Podcast Shorts

podcast-shorts — transcript-anchored vertical clips

Raw recording → word-timestamped transcript → planned cuts → styled overlay render → one-pass master composite → QA gate → social encodes → Buffer drafts.

When to invoke

• A podcast/interview recording (ideally per-speaker video + WAV exports) needs to become vertical clips.
• The user describes moments by content ("the story about the pricing call") — the transcript layer turns that into timestamps.

Do NOT invoke for single-source talking-head recuts with no cutting plan, or for meme-style captioning.

Pack layout

/
  pack.json            # the spec — see pack.example.json
  source/              # per-speaker video + lossless WAV exports
  transcripts/         # written by transcribe.py + plan_clips.py
  projects/clip_NN/    # HyperFrames overlay projects (compose_overlay.py)
  out/                 # masters + delivery encodes
  clips/               # word jsons, captions, buffer_urls.json
  review/framing.json  # optional: face_x overrides + cameo source ranges

pack.json schema

See pack.example.json. Per clip: slug, mode (square | wide | guest | duo), lead (speakera | speakerb), start/end (source seconds), start_text/end_text (the words the clip must open and close on — anchors, not guesses), hook (two overlay lines), cta, optional kicker, speaker_names, cameo_text, tx_windows, drops, blocks. Top level: sources, framing_defaults, optional series (day-order slugs for Buffer).

Workflow

1. Transcribe — python3 transcribe.py [idx]. Whisper (word timestamps) per

speaker track. Add your product names to ASR_FIXES first; whisper mangles proper nouns.

1. Plan cuts — python3 plan_clips.py . Anchors the cut on

start_text/end_text word matches, jump-cuts silences, compensates whisper's early word-end stamps (END_COMP/BLEED), writes transcripts/clip_NN.cut.json including fade_start anchored to the last word.

1. Compose overlay — python3 compose_overlay.py . Graphics-only

transparent HyperFrames project (footage never touches the browser). Keep every text card-host at data-start="0" — card hosts run their own scheduler clock, and a nonzero data-start fights the gsap timeline and flashes on frame 0.

1. Render — `npx hyperframes render /projects/clip_NN/public --format mov -o

/projects/clip_NN/renders/overlay.mov`. ProRes 4444 alpha; delete after step 5 (300-800MB each).

1. Composite master — python3 final_composite.py . One ffmpeg pass:

denoise, speed bake, crops, alpha overlay, loudnorm, end fade. The audio chain ends asetpts=N/SR/TB — do not remove it (see below).

1. Social encodes — ./make_delivery.sh. 8-bit yuv420p re-encode, both streams

fresh, asetpts=N/SR/TB on audio.

1. QA gate — python3 qa_delivery.py delivery _social. Every clip must PASS before

anything is hosted or drafted.

1. Stage drafts — host the encodes anywhere with public URLs, write

clips/buffer_urls.json ({slug: url}) and clips/captions.json, then python3 buffer_schedule.py all go. Needs BUFFER_ACCESS_TOKEN and BUFFER_ORG_ID env vars. Drafts, not scheduled posts — a human reviews.

The hidden audio-pts gap (read this before changing any audio flag)

The master's audio filter graph (atrim → concat → atempo → loudnorm) can emit a timestamp jump at a cut seam while the audio CONTENT stays continuous. Players and platform ingests play sample-continuously and never show it — masters sound perfect. But any re-encode with a timestamp-aware filter materializes the gap: aresample=async=1 turns it into time-squeezed audio followed by seconds of real silence at the start of the clip.

Rules:

• The composite's audio chain ends asetpts=N/SR/TB (timestamps rebuilt from sample

position — continuous by construction).

• Delivery encodes use -af "asetpts=N/SR/TB" and NEVER aresample=async=1.
• QA compares decoded audio, not just frames: a defect like this is invisible in

every visual check.

QA gate spec (qa_delivery.py)

| check | bar | |---|---| | silencedetect regions | count == the master's (a new region = injected dropout) | | audio cross-correlation vs master | abs lag <= 25ms at 0.2/1/2/5/10s windows | | first video packet | keyframe at pts 0 | | packet timing | uniform CFR | | duration | within 0.1s of master |

Gotchas

• Whisper word-END stamps run ~0.1s early: never clamp a cut to the next word's start

minus epsilon, or continuous speech collapses the tail and chops the final word.

• Never overwrite a published object under the same filename — CDNs serve stale bytes

for an hour or more. Version filenames and byte-verify (sha256) what the URL serves.

• Buffer: pace mutations ~1s apart (rate windows at 15m and 24h); editPost is a full

replace, resend text + assets + metadata with any change.

• gsap is fetched from jsdelivr on first run (GreenSock license — not committed).

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: shawnla90
• Source: shawnla90/gtm-coding-agent
• License: MIT

Install and usage instructions live in the source repository linked above.