how does video player calculate single frame duration?

问题

I am working on a project where I am muxing h264 raw stream into fmp4 so I can play it through MSE (Media source extension)

I am bit confused about frame duration. For example,

If I provide 30 frames and timescale is 1000, it plays for 1 second.

If I change timescale to 800, it plays for 2 seconds for the same 30 frames

If I change timescale to 500, it plays for 3 seconds for the same 30 frames

My question, how does the player calculate a single frame duration from timescale?

来源：https://stackoverflow.com/questions/45402476/how-does-video-player-calculate-single-frame-duration