VideoLab

VideoLab turns a phone into a physics measurement instrument. Film a pendulum, a falling ball or a spring in 240 fps slow motion with a plain A4 sheet on the wall, and VideoLab returns real physical constants (g, period, spring constant k) with honest error bars. SAM 3.1 tracks the object through every frame from a single tap. The A4 sheet gives a homography that turns pixels into metres and corrects camera tilt. Deterministic physics fits (damped amplitude-corrected pendulum, free-fall parabola with automatic release/impact, damped spring oscillation) produce the numbers, never the LLM. A Muse Spark agent with five tools plans the setup, runs quality checks and explains the result in a predict → observe → explain loop. Every number it writes is grounded in tool output and is a clickable chip that jumps the video to the frames behind it. Problem: millions of students learn physics without a lab. Accuracy: 20 benchmark runs with exact ground truth (tilted/far camera, dim light, noise, motion blur) all land within 2σ. Spring k within 0.03%, pendulum g within 0.02% with the string length entered, free-fall g within 1.3%. Live: https://balmca28--videolab-web.us-east.modal.run Accuracy report: https://github.com/Balu-SG/videolab/blob/main/docs/ACCURACY.md