heygen-com--hyperframes/skills/media-use/audio/references/captions/transcript-handling.md

Transcript Guide

For the transcribe CLI invocation, the .en-translates-non-English rule, and whisper model selection, see ../transcribe.md. This file covers what to do with the resulting transcript when authoring captions: input formats, mandatory quality checks, cleaning code, external-API fallbacks.

Supported Input Formats

The CLI auto-detects and normalizes these formats:

Format	Extension	Source	Word-level?
whisper.cpp JSON	.json	hyperframes init --video, hyperframes transcribe	Yes
OpenAI Whisper API	.json	openai.audio.transcriptions.create({ timestamp_granularities: ["word"] })	Yes
SRT subtitles	.srt	Video editors, subtitle tools, YouTube	No (phrase-level)
VTT subtitles	.vtt	Web players, YouTube, transcription services	No (phrase-level)
Normalized word array	.json	Pre-processed by any tool	Yes

Word-level timestamps produce better captions. SRT/VTT give phrase-level timing, which works but can't do per-word animation effects.

Transcript Quality Check (Mandatory)

After every transcription, read the transcript and check for quality issues before proceeding. Bad transcripts produce nonsensical captions. Never skip this step.

What to look for

Signal	Example	Cause
Music note tokens (♪, �)	{ "text": "♪" } or { "text": "�" }	Whisper detected music, not speech
Garbled / nonsense words	"Do a chin", "Get so gay", "huh"	Model misheard lyrics or background noise
Long gaps with no words	20+ seconds of only ♪ tokens	Instrumental section — expected, but high ratio means speech is being missed
Repeated filler	Many "huh", "uh", "oh" entries	Model is hallucinating on music
Very short word spans	Words with end - start < 0.05	Unreliable timestamp alignment

Automatic retry rules

If more than 20% of entries are ♪/� tokens, or the transcript contains obvious nonsense words, the transcription failed. Do not proceed with the bad transcript. Instead:

1. Retry with medium.en if the original used small.en or smaller:

   npx hyperframes transcribe audio.mp3 --model medium.en
   

2. If medium.en also fails (still >20% music tokens or garbled), tell the user the audio is too noisy for local transcription and suggest:
   • Providing lyrics manually as an SRT/VTT file
   • Using an external API (OpenAI or Groq Whisper — see below)
3. Always clean the transcript before building captions — filter out ♪/� tokens and entries where text is a single non-word character. Only real words should reach the caption composition.

Cleaning a transcript

After transcription (even with a good model), strip non-word entries:

var raw = JSON.parse(transcriptJson);
var words = raw.filter(function (w) {
  if (!w.text || w.text.trim().length === 0) return false;
  if (/^[♪�\u266a\u266b\u266c\u266d\u266e\u266f]+$/.test(w.text)) return false;
  if (/^(huh|uh|um|ah|oh)$/i.test(w.text) && w.end - w.start < 0.1) return false;
  return true;
});

For model-selection guidance by content type, see ../transcribe.md → "Picking a model by content type".

Using External Transcription APIs

For the best accuracy, use an external API and import the result:

OpenAI Whisper API (recommended for quality):

# Generate with word timestamps, then import
curl https://api.openai.com/v1/audio/transcriptions \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -F file=@audio.mp3 -F model=whisper-1 \
  -F response_format=verbose_json \
  -F "timestamp_granularities[]=word" \
  -o transcript-openai.json

npx hyperframes transcribe transcript-openai.json

Groq Whisper API (fast, free tier available):

curl https://api.groq.com/openai/v1/audio/transcriptions \
  -H "Authorization: Bearer $GROQ_API_KEY" \
  -F file=@audio.mp3 -F model=whisper-large-v3 \
  -F response_format=verbose_json \
  -F "timestamp_granularities[]=word" \
  -o transcript-groq.json

npx hyperframes transcribe transcript-groq.json

If No Transcript Exists

1. Check the project root for transcript.json, .srt, or .vtt files.
2. If none found, run ../transcribe.md — pick the starting model from "Picking a model by content type" there.
3. Run the quality check above. If it fails, retry with a larger model or fall back to manual lyrics / external API.