fix: dataset-root and dataset-folder-in-archive flag is empty

[hoangtnm]

In line 151-160 and Line 437 of main.py, the default value of dataset-root and dataset-folder-in-archive will be None, which prevents main.py from knowing where the dataset is actually in the computer and loading it.

Moreover, n-hidden-channels 2000 has not been defined in main.py, so it needs to be removed.

Erro log:

python main.py \
    --reduce-lr-valid \
    --dataset-train train-clean-100 train-clean-360 train-other-500 \
    --dataset-valid dev-clean \
    --batch-size 128 \
    --learning-rate .6 \
    --momentum .8 \
    --weight-decay .00001 \
    --clip-grad 0. \
    --gamma .99 \
    --hop-length 160 \
    --win-length 400 \
    --n-bins 13 \
    --normalize \
    --optimizer adadelta \
    --scheduler reduceonplateau \                                         
    --epochs 30

/home/hoangtnm/anaconda3/envs/dl/lib/python3.7/site-packages/torchaudio/backend/utils.py:54: UserWarning: "sox" backend is being deprecated. The default backend will be changed to "sox_io" backend in 0.8.0 and "sox" backend will be removed in 0.9.0. Please migrate to "sox_io" backend. Please refer to https://github.com/pytorch/audio/issues/903 for the detail.
  '"sox" backend is being deprecated. '
INFO:root:Namespace(batch_size=128, checkpoint='', clip_grad=0.0, dataset_folder_in_archive=None, dataset_root=None, dataset_train=['train-clean-100', 'train-clean-360', 'train-other-500'], dataset_valid=['dev-clean'], decoder='greedy', distributed=False, epochs=30, eps=1e-08, freq_mask=0, gamma=0.99, hop_length=160, jit=False, learning_rate=0.6, momentum=0.8, n_bins=13, normalize=True, optimizer='adadelta', progress_bar=False, reduce_lr_valid=True, rho=0.95, scheduler='reduceonplateau', seed=0, start_epoch=0, time_mask=0, type='mfcc', weight_decay=1e-05, win_length=400, workers=0, world_size=8)
INFO:root:Start time: 2020-11-28 21:18:22.337478
/home/hoangtnm/anaconda3/envs/dl/lib/python3.7/site-packages/torchaudio/backend/utils.py:64: UserWarning: The interface of "soundfile" backend is planned to change in 0.8.0 to match that of "sox_io" backend and the current interface will be removed in 0.9.0. To use the new interface, do `torchaudio.USE_SOUNDFILE_LEGACY_INTERFACE = False` before setting the backend to "soundfile". Please refer to https://github.com/pytorch/audio/issues/903 for the detail.
  'The interface of "soundfile" backend is planned to change in 0.8.0 to '
Traceback (most recent call last):
  File "main.py", line 670, in <module>
    spawn_main(main, args)
  File "main.py", line 663, in spawn_main
    main(0, args)
  File "main.py", line 454, in main
    root=args.dataset_root,
  File "/media/aiteam/DATA/workspace/hoangtnm/audio/examples/pipeline_wav2letter/src/datasets.py", line 65, in split_process_vlsp2020asr
    return tuple(create(dataset) for dataset in datasets)
  File "/media/aiteam/DATA/workspace/hoangtnm/audio/examples/pipeline_wav2letter/src/datasets.py", line 65, in <genexpr>
    return tuple(create(dataset) for dataset in datasets)
  File "/media/aiteam/DATA/workspace/hoangtnm/audio/examples/pipeline_wav2letter/src/datasets.py", line 57, in create
    for tag, transform in zip(tags, transform_list)
  File "/media/aiteam/DATA/workspace/hoangtnm/audio/examples/pipeline_wav2letter/src/datasets.py", line 57, in <listcomp>
    for tag, transform in zip(tags, transform_list)
  File "/media/aiteam/DATA/workspace/hoangtnm/audio/examples/pipeline_wav2letter/src/datasets.py", line 15, in __init__
    self._path = os.path.join(root, url)
  File "/home/hoangtnm/anaconda3/envs/dl/lib/python3.7/posixpath.py", line 80, in join
    a = os.fspath(a)
TypeError: expected str, bytes or os.PathLike object, not NoneType

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[vincentqb]

Thanks!