Tomhn/Voxtral-Mini-4B-Realtime-2602

Voxtral Mini 4B Realtime 2602

Voxtral Mini 4B Realtime 2602 is a multilingual, realtime speech-transcription model and among the first open-source solutions to achieve accuracy comparable to offline systems with a delay of <500ms. It supports 13 languages and outperforms existing open-source baselines across a range of tasks, making it ideal for applications like voice assistants and live subtitling.

Built with a natively streaming architecture and a custom causal audio encoder - it allows configurable transcription delays (240ms to 2.4s), enabling users to balance latency and accuracy based on their needs. At a 480ms delay, it matches the performance of leading offline open-source transcription models, as well as realtime APIs.

As a 4B-parameter model, is optimized for on-device deployment, requiring minimal hardware resources. It runs in realtime with on devices minimal hardware with throughput exceeding 12.5 tokens/second.

This model is released in BF16 under the Apache-2 license, ensuring flexibility for both research and commercial use.

For more details, see our:

• Blog post
• Demo
• Technical paper: Work-in-progress ⏳
• vLLM's blog on streaming input Work-in-progress ⏳ - sneak peak here

Key Features

Voxtral Mini 4B Realtime consists of two main architectural components:

• ≈3.4B Language Model
• ≈0.6B Audio Encoder
• The audio encoder was trained from scratch with causal attention enabling streaming capability
• Both the audio encoder as well as the LLM backbone use sliding window attention allowing for "infinite" streaming.

The Voxtral Mini 4B Realtime model offers the following capabilities:

• High-Quality Transcription: Transcribe audio to text with confidence.
• Multilingual: Supports dozens of languages, making it perfect for multilingual transcription tasks.
• Real-Time: Fast streaming ASR model, enabling real-time transcription use cases.
• Configurable Transcription Delays: Customize the transcription delay to balance quality and latency, from 80ms to 2.4s.

Use Cases

Real-Time Transcription Purposes:

• Private meeting transcriptions
• Live subtitle creation
• Real-time assistants with speech understanding
• And more

Bringing real-time transcription capabilities to all.

Recommended Settings

We recommend deploying with the following best practices:

• Always set the temperature to 0.0
• A single text-token is worth 80ms. Hence make sure to set your --max-model-len accordingly. To live-record a 1h meeting, you need to set --max-model-len >= 3600 / 0.8 = 45000. In theory you should be able to record with no limit; in practice pre-allocations of RoPE parameters among other things limits --max-model-len. For the best user experience, we recommend to simple instantiate vLLM with the default parameters which will automatically set a maximum model length of 131072 (~ca. 3h).
• We strongly recommend using websockets to set up audio streaming sessions. For more info on how to do so, check Usage.
• We recommend using a delay of 480ms as we found it to be the sweet spot of performance and low latency. If however you want to adapt the delay, you can change the "transcription_delay_ms": 480 parameter in the tekken.json file.

Benchmark Results

We compare Voxtral Mini 4B Realtime to similar models - both offline models and realtime. Voxtral Mini 4B Realtime is competetive to leading offline models and shows significant gains over existing open-source realtime solutions.

Fleurs

Model	Delay	AVG	Arabic	German	English	Spanish	French	Hindi	Italian	Dutch	Portuguese	Chinese	Japanese	Korean	Russian
Voxtral Mini Transcribe 2.0	Offline	5.90%	13.54%	3.54%	3.32%	2.63%	4.32%	10.33%	2.17%	4.78%	3.56%	7.30%	4.14%	12.29%	4.75%
Voxtral Mini 4B Realtime 2602	480 ms	8.72%	22.53%	6.19%	4.90%	3.31%	6.42%	12.88%	3.27%	7.07%	5.03%	10.45%	9.59%	15.74%	6.02%
	160 ms	12.60%	24.33%	9.50%	6.46%	5.34%	9.75%	15.28%	5.59%	11.39%	10.01%	17.67%	19.17%	19.81%	9.53%
	240 ms	10.80%	23.95%	8.15%	5.91%	4.59%	8.00%	14.26%	4.41%	9.23%	7.51%	13.84%	15.17%	17.56%	7.87%
	960 ms	7.70%	20.32%	4.87%	4.34%	2.98%	5.68%	11.82%	2.46%	6.76%	4.57%	8.99%	6.80%	14.90%	5.56%
	2400 ms	6.73%	14.71%	4.15%	4.05%	2.71%	5.23%	10.73%	2.37%	5.91%	3.93%	8.48%	5.50%	14.30%	5.41%

Long-form English

Model	Delay	Meanwhile (<10m)	E-21 (<10m)	E-22 (<10m)	TEDLIUM (<20m)
Voxtral Mini Transcribe 2.0	Offline	4.08%	9.81%	11.69%	2.86%
Voxtral Mini 4B Realtime 2602	480ms	5.05%	10.23%	12.30%	3.17%

Short-form English

Model	Delay	CHiME-4	GigaSpeech 2k Subset	AMI IHM	SwitchBoard	CHiME-4 SP	GISpeech 2k Subset
Voxtral Mini Transcribe 2.0	Offline	10.39%	6.81%	14.43%	11.54%	10.42%	1.74%
Voxtral Mini 4B Realtime 2602	480ms	10.50%	7.35%	15.05%	11.65%	12.41%	1.73%

Usage

We've worked hand-in-hand with the vLLM team to have production-grade support for Voxtral Mini 4B Realtime 2602 with vLLM. Special thanks goes out to Joshua Deng, Yu Luo, Chen Zhang, Nick Hill, Nicolò Lucchesi, Roger Wang, and Cyrus Leung for the amazing work and help on building a production-ready audio streaming and realtime system in vLLM.

Due to its novel architecture, Voxtral Realtime is currently only support in vLLM. We very much welcome community contributions to add the architecture to Transformers and Llama.cpp.

We've worked hand-in-hand with the vLLM team to have production-grade support for Voxtral Mini 4B Realtime 2602 with vLLM. vLLM's new Realtime API is perfectly suited to run audio streaming sessions with the model.

Installation

Make sure to install vllm from the nightly pypi package. See here for a full installation guide.

uv pip install -U vllm \
    --torch-backend=auto \
    --extra-index-url https://wheels.vllm.ai/nightly # add variant subdirectory here if needed

Doing so should automatically install mistral_common >= 1.9.0.

To check:

python -c "import mistral_common; print(mistral_common.__version__)"

You can also make use of a ready-to-go docker image or on the docker hub.

Make sure to also install all required audio processing libraries:

uv pip install soxr librosa soundfile

Serve

Due to size and the BF16 format of the weights - Voxtral-Mini-4B-Realtime-2602 can run on a single GPU with >= 16GB memory.

The model can be launched in both "eager" mode:

VLLM_DISABLE_COMPILE_CACHE=1 vllm serve mistralai/Voxtral-Mini-4B-Realtime-2602 --compilation_config '{"cudagraph_mode": "PIECEWISE"}'

Additional flags:

• You can set --max-num-batched-tokens to balance throughput and latency, higher means higher throughput but higher latency.
• You can reduce the default --max-model-length to allocate less memory for the pre-computed RoPE frequencies, if you are certain that you won't have to transcribe for more than X hours. By default the model uses a --max-model-length of 131072 (> 3h).

Usage of the model

After serving vllm, you should see that the model is compatible with vllm's new realtime endpoint:

...
(APIServer pid=3246965) INFO 02-03 17:04:43 [launcher.py:58] Route: /v1/realtime, Endpoint: realtime_endpoint
...

We have added two simple example files that allow you to:

• Stream audio files
• Simple gradio live transcription demo

To try out a demo, click here

License

This model is licensed under the Apache 2.0 License.

You must not use this model in a manner that infringes, misappropriates, or otherwise violates any third party’s rights, including intellectual property rights.