akshayDev17/ai-explainer-video

craft-video-audio — TTS and the measured timeline

Part of the explainer-video-from-coursework pipeline — stage 4 of 8. This is the primitive: it builds audio once and stops. The scene stage re-invokes it when a beat needs a hold; this skill itself never loops.

The pipeline's tools and scene hosts live in the sibling explainer-video-from-coursework skill: run them as node ../explainer-video-from-coursework/tools/<tool>.mjs, resolved against this skill's folder. Run from the project, so out/ scratch lands beside your notes.

Prerequisites: out/<name>/scripts/<NN>-*.json from the script stage; on the machine, the Gemini key in the OS secret store (see SETUP.md).

A No API key found failure means the key isn't in the OS secret store — relay the matching SETUP.md step to the user and re-run.

node ../explainer-video-from-coursework/tools/build-audio.mjs --script out/<name>/scripts/<NN>-*.json \
                           --out out/<name>/<NN> --voice Aoede

Writes narration/<seg>.wav, narration.wav, timeline.json, and timeline.js into the per-video work dir. This is the only network stage — it spends the Gemini TTS key.

Done when: the run exits 0 and prints one window per segment, ending in [out] …/timeline.json.

• Durations are measured, not estimated — each WAV is measured with ffprobe; the plan's Min was a guardrail, this is the real number later stages bind to.
• The cache is text-keyed — narration/<key>.src stores the exact spoken text, so a re-run after a wording tweak costs 0 calls. It does not cover --voice, style, or --model: change one and the old audio is silently reused. Pass --force to re-synthesize.

Maintenance

If you modify this file, or the user asks to change this stage, tell the user that the main explainer-video-from-coursework skill's "Stage 4 — /audio" section must be reconciled to match, and name that section in your reply.