Cartesia Ink 2 vs GPT Realtime Whisper
Cartesia Ink 2 is ahead on final-text delay, and GPT Realtime Whisper on time to first text. The Pipecat Dataset and The Ocular Dataset are too close to call.
Last updated Methodology by Dileep Chagam
Accuracy vs speed
Each dot is one model. Bottom-left is best: fewer errors and a faster final transcript.
Which to pick
Pick Cartesia Ink 2 for quick turn-taking once the caller stops (420ms sooner). Pick GPT Realtime Whisper for showing words while the caller is still talking (132ms sooner). For accuracy on clean, scripted audio and accuracy on real phone conversations, the gap is inside the margin of error, so neither is ahead.
The four metrics, side by side
- Cartesia Ink 2
- 2.39%6th
- GPT Realtime Whisper
- 2.16%5th
Too close to call: inside the margin of error
- Cartesia Ink 2
- 3.09%2nd
- GPT Realtime Whisper
- 3.53%4th
Too close to call: inside the margin of error
- Cartesia Ink 2
- 1.51s11th
- GPT Realtime Whisper
- 1.38s10th
GPT Realtime Whisper, 132ms sooner
- Cartesia Ink 2
- 123ms7th
- GPT Realtime Whisper
- 543ms14th
Cartesia Ink 2, 420ms sooner
Lower is better on every metric. The small figure is each model's place in the whole field. What each metric measures.
- WER · Word error rate
- Share of words the model got wrong: replaced, missing or added. Lower is better.
- Pipecat Dataset
- 1,000 short public clips from Pipecat's STT benchmark dataset.
- Ocular Dataset
- 8 recordings from 4 real phone conversations, licensed from Ocular.
- TTFT · Time to first text
- How long after the audio starts streaming until the first words appear.
- TTFS · Final-text delay
- How long after the caller stops until the full transcript arrives. A voice agent waits for this before it replies.
First text and final text, at three percentiles
Cartesia Ink 2 shows first text after 3.23s and final text after 145ms, and GPT Realtime Whisper shows first text after 2.86s and final text after 669ms, on a bad turn (P95) across the same streamed turns.
| Measure | Model | P50 | P90 | P95 |
|---|---|---|---|---|
| Time to first text | Cartesia Ink 2 | 1.51s | 2.04s | 3.23s |
| GPT Realtime Whisper | 1.38s | 1.84s | 2.86s | |
| Final-text delay | Cartesia Ink 2 | 123ms | 139ms | 145ms |
| GPT Realtime Whisper | 543ms | 647ms | 669ms |
- P50 / P90 / P95 · Typical, slow and slowest turns
- Half of turns are faster than P50. Only 1 in 10 is slower than P90, and 1 in 20 slower than P95.
How each ranks among all 17 models
Place among the 17 models on each metric. Lower is better on all four.
| Metric | Ink 2 | Realtime Whisper |
|---|---|---|
| Pipecat Dataset WER | 2.39%6th of 17 | 2.16%5th of 17 |
| Ocular Dataset WER | 3.09%2nd of 17 | 3.53%4th of 17 |
| Time to first text | 1.51s11th of 15 | 1.38s10th of 15 |
| Final-text delay | 123ms7th of 17 | 543ms14th of 17 |
How much audio each model was tested on
| Model | Pipecat clips | Ocular recordings | Turns timed | Failed |
|---|---|---|---|---|
| Cartesia Ink 2 | 1,000 | 8 | 198 | 0 |
| GPT Realtime Whisper | 1,000 | 8 | 206 | 0 |
Only clips with usable text count, so the two totals can differ. How WER is scored.
Related comparisons
- Cartesia Ink 2 vs Speechmatics Linden
- Cartesia Ink 2 vs Soniox STT-RT v5
- Cartesia Ink 2 vs Reson8
- Cartesia Ink 2 vs Inworld STT-1
- Cartesia Ink 2 vs Google Chirp 3
- Cartesia Ink 2 vs AssemblyAI Universal 3.6 Pro
- Cartesia Ink 2 vs GPT-4o Mini Transcribe
- Cartesia Ink 2 vs Deepgram Nova-3
- Cartesia Ink 2 vs Smallest Pulse
- Cartesia Ink 2 vs GPT-4o Transcribe
- Cartesia Ink 2 vs Deepgram Flux English
- Cartesia Ink 2 vs Deepgram Flux Multilingual
- Cartesia Ink 2 vs Gradium
- GPT Realtime Whisper vs Reson8
- GPT Realtime Whisper vs Google Chirp 3
- GPT Realtime Whisper vs Speechmatics Linden
- GPT Realtime Whisper vs AssemblyAI Universal 3.6 Pro
- GPT Realtime Whisper vs Soniox STT-RT v5
- GPT Realtime Whisper vs Inworld STT-1
- GPT Realtime Whisper vs GPT-4o Mini Transcribe
- GPT Realtime Whisper vs Deepgram Nova-3
- GPT Realtime Whisper vs Smallest Pulse
- GPT Realtime Whisper vs GPT-4o Transcribe
- GPT Realtime Whisper vs Deepgram Flux English
- GPT Realtime Whisper vs Deepgram Flux Multilingual
- GPT Realtime Whisper vs Gradium
Frequently asked questions
Which is more accurate, Cartesia Ink 2 or GPT Realtime Whisper?
Cartesia Ink 2 and GPT Realtime Whisper are too close to call on accuracy. On the 1,000 public Pipecat clips, Cartesia Ink 2 scores 2.39% and GPT Realtime Whisper 2.16%, with likely ranges of 2.13 to 2.65% and 1.92 to 2.41%. The ranges overlap, so the difference is too close to call. On the eight licensed Ocular recordings, Cartesia Ink 2 scores 3.09% and GPT Realtime Whisper 3.53%, with likely ranges of 2.43 to 3.84% and 2.58 to 4.51%. The ranges overlap, so the difference is too close to call. Word error rate counts incorrect, missing, and extra words, so lower is better.
Is Cartesia Ink 2 faster than GPT Realtime Whisper?
Yes. Cartesia Ink 2 finishes the transcript 420ms sooner. Cartesia Ink 2 has the final transcript 123ms after the speaker stops and GPT Realtime Whisper 543ms, at the median. Both are measured on the same 206 streamed turns.
Is Cartesia Ink 2 or GPT Realtime Whisper better for voice agents?
Cartesia Ink 2 finishes the transcript 420ms sooner, and the two are too close to call on real conversations. A voice agent cannot reply until the final transcript arrives, and the Ocular recordings are real conversations.
Do Cartesia Ink 2 and GPT Realtime Whisper stream text while the speaker is talking?
Yes, both return partial text before the speaker stops. Cartesia Ink 2 shows first text after 1.51s and GPT Realtime Whisper after 1.38s, at the median, so GPT Realtime Whisper is 132ms sooner.