add blank_id parameter

deepspeech/decoders/swig/ctc_beam_search_decoder.cpp

@@ -35,7 +35,8 @@ std::vector<std::pair<double, std::string>> ctc_beam_search_decoder(
     size_t beam_size,
     double cutoff_prob,
     size_t cutoff_top_n,
-    Scorer *ext_scorer) {
+    Scorer *ext_scorer,
+    size_t blank_id) {
     // dimension check
     size_t num_time_steps = probs_seq.size();
     for (size_t i = 0; i < num_time_steps; ++i) {
@@ -48,7 +49,7 @@ std::vector<std::pair<double, std::string>> ctc_beam_search_decoder(
 
     // assign blank id
     // size_t blank_id = vocabulary.size();
-    size_t blank_id = 0;
+    // size_t blank_id = 0;
 
     // assign space id
     auto it = std::find(vocabulary.begin(), vocabulary.end(), " ");
@@ -57,7 +58,6 @@ std::vector<std::pair<double, std::string>> ctc_beam_search_decoder(
     if ((size_t)space_id >= vocabulary.size()) {
         space_id = -2;
     }
-
     // init prefixes' root
     PathTrie root;
     root.score = root.log_prob_b_prev = 0.0;
@@ -218,7 +218,8 @@ ctc_beam_search_decoder_batch(
     size_t num_processes,
     double cutoff_prob,
     size_t cutoff_top_n,
-    Scorer *ext_scorer) {
+    Scorer *ext_scorer,
+    size_t blank_id) {
     VALID_CHECK_GT(num_processes, 0, "num_processes must be nonnegative!");
     // thread pool
     ThreadPool pool(num_processes);
@@ -234,7 +235,8 @@ ctc_beam_search_decoder_batch(
                                       beam_size,
                                       cutoff_prob,
                                       cutoff_top_n,
-                                      ext_scorer));
+                                      ext_scorer,
+                                      blank_id));
     }
 
     // get decoding results

deepspeech/decoders/swig/ctc_beam_search_decoder.h

@@ -43,7 +43,8 @@ std::vector<std::pair<double, std::string>> ctc_beam_search_decoder(
     size_t beam_size,
     double cutoff_prob = 1.0,
     size_t cutoff_top_n = 40,
-    Scorer *ext_scorer = nullptr);
+    Scorer *ext_scorer = nullptr,
+    size_t blank_id = 0);
 
 /* CTC Beam Search Decoder for batch data
 
@@ -70,6 +71,7 @@ ctc_beam_search_decoder_batch(
     size_t num_processes,
     double cutoff_prob = 1.0,
     size_t cutoff_top_n = 40,
-    Scorer *ext_scorer = nullptr);
+    Scorer *ext_scorer = nullptr,
+    size_t blank_id = 0);
 
 #endif  // CTC_BEAM_SEARCH_DECODER_H_

deepspeech/decoders/swig/ctc_greedy_decoder.cpp

@@ -17,17 +17,18 @@
 
 std::string ctc_greedy_decoder(
     const std::vector<std::vector<double>> &probs_seq,
-    const std::vector<std::string> &vocabulary) {
+    const std::vector<std::string> &vocabulary,
+    size_t blank_id) {
     // dimension check
     size_t num_time_steps = probs_seq.size();
     for (size_t i = 0; i < num_time_steps; ++i) {
         VALID_CHECK_EQ(probs_seq[i].size(),
-                       vocabulary.size() + 1,
+                       vocabulary.size(),
                        "The shape of probs_seq does not match with "
                        "the shape of the vocabulary");
     }
 
-    size_t blank_id = vocabulary.size();
+    // size_t blank_id = vocabulary.size();
 
     std::vector<size_t> max_idx_vec(num_time_steps, 0);
     std::vector<size_t> idx_vec;

deepspeech/decoders/swig/ctc_greedy_decoder.h

@@ -29,6 +29,7 @@
  */
 std::string ctc_greedy_decoder(
     const std::vector<std::vector<double>>& probs_seq,
-    const std::vector<std::string>& vocabulary);
+    const std::vector<std::string>& vocabulary,
+    size_t blank_id);
 
 #endif  // CTC_GREEDY_DECODER_H

deepspeech/decoders/swig/setup.py

@@ -85,9 +85,8 @@ FILES += glob.glob('openfst-1.6.3/src/lib/*.cc')
 
 # yapf: disable
 FILES = [
-    fn for fn in FILES
-    if not (fn.endswith('main.cc') or fn.endswith('test.cc') or fn.endswith(
-        'unittest.cc'))
+    fn for fn in FILES if not (fn.endswith('main.cc') or fn.endswith('test.cc')
+                               or fn.endswith('unittest.cc'))
 ]
 # yapf: enable
 

deepspeech/decoders/swig_wrapper.py

@@ -32,7 +32,7 @@ class Scorer(swig_decoders.Scorer):
         swig_decoders.Scorer.__init__(self, alpha, beta, model_path, vocabulary)
 
 
-def ctc_greedy_decoder(probs_seq, vocabulary):
+def ctc_greedy_decoder(probs_seq, vocabulary, blank_id):
     """Wrapper for ctc best path decoder in swig.
 
     :param probs_seq: 2-D list of probability distributions over each time
@@ -44,7 +44,8 @@ def ctc_greedy_decoder(probs_seq, vocabulary):
     :return: Decoding result string.
     :rtype: str
     """
-    result = swig_decoders.ctc_greedy_decoder(probs_seq.tolist(), vocabulary)
+    result = swig_decoders.ctc_greedy_decoder(probs_seq.tolist(), vocabulary,
+                                              blank_id)
     return result
 
 
@@ -53,7 +54,8 @@ def ctc_beam_search_decoder(probs_seq,
                             beam_size,
                             cutoff_prob=1.0,
                             cutoff_top_n=40,
-                            ext_scoring_func=None):
+                            ext_scoring_func=None,
+                            blank_id=0):
     """Wrapper for the CTC Beam Search Decoder.
 
     :param probs_seq: 2-D list of probability distributions over each time
@@ -81,7 +83,7 @@ def ctc_beam_search_decoder(probs_seq,
     """
     beam_results = swig_decoders.ctc_beam_search_decoder(
         probs_seq.tolist(), vocabulary, beam_size, cutoff_prob, cutoff_top_n,
-        ext_scoring_func)
+        ext_scoring_func, blank_id)
     beam_results = [(res[0], res[1].decode('utf-8')) for res in beam_results]
     return beam_results
 
@@ -92,7 +94,8 @@ def ctc_beam_search_decoder_batch(probs_split,
                                   num_processes,
                                   cutoff_prob=1.0,
                                   cutoff_top_n=40,
-                                  ext_scoring_func=None):
+                                  ext_scoring_func=None,
+                                  blank_id=0):
     """Wrapper for the batched CTC beam search decoder.
 
     :param probs_seq: 3-D list with each element as an instance of 2-D list
@@ -125,7 +128,7 @@ def ctc_beam_search_decoder_batch(probs_split,
 
     batch_beam_results = swig_decoders.ctc_beam_search_decoder_batch(
         probs_split, vocabulary, beam_size, num_processes, cutoff_prob,
-        cutoff_top_n, ext_scoring_func)
+        cutoff_top_n, ext_scoring_func, blank_id)
     batch_beam_results = [[(res[0], res[1]) for res in beam_results]
                           for beam_results in batch_beam_results]
     return batch_beam_results

deepspeech/models/ds2/deepspeech2.py

@@ -141,7 +141,8 @@ class DeepSpeech2Model(nn.Layer):
                  num_rnn_layers=3,
                  rnn_size=1024,
                  use_gru=False,
-                 share_rnn_weights=True):
+                 share_rnn_weights=True,
+                 blank_id=0):
         super().__init__()
         self.encoder = CRNNEncoder(
             feat_size=feat_size,
@@ -156,7 +157,7 @@ class DeepSpeech2Model(nn.Layer):
         self.decoder = CTCDecoder(
             odim=dict_size,  # <blank> is in  vocab
             enc_n_units=self.encoder.output_size,
-            blank_id=0,  # first token is <blank>
+            blank_id=blank_id,
             dropout_rate=0.0,
             reduction=True,  # sum
             batch_average=True)  # sum / batch_size
@@ -221,7 +222,8 @@ class DeepSpeech2Model(nn.Layer):
                     num_rnn_layers=config.model.num_rnn_layers,
                     rnn_size=config.model.rnn_layer_size,
                     use_gru=config.model.use_gru,
-                    share_rnn_weights=config.model.share_rnn_weights)
+                    share_rnn_weights=config.model.share_rnn_weights,
+                    blank_id=config.model.blank_id)
         infos = Checkpoint().load_parameters(
             model, checkpoint_path=checkpoint_path)
         logger.info(f"checkpoint info: {infos}")
@@ -246,7 +248,8 @@ class DeepSpeech2Model(nn.Layer):
                     num_rnn_layers=config.num_rnn_layers,
                     rnn_size=config.rnn_layer_size,
                     use_gru=config.use_gru,
-                    share_rnn_weights=config.share_rnn_weights)
+                    share_rnn_weights=config.share_rnn_weights,
+                    blank_id=config.blank_id)
         return model
 
 
@@ -258,7 +261,8 @@ class DeepSpeech2InferModel(DeepSpeech2Model):
                  num_rnn_layers=3,
                  rnn_size=1024,
                  use_gru=False,
-                 share_rnn_weights=True):
+                 share_rnn_weights=True,
+                 blank_id=0):
         super().__init__(
             feat_size=feat_size,
             dict_size=dict_size,
@@ -266,7 +270,8 @@ class DeepSpeech2InferModel(DeepSpeech2Model):
             num_rnn_layers=num_rnn_layers,
             rnn_size=rnn_size,
             use_gru=use_gru,
-            share_rnn_weights=share_rnn_weights)
+            share_rnn_weights=share_rnn_weights,
+            blank_id=blank_id)
 
     def forward(self, audio, audio_len):
         """export model function

deepspeech/models/ds2_online/deepspeech2.py

@@ -254,6 +254,7 @@ class DeepSpeech2ModelOnline(nn.Layer):
                 num_fc_layers=2,
                 fc_layers_size_list=[512, 256],
                 use_gru=True,  #Use gru if set True. Use simple rnn if set False.
+                blank_id=0,  # index of blank in vocob.txt
             ))
         if config is not None:
             config.merge_from_other_cfg(default)
@@ -268,7 +269,8 @@ class DeepSpeech2ModelOnline(nn.Layer):
                  rnn_direction='forward',
                  num_fc_layers=2,
                  fc_layers_size_list=[512, 256],
-                 use_gru=False):
+                 use_gru=False,
+                 blank_id=0):
         super().__init__()
         self.encoder = CRNNEncoder(
             feat_size=feat_size,
@@ -284,7 +286,7 @@ class DeepSpeech2ModelOnline(nn.Layer):
         self.decoder = CTCDecoder(
             odim=dict_size,  # <blank> is in  vocab
             enc_n_units=self.encoder.output_size,
-            blank_id=0,  # first token is <blank>
+            blank_id=blank_id,
             dropout_rate=0.0,
             reduction=True,  # sum
             batch_average=True)  # sum / batch_size
@@ -353,7 +355,8 @@ class DeepSpeech2ModelOnline(nn.Layer):
                     rnn_direction=config.model.rnn_direction,
                     num_fc_layers=config.model.num_fc_layers,
                     fc_layers_size_list=config.model.fc_layers_size_list,
-                    use_gru=config.model.use_gru)
+                    use_gru=config.model.use_gru,
+                    blank_id=config.model.blank_id)
         infos = Checkpoint().load_parameters(
             model, checkpoint_path=checkpoint_path)
         logger.info(f"checkpoint info: {infos}")
@@ -380,7 +383,8 @@ class DeepSpeech2ModelOnline(nn.Layer):
                     rnn_direction=config.rnn_direction,
                     num_fc_layers=config.num_fc_layers,
                     fc_layers_size_list=config.fc_layers_size_list,
-                    use_gru=config.use_gru)
+                    use_gru=config.use_gru,
+                    blank_id=config.blank_id)
         return model
 
 
@@ -394,7 +398,8 @@ class DeepSpeech2InferModelOnline(DeepSpeech2ModelOnline):
                  rnn_direction='forward',
                  num_fc_layers=2,
                  fc_layers_size_list=[512, 256],
-                 use_gru=False):
+                 use_gru=False,
+                 blank_id=0):
         super().__init__(
             feat_size=feat_size,
             dict_size=dict_size,
@@ -404,7 +409,8 @@ class DeepSpeech2InferModelOnline(DeepSpeech2ModelOnline):
             rnn_direction=rnn_direction,
             num_fc_layers=num_fc_layers,
             fc_layers_size_list=fc_layers_size_list,
-            use_gru=use_gru)
+            use_gru=use_gru,
+            blank_id=blank_id)
 
     def forward(self, audio_chunk, audio_chunk_lens, chunk_state_h_box,
                 chunk_state_c_box):

deepspeech/modules/ctc.py

@@ -136,7 +136,7 @@ class CTCDecoder(nn.Layer):
         results = []
         for i, probs in enumerate(probs_split):
             output_transcription = ctc_greedy_decoder(
-                probs_seq=probs, vocabulary=vocab_list)
+                probs_seq=probs, vocabulary=vocab_list, blank_id=self.blank_id)
             results.append(output_transcription)
         return results
 
@@ -216,7 +216,8 @@ class CTCDecoder(nn.Layer):
             num_processes=num_processes,
             ext_scoring_func=self._ext_scorer,
             cutoff_prob=cutoff_prob,
-            cutoff_top_n=cutoff_top_n)
+            cutoff_top_n=cutoff_top_n,
+            blank_id=self.blank_id)
 
         results = [result[0][1] for result in beam_search_results]
         return results

examples/aishell/s0/conf/deepspeech2.yaml

@@ -40,6 +40,7 @@ model:
   rnn_layer_size: 1024
   use_gru: True 
   share_rnn_weights: False
+  blank_id: 0
 
 training:
   n_epoch: 80

examples/aishell/s0/conf/deepspeech2_online.yaml

@@ -36,17 +36,18 @@ collator:
 
 model:
   num_conv_layers: 2
-  num_rnn_layers: 3
+  num_rnn_layers: 5
   rnn_layer_size: 1024
   rnn_direction: forward # [forward, bidirect]
-  num_fc_layers: 1
-  fc_layers_size_list: 512,
+  num_fc_layers: 0
+  fc_layers_size_list: -1,
   use_gru: False 
-
+  blank_id: 0
+  
 training:
   n_epoch: 50
   lr: 2e-3
-  lr_decay: 0.91  # 0.83
+  lr_decay: 0.9  # 0.83
   weight_decay: 1e-06
   global_grad_clip: 3.0
   log_interval: 100
@@ -59,7 +60,7 @@ decoding:
   error_rate_type: cer 
   decoding_method: ctc_beam_search
   lang_model_path: data/lm/zh_giga.no_cna_cmn.prune01244.klm
-  alpha: 1.9
+  alpha: 2.2 #1.9
   beta: 5.0
   beam_size: 300
   cutoff_prob: 0.99

examples/librispeech/s0/conf/deepspeech2.yaml

@@ -40,6 +40,7 @@ model:
   rnn_layer_size: 2048
   use_gru: False 
   share_rnn_weights: True
+  blank_id: 0
 
 training:
   n_epoch: 50

examples/librispeech/s0/conf/deepspeech2_online.yaml

@@ -42,6 +42,7 @@ model:
   num_fc_layers: 2
   fc_layers_size_list: 512, 256
   use_gru: False 
+  blank_id: 0
 
 training:
   n_epoch: 50

examples/tiny/s0/conf/deepspeech2.yaml

@@ -41,6 +41,7 @@ model:
   rnn_layer_size: 2048
   use_gru: False 
   share_rnn_weights: True 
+  blank_id: 0
 
 training:
   n_epoch: 10

examples/tiny/s0/conf/deepspeech2_online.yaml

@@ -43,6 +43,7 @@ model:
   num_fc_layers: 2
   fc_layers_size_list: 512, 256
   use_gru: True 
+  blank_id: 0
 
 training:
   n_epoch: 10