Add jni interface and kotlin API examples for TTS. (#381)

+hs_err*
+main.jar
+vits-zh-aishell3

@@ -3,6 +3,28 @@ package com.k2fsa.sherpa.onnx
 import android.content.res.AssetManager
 
 fun main() {
+  testTts()
+  testAsr()
+}
+
+fun testTts() {
+  var config = OfflineTtsConfig(
+    model=OfflineTtsModelConfig(
+      vits=OfflineTtsVitsModelConfig(
+        model="./vits-zh-aishell3/vits-aishell3.onnx",
+        lexicon="./vits-zh-aishell3/lexicon.txt",
+        tokens="./vits-zh-aishell3/tokens.txt",
+      ),
+      numThreads=1,
+      debug=true,
+    )
+  )
+  val tts = OfflineTts(config=config)
+  val audio = tts.generate(text="林美丽最美丽!", sid=99, speed=1.2f)
+  audio.save(filename="99.wav")
+}
+
+fun testAsr() {
     var featConfig = FeatureConfig(
         sampleRate = 16000,
         featureDim = 80,

+// Copyright (c)  2023  Xiaomi Corporation
+package com.k2fsa.sherpa.onnx
+
+import android.content.res.AssetManager
+
+data class OfflineTtsVitsModelConfig(
+    var model: String,
+    var lexicon: String,
+    var tokens: String,
+    var noiseScale: Float = 0.667f,
+    var noiseScaleW: Float = 0.8f,
+    var lengthScale: Float = 1.0f,
+)
+
+data class OfflineTtsModelConfig(
+    var vits: OfflineTtsVitsModelConfig,
+    var numThreads: Int = 1,
+    var debug: Boolean = false,
+    var provider: String = "cpu",
+)
+
+data class OfflineTtsConfig(
+    var model: OfflineTtsModelConfig,
+)
+
+class GeneratedAudio(
+    val samples : FloatArray,
+    val sampleRate: Int,
+) {
+    fun save(filename: String) = saveImpl(filename=filename, samples=samples, sampleRate=sampleRate)
+
+    private external fun saveImpl(
+        filename: String,
+        samples: FloatArray,
+        sampleRate: Int
+    ): Boolean
+}
+
+class OfflineTts(
+    assetManager: AssetManager? = null,
+    var config: OfflineTtsConfig,
+) {
+    private var ptr: Long
+
+    init {
+        if (assetManager != null) {
+            ptr = new(assetManager, config)
+        } else {
+            ptr = newFromFile(config)
+        }
+    }
+
+    fun generate(
+        text: String,
+        sid: Int = 0,
+        speed: Float = 1.0f
+    ): GeneratedAudio {
+      var objArray = generateImpl(ptr, text=text, sid=sid, speed=speed)
+      return GeneratedAudio(samples=objArray[0] as FloatArray,
+                            sampleRate=objArray[1] as Int)
+    }
+
+    fun allocate(assetManager: AssetManager? = null) {
+      if (ptr == 0L) {
+        if (assetManager != null) {
+          ptr = new(assetManager, config)
+        } else {
+          ptr = newFromFile(config)
+        }
+      }
+    }
+
+    fun free() {
+      if (ptr != 0L) {
+        delete(ptr)
+        ptr = 0
+      }
+    }
+
+    protected fun finalize() {
+        delete(ptr)
+    }
+
+    private external fun new(
+        assetManager: AssetManager,
+        config: OfflineTtsConfig,
+    ): Long
+
+    private external fun newFromFile(
+        config: OfflineTtsConfig,
+    ): Long
+
+    private external fun delete(ptr: Long)
+
+    // The returned array has two entries:
+    //  - the first entry is an 1-D float array containing audio samples.
+    //    Each sample is normalized to the range [-1, 1]
+    //  - the second entry is the sample rate
+    external fun generateImpl(
+        ptr: Long,
+        text: String,
+        sid: Int = 0,
+        speed: Float = 1.0f
+    ): Array<Any>
+
+    companion object {
+        init {
+            System.loadLibrary("sherpa-onnx-jni")
+        }
+    }
+
+}

@@ -6,11 +6,13 @@
 
 set -e
 
+
 cd ..
 mkdir -p build
 cd build
 
-cmake \
+if [ ! -f ../build/lib/libsherpa-onnx-jni.dylib ]; then
+  cmake \
     -DSHERPA_ONNX_ENABLE_PYTHON=OFF \
     -DSHERPA_ONNX_ENABLE_TESTS=OFF \
     -DSHERPA_ONNX_ENABLE_CHECK=OFF \
@@ -19,8 +21,9 @@ cmake \
     -DSHERPA_ONNX_ENABLE_JNI=ON \
     ..
 
-make -j4
-ls -lh lib
+  make -j4
+  ls -lh lib
+fi
 
 export LD_LIBRARY_PATH=$PWD/build/lib:$LD_LIBRARY_PATH
 
@@ -31,7 +34,7 @@ if [ ! -f ./sherpa-onnx-streaming-zipformer-en-2023-02-21/tokens.txt ]; then
   git clone https://huggingface.co/csukuangfj/sherpa-onnx-streaming-zipformer-en-2023-02-21
 fi
 
-kotlinc-jvm -include-runtime -d main.jar Main.kt WaveReader.kt SherpaOnnx.kt faked-asset-manager.kt
+kotlinc-jvm -include-runtime -d main.jar Main.kt WaveReader.kt SherpaOnnx.kt faked-asset-manager.kt Tts.kt
 
 ls -lh main.jar
 

@@ -10,7 +10,15 @@
 #include <sstream>
 #include <utility>
 
+#if __ANDROID_API__ >= 9
+#include <strstream>
+
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/onnx-utils.h"
 #include "sherpa-onnx/csrc/text-utils.h"
 
 namespace sherpa_onnx {
@@ -22,11 +30,9 @@ static void ToLowerCase(std::string *in_out) {
 
 // Note: We don't use SymbolTable here since tokens may contain a blank
 // in the first column
-static std::unordered_map<std::string, int32_t> ReadTokens(
-    const std::string &tokens) {
+static std::unordered_map<std::string, int32_t> ReadTokens(std::istream &is) {
   std::unordered_map<std::string, int32_t> token2id;
 
-  std::ifstream is(tokens);
   std::string line;
 
   std::string sym;
@@ -80,11 +86,43 @@ Lexicon::Lexicon(const std::string &lexicon, const std::string &tokens,
                  bool debug /*= false*/)
     : debug_(debug) {
   InitLanguage(language);
-  InitTokens(tokens);
-  InitLexicon(lexicon);
+
+  {
+    std::ifstream is(tokens);
+    InitTokens(is);
+  }
+
+  {
+    std::ifstream is(lexicon);
+    InitLexicon(is);
+  }
+
   InitPunctuations(punctuations);
 }
 
+#if __ANDROID_API__ >= 9
+Lexicon::Lexicon(AAssetManager *mgr, const std::string &lexicon,
+                 const std::string &tokens, const std::string &punctuations,
+                 const std::string &language, bool debug /*= false*/)
+    : debug_(debug) {
+  InitLanguage(language);
+
+  {
+    auto buf = ReadFile(mgr, tokens);
+    std::istrstream is(buf.data(), buf.size());
+    InitTokens(is);
+  }
+
+  {
+    auto buf = ReadFile(mgr, lexicon);
+    std::istrstream is(buf.data(), buf.size());
+    InitLexicon(is);
+  }
+
+  InitPunctuations(punctuations);
+}
+#endif
+
 std::vector<int64_t> Lexicon::ConvertTextToTokenIds(
     const std::string &text) const {
   switch (language_) {
@@ -192,9 +230,7 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsEnglish(
   return ans;
 }
 
-void Lexicon::InitTokens(const std::string &tokens) {
-  token2id_ = ReadTokens(tokens);
-}
+void Lexicon::InitTokens(std::istream &is) { token2id_ = ReadTokens(is); }
 
 void Lexicon::InitLanguage(const std::string &_lang) {
   std::string lang(_lang);
@@ -209,9 +245,7 @@ void Lexicon::InitLanguage(const std::string &_lang) {
   }
 }
 
-void Lexicon::InitLexicon(const std::string &lexicon) {
-  std::ifstream is(lexicon);
-
+void Lexicon::InitLexicon(std::istream &is) {
   std::string word;
   std::vector<std::string> token_list;
   std::string line;

@@ -6,11 +6,17 @@
 #define SHERPA_ONNX_CSRC_LEXICON_H_
 
 #include <cstdint>
+#include <iostream>
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 namespace sherpa_onnx {
 
 // TODO(fangjun): Refactor it to an abstract class
@@ -20,6 +26,12 @@ class Lexicon {
           const std::string &punctuations, const std::string &language,
           bool debug = false);
 
+#if __ANDROID_API__ >= 9
+  Lexicon(AAssetManager *mgr, const std::string &lexicon,
+          const std::string &tokens, const std::string &punctuations,
+          const std::string &language, bool debug = false);
+#endif
+
   std::vector<int64_t> ConvertTextToTokenIds(const std::string &text) const;
 
  private:
@@ -30,8 +42,8 @@ class Lexicon {
       const std::string &text) const;
 
   void InitLanguage(const std::string &lang);
-  void InitTokens(const std::string &tokens);
-  void InitLexicon(const std::string &lexicon);
+  void InitTokens(std::istream &is);
+  void InitLexicon(std::istream &is);
   void InitPunctuations(const std::string &punctuations);
 
  private:

@@ -16,4 +16,12 @@ std::unique_ptr<OfflineTtsImpl> OfflineTtsImpl::Create(
   return std::make_unique<OfflineTtsVitsImpl>(config);
 }
 
+#if __ANDROID_API__ >= 9
+std::unique_ptr<OfflineTtsImpl> OfflineTtsImpl::Create(
+    AAssetManager *mgr, const OfflineTtsConfig &config) {
+  // TODO(fangjun): Support other types
+  return std::make_unique<OfflineTtsVitsImpl>(mgr, config);
+}
+#endif
+
 }  // namespace sherpa_onnx

@@ -8,6 +8,11 @@
 #include <memory>
 #include <string>
 
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "sherpa-onnx/csrc/offline-tts.h"
 
 namespace sherpa_onnx {
@@ -18,6 +23,11 @@ class OfflineTtsImpl {
 
   static std::unique_ptr<OfflineTtsImpl> Create(const OfflineTtsConfig &config);
 
+#if __ANDROID_API__ >= 9
+  static std::unique_ptr<OfflineTtsImpl> Create(AAssetManager *mgr,
+                                                const OfflineTtsConfig &config);
+#endif
+
   virtual GeneratedAudio Generate(const std::string &text, int64_t sid = 0,
                                   float speed = 1.0) const = 0;
 };

@@ -9,6 +9,11 @@
 #include <utility>
 #include <vector>
 
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "sherpa-onnx/csrc/lexicon.h"
 #include "sherpa-onnx/csrc/macros.h"
 #include "sherpa-onnx/csrc/offline-tts-impl.h"
@@ -24,6 +29,14 @@ class OfflineTtsVitsImpl : public OfflineTtsImpl {
                  model_->Punctuations(), model_->Language(),
                  config.model.debug) {}
 
+#if __ANDROID_API__ >= 9
+  OfflineTtsVitsImpl(AAssetManager *mgr, const OfflineTtsConfig &config)
+      : model_(std::make_unique<OfflineTtsVitsModel>(mgr, config.model)),
+        lexicon_(mgr, config.model.vits.lexicon, config.model.vits.tokens,
+                 model_->Punctuations(), model_->Language(),
+                 config.model.debug) {}
+#endif
+
   GeneratedAudio Generate(const std::string &text, int64_t sid = 0,
                           float speed = 1.0) const override {
     int32_t num_speakers = model_->NumSpeakers();

@@ -26,6 +26,17 @@ class OfflineTtsVitsModel::Impl {
     Init(buf.data(), buf.size());
   }
 
+#if __ANDROID_API__ >= 9
+  Impl(AAssetManager *mgr, const OfflineTtsModelConfig &config)
+      : config_(config),
+        env_(ORT_LOGGING_LEVEL_WARNING),
+        sess_opts_(GetSessionOptions(config)),
+        allocator_{} {
+    auto buf = ReadFile(mgr, config.vits.model);
+    Init(buf.data(), buf.size());
+  }
+#endif
+
   Ort::Value Run(Ort::Value x, int64_t sid, float speed) {
     auto memory_info =
         Ort::MemoryInfo::CreateCpu(OrtDeviceAllocator, OrtMemTypeDefault);
@@ -141,6 +152,12 @@ class OfflineTtsVitsModel::Impl {
 OfflineTtsVitsModel::OfflineTtsVitsModel(const OfflineTtsModelConfig &config)
     : impl_(std::make_unique<Impl>(config)) {}
 
+#if __ANDROID_API__ >= 9
+OfflineTtsVitsModel::OfflineTtsVitsModel(AAssetManager *mgr,
+                                         const OfflineTtsModelConfig &config)
+    : impl_(std::make_unique<Impl>(mgr, config)) {}
+#endif
+
 OfflineTtsVitsModel::~OfflineTtsVitsModel() = default;
 
 Ort::Value OfflineTtsVitsModel::Run(Ort::Value x, int64_t sid /*=0*/,

@@ -8,6 +8,11 @@
 #include <memory>
 #include <string>
 
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "onnxruntime_cxx_api.h"  // NOLINT
 #include "sherpa-onnx/csrc/offline-tts-model-config.h"
 
@@ -18,6 +23,9 @@ class OfflineTtsVitsModel {
   ~OfflineTtsVitsModel();
 
   explicit OfflineTtsVitsModel(const OfflineTtsModelConfig &config);
+#if __ANDROID_API__ >= 9
+  OfflineTtsVitsModel(AAssetManager *mgr, const OfflineTtsModelConfig &config);
+#endif
 
   /** Run the model.
    *

@@ -26,6 +26,11 @@ std::string OfflineTtsConfig::ToString() const {
 OfflineTts::OfflineTts(const OfflineTtsConfig &config)
     : impl_(OfflineTtsImpl::Create(config)) {}
 
+#if __ANDROID_API__ >= 9
+OfflineTts::OfflineTts(AAssetManager *mgr, const OfflineTtsConfig &config)
+    : impl_(OfflineTtsImpl::Create(mgr, config)) {}
+#endif
+
 OfflineTts::~OfflineTts() = default;
 
 GeneratedAudio OfflineTts::Generate(const std::string &text, int64_t sid /*=0*/,

@@ -9,6 +9,11 @@
 #include <string>
 #include <vector>
 
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "sherpa-onnx/csrc/offline-tts-model-config.h"
 #include "sherpa-onnx/csrc/parse-options.h"
 
@@ -38,6 +43,11 @@ class OfflineTts {
  public:
   ~OfflineTts();
   explicit OfflineTts(const OfflineTtsConfig &config);
+
+#if __ANDROID_API__ >= 9
+  OfflineTts(AAssetManager *mgr, const OfflineTtsConfig &config);
+#endif
+
   // @param text A string containing words separated by spaces
   // @param sid Speaker ID. Used only for multi-speaker models, e.g., models
   //            trained using the VCTK dataset. It is not used for

@@ -7,12 +7,13 @@
 #include <cassert>
 #include <fstream>
 #include <sstream>
-#include <strstream>
 
 #include "sherpa-onnx/csrc/base64-decode.h"
 #include "sherpa-onnx/csrc/onnx-utils.h"
 
 #if __ANDROID_API__ >= 9
+#include <strstream>
+
 #include "android/asset_manager.h"
 #include "android/asset_manager_jni.h"
 #endif

@@ -21,10 +21,12 @@
 
 #include "sherpa-onnx/csrc/macros.h"
 #include "sherpa-onnx/csrc/offline-recognizer.h"
+#include "sherpa-onnx/csrc/offline-tts.h"
 #include "sherpa-onnx/csrc/online-recognizer.h"
 #include "sherpa-onnx/csrc/onnx-utils.h"
 #include "sherpa-onnx/csrc/voice-activity-detector.h"
 #include "sherpa-onnx/csrc/wave-reader.h"
+#include "sherpa-onnx/csrc/wave-writer.h"
 
 #define SHERPA_ONNX_EXTERN_C extern "C"
 
@@ -124,7 +126,7 @@ class SherpaOnnxVad {
 
   void Pop() { vad_.Pop(); }
 
-  void Clear() { vad_.Clear();}
+  void Clear() { vad_.Clear(); }
 
   const SpeechSegment &Front() const { return vad_.Front(); }
 
@@ -491,9 +493,173 @@ static VadModelConfig GetVadModelConfig(JNIEnv *env, jobject config) {
   return ans;
 }
 
+class SherpaOnnxOfflineTts {
+ public:
+#if __ANDROID_API__ >= 9
+  SherpaOnnxOfflineTts(AAssetManager *mgr, const OfflineTtsConfig &config)
+      : tts_(mgr, config) {}
+#endif
+  explicit SherpaOnnxOfflineTts(const OfflineTtsConfig &config)
+      : tts_(config) {}
+
+  GeneratedAudio Generate(const std::string &text, int64_t sid = 0,
+                          float speed = 1.0) const {
+    return tts_.Generate(text, sid, speed);
+  }
+
+ private:
+  OfflineTts tts_;
+};
+
+static OfflineTtsConfig GetOfflineTtsConfig(JNIEnv *env, jobject config) {
+  OfflineTtsConfig ans;
+
+  jclass cls = env->GetObjectClass(config);
+  jfieldID fid;
+
+  fid = env->GetFieldID(cls, "model",
+                        "Lcom/k2fsa/sherpa/onnx/OfflineTtsModelConfig;");
+  jobject model = env->GetObjectField(config, fid);
+  jclass model_config_cls = env->GetObjectClass(model);
+
+  fid = env->GetFieldID(model_config_cls, "vits",
+                        "Lcom/k2fsa/sherpa/onnx/OfflineTtsVitsModelConfig;");
+  jobject vits = env->GetObjectField(model, fid);
+  jclass vits_cls = env->GetObjectClass(vits);
+
+  fid = env->GetFieldID(vits_cls, "model", "Ljava/lang/String;");
+  jstring s = (jstring)env->GetObjectField(vits, fid);
+  const char *p = env->GetStringUTFChars(s, nullptr);
+  ans.model.vits.model = p;
+  env->ReleaseStringUTFChars(s, p);
+
+  fid = env->GetFieldID(vits_cls, "lexicon", "Ljava/lang/String;");
+  s = (jstring)env->GetObjectField(vits, fid);
+  p = env->GetStringUTFChars(s, nullptr);
+  ans.model.vits.lexicon = p;
+  env->ReleaseStringUTFChars(s, p);
+
+  fid = env->GetFieldID(vits_cls, "tokens", "Ljava/lang/String;");
+  s = (jstring)env->GetObjectField(vits, fid);
+  p = env->GetStringUTFChars(s, nullptr);
+  ans.model.vits.tokens = p;
+  env->ReleaseStringUTFChars(s, p);
+
+  fid = env->GetFieldID(vits_cls, "noiseScale", "F");
+  ans.model.vits.noise_scale = env->GetFloatField(vits, fid);
+
+  fid = env->GetFieldID(vits_cls, "noiseScaleW", "F");
+  ans.model.vits.noise_scale_w = env->GetFloatField(vits, fid);
+
+  fid = env->GetFieldID(vits_cls, "lengthScale", "F");
+  ans.model.vits.length_scale = env->GetFloatField(vits, fid);
+
+  fid = env->GetFieldID(model_config_cls, "numThreads", "I");
+  ans.model.num_threads = env->GetIntField(model, fid);
+
+  fid = env->GetFieldID(model_config_cls, "debug", "Z");
+  ans.model.debug = env->GetBooleanField(model, fid);
+
+  fid = env->GetFieldID(model_config_cls, "provider", "Ljava/lang/String;");
+  s = (jstring)env->GetObjectField(model, fid);
+  p = env->GetStringUTFChars(s, nullptr);
+  ans.model.provider = p;
+  env->ReleaseStringUTFChars(s, p);
+
+  return ans;
+}
+
 }  // namespace sherpa_onnx
 
 SHERPA_ONNX_EXTERN_C
+JNIEXPORT jlong JNICALL Java_com_k2fsa_sherpa_onnx_OfflineTts_new(
+    JNIEnv *env, jobject /*obj*/, jobject asset_manager, jobject _config) {
+#if __ANDROID_API__ >= 9
+  AAssetManager *mgr = AAssetManager_fromJava(env, asset_manager);
+  if (!mgr) {
+    SHERPA_ONNX_LOGE("Failed to get asset manager: %p", mgr);
+  }
+#endif
+  auto config = sherpa_onnx::GetOfflineTtsConfig(env, _config);
+  SHERPA_ONNX_LOGE("config:\n%s", config.ToString().c_str());
+  auto tts = new sherpa_onnx::SherpaOnnxOfflineTts(
+#if __ANDROID_API__ >= 9
+      mgr,
+#endif
+      config);
+
+  return (jlong)tts;
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jlong JNICALL Java_com_k2fsa_sherpa_onnx_OfflineTts_newFromFile(
+    JNIEnv *env, jobject /*obj*/, jobject _config) {
+  auto config = sherpa_onnx::GetOfflineTtsConfig(env, _config);
+  SHERPA_ONNX_LOGE("config:\n%s", config.ToString().c_str());
+  auto tts = new sherpa_onnx::SherpaOnnxOfflineTts(config);
+
+  return (jlong)tts;
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT void JNICALL Java_com_k2fsa_sherpa_onnx_OfflineTts_delete(
+    JNIEnv *env, jobject /*obj*/, jlong ptr) {
+  delete reinterpret_cast<sherpa_onnx::SherpaOnnxOfflineTts *>(ptr);
+}
+
+// see
+// https://stackoverflow.com/questions/29043872/android-jni-return-multiple-variables
+static jobject NewInteger(JNIEnv *env, int32_t value) {
+  jclass cls = env->FindClass("java/lang/Integer");
+  jmethodID constructor = env->GetMethodID(cls, "<init>", "(I)V");
+  return env->NewObject(cls, constructor, value);
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jobjectArray JNICALL
+Java_com_k2fsa_sherpa_onnx_OfflineTts_generateImpl(JNIEnv *env, jobject /*obj*/,
+                                                   jlong ptr, jstring text,
+                                                   jint sid, jfloat speed) {
+  const char *p_text = env->GetStringUTFChars(text, nullptr);
+  SHERPA_ONNX_LOGE("string is: %s", p_text);
+
+  auto audio =
+      reinterpret_cast<sherpa_onnx::SherpaOnnxOfflineTts *>(ptr)->Generate(
+          p_text, sid, speed);
+
+  jfloatArray samples_arr = env->NewFloatArray(audio.samples.size());
+  env->SetFloatArrayRegion(samples_arr, 0, audio.samples.size(),
+                           audio.samples.data());
+
+  jobjectArray obj_arr = (jobjectArray)env->NewObjectArray(
+      2, env->FindClass("java/lang/Object"), nullptr);
+
+  env->SetObjectArrayElement(obj_arr, 0, samples_arr);
+  env->SetObjectArrayElement(obj_arr, 1, NewInteger(env, audio.sample_rate));
+
+  env->ReleaseStringUTFChars(text, p_text);
+
+  return obj_arr;
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jboolean JNICALL Java_com_k2fsa_sherpa_onnx_GeneratedAudio_saveImpl(
+    JNIEnv *env, jobject /*obj*/, jstring filename, jfloatArray samples,
+    jint sample_rate) {
+  const char *p_filename = env->GetStringUTFChars(filename, nullptr);
+
+  jfloat *p = env->GetFloatArrayElements(samples, nullptr);
+  jsize n = env->GetArrayLength(samples);
+
+  bool ok = sherpa_onnx::WriteWave(p_filename, sample_rate, p, n);
+
+  env->ReleaseStringUTFChars(filename, p_filename);
+  env->ReleaseFloatArrayElements(samples, p, JNI_ABORT);
+
+  return ok;
+}
+
+SHERPA_ONNX_EXTERN_C
 JNIEXPORT jlong JNICALL Java_com_k2fsa_sherpa_onnx_Vad_new(
     JNIEnv *env, jobject /*obj*/, jobject asset_manager, jobject _config) {
 #if __ANDROID_API__ >= 9
@@ -513,6 +679,7 @@ JNIEXPORT jlong JNICALL Java_com_k2fsa_sherpa_onnx_Vad_new(
   return (jlong)model;
 }
 
+SHERPA_ONNX_EXTERN_C
 JNIEXPORT jlong JNICALL Java_com_k2fsa_sherpa_onnx_Vad_newFromFile(
     JNIEnv *env, jobject /*obj*/, jobject _config) {
   auto config = sherpa_onnx::GetVadModelConfig(env, _config);
@@ -566,14 +733,6 @@ JNIEXPORT void JNICALL Java_com_k2fsa_sherpa_onnx_Vad_clear(JNIEnv *env,
   model->Clear();
 }
 
-// see
-// https://stackoverflow.com/questions/29043872/android-jni-return-multiple-variables
-static jobject NewInteger(JNIEnv *env, int32_t value) {
-  jclass cls = env->FindClass("java/lang/Integer");
-  jmethodID constructor = env->GetMethodID(cls, "<init>", "(I)V");
-  return env->NewObject(cls, constructor, value);
-}
-
 SHERPA_ONNX_EXTERN_C
 JNIEXPORT jobjectArray JNICALL
 Java_com_k2fsa_sherpa_onnx_Vad_front(JNIEnv *env, jobject /*obj*/, jlong ptr) {