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Reference

Render and export

How the deterministic render engine compiles, renders, and automatically validates every export before it reaches you.

Rendering in FramePilot is deliberately separate from the AI and from the editor preview. The AI proposes structured operations; a deterministic Python engine (MoviePy + FFmpeg) executes them the same way every time and validates the result. This page covers how a render runs, the export presets, and what to do when a render fails.

Preview vs. render

These are two different systems, on purpose.

  • Preview uses HTML video, canvas overlays, and proxy/low-res media in the editor. It is built for instant scrubbing and immediate feedback while you work.
  • Render is the deterministic export pipeline. MoviePy composes the edit in Python and FFmpeg handles encoding. It is not the realtime preview engine — it runs when you export.

Keeping them separate is why preview stays responsive while final output stays deterministic and reproducible.

How a render runs

When you export, the timeline compiles to a render plan and the engine executes it through a defined lifecycle:

queued
preparing_assets
rendering_frames
encoding
validating_output
completed

The important stage is validating_output: every export is checked automatically before you get the file, so a broken render never silently reaches your audience.

Automatic render validation

After rendering, the engine validates the output against the timeline it was asked to produce:

  • the file exists and is not zero bytes,
  • the duration matches the expected timeline duration,
  • a video stream exists,
  • an audio stream exists when one is expected,
  • there are no unexpected black frames,
  • audio is not clipping.

If any check fails, the render is reported as failed rather than handed to you as a bad file. This is the render-side half of the same reliability loop the AI uses — see the AI agent for the patch → validate → preview → validate-render flow.

Export presets

FramePilot targets platform-ready outputs directly. Common presets:

Preset Aspect ratio Typical use
Reels 9:16 Instagram Reels, TikTok, Shorts
Square 1:1 Feed posts
Wide 16:9 YouTube, landscape embeds
Custom your choice Any dimensions and settings you set

For turning a raw recording into a vertical short, see captions, silence, and shorts.

Where files land

FramePilot is local-first. Renders are written to your local project workspace alongside your project files and media — nothing is uploaded to render. The export dialog confirms the output location before the job runs.

When a render fails

A failed render usually means validation caught a mismatch between the intended timeline and the produced file. Approach it as a regression, not a mystery:

  1. Read the failure reason. The validation step reports which check failed (duration, missing stream, black frames, clipping).
  2. Check the timeline. Confirm the offending clip, gap, or audio level is what you expect in the editor.
  3. Re-preview the range the validator flagged to see the problem before re-exporting.
  4. Re-export once the underlying timeline issue is fixed.

Because the engine is deterministic, the same timeline produces the same output — so a fix that resolves the flagged range resolves the render.

Next steps