NeMo Speech Intent Classification and Slot Filling Configuration Files#

This page covers NeMo configuration file setup that is specific to models in the Speech Intent Classification and Slot Filling collection. For general information about how to set up and run experiments that is common to all NeMo models (e.g. experiment manager and PyTorch Lightning trainer parameters), see the NeMo Models page.

Dataset Configuration#

Dataset configuration for Speech Intent Classification and Slot Filling model is mostly the same as for standard ASR training, covered here. One exception is that use_start_end_token must be set to True.

An example of train and validation configuration should look similar to the following:

    manifest_filepath: ???
    sample_rate: ${model.sample_rate}
    batch_size: 16 # you may increase batch_size if your memory allows
    shuffle: true
    num_workers: 8
    pin_memory: false
    use_start_end_token: true
    trim_silence: false
    max_duration: 11.0
    min_duration: 0.0
    # tarred datasets
    is_tarred: false
    tarred_audio_filepaths: null
    shuffle_n: 2048
    # bucketing params
    bucketing_strategy: "synced_randomized"
    bucketing_batch_size: null

    manifest_filepath: ???
    sample_rate: ${model.sample_rate}
    batch_size: 16 # you may increase batch_size if your memory allows
    shuffle: false
    num_workers: 8
    pin_memory: true
    use_start_end_token: true
    min_duration: 8.0

Preprocessor Configuration#

Preprocessor helps to compute MFCC or mel spectrogram features that are given as inputs to model. For details on how to write this section, refer to Preprocessor Configuration

Augmentation Configurations#

There are a few on-the-fly spectrogram augmentation options for NeMo ASR, which can be specified by the configuration file using the augmentor and spec_augment section. For details on how to write this section, refer to Augmentation Configuration

Model Architecture Configurations#

The encoder of the model is a Conformer-large model without the text decoder, and can be initialized with pretrained checkpoints. The decoder is a Transforemr model, with additional embedding and classifier modules.

An example config for the model can be:

  name: stt_en_conformer_ctc_large  # which model use to initialize the encoder, set to null if not using any. Only used to initialize training, not used in resuming from checkpoint.
  freeze: false  # whether to freeze the encoder during training.

  sample_rate: 16000
    _target_: nemo.collections.asr.modules.ConformerEncoder
    feat_in: ${model.preprocessor.features}
    feat_out: -1 # you may set it if you need different output size other than the default d_model
    n_layers: 17  # SSL conformer-large have only 17 layers
    d_model: 512

    # Sub-sampling params
    subsampling: striding # vggnet or striding, vggnet may give better results but needs more memory
    subsampling_factor: 4 # must be power of 2
    subsampling_conv_channels: -1 # -1 sets it to d_model

    # Reduction parameters: Can be used to add another subsampling layer at a given position.
    # Having a 2x reduction will speedup the training and inference speech while keeping similar WER.
    # Adding it at the end will give the best WER while adding it at the beginning will give the best speedup.
    reduction: null # pooling, striding, or null
    reduction_position: null # Encoder block index or -1 for subsampling at the end of encoder
    reduction_factor: 1

    # Feed forward module's params
    ff_expansion_factor: 4

    # Multi-headed Attention Module's params
    self_attention_model: rel_pos # rel_pos or abs_pos
    n_heads: 8 # may need to be lower for smaller d_models
    # [left, right] specifies the number of steps to be seen from left and right of each step in self-attention
    att_context_size: [-1, -1] # -1 means unlimited context
    xscaling: true # scales up the input embeddings by sqrt(d_model)
    untie_biases: true # unties the biases of the TransformerXL layers
    pos_emb_max_len: 5000

    # Convolution module's params
    conv_kernel_size: 31
    conv_norm_type: 'batch_norm' # batch_norm or layer_norm

    ### regularization
    dropout: 0.1 # The dropout used in most of the Conformer Modules
    dropout_pre_encoder: 0.1 # The dropout used before the encoder
    dropout_emb: 0.0 # The dropout used for embeddings
    dropout_att: 0.1 # The dropout for multi-headed attention modules

    _target_: nemo.collections.asr.modules.transformer.TransformerEmbedding
    vocab_size: -1
    hidden_size: ${model.encoder.d_model}
    max_sequence_length: 512
    num_token_types: 1
    embedding_dropout: 0.0
    learn_positional_encodings: false

    _target_: nemo.collections.asr.modules.transformer.TransformerDecoder
    num_layers: 3
    hidden_size: ${model.encoder.d_model}
    inner_size: 2048
    num_attention_heads: 8
    attn_score_dropout: 0.0
    attn_layer_dropout: 0.0
    ffn_dropout: 0.0

    hidden_size: ${model.encoder.d_model}
    num_classes: -1
    num_layers: 1
    activation: 'relu'
    log_softmax: true

Loss Configurations#

The loss function by default is the negative log-likelihood loss, where optional label-smoothing can be applied by using the following config (default is 0.0):

  label_smoothing: 0.0

Inference Configurations#

During inference, three types of sequence generation strategies can be applied: greedy search, beam search and top-k search.

  type: greedy  # choices=[greedy, topk, beam]
  max_sequence_length: ${model.embedding.max_sequence_length}
  temperature: 1.0  # for top-k sampling
  beam_size: 1  # K for top-k sampling, N for beam search
  len_pen: 0  # for beam-search