Add an example for computing RTF about streaming ASR. (#1501)

@@ -3,6 +3,9 @@ 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)
 
+add_executable(streaming-zipformer-rtf-cxx-api ./streaming-zipformer-rtf-cxx-api.cc)
+target_link_libraries(streaming-zipformer-rtf-cxx-api sherpa-onnx-cxx-api)
+
 add_executable(whisper-cxx-api ./whisper-cxx-api.cc)
 target_link_libraries(whisper-cxx-api sherpa-onnx-cxx-api)
 

+// cxx-api-examples/streaming-zipformer-rtf-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(int argc, char *argv[]) {
+  int32_t num_runs = 1;
+  if (argc == 2) {
+    num_runs = atoi(argv[1]);
+    if (num_runs < 0) {
+      num_runs = 1;
+    }
+  }
+
+  using namespace sherpa_onnx::cxx;  // NOLINT
+  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";
+  float total_elapsed_seconds = 0;
+  OnlineRecognizerResult result;
+  for (int32_t i = 0; i < num_runs; ++i) {
+    const auto begin = std::chrono::steady_clock::now();
+
+    OnlineStream stream = recongizer.CreateStream();
+    stream.AcceptWaveform(wave.sample_rate, wave.samples.data(),
+                          wave.samples.size());
+    stream.InputFinished();
+
+    while (recongizer.IsReady(&stream)) {
+      recongizer.Decode(&stream);
+    }
+
+    result = recongizer.GetResult(&stream);
+
+    auto end = std::chrono::steady_clock::now();
+    float elapsed_seconds =
+        std::chrono::duration_cast<std::chrono::milliseconds>(end - begin)
+            .count() /
+        1000.;
+    printf("Run %d/%d, elapsed seconds: %.3f\n", i, num_runs, elapsed_seconds);
+    total_elapsed_seconds += elapsed_seconds;
+  }
+  float average_elapsed_secodns = total_elapsed_seconds / num_runs;
+  float duration = wave.samples.size() / static_cast<float>(wave.sample_rate);
+  float rtf = total_elapsed_seconds / num_runs / duration;
+
+  std::cout << "text: " << result.text << "\n";
+  printf("Number of threads: %d\n", config.model_config.num_threads);
+  printf("Duration: %.3fs\n", duration);
+  printf("Total Elapsed seconds: %.3fs\n", total_elapsed_seconds);
+  printf("Num runs: %d\n", num_runs);
+  printf("Elapsed seconds per run: %.3f/%d=%.3f\n", total_elapsed_seconds,
+         num_runs, average_elapsed_secodns);
+  printf("(Real time factor) RTF = %.3f / %.3f = %.3f\n",
+         average_elapsed_secodns, duration, rtf);
+
+  return 0;
+}