moviemin

Overview ¶

Command moviemin shrinks an .fm2 movie to the shortest version that still passes a given Go test, using that test as the pass/fail oracle.

A recorded movie carries a lot of slack: a human holds each button far longer than the ROM needs and pauses between presses, so a faithful recording is mostly wasted frames. moviemin removes that slack automatically.

It groups the movie into runs of identical input (a held button, an idle gap), then binary-searches each run's length down to the fewest frames for which the test still passes, adding a small margin back so the result is not balanced on a knife's edge. Because the oracle is a real `go test` run, moviemin needs no knowledge of how the test decides success (screen text, a $6000 result byte, a RAM location, anything): the test announces it by passing or failing, and the test reads the very movie file moviemin is rewriting.

Usage:

go run ./tools/moviemin -test <TestName> -movie <path.fm2> [-pkg ./test/] [-margin 2]

Example (run from the repo root):

go run ./tools/moviemin -test TestReadJoy_Buttons_MovieDriven \
    -movie test/test_buttons.fm2

moviemin overwrites -movie in place as it searches and leaves the minimized movie there on success; recover the original from git if you need it. It assumes monotonicity: if a run length passes, any longer length also passes. That holds for timing-gated input (hold until the press is detected, release past the debounce) but not for ROMs that require an exact frame count, which are not candidates for this tool.