people seem to swear by avidemux/virtual dub, it seems both give me the same results overall.

Then some people swear by the somewes site, this seems to give different results than the above two and a different calculated frame -> time result than zapstudio would, so it seemed inaccurate.

Somewes.com / creep.io/smb1/bowserframes/ are definitely the best websites to retime runs without a doubt. An experienced mod can tell by the video by Mario's position how many frames someone lost on axe, then it's just looking what pattern the person got and boom. Everyone can retime like that.

Just check about what time you got in the video(if you have one). Just manually retime your run, then check all frames in about a .4 second range to see what time you got.

If you don’t have a video, just know what your tendency is regarding starting the timer too early or too late, and the same for stopping the timer, and do the same thing as if you had a video.

The context is another game btw, if anyone missed that. It sounds like somewes might be better for mario? I just found it wasn't consistent for some other games.

It also seems like downloading twitch vods for avidemux or vdub doesn't really work, most of the files seem to get corrupted even though they play fine in any video player

I think I found my answer, Yua doesn't corrupt the twitch vods. But maybe that will never be as accurate as frame counting the raw recording

So, a lot of games are frame counted using the video, but we use the framerate of the console itself which is different and gives you different values.

Each frame of a 60 FPS video recording is 0.0166666666666667 seconds Each frame of the game/console (60.0988139 FPS) is 0.0166392634913549 seconds

This is why retiming your local recording vs. somewes.com gives you different values.

Since the framerate of the console is faster than what your local recording is, there will be missed frames in the video and it becomes a problem if the skipped frame in the video happens when you touch the 8-4 axe.