add blank_penalty for online transducer (#548)

sherpa-onnx/python/csrc/online-recognizer.cc

@@ -33,12 +33,13 @@ static void PybindOnlineRecognizerConfig(py::module *m) {
   py::class_<PyClass>(*m, "OnlineRecognizerConfig")
       .def(py::init<const FeatureExtractorConfig &, const OnlineModelConfig &,
                     const OnlineLMConfig &, const EndpointConfig &, bool,
-                    const std::string &, int32_t, const std::string &, float>(),
+                    const std::string &, int32_t, const std::string &, float,
+                    float>(),
            py::arg("feat_config"), py::arg("model_config"),
            py::arg("lm_config") = OnlineLMConfig(), py::arg("endpoint_config"),
            py::arg("enable_endpoint"), py::arg("decoding_method"),
            py::arg("max_active_paths") = 4, py::arg("hotwords_file") = "",
-           py::arg("hotwords_score") = 0)
+           py::arg("hotwords_score") = 0, py::arg("blank_penalty") = 0.0)
       .def_readwrite("feat_config", &PyClass::feat_config)
       .def_readwrite("model_config", &PyClass::model_config)
       .def_readwrite("lm_config", &PyClass::lm_config)
@@ -48,6 +49,7 @@ static void PybindOnlineRecognizerConfig(py::module *m) {
       .def_readwrite("max_active_paths", &PyClass::max_active_paths)
       .def_readwrite("hotwords_file", &PyClass::hotwords_file)
       .def_readwrite("hotwords_score", &PyClass::hotwords_score)
+      .def_readwrite("blank_penalty", &PyClass::blank_penalty)
       .def("__str__", &PyClass::ToString);
 }
 

sherpa-onnx/python/sherpa_onnx/online_recognizer.py

@@ -48,6 +48,7 @@ class OnlineRecognizer(object):
         decoding_method: str = "greedy_search",
         max_active_paths: int = 4,
         hotwords_score: float = 1.5,
+        blank_penalty: float = 0.0,
         hotwords_file: str = "",
         provider: str = "cpu",
         model_type: str = "",
@@ -100,6 +101,8 @@ class OnlineRecognizer(object):
           max_active_paths:
             Use only when decoding_method is modified_beam_search. It specifies
             the maximum number of active paths during beam search.
+          blank_penalty:
+            The penalty applied on blank symbol during decoding.
           hotwords_file:
             The file containing hotwords, one words/phrases per line, and for each
             phrase the bpe/cjkchar are separated by a space.
@@ -172,6 +175,7 @@ class OnlineRecognizer(object):
             max_active_paths=max_active_paths,
             hotwords_score=hotwords_score,
             hotwords_file=hotwords_file,
+            blank_penalty=blank_penalty,
         )
 
         self.recognizer = _Recognizer(recognizer_config)