ASR

Introduction

Please refer to https://k2-fsa.github.io/icefall/recipes/Non-streaming-ASR/librispeech/index.html for how to run models in this recipe.

./RESULTS.md contains the latest results.

Transducers

There are various folders containing the name transducer in this folder. The following table lists the differences among them.

	Encoder	Decoder	Comment
transducer	Conformer	LSTM
transducer_stateless	Conformer	Embedding + Conv1d	Using optimized_transducer from computing RNN-T loss
transducer_stateless2	Conformer	Embedding + Conv1d	Using torchaudio for computing RNN-T loss
transducer_lstm	LSTM	LSTM
transducer_stateless_multi_datasets	Conformer	Embedding + Conv1d	Using data from GigaSpeech as extra training data
pruned_transducer_stateless	Conformer	Embedding + Conv1d	Using k2 pruned RNN-T loss
pruned_transducer_stateless2	Conformer(modified)	Embedding + Conv1d	Using k2 pruned RNN-T loss
pruned_transducer_stateless3	Conformer(modified)	Embedding + Conv1d	Using k2 pruned RNN-T loss + using GigaSpeech as extra training data
pruned_transducer_stateless4	Conformer(modified)	Embedding + Conv1d	same as pruned_transducer_stateless2 + save averaged models periodically during training + delay penalty
pruned_transducer_stateless5	Conformer(modified)	Embedding + Conv1d	same as pruned_transducer_stateless4 + more layers + random combiner
pruned_transducer_stateless6	Conformer(modified)	Embedding + Conv1d	same as pruned_transducer_stateless4 + distillation with hubert
pruned_transducer_stateless7	Zipformer	Embedding + Conv1d	First experiment with Zipformer from Dan
pruned_transducer_stateless7_ctc	Zipformer	Embedding + Conv1d	Same as pruned_transducer_stateless7, but with extra CTC head
pruned_transducer_stateless7_ctc_bs	Zipformer	Embedding + Conv1d	pruned_transducer_stateless7_ctc + blank skip
pruned_transducer_stateless7_streaming	Streaming Zipformer	Embedding + Conv1d	streaming version of pruned_transducer_stateless7
pruned_transducer_stateless7_streaming_multi	Streaming Zipformer	Embedding + Conv1d	same as pruned_transducer_stateless7_streaming, trained on LibriSpeech + GigaSpeech
pruned_transducer_stateless8	Zipformer	Embedding + Conv1d	Same as pruned_transducer_stateless7, but using extra data from GigaSpeech
pruned_stateless_emformer_rnnt2	Emformer(from torchaudio)	Embedding + Conv1d	Using Emformer from torchaudio for streaming ASR
conv_emformer_transducer_stateless	ConvEmformer	Embedding + Conv1d	Using ConvEmformer for streaming ASR + mechanisms in reworked model
conv_emformer_transducer_stateless2	ConvEmformer	Embedding + Conv1d	Using ConvEmformer with simplified memory for streaming ASR + mechanisms in reworked model
lstm_transducer_stateless	LSTM	Embedding + Conv1d	Using LSTM with mechanisms in reworked model
lstm_transducer_stateless2	LSTM	Embedding + Conv1d	Using LSTM with mechanisms in reworked model + gigaspeech (multi-dataset setup)
lstm_transducer_stateless3	LSTM	Embedding + Conv1d	Using LSTM with mechanisms in reworked model + gradient filter + delay penalty
zipformer	Upgraded Zipformer	Embedding + Conv1d	The latest recipe
zipformer_adapter	Upgraded Zipformer	Embedding + Conv1d	It supports domain adaptation of Zipformer using parameter efficient adapters
zipformer_adapter	Upgraded Zipformer	Embedding + Conv1d	Finetune Zipformer with LoRA

The decoder in transducer_stateless is modified from the paper Rnn-Transducer with Stateless Prediction Network. We place an additional Conv1d layer right after the input embedding layer.

CTC

	Encoder	Comment
conformer-ctc	Conformer	Use auxiliary attention head
conformer-ctc2	Reworked Conformer	Use auxiliary attention head
conformer-ctc3	Reworked Conformer	Streaming version + delay penalty
zipformer-ctc	Zipformer	Use auxiliary attention head
zipformer	Upgraded Zipformer	Use auxiliary transducer head / attention-decoder head (the latest recipe)

MMI

	Encoder	Comment
conformer-mmi	Conformer
zipformer-mmi	Zipformer	CTC warmup + use HP as decoding graph for decoding

CR-CTC

	Encoder	Comment
zipformer	Upgraded Zipformer	Could also be an auxiliary loss to improve transducer or CTC/AED (the latest recipe)