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Crash / Critical

Error 17::17 — "zero denominator in ratio multiply"

The error

"After Effects error: zero denominator in ratio multiply ( 17 :: 17 )" — usually during preview/render, sometimes looping into an unrecoverable error storm.

Why this happens

AE’s timeline engine works in exact rational fractions (not floats) for sub-frame accuracy. Variable-frame-rate (VFR) footage — common from phones or OBS screen captures — produces frame durations that don’t reduce to a valid fraction, especially combined with Luma Matte blending, producing a mathematically impossible (zero-denominator) ratio.

How to fix it

1. Open Interpret Footage on the offending clip and enable "Preserve RGB" — this bypasses the dynamic color-conversion path that triggers the crash.
2. Transcode the source to a constant frame rate (CFR) — e.g. ProRes or an image sequence — before importing.
3. For 3D comps, switch the renderer from Cinema 4D to Classic 3D.

Source: Error Database + Diagnostic Report · Adobe Community / Reddit threads · error 17::17

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