multitalker-parakeet-streaming

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This model is a streaming multitalker ASR model based on the Nemotron-Speech-Streaming model. The model only takes the speaker diarization outputs as external information and eliminates the need for explicit speaker queries or enrollment audio [Wang et al., 2025]. Unlike conventional target-speaker ASR approaches that require speaker embeddings, this model dynamically adapts to individual speakers through speaker-wise speech activity prediction.

The key innovation involves injecting learnable speaker kernels into the pre-encode layer of the Fast-Conformer encoder. These speaker kernels are generated via speaker supervision activations, enabling instantaneous adaptation to target speakers. This approach leverages the inherent tendency of streaming ASR systems to prioritize specific speakers, repurposing this mechanism to achieve robust speaker-focused recognition.

The model architecture requires deploying one model instance per speaker, meaning the number of model instances matches the number of speakers in the conversation. While this necessitates additional computational resources, it achieves state-of-the-art performance in handling fully overlapped speech in both offline and streaming scenarios.

Video Demo

Key Advantages

This self-speaker adaptation approach offers several advantages over traditional multitalker ASR methods:

1. No Speaker Enrollment: Unlike target-speaker ASR systems that require pre-enrollment audio or speaker embeddings, this model only needs speaker activity information from diarization
2. Handles Severe Overlap: Each instance focuses on a single speaker, enabling accurate transcription even during fully overlapped speech
3. Streaming Capable: Designed for real-time streaming scenarios with configurable latency-accuracy tradeoffs
4. Leverages Single-Speaker Models: Can be fine-tuned from strong pre-trained single-speaker ASR models, and single speaker ASR performance is also preserved

Discover more from NVIDIA:

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Explore more from NVIDIA:

What is Nemotron? NVIDIA Developer Nemotron NVIDIA Riva Speech NeMo Documentation

Model Architecture

Speaker Kernel Injection

The streaming multitalker Parakeet model employs a speaker kernel injection mechanism at some layers of the Fast-Conformer encoder. As shown in the figure below, learnable speaker kernels are injected into selected encoder layers, enabling the model to dynamically adapt to specific speakers.

The speaker kernels are generated through speaker supervision activations that detect speech activity for each target speaker. This enables the encoder states to become more responsive to the targeted speaker's speech characteristics, even during periods of fully overlapped speech.

Multi-Instance Architecture

The model is based on the Parakeet architecture and consists of a NeMo Encoder for Speech Tasks (NEST)[4] which is based on Fast-Conformer[5] encoder. The key architectural innovation is the multi-instance approach, where one model instance is deployed per speaker as illustrated below:

Each model instance:

• Receives the same mixed audio input
• Injects speaker-specific kernels at the pre-encode layer
• Produces transcription output specific to its target speaker
• Operates independently and can run in parallel with other instances

This architecture enables the model to handle severe speech overlap by having each instance focus exclusively on one speaker, eliminating the permutation problem that affects other multitalker ASR approaches.

NVIDIA NeMo

To train, fine-tune or perform multitalker ASR with this model, you will need to install NVIDIA NeMo[7]. We recommend you install it after you've installed Cython and latest PyTorch version.

apt-get update && apt-get install -y libsndfile1 ffmpeg
pip install Cython packaging
pip install git+https://github.com/NVIDIA/NeMo.git@main#egg=nemo_toolkit[asr]

How to Use this Model

The model is available for use in the NeMo Framework[7], and can be used as a pre-trained checkpoint for inference or for fine-tuning on another dataset.

Important: This model uses a multi-instance architecture where you need to deploy one model instance per speaker. Each instance receives the same audio input along with speaker-specific diarization information to perform self-speaker adaptation.

Method 1. Code snippet

Load one of the NeMo speaker diarization models: Streaming Sortformer Diarizer v2, Streaming Sortformer Diarizer v2.1

from nemo.collections.asr.models import SortformerEncLabelModel, ASRModel
import torch
# A speaker diarization model is needed for tracking the speech activity of each speaker.
diar_model = SortformerEncLabelModel.from_pretrained("nvidia/diar_streaming_sortformer_4spk-v2.1").eval().to(to