CLST-ASR

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====== Evaluation of Forced aligners ======
This page contains information on forced alignment tools available here at CLST and from other third parties. They are compared and evaluated. It is in no way a formal evaluation, but more an evaluation of experiences and intuitions while working with them.

===== Montreal Forced Aligner =====
**Montreal Forced Aligner (MFA)**: [[https://github.com/MontrealCorpusTools/Montreal-Forced-Aligner]]\\
"MFA is quite user-friendly and easy to use. There are several options, you can use the pre-trained models or you can train the models on your own data/speakers. Attached you will find some examples of why I am not too happy with MFA (especially with the pretrained models), but I am not quite sure how to get a better system. It is especially hard because some of the speakers reduce and the dictionary is not equipped to handle reduction. I have not formally evaluated MFA yet, so I cannot make a general statement about its performance. However looking at just a few files, it seems like that training on the speaker yields better results." ([[https://www.ru.nl/english/people/marcoux-k/|Katherine Marcoux]])\\
By default MFA trains the acoustic models to the stage of speaker-adapted triphones (HMM-GMM). The pretrained models on their website also seem to be HMM-GMM. I assume Katherine uses these pretrained models and trains speaker-adapted models using the pretrained as a basis?\\
They do have code to also train acoustic models based on DNNs (Kaldi's NNet2), but they say:
"The DNN framework for the Montreal Forced aligner is operational, but may not give a better result than the alignments produced by the standard HMM-GMM pipeline. Preliminary experiments suggest that results may improve when the DNN model used to produce alignments is pre-trained on a corpus similar in quality (conversational vs. clean speech) and longer in length than the test corpus." --> https://montreal-forced-aligner.readthedocs.io/en/latest/alignment_techniques.html#deep-neural-networks-dnns ([[https://www.ru.nl/english/people/ganzeboom-m/|Mario Ganzeboom]])\\

===== Kaldi vs. HTK =====
**Kaldi ASR toolkit**: [[http://kaldi-asr.org]]\\
**HTK ASR toolkit**: [[http://htk.eng.cam.ac.uk]]\\
"KALDI outperforms HTK, in  general, but the output quality largely depends on the adequacy of the orthographic input." ([[https://www.ru.nl/english/people/bosch-l-ten/|Louis ten Bosch]], [[https://www.ru.nl/english/people/marcoux-k/|Katherine Marcoux]])
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