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Components

The mexca package contains five components that can be used to build the MEXCA pipeline.

FaceExtractor

This component takes a video file as input as and applies four steps:

  1. Detection: Faces displayed in the video frames are detected using a pretrained MTCNN model from facenet-pytorch [1].
  2. Encoding: Faces are extracted from the frames and encoded into an embedding space using InceptionResnetV1 from facenet-pytorch.
  3. Identification: IDs are assigned to faces by clustering the embeddings using spectral clustering (k-means).
  4. Extraction: Facial features (landmarks, action units) are extracted from the faces using pyfeat [2]. Available models are PFLD, MobileFaceNet, and MobileNet for landmark extraction and svm, and xgb for action unit extraction.

Note

The two available AU extraction models give different output: svm returns binary unit activations, whereas xgb returns continuous activations (from a tree ensemble).

SpeakerIdentifier

This component takes an audio file as input and applies three steps using the speaker diarization pipeline from pyannote.audio [3]:

  1. Segmentation: Speech segments are detected using pyannote/segmentation (this step includes voice activity detection).
  2. Encoding: Speaker embeddings are computed for each speech segment using ECAPA-TDNN from speechbrain [4].
  3. Identification: IDs are assigned to speech segments based on clustering with a Gaussian hidden Markov model.

VoiceExtractor

This component takes the audio file as input and extracts voice features using praat-parselmouth [5]. Currently, only the fundamental frequency (F0) can be extracted.

AudioTranscriber

This component takes the audio file and speech segments information as input. It transcribes the speech segments to text using a pretrained Whisper model. The resulting transcriptions are aligned with the speaker segments. The transcriptions are split into sentences using a regular expression.

SentimentExtractor

This component takes the transcribed text sentences as input and predicts sentiment scores (positive, negative, neutral) for each sentence using a pretrained multilingual RoBERTa model [6].

References

[1]Barbieri, F., Camacho-Collados, J., Neves, L., & Espinosa-Anke, L.. (2020). TweetEval: Unified benchmark and comparative evaluation for tweet classification. arxiv. https://doi.org/10.48550/arxiv.2010.12421
[2]Bredin, H., & Laurent, A. (2021). End-to-end speaker segmentation for overlap-aware resegmentation. arXiv. https://doi.org/10.48550/arXiv.2104.04045
[3]Cheong, J. H., Xie, T., Byrne, S., & Chang, L. J. (2021). Py-feat: Python facial expression analysis toolbox. arXiv. https://doi.org/10.48550/arXiv.2104.03509
[4]Jadoul, Y., Thompson, B., & de Boer, B. (2018). Introducing Parselmouth: A Python interface to Praat. Journal of Phonetics, 71, 1-15. https://doi.org/10.1016/j.wocn.2018.07.001
[5]Radford, A., Kim, J. W., Xu, T., Brockman, G., McLeavey, C., Sutskever, I. (2022). Robust speech recognition via large-scale weak supervision. https://cdn.openai.com/papers/whisper.pdf
[6]Ravanelli, M., Parcollet, T., Plantinga, P., Rouhe, A., Cornell, S., Lugosch, L., … Bengio, Y. (2021). SpeechBrain: A general-purpose speech toolkit. arXiv. https://doi.org/10.48550/arXiv.2106.04624
[7]Schroff, F., Kalenichenko, D., & Philbin, J. (2015). FaceNet: A unified embedding for face recognition and clustering. arXiv. https://doi.org/10.48550/arXiv.1503.03832