ESPnet: end-to-end speech processing toolkit

ESPnet is an end-to-end speech processing toolkit, mainly focuses on end-to-end speech recognition. ESPnet uses chainer and pytorch as a main deep learning engine, and also follows Kaldi style data processing, feature extraction/format, and recipes to provide a complete setup for speech recognition and other speech processing experiments.

Key Features

• Hybrid CTC/attention based end-to-end ASR
  • Fast/accurate training with CTC/attention multitask training
  • CTC/attention joint decoding to boost monotonic alignment decoding
• Encoder: VGG-like CNN + BLSTM or pyramid BLSTM
• Attention: Dot product, location-aware attention, variants of multihead (pytorch only)
• Incorporate RNNLM/LSTMLM trained only with text data
• Flexible network architecture thanks to chainer and pytorch
• Kaldi style complete recipe
  • Support numbers of ASR benchmarks (WSJ, Switchboard, CHiME-4, Librispeech, TED, CSJ, AMI, HKUST, Voxforge, etc.)
• State-of-the-art performance in Japanese/Chinese benchmarks (comparable/superior to hybrid DNN/HMM and CTC)
• Moderate performance in standard English benchmarks

Installation

Install Kaldi, Python libraries and other required tools using system python and virtualenv

$ cd tools
$ make -j

or using local miniconda

$ cd tools
$ make -f conda.mk -j

To use cuda (and cudnn), make sure to set paths in your .bashrc or .bash_profile appropriately.

CUDAROOT=/path/to/cuda

export PATH=$CUDAROOT/bin:$PATH
export LD_LIBRARY_PATH=$CUDAROOT/lib64:$LD_LIBRARY_PATH
export CUDA_HOME=$CUDAROOT
export CUDA_PATH=$CUDAROOT

Execution of example scripts

Move to an example directory under the egs directory. We prepare several major ASR benchmarks including WSJ, CHiME-4, and TED. The following directory is an example of performing ASR experiment with the VoxForge Italian Corpus.

$ cd egs/voxforge/asr1

Once move to the directory, then, execute the following main script with a chainer backend:

$ ./run.sh

or execute the following main script with a pytorch backend (currently the pytorch backend does not support VGG-like layers):

$ ./run.sh --backend pytorch --etype blstmp

With this main script, you can perform a full procedure of ASR experiments including

• Data download
• Data preparation (Kaldi style, see http://kaldi-asr.org/doc/data_prep.html)
• Feature extraction (Kaldi style, see http://kaldi-asr.org/doc/feat.html)
• Dictionary and JSON format data preparation
• Training based on chainer or pytorch.
• Recognition and scoring

Use of GPU

If you use GPU in your experiment, set --gpu option in run.sh appropriately, e.g.,

$ ./run.sh --gpu 0

Default setup uses CPU (--gpu -1).

Setup in your cluster

Change cmd.sh according to your cluster setup. If you run experiments with your local machine, please use default cmd.sh. For more information about cmd.sh see http://kaldi-asr.org/doc/queue.html. It supports Grid Engine (queue.pl), SLURM (slurm.pl), etc.

Error due to matplotlib

If you have the following error (or other numpy related errors),

RuntimeError: module compiled against API version 0xc but this version of numpy is 0xb
Exception in main training loop: numpy.core.multiarray failed to import
Traceback (most recent call last):
;
:
from . import _path, rcParams
ImportError: numpy.core.multiarray failed to import

Then, please reinstall matplotlib with the following command:

$ cd egs/voxforge/asr1
$ . ./path.sh
$ pip install pip --upgrade; pip uninstall matplotlib; pip --no-cache-dir install matplotlib

Results

We list the character error rate (CER) and word error rate (WER) of major ASR tasks.

	CER (%)	WER (%)
WSJ dev93	5.5	13.1
WSJ eval92	3.8	9.3
CSJ eval1	8.7	N/A
CSJ eval2	6.2	N/A
CSJ eval3	6.9	N/A
HKUST train_dev	29.7	N/A
HKUST dev	28.3	N/A
Librispeech dev_clean	2.9	7.7
Librispeech test_clean	2.7	7.7

Chainer and Pytorch backends

	Chainer	Pytorch
Performance	◎	○
Speed	○	◎
VGG-like encoder	supported	no support
RNNLM integration	supported	supported
#Attention types	3 (no attention, dot, location)	12 including variants of multihead

References (Please cite the following articles)

[1] Suyoun Kim, Takaaki Hori, and Shinji Watanabe, "Joint CTC-attention based end-to-end speech recognition using multi-task learning," Proc. ICASSP'17, pp. 4835--4839 (2017)

[2] Shinji Watanabe, Takaaki Hori, Suyoun Kim, John R. Hershey and Tomoki Hayashi, "Hybrid CTC/Attention Architecture for End-to-End Speech Recognition," IEEE Journal of Selected Topics in Signal Processing, vol. 11, no. 8, pp. 1240-1253, Dec. 2017