Lesson 207: Playtest VOD Whisper Path Decision Tree When concat_ok Fails (2026)

Direct answer: When concat_ok is false, you must pick an explicit Whisper path—do not silently run batch ASR on a broken merge. This lesson ships ffmpeg_concat_decision_receipt_v1.json with chosen_path (per_clip_local, reencode_concat, or cloud_chunked) and sets whisper_batch_allowed on playtest_vod_triage_receipt_v1.json only when the path’s verification gates pass—after Lesson 200 concat_ok and Lesson 206 facilitator contract.

Why this matters now (June 2026 post-concat stack)

June 2026 teams adopted OBS Replay Buffer concat and normalize preflight—then hit a new Discord question: “concat failed—should we Whisper each clip or pay for API?”

Wrong answers waste money and mis-file bugs:

• Per-clip Whisper with merged-timeline issue IDs (quotes don’t match facilitator timestamps).
• Cloud API on twenty clips without consent README approval.
• whisper_batch_allowed: true while concat_ok: false (downstream summaries lie).

The blog When ffmpeg concat fails — per-clip vs cloud API is the strategy article; this lesson is the receipt milestone for your RPG live-ops course.

Beginner path (20-minute decision)

Time: ~20 minutes to decide; 72 minutes if you implement all three lanes in a drill.

Developer path (gates D1–D6)

Decision tree (ASCII)

concat_ok == true?
  yes → whisper_batch_allowed = true (Lesson 200)
  no  → ffprobe all fragments
        ├─ any fragment audio_stream_ok false?
        │     → fix OBS ([zero-duration audio help](/help/obs-replay-buffer-export-zero-duration-audio-whisper-vod-triage-fix)); STOP
        ├─ single bad fragment + urgent triage?
        │     → chosen_path: per_clip_local (debug only)
        ├─ all fragments OK, concat demuxer fails?
        │     → chosen_path: reencode_concat (+genpts)
        └─ consent + budget + deadline?
              → chosen_path: cloud_chunked ([API chunking help](/help/openai-whisper-api-413-payload-too-large-playtest-vod-chunking-fix))

ffmpeg_concat_decision_receipt_v1.json

{
  "schema": "ffmpeg_concat_decision_receipt_v1",
  "build_label": "fest-demo-2026-06-02-rc3",
  "concat_ok": false,
  "chosen_path": "reencode_concat",
  "paths_considered": ["per_clip_local", "reencode_concat", "cloud_chunked"],
  "ffprobe_table_sha256": "sha256:REPLACE",
  "reencode_command": "ffmpeg -fflags +genpts -f concat ...",
  "post_path_concat_ok": true,
  "whisper_batch_allowed_after_path": true,
  "consent_readme_present": true,
  "cloud_api_used": false,
  "gates": {
    "D1_concat_honest": "pass",
    "D2_ffprobe_archived": "pass",
    "D3_path_documented": "pass",
    "D4_lane_smoke": "pass",
    "D5_whisper_policy": "pass",
    "D6_build_receipt": "pass"
  }
}

Pin under release-evidence/playtest/vod/FFMPEG_CONCAT_DECISION_RECEIPT.json.

whisper_batch_allowed policy (on triage receipt)

{
  "schema": "playtest_vod_triage_receipt_v1",
  "build_label": "fest-demo-2026-06-02-rc3",
  "concat_ok": false,
  "ffmpeg_concat_decision_receipt": "release-evidence/playtest/vod/FFMPEG_CONCAT_DECISION_RECEIPT.json",
  "chosen_path": "reencode_concat",
  "whisper_batch_allowed": true,
  "per_clip_transcripts_ok": false
}

Lane sketches

Lane A — per_clip_local

Use when one fragment is bad or you need same-night quotes without fixing merge.

for f in playtest-vod/fragments/*.mkv; do
  whisper "$f" --model small --output_dir playtest-vod/per_clip_txt/
done

Honest limit: GitHub issues must tag fragment_id, not merged timeline offset.

Lane B — reencode_concat

Use when fragments pass N1–N4 but concat demuxer fails.

ffmpeg -y -fflags +genpts -f concat -safe 0 -i lists/concat.txt \
  -c:a pcm_s16le -ar 48000 playtest-vod/merged_reencode.wav

Set post_path_concat_ok: true before enabling batch Whisper.

Lane C — cloud_chunked

Use only with documented consent and API chunking discipline.

• Chunk < 25 MB per request
• Log cloud_whisper_receipt_v1.json
• Never upload raw MKV without README approval

Publish gate

ALTER TABLE release_publish_gate ADD COLUMN IF NOT EXISTS
  whisper_path_undocumented_blocked BOOLEAN NOT NULL DEFAULT false;

CI verify_whisper_path_decision_v1 fails when concat_ok = false and no ffmpeg_concat_decision_receipt_v1.json exists for that build_label.

Prerequisites

• Lesson 200 — concat_ok baseline
• Lesson 206 — facilitator OBS/VOD clauses
• 16 free OBS/ffmpeg/Silero tools
• Local Whisper VOD pipeline

Common mistakes

• Running batch Whisper on a failed concat “to save time.”
• Choosing cloud without updating consent README.
• per_clip_local transcripts referenced as if merged.
• Fixing concat without updating post_path_concat_ok.

Troubleshooting

Mini exercise (60 minutes)

1. Start with concat_ok: false on a test receipt.
2. Walk tree; pick reencode_concat.
3. Produce merged WAV; flip post_path_concat_ok.
4. Write both JSON receipts; verify whisper_batch_allowed.
5. Add BUILD_RECEIPT column whisper_path; link from OBS concat blog.

Continuity

• Previous: Lesson 206 — facilitator contract
• Next: Lesson 208 — Construct CORS hosting decision
• Guide: OBS normalize preflight
• Help (planned): OBS MKV concat fix (Help queue #5)
• Blog: ffmpeg concat failure decision tree
• H2 batch: Lesson 220 — facilitator concat batch receipt when multiple sessions merge into one Whisper run
• MKV gap BUILD_RECEIPT: Lesson 224 — mkv_gap_reencode_receipt when reencode_concat is the promoted lane

FAQ

Can we always use per-clip Whisper?
Yes for debug—set whisper_batch_allowed: false and document chosen_path: per_clip_local.

Does reencode_concat count as concat_ok?
Set concat_ok false on the failed attempt; set post_path_concat_ok true on the recovery receipt row—or regenerate a green triage receipt after merge.

Cloud vs local?
Default local per facilitator contract; cloud only with consent + budget receipt.

A false concat_ok without a chosen_path is not “almost ready for Whisper”—it is an undocumented ops failure until ffmpeg_concat_decision_receipt_v1.json says otherwise.