Add C++ API for streaming ASR. (#1455)

It is a wrapper around the C API.

cxx-api-examples/CMakeLists.txt

@@ -0,0 +1,4 @@
+include_directories(${CMAKE_SOURCE_DIR})
+
+add_executable(streaming-zipformer-cxx-api ./streaming-zipformer-cxx-api.cc)
+target_link_libraries(streaming-zipformer-cxx-api sherpa-onnx-cxx-api)

cxx-api-examples/streaming-zipformer-cxx-api.cc

@@ -0,0 +1,91 @@
+// cxx-api-examples/streaming-zipformer-cxx-api.cc
+// Copyright (c)  2024  Xiaomi Corporation
+
+//
+// This file demonstrates how to use streaming Zipformer
+// with sherpa-onnx's C++ API.
+//
+// clang-format off
+//
+// wget https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
+// tar xvf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
+// rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
+//
+// clang-format on
+
+#include <chrono>  // NOLINT
+#include <iostream>
+#include <string>
+
+#include "sherpa-onnx/c-api/cxx-api.h"
+
+int32_t main() {
+  using namespace sherpa_onnx::cxx;
+  OnlineRecognizerConfig config;
+
+  // please see
+  // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-transducer/zipformer-transducer-models.html#csukuangfj-sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20-bilingual-chinese-english
+  config.model_config.transducer.encoder =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/"
+      "encoder-epoch-99-avg-1.int8.onnx";
+
+  // Note: We recommend not using int8.onnx for the decoder.
+  config.model_config.transducer.decoder =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/"
+      "decoder-epoch-99-avg-1.onnx";
+
+  config.model_config.transducer.joiner =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/"
+      "joiner-epoch-99-avg-1.int8.onnx";
+
+  config.model_config.tokens =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/tokens.txt";
+
+  config.model_config.num_threads = 1;
+
+  std::cout << "Loading model\n";
+  OnlineRecognizer recongizer = OnlineRecognizer::Create(config);
+  if (!recongizer.Get()) {
+    std::cerr << "Please check your config\n";
+    return -1;
+  }
+  std::cout << "Loading model done\n";
+
+  std::string wave_filename =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/test_wavs/"
+      "0.wav";
+  Wave wave = ReadWave(wave_filename);
+  if (wave.samples.empty()) {
+    std::cerr << "Failed to read: '" << wave_filename << "'\n";
+    return -1;
+  }
+
+  std::cout << "Start recognition\n";
+  const auto begin = std::chrono::steady_clock::now();
+
+  OnlineStream stream = recongizer.CreateStream();
+  stream.AcceptWaveform(wave.sample_rate, wave.samples.data(),
+                        wave.samples.size());
+  while (recongizer.IsReady(&stream)) {
+    recongizer.Decode(&stream);
+  }
+
+  OnlineRecognizerResult result = recongizer.GetResult(&stream);
+
+  const auto end = std::chrono::steady_clock::now();
+  const float elapsed_seconds =
+      std::chrono::duration_cast<std::chrono::milliseconds>(end - begin)
+          .count() /
+      1000.;
+  float duration = wave.samples.size() / static_cast<float>(wave.sample_rate);
+  float rtf = elapsed_seconds / duration;
+
+  std::cout << "text: " << result.text << "\n";
+  printf("Number of threads: %d\n", config.model_config.num_threads);
+  printf("Duration: %.3fs\n", duration);
+  printf("Elapsed seconds: %.3fs\n", elapsed_seconds);
+  printf("(Real time factor) RTF = %.3f / %.3f = %.3f\n", elapsed_seconds,
+         duration, rtf);
+
+  return 0;
+}