i thought the agent can execute real ffmpeg to compare
It's certainly possible to reverse-engineer it from a blackbox access, but it would take *years* and this test has a time limit.
I’m not sure this benchmark is even very interesting because it requires a language model do something that it really cannot do. Maybe it would be possible with a novel harness in an ensemble system, but I would never expect a pure language model that is run in a minimal harness to ever be able to do this.