There are two main ways to load pretrained checkpoints in NeMo:

  • Using the restore_from() method to load a local checkpoint file (.nemo), or

  • Using the from_pretrained() method to download and set up a checkpoint from NGC.

See the following sections for instructions and examples for each.

Note that these instructions are for loading fully trained checkpoints for evaluation or fine-tuning. For resuming an unfinished training experiment, please use the experiment manager to do so by setting the resume_if_exists flag to True.

Loading Local Checkpoints

NeMo will automatically save checkpoints of a model you are training in a .nemo format. You can also manually save your models at any point using model.save_to(<checkpoint_path>.nemo).

If you have a local .nemo checkpoint that you’d like to load, simply use the restore_from() method:

import nemo.collections.asr as nemo_asr
model = nemo_asr.models.<MODEL_BASE_CLASS>.restore_from(restore_path="<path/to/checkpoint/file.nemo>")

Where the model base class is the ASR model class of the original checkpoint, or the general ASRModel class.

Speaker Label Inference

The goal of speaker label inference is to infer speaker labels using a speaker model with known speaker labels from enrollment set. We provide script for this purpose under <NeMo_root>/examples/speaker_tasks/recognition folder. Currently supported backends are cosine_similarity and neural classifier.

The audio files should be 16KHz mono channel wav files.

The script takes two manifest files:

  • enrollment_manifest : This manifest contains enrollment data with known speaker labels.

  • test_manifest: This manifest contains test data for which we map speaker labels captured from enrollment manifest using one of provided backend

sample format for each of these manifests is provided in <NeMo_root>/examples/speaker_tasks/recognition/conf/speaker_identification_infer.yaml config file.

To infer speaker labels using cosine_similarity backend

python data.enrollment_manifest=<path/to/enrollment_manifest> data.test_manifest=<path/to/test_manifest> backend.backend_model=cosine_similarity

Speaker Embedding Extraction

Speaker Embedding Extraction, is to extract speaker embeddings for any wav file (from known or unknown speakers). We provide two ways to do this:

  • single Python liner for extracting embeddings from a single file

  • Python script for extracting embeddings from a bunch of files provided through manifest file

For extracting embeddings from a single file:

speaker_model = EncDecSpeakerLabelModel.from_pretrained(model_name="<pretrained_model_name or path/to/nemo/file>")
embs = speaker_model.get_embedding('audio_path')

For extracting embeddings from a bunch of files:

The audio files should be 16KHz mono channel wav files.

Write audio files to a manifest.json file with lines as in format:

{"audio_filepath": "<absolute path to dataset>/audio_file.wav", "duration": "duration of file in sec", "label": "speaker_id"}

This python call will download best pretrained model from NGC and writes embeddings pickle file to current working directory

python examples/speaker_tasks/recognition/ --manifest=manifest.json

Speaker Verification Inference

Speaker Verification is a task of verifying if two utterances are from the same speaker or not.

We provide a helper function to verify the audio files and return True if two provided audio files are from the same speaker, False otherwise.

The audio files should be 16KHz mono channel wav files.

speaker_model = EncDecSpeakerLabelModel.from_pretrained(model_name="titanet_large")
decision = speaker_model.verify_speakers('path/to/one/audio_file','path/to/other/audio_file')

NGC Pretrained Checkpoints

The SpeakerNet-ASR collection has checkpoints of several models trained on various datasets for a variety of tasks. TitaNet , ECAPA_TDNN and Speaker_Verification model cards on NGC contain more information about each of the checkpoints available.

The tables below list the speaker embedding extractor models available from NGC, and the models can be accessed via the from_pretrained() method inside the EncDecSpeakerLabelModel Model class.

In general, you can load any of these models with code in the following format:

import nemo.collections.asr as nemo_asr
model = nemo_asr.models.<MODEL_CLASS_NAME>.from_pretrained(model_name="<MODEL_NAME>")

where the model name is the value under “Model Name” entry in the tables below.

If you would like to programatically list the models available for a particular base class, you can use the list_available_models() method.


Speaker Recognition Models

Model Name

Model Base Class

Model Card