software-video

name	software-video
description	Produce software videos end to end - product demos, feature launches, explainers, walkthroughs, tutorials, release notes, onboarding and social cuts - from a script, an AI voiceover, animated HTML slides and real screen recordings, rendered deterministically to MP4 with ffmpeg. Use when asked to create, edit, re-cut, re-voice, shorten or re-brand any video about software.

Software video

Build videos about software as code: an HTML deck driven by a deterministic timeline, an AI voiceover, real screen recordings of the product, and an ffmpeg audio master. Everything is reproducible, diffable and re-renderable, so revisions cost minutes instead of a rebuild.

This is not a video editor. It is a pipeline. The output is an MP4.

The one idea that matters

Audio first, then timing, then picture.

Generate the narration before deciding how long anything is on screen. Measure each clip, derive scene durations from those measurements, and only then render frames. The alternatives - guessing durations, or writing narration to fit a fixed storyboard - produce visuals that drift out of sync with the voice and force a re-render every time a line is reworded.

script.json ──► TTS ──► measure ──► timings.json ──► render ──► composite ──► mux ──► MP4
                              ▲                          ▲            ▲
                        assemble.py                 render.py    composite.py

For a video with no narration (a title sting, a silent loop, a muted social clip), skip stage 1 and write timings.json by hand. Everything downstream is unchanged.

Pipeline

Stage	Script	Produces
1. Narration	your TTS tool of choice	audio/vo_NN.mp3, one per scene
2. Timing + voice track	scripts/assemble.py	timings.json, out/voice.wav
3. Picture	scripts/render.py	out/silent.mp4
4. Screen footage (optional)	scripts/capture/tour.py	capture/clips/*.mp4
5. Compositing (optional)	scripts/composite.py	out/composited.mp4
6. Audio master	scripts/mux.py	final MP4

Read references/PIPELINE.md for the walkthrough, references/AUDIO.md for voice and music, references/SCREEN-CAPTURE.md for product footage, and references/PITFALLS.md before debugging anything - it lists the failures this pipeline has actually hit.

Kinds of video

Same pipeline throughout; what changes is structure, pacing and how much of the frame is real product. Establish which of these you are making before writing a line, because it decides everything else.

Kind	Typical length	Shape	Footage
Product explainer	1-3 min	problem → turn → how it works → proof → close	a little, as proof
Feature launch	30-90s	what changed → why it matters → see it → how to get it	medium
Demo / walkthrough	2-5 min	one real task, start to finish	dominant
Tutorial	3-10 min	step by step, chaptered, pauses to follow along	dominant
Release notes	30-90s	one item per beat, dense	screenshots or short clips
Onboarding	1-3 min	the first-run path, as the user meets it	dominant
Title sting / loop	5-20s	one idea, often silent	none
Social cut	under 60s	hook first, derived from a longer cut	short, punchy

Rules of thumb that follow from the type:

• Demos and tutorials are footage-first. The deck is chrome around the product - title cards, callouts, chapter breaks. Do not narrate what the screen already says.
• Explainers and launches are narration-first. Footage appears as evidence for a claim you just made; that adjacency is what makes it land.
• Tutorials need air. Leave a beat after each step. Use --tail generously; a viewer is following along, not watching.
• Release notes are dense. On-screen text carries, narration summarises. One item per beat, no lingering.
• Social cuts are derived, never written twice. Build them as a scene subset of the long cut so they cannot drift (see PIPELINE.md).

Quick start

Setup, once: pip install -r requirements.txt && playwright install chromium. ffmpeg and ffprobe must also be on PATH.

Silent first, to check the deck renders at all:

cp templates/deck.html .
python3 scripts/render.py --preview 2 8 18   # stills
python3 scripts/render.py                    # -> out/silent.mp4

Then the full pipeline once narration exists:

cp templates/script.example.json script.json
# generate audio/vo_01.mp3 ... one per scene, then:
python3 scripts/assemble.py                    # timings.json + out/voice.wav
python3 scripts/render.py                      # out/silent.mp4
python3 scripts/mux.py --final out/final.mp4   # add voice (+ music if audio/bed.mp3 exists)

assemble.py is the only stage that needs audio; without it render.py uses the durations declared in the deck.

Rules that keep this working

Never drive the timeline from wall-clock time. The renderer seeks to an explicit t and screenshots. render.py calls window.__seek(t) for each frame, so a slow machine produces an identical file to a fast one. Anything using requestAnimationFrame or CSS animation playback will tear or drop frames under a screenshot loop.

Pin every animation to a narration beat. If the voice says "three things" at 4.2s, the third card appears at 4.2s. After any rewrite, re-check the beats - a line that comes back 3s shorter will strand its visuals. This is the single biggest driver of whether the result looks directed or generic.

Render in resumable chunks. render.py writes out/parts/part_NNN.mp4 and skips completed parts on re-run. A stalled screenshot costs one chunk, not the whole pass. Never run two renders against the same parts directory.

Measure, don't assume. Verify with numbers, not vibes:

• blank-frame detection: count dark pixels ((pixels < 200).mean()), not standard deviation - a legitimately white-heavy UI page has low deviation too
• pronunciation: run the generated audio back through speech-to-text and read it
• levels: ffmpeg -af volumedetect on the final file, every time
• geometry: read getBoundingClientRect() out of the DOM rather than hardcoding

One source, many cuts. Select scene subsets from a single deck with a query parameter (deck.html?cut=short) so a long demo and a 40-second social cut cannot drift apart. See references/PIPELINE.md.

Design guidance

The deck is HTML/CSS, so the design is entirely yours. Two things are worth knowing:

Social and autoplay contexts run muted. The on-screen headline must carry each beat on its own, and the hook has to land in the first second or two. Treat the voiceover as enhancement, not as the delivery mechanism.

If asked for something visually distinctive, ground it in the subject's own world - its artifacts, instruments and vernacular - rather than reaching for a dark background with one bright accent colour, which is where generic output clusters. Anthropic's frontend-design skill covers this well and composes cleanly with this one.