[runtime] add blank_sacle in ctc_endpoint

runtime/core/decoder/ctc_endpoint.cc

@@ -54,7 +54,7 @@ bool CtcEndpoint::IsEndpoint(
     float blank_prob = expf(logp_t[config_.blank]);
 
     num_frames_decoded_++;
-    if (blank_prob > config_.blank_threshold) {
+    if (blank_prob > config_.blank_threshold * config_.blank_scale) {
       num_frames_trailing_blank_++;
     } else {
       num_frames_trailing_blank_ = 0;

runtime/core/decoder/ctc_endpoint.h

@@ -34,6 +34,7 @@ struct CtcEndpointRule {
 struct CtcEndpointConfig {
   /// We consider blank as silence for purposes of endpointing.
   int blank = 0;                // blank id
+  float blank_scale = 1.0;      // blank scale
   float blank_threshold = 0.8;  // blank threshold to be silence
   /// We support three rules. We terminate decoding if ANY of these rules
   /// evaluates to "true". If you want to add more rules, do it by changing this

runtime/core/decoder/params.h

@@ -157,6 +157,7 @@ std::shared_ptr<DecodeOptions> InitDecodeOptionsFromFlags() {
   decode_config->ctc_prefix_search_opts.second_beam_size = FLAGS_nbest;
   decode_config->ctc_prefix_search_opts.blank = FLAGS_blank_id;
   decode_config->ctc_endpoint_config.blank = FLAGS_blank_id;
+  decode_config->ctc_endpoint_config.blank_scale = FLAGS_blank_scale;
   return decode_config;
 }