PortraitCaptions

Overview

End-to-end: take a long-form recording (Twitch VOD, podcast session, livestream) and ship five ready-to-post 9:16 clips into a Google shared drive with caption quality that survives iteration. Every file in Drive has a stable webViewLink that never changes, no matter how many times you re-transcribe or re-render.

The pipeline is two project skills working in sequence: portrait-foreignfilm-clips (first pass, end-to-end) and caption-quality-boost (re-transcribe + replace in place). Both live in .claude/skills/.

Why this matters

Short-form vertical is where distribution happens — TikTok, Reels, Shorts, LinkedIn video. Most creators solve this one of two ways, and both hurt: (a) sit in a timeline editor for an hour per clip, or (b) trust an auto-crop tool that guillotines faces and drops the dock on top of captions. Neither scales.

This pipeline exists because the second you treat portrait as the default — not a post-hoc conversion from a landscape master — three things fall out:

• Faces stay where they belong. The face PiP gets its own third of the frame, upscaled. No more scanning for a head that's been cropped in half.
• Captions don't fight the UI. A deliberate cover bar in the bottom quarter hides platform overlays, progress scrubs, and whatever the source already had baked in.
• Share links stay stable. Every iteration PATCHes the existing Drive file. When a sponsor, editor, or collaborator has a link, that link keeps working — and the quality keeps going up on the other end of it.

The net effect: a 60-minute session becomes five posted-quality verticals in about half an hour, and you can re-transcribe with a better model two weeks later without anyone's link ever going stale.

Kickoff — drop a link, walk away

The pipeline triggers on any longform link or file path — YouTube, Twitch VOD, local .mp4. Defaults are committed to project memory: don't ask about count, selection, orientation, or layout. Run the full flow; pause at one checkpoint only.

Timings — fire and forget

The only stages that need you are source and select. Everything from extract onward runs in the background, in parallel across all clips, and uploads itself to Drive as each one finishes. You kick it off and walk away.

Approximate wall-clock times for a typical run: one 60-minute source, five clips averaging 45 seconds each, on an M-series Mac. Stages 3–6 run concurrently across all clips with one renderer + watcher invocation.

Pipeline

This guide is written in the order of the pipeline. If you already have landscape -captioned clips on disk, skip to #portrait. If you're starting from a raw recording, begin at #source.

Source — acquire the long-form

Two common sources: a Twitch VOD / YouTube upload, or a locally-recorded podcast session. Both end in the same place: one large .mp4 on disk.

# youtube / twitch
yt-dlp -f "bv*[height<=1080]+ba/b[height<=1080]" \
       -o "source/%(title)s.%(ext)s" \
       "https://youtu.be/<id>"

# or just drop a local recording into source/
cp ~/Movies/Session-2026-04-16.mp4 source/

Select — pick the moments

Three ways, pick one.

a · transcript + LLM (fastest)

Transcribe the whole long-form once, then ask Claude to rank the top N moments against a rubric: hook strength, standalone coherence, quotability, visible screen activity. Output: a JSON list of {start, end, slug, title}.

b · best-clips skill

Existing skill at .claude/skills/best-clips/. Scores long-form windows on visible coding activity + transcript energy. Good for stream recordings where the screen right-side moves.

c · manual list

For a curated show, write the timestamps by hand into a CSV.

# clip-list.csv
slug,start,end,title
experiment-until-you-beat-the-record,00:03:14,00:04:19,"Experiment until you beat the record"
i-wasnt-crazy-this-works,00:07:02,00:07:50,"I wasn't crazy — this works"
mcp-reliability-is-a-gamble,00:12:45,00:13:17,"MCP reliability is a gamble"
put-your-expertise-in-the-skills,00:21:30,00:22:19,"Put your expertise in the skills"
same-team-more-clients,00:33:12,00:34:00,"Same team, more clients"

Extract — cut portrait clips direct from source

Portrait is the default — every clip goes straight to 1080×1920, never through a landscape intermediate. The layout transform (face crop + screen crop + cover bar) happens during extraction, not after.

mkdir -p clips-portrait
while IFS=, read -r slug start end title; do
  [[ "$slug" == "slug" ]] && continue
  ffmpeg -y -ss "$start" -to "$end" -i "source/session.mp4" \
    -filter_complex "
      [0:v]crop=260:260:1370:790,scale=1080:1080[face];
      [0:v]crop=1340:1080:0:0,scale=1080:-2,crop=1080:840[screen];
      [face][screen]vstack
    " \
    -c:v libx264 -preset medium -crf 20 \
    -c:a aac -b:a 128k \
    "clips-portrait/${slug}.mp4"
done < clip-list.csv

Output: five 1080×1920 clips, face on top, screen below. Face PiP is already baked into the source recording at roughly (1370, 790) with size 260×260; tune those numbers per session.

Transcribe — word-level timing

openai-whisper on CPU. small is ~real-time; medium is ~3× slower but meaningfully better on proper nouns and jargon — start with small on the first pass, upgrade in iteration.

python3 .claude/skills/portrait-foreignfilm-clips/scripts/transcribe.py \
        landscape-masters/

# writes landscape-masters/_transcripts/{slug}.json — whisper raw, word_timestamps=true

Burn-in v1 — the landscape master caption

Optional but conventional in this project. Many upstream clips already ship with a yellow all-caps caption burned into the landscape master. If yours do, call that folder *-captioned/ and continue. If not, you can skip straight to the portrait stage — the foreignfilm caption layer in stage 7 stands on its own.

The cover bar in stage 6 is sized to fully obscure any existing burned-in captions at y ≈ 860–890 of the 1080-tall source. If your source has no prior captions, you can drop or shrink the bar.

Portrait — face top, screen below

The layout transform. Two independent crops from the same 1662×1080 landscape master, vertically stacked into a 1080×1920 canvas.

Captions — the foreign-film look

Homebrew's ffmpeg 8 ships without libass, the subtitles filter, or even drawtext. So SRT/ASS burn-in is off the table. Instead: pre-rasterise each cue to a transparent PNG with PIL, then composite with moviepy.

# group whisper words into screen-cue chunks
groups = []; cur = []
for w in words:
    cur.append(w)
    if len(cur) >= 5 or cur[-1].end - cur[0].start >= 2.5 \
       or len(" ".join(x.word for x in cur)) >= 34:
        groups.append(cur); cur = []

Each group becomes a PNG drawn with Georgia Bold Italic 60pt, fill #F2D21B, 4px black stroke, centered, wrapped at ~22 chars. Positioned y = 1920 - img_h - 30.

Drive — upload & link-stable replace

gws drive files update --upload replaces the media content of an existing file. The fileId and every webViewLink you've already sent keep working. Never create during iteration.

# list the destination folder, build a name → id inventory
gws drive files list \
  --params '{"q":"\"<folder-id>\" in parents and trashed=false",
             "driveId":"0AI4JyAzsoqRJUk9PVA",
             "corpora":"drive",
             "includeItemsFromAllDrives":true,
             "supportsAllDrives":true,
             "pageSize":200,
             "fields":"files(id,name)"}'

# for each local mp4 — replace if match, create if new
cd "$OUT_DIR"
gws drive files update \
  --params "{\"fileId\":\"$ID\",\"supportsAllDrives\":true}" \
  --upload "$f" --upload-content-type video/mp4

Run it

Two-skill orchestration. Skill 1 does the first render and uploads. Skill 2 upgrades and replaces.

First pass

SESSION=measure-summit-2026
SRC="public/clips/portrait/podcast-clips/${SESSION}-captioned"
OUT="public/clips/portrait/podcast-clips/${SESSION}-portrait-ff"

python3 .claude/skills/portrait-foreignfilm-clips/scripts/transcribe.py          "$SRC"
python3 .claude/skills/portrait-foreignfilm-clips/scripts/render_portrait_ff.py  "$SRC" "$OUT"
bash    .claude/skills/portrait-foreignfilm-clips/scripts/upload_clips.sh        "$OUT" "${SESSION}-portrait-ff"

Iterate — better model, same links

python3 .claude/skills/caption-quality-boost/scripts/retranscribe.py             "$SRC" --model medium
python3 .claude/skills/portrait-foreignfilm-clips/scripts/render_portrait_ff.py  "$SRC" "$OUT"
bash    .claude/skills/caption-quality-boost/scripts/drive_replace.sh            "$OUT" "${SESSION}-portrait-ff"

Live replace (parallel)

Render in one shell; the watcher in another uploads each clip the instant its .done sentinel appears.

# shell 1 — renderer touches {out}.done after each clip
python3 .claude/skills/portrait-foreignfilm-clips/scripts/render_portrait_ff.py  "$SRC" "$OUT"

# shell 2 — watcher polls, replaces in place, writes .replaced
/bin/bash .claude/skills/caption-quality-boost/scripts/drive_replace_watch.sh    "$OUT" "${SESSION}-portrait-ff"

Quality levers

Layouts — A default, alternates on demand

A · face-top is the committed default. Face cropped from the source PiP, upscaled into the top 1080px. Screen cropped to the left ~1320 columns, scaled to 1080×840 in the bottom half. Cover bar 1080×220 at y=1700 hides platform UI, dock, and any baked-in captions.

After the A batch uploads, the runner asks once whether to render alternates. Pick any subset:

Alternates land in {session}-portrait-ff/alternates/layout-{b,c,d}/. Share links on the A originals stay stable.

Speaker-aware captions

Multi-speaker clips get color-coded captions per speaker, optionally with a matching font. Built on pyannote diarization over the source audio.

Flow for a multi-speaker source:

1. Diarize the full source audio — output {speaker_0, speaker_1, …} timestamped turns.
2. Speaker manifest — per detected speaker, extract a 3–5s clearest-audio sample + a video frame from that moment. Written to {source}.speakers/{id}.{wav,jpg}.
3. Verification checkpoint — present each speaker's sample to the user. User maps speaker_id → person_name.
4. Name → colour/font map — project-level registry. Known speakers inherit committed colours.
5. Render — per caption cue, the dominant speaker drives colour and font. Cues that span a speaker switch split at the boundary.
6. Per-clip override — if a rendered clip misattributes, an overrides.json entry re-renders that clip without redoing diarization.

Known speaker registry (HICAM):

Verified mappings cache to {session}.speakers.json so re-renders skip the checkpoint. Single-speaker sources bypass diarization entirely and render with the default foreign-film yellow.

Multi-speaker podcast processing

HICAM-style podcasts ship as multi-ISO recordings — one dedicated microphone track per speaker plus multiple camera angles. Each ISO has its own signal characteristics (mic placement, gain staging, room noise). Quality is not constant across ISOs, and it differs speaker-to-speaker because each person has a different mic on their voice.

Before anything renders, the pipeline scores each ISO and picks the best source per speaker. Wrong ISO choice = muddy captions, mis-transcriptions, wrong color attribution. Audio quality is gating.

Audio — ISO quality step

scripts/hicam-iso-quality.py ingests all staged ISO WAVs for a session and grades each one on ffmpeg-measured signal:

# check every ISO in a HICAM session
python3 scripts/hicam-iso-quality.py \
  --session public/clips/hicam/260316/hicam-session.json \
  --json public/clips/hicam/260316/iso-quality.json

# or ad-hoc across specific WAVs
python3 scripts/hicam-iso-quality.py mic1.wav mic2.wav cam1-audio.wav

Sample output from session 260316:

       name        grade        dur_s      mean_dB      peak_dB      silence
cam1-audio             B       7529.0        -30.2         -4.2        0.038
program-aud            F        900.0        -91.0        -91.0        1.000

The existing HICAM notes confirmed what the grader caught automatically: program-audio is silent at -91 dB; cam1-audio (camera room mic) is the only usable local track. Catch this in seconds, not after a failed transcription run.

Per-speaker ISO routing

On well-recorded sessions, each speaker has their own lavalier or hand mic. That mic is the correct ISO for that speaker — not the program mix, not the room mic. The pipeline builds a speaker_id → iso_path map after grading:

1. Grade every ISO (step above).
2. Drop tracks graded F (silent / clipped).
3. Diarize the program mix to get speaker_id turns.
4. For each diarized speaker, correlate which ISO has the highest speech energy during that speaker's turns — that ISO is their mic.
5. Cache {session}.speakers.json including iso_path per speaker.
6. At render time, extract each speaker's cue audio from their own ISO (never the program mix).

Visual — active-speaker crop

Parallel to ISO routing, layout A's top region follows whoever is speaking right now. Two paths:

• Preferred — multi-ISO video: use the per-speaker camera ISO when available. Each speaker has a full-frame dedicated camera; no cropping a composite.
• Fallback — composite crop: if only the YouTube composite exists, establish each speaker_id's x-range in the wide shot (manual label from a clear frame, or face-cluster by x-position). At each caption cue boundary, crop that speaker's region into the top 1080×1080. Hard-cut at the utterance boundary; no fade (keeps rendering deterministic).

Combined verification checkpoint

Speaker identity drives three things at once: caption colour, caption font (optional), and top-crop source. The user verifies the mapping in one checkpoint, not three:

speaker_0  →  iso: mic1.wav  (grade A, mean -22 dB)
              x_range: 120–420  (composite frame)
              → name?   [jordaaan]

speaker_1  →  iso: mic2.wav  (grade A, mean -25 dB)
              x_range: 420–720
              → name?   [colin]

speaker_2  →  iso: cam3-audio.wav  (grade B, mean -31 dB)
              x_range: 720–1020
              → name?   [steven]

Once confirmed, colour/font/crop are locked. The cache in {session}.speakers.json skips this on re-renders.

Known pitfalls on multi-ISO sources

• Silent MIC tracks. Lavaliers that weren't armed during record produce a -91 dB file. The grader flags them before transcription wastes CPU.
• Mic bleed. ISO A picks up speaker B faintly; naive energy correlation can mis-route. Weight the correlation by a 5–10 dB margin.
• Clock drift between ISOs. Rare but possible with separate recorders. If transcripts from two ISOs disagree on timing by >100 ms late in the session, align to the program mix and flag.
• Cross-talk segments. When two speakers overlap, diarization still attributes to one. Keep both ISOs open for overlapping windows and burn the caption for whichever had higher energy.

Queueing multiple sources

Drop multiple longform links in any turn. Each gets its own project folder under Clips/ and runs through the full kickoff flow independently. The runner chains them so downloads + transcriptions overlap where possible — next source's download starts while the current source is rendering.

# typical multi-source turn
make clips for these:
  https://youtu.be/abc123           # source 1
  https://twitch.tv/videos/456789  # source 2
  /Users/me/local-recording.mp4     # source 3

# result: three project folders in Clips/
#   source-1-slug-portrait-ff/
#   source-2-slug-portrait-ff/
#   source-3-slug-portrait-ff/
# each with 5 clips; only one post-completion alternate-layout prompt per source

Pitfalls

• Cover-bar opacity must be 1.0. At 0.9 the landscape v1 captions ghost through visibly.
• Homebrew ffmpeg has no libass / drawtext. Don't try -vf subtitles=. Use the PIL+moviepy renderer.
• macOS default bash is 3.x. Associative arrays need /bin/bash (Homebrew 5.x) or a case statement.
• gws refuses absolute upload paths outside cwd. Always cd first.
• iCloud FUSE breaks Remotion SSR but does not break moviepy — pure Python frame IO avoids the Chromium ETIMEDOUT bug. This is why this pipeline lives in Python, not Remotion.
• Replace, don't re-upload. drive files create mints a new fileId and breaks every share link you sent. Use drive files update for iteration.
• whisper small mishears names. If your content is jargon-dense, jump to medium for the first pass and skip the re-render cycle.

Appendix — file layout

project/
├── source/                                         # long-form recordings (gitignored)
├── landscape-masters/                              # extracted 1662×1080 cuts
│   └── _transcripts/{slug}.json                    # whisper output
├── public/clips/portrait/podcast-clips/
│   ├── {session}-captioned/{slug}-captioned.mp4    # landscape + v1 caption
│   └── {session}-portrait-ff/{slug}-ff.mp4         # final 1080×1920
├── .claude/skills/
│   ├── portrait-foreignfilm-clips/                 # first render + upload
│   └── caption-quality-boost/                      # re-transcribe + replace
└── DOCUMENTATION/PORTRAIT-CAPTIONS-GUIDE.html      # this doc