How to cut dev videos with Claude Code and FFmpeg

Reddit author ustype was making short videos about developer tools and found editing much slower than recording. They built a workflow using local whisper.cpp transcription, Claude Code to select cuts from the transcript, and FFmpeg to render the result. The author reports that a first raw take of 118 seconds became a 59.5-second cut.

The difficult part was trusting the render. Their post describes phone footage whose reported dimensions differed from its decoded display dimensions because of rotation metadata. It also describes speed-change mistakes caused by the placement of FFmpeg timing arguments, audible pops at cut boundaries and judder from mismatched overlay frame rates. These are the author's findings from the workflow, not errors independently reproduced for this entry.

The author says they now extract frames at every cut and measure audio levels before trusting a render. They also collected the lessons in a HARD-RULES.md file in an open-source repository. The post does not provide a measured end-to-end editing-time saving or claim that Claude Code independently found every rendering problem.

Who it's for: developers editing spoken tool demonstrations who want AI-assisted cut selection while keeping explicit audiovisual checks. The concrete result is a completed shorter video and a working editing workflow with reported failure checks, rather than a guarantee that a successful FFmpeg exit means the output is correct.

Prompt
Suggested prompt (written by Agents In Use, not the author's)

Source: Reddit · u/ustype