You know what? I think I can figure out a way to estimate final file size and display it to the user. It’ll only work if “Precision Mode” is off though - that uses “CRF” or “Constant Rate Factor” which basically tells the encoder “be efficient, but make the file as big as it needs to be to look good”. As a result there’s no way to tell how big the file will end up being - the encoder makes the decision on the fly.

With “Precision Mode” off, HISTV has two gears:

1. If your file is already small enough (at or below the target bitrate), it uses “CQP” or “Constant Quantisation Parameter” (the QP I/P numbers), which tells the encoder “Use this quality level for every frame, I don’t care how big the file ends up”. It’s fast and consistent - every frame gets the same treatment.
2. If your file is too big, it switches to VBR (Variable Bit Rate), which tells the encoder “Stay around this target bitrate, spike up to the peak ceiling on complex scenes, but don’t go over”. It’s how the app actually shrinks files. You can estimate the output size with target mbps * seconds / 8 - so a 60-second clip at 4Mbps lands around 30MB. <- This is the maths I’m thinking about doing to display the estimate to the user.