How much performance can data augmentation improve？

[BLack-yzf]

I used the kaldi/egs/dihard_2018/v2 recipe to make front-end processing,and get the MFCC feature for training X-vector model. Then I reproduce the code of training x-vector on pytorch, the x-vector model is totally same as yours. The PLDA and AHC procedure also never change. Then I used the trained x-vector model of pytorch version to test Diarization performance, and get the following resluts.
The first doesn't use the data augmentation, then get DER=27.38% on dihard2_dev.
Another version use the data augmentation(same as the v2 recipe),and only get DER=27.60%.
Theoretically, using data augmentation will improve performance, but the results are terrible. I don't know which part caused the problem,I need help.
Thanks sincerely!

[BLack-yzf]

@manojpamk

[manojpamk]

If I understood your procedure correctly, you have prepared the training data using Kaldi's dihard recipe, and trained xvectors using this repo, right?

The Kaldi repo reports 26.30% DER using supervised calibiration (https://github.com/kaldi-asr/kaldi/blob/master/egs/dihard_2018/v2/run.sh), while Pytorch xvectors returned similar numbers using spectral clustering (https://github.com/manojpamk/pytorch_xvectors/blob/master/README.md). Note that the dihard recipe uses voxceleb corpora for xvector training.

Now as to why the non-augmented model returned similar DER, I am not sure. It is likely that the clean data is large enough to show significant improvements in this task.

Manoj

[BLack-yzf]

Thanks for your relpy.
Sorry to bother you. I have seen you achieve better results, so I want to consult you on a few quetions.
I didn't use your repo to train xvector model. I have reproduced the x-vector model before. The model structure is same as yours. But the training steps are a bit different from yours. I didn't execute the 'prepare for egs' procedure. Instead, I used the MFCC features obtained from the voxceleb copora to train x-vector model directly. But yours are the 'egs'. I think maybe it causes the difference in performence.

Another question, I have seen some resluts in 'diarize.sh'.(https://github.com/manojpamk/pytorch_xvectors/blob/master/egs/diarize.sh). The results on DIHARD2-dev using plda are worse than the kaldi baseline. Is there any trouble on computing plda score?

Yuan

[manojpamk]

Preparing features in the egs format mainly assists training - by ensuring samples have the same duration (i.e number of frames) within a batch. Further, samples in egs files are subset from the utterances themselves, so you can think of them as generating multiple equal-duration examples from the same utterance. Note that both kaldi and this repo perform CMVN and remove non-speech frames before egs file preparation.

All things said, I dont think 27% DER is too bad.

I believe the higher PLDA numbers are due to the AHC threshold not optimized - I currently set it to 0.

[BLack-yzf]

Thanks a lot. I will add the 'egs' on my experiment.
Hope to ask you more question.
Thanks again!

[BLack-yzf]

Hi, Manoji
Sorry to bother you. I don't konw how to make evaluation on AMI dataset. Is there any recipe about it?
Thanks.

[BLack-yzf]

@manojpamk

[manojpamk]

Hi Yuan,

Do you already have the AMI corpus downloaded?

1. For audio, check out the kaldi recipe (https://github.com/kaldi-asr/kaldi/blob/master/egs/ami/s5/run_ihm.sh)
2. I don't know if the RTTMs are available, but they can be created using the segments and utt2spk files prepared using the kaldi recipe.
3. To evaluate diarization, use this script (https://github.com/manojpamk/pytorch_xvectors/blob/master/egs/diarize.sh) after setting the wavDir and rttmDir variables appropriately.
4. To determine the train-dev-eval session splits, check out this paper: https://arxiv.org/pdf/1902.03190.pdf

Manoj