transcribe-video

Transcribe Video

Transcribes any video/audio file locally using a bundled whisper.cpp service. No external project or cloud API. Returns word-level timestamps (needed for synced overlays/captions).

When to use

• "Transcribe this clip / video / audio", "get me a transcript with timestamps".
• As a sub-step of /produce-video.

How it runs

Everything is driven by the bundled runner — never ask the user to manage Docker:

node scripts/transcribe.mjs <path-to-video-or-audio> [--out <dir>] [--port 9111] [--language en] [--no-word-ts] [--task transcribe|translate]
node scripts/transcribe.mjs --stop      # stop the warm container

The runner:

1. Checks the Docker daemon is reachable (fails loud with guidance if not).
2. Builds the transcribe-video-whisper image from assets/whisper-service/ if it is missing (first build is slow: it compiles whisper.cpp and bakes the ggml-base.en.bin model).
3. Starts the transcribe-video-whisper container (host port 9111 → container 9001); reuses it if already running, docker starts it if stopped.
4. Waits for GET /healthz to report ok.
5. Extracts a 16 kHz mono WAV from the input with local ffmpeg (whisper.cpp only decodes WAV), then POSTs it to /transcribe with word_ts=true.
6. Writes transcript.txt, transcript.srt, transcript.words.json to --out (default: the input file's directory), and prints a JSON result line to stdout.

Outputs

• transcript.txt — plain text.
• transcript.srt — subtitle text.
• transcript.words.json — [{ "word", "start", "end" }], seconds, time-ordered. This is the sync source for overlays/captions.

stdout result line (for programmatic callers like /produce-video):

{ "ok": true, "outDir": "...", "wordCount": 38, "segmentCount": 2, "files": { "txt": "transcript.txt", "srt": "transcript.srt", "words": "transcript.words.json" } }

Requirements

• Docker is REQUIRED — the Whisper service runs in a container, so Docker Desktop must be installed AND running. The runner checks this first and fails loud with install/start guidance if Docker is missing or its daemon is down; there is no non-Docker fallback.
• ffmpeg is REQUIRED (used to extract a 16 kHz mono WAV for Whisper) — the runner checks for it up front and fails loud if it is not on PATH.
• Node ≥ 22.

Notes

• The container is left running (--restart unless-stopped) for warm reuse; stop with --stop.
• If word timestamps are requested but none come back, the runner fails loud (overlay sync depends on them).
• See references/ for the Docker lifecycle, the API shape, and the vendoring provenance.