cut-silences

# Cut Silences (Pipeline Agent 1) First step of the automated edit. Takes a raw recording + its word-level transcript and removes **only silence**: dead air before the first word and after the last word, plus inter-word pauses longer than a threshold (trimmed down to a natural breath, never a hard zero-gap). It leaves the speaker's words untouched — false starts, retakes, and stutters are the **cut-mistakes** agent's job (Agent 2). This agent is deterministic and transcript-driven, so its output (`*.silence-transcript.json`) feeds cleanly into the next agents and the beat-sync validator. ## When to use - "cut the silences", "trim the pauses", "remove dead air", "tighten the pacing" - As the first stage of the master edit workflow, right after transcription. ## Prerequisites A word-level transcript JSON. Either the ElevenLabs Scribe shape (`{ words: [{ text, start, end, type }], audio_duration_secs }`) or a generic `{ words: [{ text, start, end }] }`. Generate one with the workspace transcriber: ```bash node scripts/transcribe-elevenlabs.mjs path/to/raw.mp4 # -> path/to/raw.json ``` ## Usage ```bash # 1) Plan only — compute the cut, write EDL + re-timed transcript (no video touched) node .agents/skills/cut-silences/scripts/cut-silences.mjs <transcript.json> \ --out-dir video-projects/<slug>/assets # 2) With a video — also write the ffmpeg command (still does not render yet) node .agents/skills/cut-silences/scripts/cut-silences.mjs <transcript.json> \ --video video-projects/<slug>/assets/raw.mp4 --out-dir video-projects/<slug>/assets # 3) Render the cut video (local ffmpeg, re-encode, A/V kept in sync) # add --apply to actually run ffmpeg node .agents/skills/cut-silences/scripts/cut-silences.mjs <transcript.json> \ --video video-projects/<slug>/assets/raw.mp4 --apply \ --output video-projects/<slug>/assets/edited-silenced.mp4 ``` ### Options | Flag | Default | Meaning | | --- | --- | --- | | `--video <path>` | — | Source video; enables the ffmpeg command / render | | `--out-dir <dir>` | next to transcript | Where outputs are written | | `--output <path>` | `<video-stem>.silenced.mp4` | Cut-video path | | `--gap <s>` | `0.55` | Minimum pause treated as trimmable silence | | `--head-pad <s>` | `0.22` | Silence kept before the first word | | `--tail-pad <s>` | `0.34` | Silence kept after the last word | | `--apply` | off | Actually run ffmpeg to render the cut | ## How it decides (the silence rules) - Pauses below `--gap` (0.55s) are left alone — natural speech rhythm. - For a trimmed pause, a **natural breath is kept**, scaled by context: `0.24s` for long pauses (≥2s), `0.20s` after a sentence ender (`. ! ?`), `0.14s` otherwise. The kept breath is biased slightly toward the end of the previous phrase. - Head/tail dead air is trimmed to `--head-pad` / `--tail-pad`. - Delete ranges are merged; keep ranges are the complement. The cut is rendered with an ffmpeg `trim`/`atrim` + `concat` filtergraph (written to a `*.silence-filter.txt` script and passed via `-/filter_complex`), so video and audio stay in sync. ## Outputs (written to `--out-dir`) | File | Purpose | | --- | --- | | `<stem>.silence-edl.json` | Keep/delete ranges, durations, params — the edit list | | `<stem>.silence-transcript.json` | Words re-timed onto the edited timeline (feeds Agent 2 + beats) | | `<stem>.silence-decisions.md` | Human-readable summary + largest pauses trimmed | | `<stem>.silence-filter.txt` | The ffmpeg filtergraph (only with `--video`) | | `<video-stem>.silenced.mp4` | The cut video (only with `--apply`) | The JSON summary printed to stdout includes `removed`, `removedPct`, range counts, and output paths — useful for the master workflow to log and chain. ## Tuning notes - Talking-head YouTube default (`--gap 0.55`) removes roughly 15-20% of a typical raw take as pure silence. Lower `--gap` for a punchier, faster cut; raise it to preserve more natural breathing room. - If a cut feels too aggressive at sentence boundaries, raise the sentence-break breath, or raise `--gap`. ## Hand-off to the next agent Pass `<stem>.silence-transcript.json` (and the `silenced.mp4` if rendered) to the **cut-mistakes** agent. Because timestamps are already on the edited timeline, downstream beat timing and `scripts/validate-beat-sync.mjs` work without further adjustment.