Support streaming conformer CTC models from wenet (#427)

sherpa-onnx/csrc/online-wenet-ctc-model-config.cc

@@ -0,0 +1,59 @@
+// sherpa-onnx/csrc/online-wenet-ctc-model-config.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/online-wenet-ctc-model-config.h"
+
+#include "sherpa-onnx/csrc/file-utils.h"
+#include "sherpa-onnx/csrc/macros.h"
+
+namespace sherpa_onnx {
+
+void OnlineWenetCtcModelConfig::Register(ParseOptions *po) {
+  po->Register("wenet-ctc-model", &model,
+               "Path to CTC model.onnx from WeNet. Please see "
+               "https://github.com/k2-fsa/sherpa-onnx/pull/425");
+  po->Register("wenet-ctc-chunk-size", &chunk_size,
+               "Chunk size after subsampling used for decoding.");
+  po->Register("wenet-ctc-num-left-chunks", &num_left_chunks,
+               "Number of left chunks after subsampling used for decoding.");
+}
+
+bool OnlineWenetCtcModelConfig::Validate() const {
+  if (!FileExists(model)) {
+    SHERPA_ONNX_LOGE("WeNet CTC model %s does not exist", model.c_str());
+    return false;
+  }
+
+  if (chunk_size <= 0) {
+    SHERPA_ONNX_LOGE(
+        "Please specify a positive value for --wenet-ctc-chunk-size. Currently "
+        "given: %d",
+        chunk_size);
+    return false;
+  }
+
+  if (num_left_chunks <= 0) {
+    SHERPA_ONNX_LOGE(
+        "Please specify a positive value for --wenet-ctc-num-left-chunks. "
+        "Currently given: %d. Note that if you want to use -1, please consider "
+        "using a non-streaming model.",
+        num_left_chunks);
+    return false;
+  }
+
+  return true;
+}
+
+std::string OnlineWenetCtcModelConfig::ToString() const {
+  std::ostringstream os;
+
+  os << "OnlineWenetCtcModelConfig(";
+  os << "model=\"" << model << "\", ";
+  os << "chunk_size=" << chunk_size << ", ";
+  os << "num_left_chunks=" << num_left_chunks << ")";
+
+  return os.str();
+}
+
+}  // namespace sherpa_onnx