Cartesia Ink vs Groq Speech-to-Text

Cartesia Ink

Ink 2 streams transcripts with turn detection built into the model, documented by an AsyncAPI file with typed ranges and structured errors. The terms, last revised 14 June 2024, let Cartesia train on inputs and outputs unless the customer opts out, and zero data retention is an Enterprise setting. Ink 2 has no batch endpoint and no diarisation.

Groq Speech-to-Text

Whisper Large v3 Turbo costs $0.04 an audio hour and Whisper Large v3 $0.111, with a no-card free plan and zero data retention as a self-serve setting. There is no streaming endpoint, no diarisation and no subtitle output, and uploads stop at 25 MB on the free plan and 100 MB on the Developer plan.

Cartesia Ink

1. Use wss://api.cartesia.ai/stt/turns/websocket with model=ink-2, encoding, sample_rate and cartesia_version=2026-08-14. All four are required.
2. Send raw mono audio in chunks of about 100 ms at the speed it was spoken. Pushing a whole file into the socket can return an internal server error.
3. Read the final text from turn.end only. transcript is cumulative within a turn, so joining turn.update events duplicates text.
4. Send {"type": "close"} after the last audio and keep reading until the server closes the socket, or the buffered tail is lost.
5. Check encoding and sample_rate against the source before sending. The docs say the server might not return an error when they are wrong.

Groq Speech-to-Text

1. Send whisper-large-v3-turbo for transcription and whisper-large-v3 for translation to English. The translations endpoint does not accept Turbo.
2. Pass url instead of file for audio over 25 MB, and split anything over the plan's size limit into overlapping chunks before sending.
3. Set response_format to verbose_json before asking for timestamp_granularities[]. Word timestamps add latency, segment timestamps do not.
4. Every request is billed as at least 10 seconds of audio, so join very short clips where the task allows.
5. Read retry-after on a 429 and back off. Audio limits count seconds an hour and a day as well as requests.