Sentence Embedder Guided Utterance Encoder (SEGUE) for Spoken Language Understanding

Paper | Model checkpoint

SEGUE is a pre-training approach for sequence-level spoken language understanding (SLU) tasks. We use knowledge distillation on a parallel speech-text corpus (e.g. an ASR corpus) to distil language understanding knowledge from a textual sentence embedder to a pre-trained speech encoder. SEGUE applied to Wav2Vec 2.0 improves performance for many SLU tasks, including intent classification / slot-filling, spoken sentiment analysis, and spoken emotion classification. These improvements were observed in both fine-tuned and non-fine-tuned settings, as well as few-shot settings.

Usage

Requirements

We provide a conda environment file environment.yml for reference, though the packages such as PyTorch and CUDA support may need to be installed manually depending on your system setup.

Pre-training

Note: we provide a pre-trained checkpoint, so you may skip this step if you want to run downstream tasks.

Use the pre-training script pretrain_segue.py, for example:

python -m torch.distributed.launch pretrain_segue.py

After that, optionally use pretrain_avg.py for checkpoint averaging:

python pretrain_avg.py

Modify the above scripts as appropriate for your use case, e.g. output directories, training settings, range of checkpoints to average, HF Datasets cache directory.

Downstream tasks

The downstream task scripts we used are under the tasks/ directory. Each task may have some or all of the following scripts:

• *avg.py for task-specific checkpoint averaging
• finetune.py for task-specific fine-tuning
• finetune_w2v2.py if Wav2Vec 2.0 requires different training settings than SEGUE's
• train_tl.py for task-specific transfer learning w/ a frozen backbone
• few_shot.py for few-shot learning

Modify the above scripts as appropriate for your use case, e.g. output directories, training settings, range of checkpoints to average, HF Datasets cache directory.

If you want to write your own tasks, we also have the classes SegueForRegression and SegueForClassification. For classification, the number of classes can be specified through the n_classes field in model config, e.g. SegueForClassification.from_pretrained('...', n_classes=7). Multi-label classification is also supported, e.g. n_classes=[3, 7] for two labels with 3 and 7 classes respectively.

Other files

• plots/ - scatterplot scripts for few-shot tasks
• segue/ - model classes
• custom_trainer.py - a custom Trainer class for logging additional metrics

Results

We show only simplified MInDS-14 and MELD results for brevity. Please refer to the paper for full results.

MInDS-14 (intent classification)

Note: we used only the en-US subset of MInDS-14.

Fine-tuning

Model	Accuracy
w2v 2.0	89.4±2.3
SEGUE	97.6±0.5

Note: Wav2Vec 2.0 fine-tuning was unstable. Only 3 out of 6 runs converged, the result shown were taken from converged runs only.

Frozen encoder

Model	Accuracy
w2v 2.0	54.0
SEGUE	77.9

Few-shot

Plots of k-shot per class accuracy against k:

MELD (sentiment and emotion classification)

Fine-tuning

Model	Sentiment F1	Emotion F1
w2v 2.0	47.3	39.3
SEGUE	53.2	41.1
SEGUE (higher LR)	54.1	47.2

Note: Wav2Vec 2.0 fine-tuning was unstable at the higher LR.

Frozen encoder

Model	Sentiment F1	Emotion F1
w2v 2.0	45.0±0.7	34.3±1.2
SEGUE	45.8±0.1	35.7±0.3

Few-shot

Plots of MELD k-shot per class F1 score against k - sentiment and emotion respectively:

Limitations

In the paper, we hypothesized that SEGUE may perform worse on tasks that rely less on understanding and more on word detection. This may explain why SEGUE did not manage to improve upon Wav2Vec 2.0 on the Fluent Speech Commands (FSC) task. We also experimented with an ASR task (FLEURS), which heavily relies on word detection, to further demonstrate this.

However, this is does not mean that SEGUE performs worse on intent classification tasks in general. MInDS-14, was able to benifit greatly from SEGUE despite also being an intent classification task, as it has more free-form utterances that may benefit more from understanding.

Citation

@inproceedings{segue2023,
  title={Sentence Embedder Guided Utterance Encoder (SEGUE) for Spoken Language Understanding},
  author={Tan, Yi Xuan and Majumder, Navonil and Poria, Soujanya},
  booktitle={Interspeech},
  year={2023}
}