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The CLI can call Typecast Timestamp TTS and save alignment data alongside the generated audio. Use this when an agent needs subtitles for Shorts, caption timing for social video, karaoke-style highlights, or lip-sync metadata.

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Generate subtitles

# Save audio and SRT subtitles
cast "Hello, world. This is a test." \
  --out hello.wav \
  --timestamps-out hello.srt

# Save audio and WebVTT subtitles
cast "Hello, world. This is a test." \
  --out hello.wav \
  --timestamps-out hello.vtt \
  --timestamps-format vtt
When --timestamps-format is omitted, CLI infers srt or vtt from the --timestamps-out extension and falls back to json.

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Save raw timestamp JSON

cast "Hello, world. This is a test." \
  --out hello.wav \
  --timestamps-out hello.timestamps.json
JSON is useful when another tool will create captions, animate text, or align visuals manually.

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Choose granularity

cast "Hello, world." \
  --out hello.wav \
  --timestamps-out hello.srt \
  --granularity both
For languages without whitespace between words, such as Japanese (jpn) or Chinese (zho), use character-level timestamps for usable subtitle timing: 
cast "こんにちは。世界。" \
  --language jpn \
  --out hello.wav \
  --timestamps-out hello.srt

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Caption workflow for agents

Create narration audio and captions from script.txt.
Use the CLI.
Write audio to ./video/voiceover.wav.
Write subtitles to ./video/voiceover.srt.
Keep the subtitle file next to the audio file.

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Output choices

OutputUse when
.srtVideo editors, Shorts/Reels/TikTok caption import
.vttWeb video players and browser-based previews
.jsonCustom rendering, karaoke highlights, lip-sync, downstream automation
For social video, generate captions in the same step as audio. It keeps the final narration and subtitle timing tied to the exact same synthesis result.