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Taris

Transformer-based online speech recognition system with TensorFlow 2

About

Taris is an approach to online speech recognition described in [1]. The system dynamically segments a spoken sentence by learning to count the number of spoken words therein. Decoding is conditioned on a dynamic window of segments, instead of an entire utterance as in the original sequence to sequence architecture.

This repository also maintains the audio-visual alignment and fusion strategy AV Align [2,3] currently implemented with the Transformer stacks instead of the original recurrent networks [4]

Overview

To decode online, Taris learns to count the number of words in a spoken sentence. As we show in [1], this task facilitates the partitioning of the speech input into segments that can be decoded eagerly. However, a longer context is needed in order to match the accuracy of an offline system.

The figure below illustrates an example where the decoder uses two look-back and look-ahead segments to condition all the characters within a given word in the output modality.

diagram

Once all the characters in decision are processed and the system predicts a blank space token, the attention distribution advances by one more segment, and is used in computing audio context vectors for every character in the next word away.

diagram

How to use

Launch scripts

The script run_audio.py launches audio-only experiments.
Relevant system flags are:

  • --architecture (default: transformer)
  • --transformer_online_encoder (default: False)
  • --transformer_encoder_lookahead (default: 11)
  • --transformer_encoder_lookback (default: 11)
  • --transformer_online_decoder (default: False)
  • --transformer_decoder_lookahead (default: 5)
  • --transformer_decoder_lookback (default: 5)

The script run_audiovisual.py launches audio-visual experiments implementing the AV Align strategy with a Transformer, reproducing the work in [4, 5]. By default, the Action Unit regularisation loss, controlled by the --au_loss flag, is set to False. Please ensure that --architecture=av_transformer.

Data preparation

Our published articles used the legacy avsr-tf1 project for data preparation.
The most notable change in Taris is the audio spectrogram processing with librosa as opposed to the native TensorFlow signal processing API. Therefore, this repository provides experimental support only, and has not been validated thoroughly.

Please see the example script write_records.py

For AVSR experiments it is required to process your video clips in advance with the TadasBaltrusaitis/OpenFace tool.
Please refer to the example script extract_faces.py.

References

[1] Learning to Count Words in Fluent Speech enables Online Speech Recognition
George Sterpu, Christian Saam, Naomi Harte
IEEE Spoken Language Technology Workshop (SLT 2021).
[arXiv]

[2] How to Teach DNNs to Pay Attention to the Visual Modality in Speech Recognition
George Sterpu, Christian Saam, Naomi Harte
IEEE/ACM Transactions on Audio, Speech, and Language Processing, 2020
[ pdf accepted version ] [IEEE version]

[3] Attention-based Audio-Visual Fusion for Robust Automatic Speech Recognition
George Sterpu, Christian Saam, Naomi Harte
in ICMI 2018
[arXiv]

[4] Should we hard-code the recurrence concept or learn it instead ? Exploring the Transformer architecture for Audio-Visual Speech Recognition
George Sterpu, Christian Saam, Naomi Harte
Interspeech 2020
[arXiv]

[5] AV Taris: Online Audio-Visual Speech Recognition
George Sterpu and Naomi Harte
Under Review [arXiv]

Dependencies

tensorflow >= 2.4
tensorflow_addons
matplotlib

For data preparation:

librosa
imageio (AVSR)
cv2 (AVSR)
TadasBaltrusaitis/OpenFace (AVSR)

Please use the latest versions available on your platform, and let me know of any breakings and deprecations.
This project is actively maintained.