kaldi-ctc

Connectionist Temporal Classification (CTC) Automatic Speech Recognition. Training and Decoding are extremely fast.

Intoduction

kaldi-ctc is based on kaldi, warp-ctc and cudnn.

Components	Role
kaldi	Parent body, data prepare / build decoding WFST
warp-ctc	Fast parallel implementation of CTC
cudnn(>=5.0)	Fast recurrent neural networks(LSTM,GRU,ReLU,Tanh)

Compilation

# install dependents
cd tools
make -j
make openblas
# Install cudnn, reference script `extras/install_cudnn.sh`
bash extras/install_cudnn.sh

cd ../src
./configure --cudnn-root=CUDNN_ROOT --openblas-root=../tools/OpenBLAS/install
make depend -j
make -j

Example scripts

Make sure the GPU's memory is enough, default setting can run on GTX TITAN X/1080( >= 8G).
Using smaller minibatch_size(default 16) / max_allow_frames(default 2000) or bigger frame_subsampling_factor(default 1) if your GPUs are older.

librispeech

CTC-monophone

cd egs/librispeech/ctc
bash run.sh --stage -2 --num-gpus 4(change to your GPU devices amount)

Edit Distance Accuracy

steps/ctc/report/generate_plots.py exp/ctc/cudnn_google_fs3 reports/ctc-google

WER RESULITS (LM tgsmall)

Models	Real Time Factor(RTF)	test_clean	dev_clean	test_other	dev_other
chain		6.20	5.83	14.73	14.56
CTC-monophone	(0.05 ~ 0.06) / frame_subsampling_factor	8.63	9.02	20.75	22.16
CTC-character

• There are many Out Of Vocabularies(OOVs) in training transcriptions now

awk 'FNR==NR{T[$1]=1;} FNR<NR{for(i=2;i<=NF;i++) {if (!($i in T)) print $i;}}' data/lang_nosp/words.txt   data/train_960/text | sort -u | wc -l
14291

• CTC system gets better results than chain system on a larger corpu.

TODO

Cleanup librispeech corpus(Fix OOVs), Fine tune parameters

CTC-character example script

FLAT START TRAINING CTC-RNN ACOUSTIC MODELS, CTC-triphone

• google - FLAT START TRAINING OF CD-CTC-SMBR LSTM RNN ACOUSTIC MODELS