diff --git a/.github/scripts/test-nodejs-npm.sh b/.github/scripts/test-nodejs-npm.sh
index 0dc79928..8da89ffa 100755
--- a/.github/scripts/test-nodejs-npm.sh
+++ b/.github/scripts/test-nodejs-npm.sh
@@ -52,14 +52,13 @@ node ./test-online-transducer.js
 rm -rf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20
 
 # offline tts
-curl -LS -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-vctk.tar.bz2
-tar xvf vits-vctk.tar.bz2
-rm vits-vctk.tar.bz2
+
+curl -LS -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+tar xf vits-piper-en_US-amy-low.tar.bz2
 node ./test-offline-tts-en.js
-rm -rf vits-vctk
+rm vits-piper-en_US-amy-low.tar.bz2
 
 curl -LS -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-zh-aishell3.tar.bz2
 tar xvf vits-zh-aishell3.tar.bz2
-rm vits-zh-aishell3.tar.bz2
 node ./test-offline-tts-zh.js
-rm -rf vits-zh-aishell3
+rm vits-zh-aishell3.tar.bz2
diff --git a/.github/scripts/test-offline-tts.sh b/.github/scripts/test-offline-tts.sh
index 15be2d92..dca90b1d 100755
--- a/.github/scripts/test-offline-tts.sh
+++ b/.github/scripts/test-offline-tts.sh
@@ -16,6 +16,24 @@ which $EXE
 # test waves are saved in ./tts
 mkdir ./tts
 
+log "------------------------------------------------------------"
+log "vits-piper-en_US-amy-low"
+log "------------------------------------------------------------"
+curl -O -SL https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+tar xf vits-piper-en_US-amy-low.tar.bz2
+rm vits-piper-en_US-amy-low.tar.bz2
+
+$EXE \
+  --vits-model=./vits-piper-en_US-amy-low/en_US-amy-low.onnx \
+  --vits-tokens=./vits-piper-en_US-amy-low/tokens.txt \
+  --vits-data-dir=./vits-piper-en_US-amy-low/espeak-ng-data \
+  --debug=1 \
+  --output-filename=./tts/amy.wav \
+  "“Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.” The sun shone bleakly in the sky, its meager light struggling to penetrate the thick foliage of the forest. Birds sang their songs up in the crowns of the trees, fluttering from one branch to the other. A blanket of total tranquility lied over the forest. The peace was only broken by the steady gallop of the horses of the soldiers who were traveling to their upcoming knighting the morrow at Camelot, and rowdy conversation. “Finally we will get what we deserve,” “It’s been about time,” Perceval agreed. “We’ve been risking our arses for the past two years. It’s the least they could give us.” Merlin remained ostensibly silent, refusing to join the verbal parade of self-aggrandizing his fellow soldiers have engaged in. He found it difficult to happy about anything, when even if they had won the war, he had lost everything else in the process."
+
+file ./tts/amy.wav
+rm -rf vits-piper-en_US-amy-low
+
 log "------------------------------------------------------------"
 log "vits-ljs test"
 log "------------------------------------------------------------"
diff --git a/.github/workflows/apk-tts.yaml b/.github/workflows/apk-tts.yaml
index ffd7ab1d..6672cc50 100644
--- a/.github/workflows/apk-tts.yaml
+++ b/.github/workflows/apk-tts.yaml
@@ -26,8 +26,8 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        total: ["12"]
-        index: ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"]
+        total: ["30"]
+        index: ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29"]
 
     steps:
       - uses: actions/checkout@v4
diff --git a/.github/workflows/test-build-wheel.yaml b/.github/workflows/test-build-wheel.yaml
new file mode 100644
index 00000000..ddbc4099
--- /dev/null
+++ b/.github/workflows/test-build-wheel.yaml
@@ -0,0 +1,80 @@
+name: test-build-wheel
+
+on:
+  push:
+    branches:
+      - master
+
+  pull_request:
+
+  workflow_dispatch:
+
+concurrency:
+  group: test-build-wheel-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test-build-wheel:
+    name: ${{ matrix.os }} ${{ matrix.python_version }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: ccache
+        uses: hendrikmuhs/ccache-action@v1.2
+        with:
+          key: ${{ matrix.os }}-${{ matrix.python_version }}
+
+      - name: Install python dependencies
+        shell: bash
+        run: |
+          python3 -m pip install --upgrade pip
+          python3 -m pip install wheel twine setuptools
+
+      - name: Build
+        shell: bash
+        run: |
+          export CMAKE_CXX_COMPILER_LAUNCHER=ccache
+          export PATH="/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH"
+          cmake --version
+
+          export SHERPA_ONNX_MAKE_ARGS="VERBOSE=1 -j"
+
+          python3 setup.py bdist_wheel
+          ls -lh dist
+
+      - name: Display wheel
+        shell: bash
+        run: |
+          ls -lh dist
+
+      - name: Install wheel
+        shell: bash
+        run: |
+          pip install --verbose ./dist/*.whl
+
+      - name: Test
+        shell: bash
+        run: |
+          # For windows
+          export PATH=/c/hostedtoolcache/windows/Python/3.7.9/x64/bin:$PATH
+          export PATH=/c/hostedtoolcache/windows/Python/3.8.10/x64/bin:$PATH
+          export PATH=/c/hostedtoolcache/windows/Python/3.9.13/x64/bin:$PATH
+          export PATH=/c/hostedtoolcache/windows/Python/3.10.11/x64/bin:$PATH
+          export PATH=/c/hostedtoolcache/windows/Python/3.11.6/x64/bin:$PATH
+
+          which sherpa-onnx
+          sherpa-onnx --help
diff --git a/.github/workflows/test-nodejs.yaml b/.github/workflows/test-nodejs.yaml
index c65ebecc..8dd94406 100644
--- a/.github/workflows/test-nodejs.yaml
+++ b/.github/workflows/test-nodejs.yaml
@@ -70,6 +70,10 @@ jobs:
             mkdir -p scripts/nodejs/lib/win-x64
             dst=scripts/nodejs/lib/win-x64
           fi
+          ls -lh build/install/lib/
+
+          rm -rf build/install/lib/pkgconfig
+
           cp -v build/install/lib/* $dst/
 
       - name: replace files
diff --git a/.gitignore b/.gitignore
index 0b429133..d63a3eee 100644
--- a/.gitignore
+++ b/.gitignore
@@ -77,3 +77,6 @@ xcuserdata/
 vits-vctk
 vits-zh-aishell3
 jslint.mjs
+vits-piper-en_US-amy-low
+vits-piper-*-*-*
+log
diff --git a/android/SherpaOnnxTts/app/src/main/AndroidManifest.xml b/android/SherpaOnnxTts/app/src/main/AndroidManifest.xml
index 584bbec5..628423a2 100644
--- a/android/SherpaOnnxTts/app/src/main/AndroidManifest.xml
+++ b/android/SherpaOnnxTts/app/src/main/AndroidManifest.xml
@@ -2,6 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
+
     <application
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
diff --git a/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/MainActivity.kt b/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/MainActivity.kt
index 72bba99e..50caa49f 100644
--- a/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/MainActivity.kt
+++ b/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/MainActivity.kt
@@ -1,5 +1,6 @@
 package com.k2fsa.sherpa.onnx
 
+import android.content.res.AssetManager
 import android.media.MediaPlayer
 import android.net.Uri
 import android.os.Bundle
@@ -9,6 +10,8 @@ import android.widget.EditText
 import android.widget.Toast
 import androidx.appcompat.app.AppCompatActivity
 import java.io.File
+import java.io.FileOutputStream
+import java.io.IOException
 
 const val TAG = "sherpa-onnx"
 
@@ -19,7 +22,6 @@ class MainActivity : AppCompatActivity() {
     private lateinit var speed: EditText
     private lateinit var generate: Button
     private lateinit var play: Button
-    private var hasFile: Boolean = false
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -46,10 +48,10 @@ class MainActivity : AppCompatActivity() {
         val sampleText = ""
         text.setText(sampleText)
 
-        play.isEnabled = false;
+        play.isEnabled = false
     }
 
-    fun onClickGenerate() {
+    private fun onClickGenerate() {
         val sidInt = sid.text.toString().toIntOrNull()
         if (sidInt == null || sidInt < 0) {
             Toast.makeText(
@@ -77,7 +79,7 @@ class MainActivity : AppCompatActivity() {
             return
         }
 
-        play.isEnabled = false;
+        play.isEnabled = false
         val audio = tts.generate(text = textStr, sid = sidInt, speed = speedFloat)
 
         val filename = application.filesDir.absolutePath + "/generated.wav"
@@ -89,7 +91,7 @@ class MainActivity : AppCompatActivity() {
         }
     }
 
-    fun onClickPlay() {
+    private fun onClickPlay() {
         val filename = application.filesDir.absolutePath + "/generated.wav"
         val mediaPlayer = MediaPlayer.create(
             applicationContext,
@@ -98,10 +100,13 @@ class MainActivity : AppCompatActivity() {
         mediaPlayer.start()
     }
 
-    fun initTts() {
-        var modelDir :String?
-        var modelName :String?
+    private fun initTts() {
+        var modelDir: String?
+        var modelName: String?
         var ruleFsts: String?
+        var lexicon: String?
+        var dataDir: String?
+        var assets: AssetManager? = application.assets
 
         // The purpose of such a design is to make the CI test easier
         // Please see
@@ -109,21 +114,90 @@ class MainActivity : AppCompatActivity() {
         modelDir = null
         modelName = null
         ruleFsts = null
+        lexicon = null
+        dataDir = null
 
         // Example 1:
         // modelDir = "vits-vctk"
         // modelName = "vits-vctk.onnx"
+        // lexicon = "lexicon.txt"
 
         // Example 2:
-        // modelDir = "vits-piper-en_US-lessac-medium"
-        // modelName = "en_US-lessac-medium.onnx"
+        // https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
+        // https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+        // modelDir = "vits-piper-en_US-amy-low"
+        // modelName = "en_US-amy-low.onnx"
+        // dataDir = "vits-piper-en_US-amy-low/espeak-ng-data"
 
         // Example 3:
         // modelDir = "vits-zh-aishell3"
         // modelName = "vits-aishell3.onnx"
         // ruleFsts = "vits-zh-aishell3/rule.fst"
+        // lexcion = "lexicon.txt"
 
-        val config = getOfflineTtsConfig(modelDir = modelDir!!, modelName = modelName!!, ruleFsts = ruleFsts ?: "")!!
-        tts = OfflineTts(assetManager = application.assets, config = config)
+        if (dataDir != null) {
+            val newDir = copyDataDir(modelDir)
+            modelDir = newDir + "/" + modelDir
+            dataDir = newDir + "/" + dataDir
+            assets = null
+        }
+
+        val config = getOfflineTtsConfig(
+            modelDir = modelDir!!, modelName = modelName!!, lexicon = lexicon ?: "",
+            dataDir = dataDir ?: "",
+            ruleFsts = ruleFsts ?: ""
+        )!!
+
+        tts = OfflineTts(assetManager = assets, config = config)
+    }
+
+
+    private fun copyDataDir(dataDir: String): String {
+        println("data dir is $dataDir")
+        copyAssets(dataDir)
+
+        val newDataDir = application.getExternalFilesDir(null)!!.absolutePath
+        println("newDataDir: $newDataDir")
+        return newDataDir
+    }
+
+    private fun copyAssets(path: String) {
+        val assets: Array<String>?
+        try {
+            assets = application.assets.list(path)
+            if (assets!!.isEmpty()) {
+                copyFile(path)
+            } else {
+                val fullPath = "${application.getExternalFilesDir(null)}/$path"
+                val dir = File(fullPath)
+                dir.mkdirs()
+                for (asset in assets.iterator()) {
+                    val p: String = if (path == "") "" else path + "/"
+                    copyAssets(p + asset)
+                }
+            }
+        } catch (ex: IOException) {
+            Log.e(TAG, "Failed to copy $path. ${ex.toString()}")
+        }
+    }
+
+    private fun copyFile(filename: String) {
+        try {
+            val istream = application.assets.open(filename)
+            val newFilename = application.getExternalFilesDir(null).toString() + "/" + filename
+            val ostream = FileOutputStream(newFilename)
+            // Log.i(TAG, "Copying $filename to $newFilename")
+            val buffer = ByteArray(1024)
+            var read = 0
+            while (read != -1) {
+                ostream.write(buffer, 0, read)
+                read = istream.read(buffer)
+            }
+            istream.close()
+            ostream.flush()
+            ostream.close()
+        } catch (ex: Exception) {
+            Log.e(TAG, "Failed to copy $filename, ${ex.toString()}")
+        }
     }
 }
diff --git a/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/Tts.kt b/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/Tts.kt
index cf6b1e25..132e8b06 100644
--- a/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/Tts.kt
+++ b/android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/Tts.kt
@@ -5,8 +5,9 @@ import android.content.res.AssetManager
 
 data class OfflineTtsVitsModelConfig(
     var model: String,
-    var lexicon: String,
+    var lexicon: String = "",
     var tokens: String,
+    var dataDir: String = "",
     var noiseScale: Float = 0.667f,
     var noiseScaleW: Float = 0.8f,
     var lengthScale: Float = 1.0f,
@@ -22,6 +23,7 @@ data class OfflineTtsModelConfig(
 data class OfflineTtsConfig(
     var model: OfflineTtsModelConfig,
     var ruleFsts: String = "",
+    var maxNumSentences: Int = 2,
 )
 
 class GeneratedAudio(
@@ -117,18 +119,25 @@ class OfflineTts(
 // please refer to
 // https://k2-fsa.github.io/sherpa/onnx/tts/pretrained_models/index.html
 // to download models
-fun getOfflineTtsConfig(modelDir: String, modelName: String, ruleFsts: String): OfflineTtsConfig? {
+fun getOfflineTtsConfig(
+    modelDir: String,
+    modelName: String,
+    lexicon: String,
+    dataDir: String,
+    ruleFsts: String
+): OfflineTtsConfig? {
     return OfflineTtsConfig(
         model = OfflineTtsModelConfig(
             vits = OfflineTtsVitsModelConfig(
                 model = "$modelDir/$modelName",
-                lexicon = "$modelDir/lexicon.txt",
-                tokens = "$modelDir/tokens.txt"
+                lexicon = "$modelDir/$lexicon",
+                tokens = "$modelDir/tokens.txt",
+                dataDir = "$dataDir"
             ),
             numThreads = 2,
             debug = true,
             provider = "cpu",
         ),
-        ruleFsts=ruleFsts,
+        ruleFsts = ruleFsts,
     )
 }
diff --git a/build-android-arm64-v8a.sh b/build-android-arm64-v8a.sh
index 8297561f..a424cbca 100755
--- a/build-android-arm64-v8a.sh
+++ b/build-android-arm64-v8a.sh
@@ -92,3 +92,4 @@ cmake -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK/build/cmake/android.toolchain.cmake"
 make -j4
 make install/strip
 cp -fv android-onnxruntime-libs/jni/arm64-v8a/libonnxruntime.so install/lib
+rm -rf install/lib/pkgconfig
diff --git a/build-android-armv7-eabi.sh b/build-android-armv7-eabi.sh
index 9157f4cd..fc93a627 100755
--- a/build-android-armv7-eabi.sh
+++ b/build-android-armv7-eabi.sh
@@ -92,3 +92,4 @@ cmake -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK/build/cmake/android.toolchain.cmake"
 make -j4
 make install/strip
 cp -fv android-onnxruntime-libs/jni/armeabi-v7a/libonnxruntime.so install/lib
+rm -rf install/lib/pkgconfig
diff --git a/build-android-x86-64.sh b/build-android-x86-64.sh
index 02a7b959..728f38d2 100755
--- a/build-android-x86-64.sh
+++ b/build-android-x86-64.sh
@@ -94,3 +94,4 @@ cmake -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK/build/cmake/android.toolchain.cmake"
 make -j4
 make install/strip
 cp -fv android-onnxruntime-libs/jni/x86_64/libonnxruntime.so install/lib
+rm -rf install/lib/pkgconfig
diff --git a/build-android-x86.sh b/build-android-x86.sh
index 1b6194f3..99091a17 100755
--- a/build-android-x86.sh
+++ b/build-android-x86.sh
@@ -94,3 +94,4 @@ cmake -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK/build/cmake/android.toolchain.cmake"
 make -j4
 make install/strip
 cp -fv android-onnxruntime-libs/jni/x86/libonnxruntime.so install/lib
+rm -rf install/lib/pkgconfig
diff --git a/build-ios.sh b/build-ios.sh
index 5f82c40b..bed00c47 100755
--- a/build-ios.sh
+++ b/build-ios.sh
@@ -140,7 +140,8 @@ echo "Generate xcframework"
 
 mkdir -p "build/simulator/lib"
 for f in libkaldi-native-fbank-core.a libsherpa-onnx-c-api.a libsherpa-onnx-core.a \
-         libsherpa-onnx-fst.a libsherpa-onnx-kaldifst-core.a libkaldi-decoder-core.a; do
+         libsherpa-onnx-fst.a libsherpa-onnx-kaldifst-core.a libkaldi-decoder-core.a \
+         libucd.a libpiper_phonemize.a libespeak-ng.a; do
   lipo -create build/simulator_arm64/lib/${f} \
                build/simulator_x86_64/lib/${f} \
        -output build/simulator/lib/${f}
@@ -154,7 +155,10 @@ libtool -static -o build/simulator/sherpa-onnx.a \
   build/simulator/lib/libsherpa-onnx-core.a  \
   build/simulator/lib/libsherpa-onnx-fst.a   \
   build/simulator/lib/libsherpa-onnx-kaldifst-core.a \
-  build/simulator/lib/libkaldi-decoder-core.a
+  build/simulator/lib/libkaldi-decoder-core.a \
+  build/simulator/lib/libucd.a \
+  build/simulator/lib/libpiper_phonemize.a \
+  build/simulator/lib/libespeak-ng.a \
 
 libtool -static -o build/os64/sherpa-onnx.a \
   build/os64/lib/libkaldi-native-fbank-core.a \
@@ -162,7 +166,10 @@ libtool -static -o build/os64/sherpa-onnx.a \
   build/os64/lib/libsherpa-onnx-core.a \
   build/os64/lib/libsherpa-onnx-fst.a   \
   build/os64/lib/libsherpa-onnx-kaldifst-core.a \
-  build/os64/lib/libkaldi-decoder-core.a
+  build/os64/lib/libkaldi-decoder-core.a \
+  build/os64/lib/libucd.a \
+  build/os64/lib/libpiper_phonemize.a \
+  build/os64/lib/libespeak-ng.a \
 
 
 rm -rf sherpa-onnx.xcframework
diff --git a/build-swift-macos.sh b/build-swift-macos.sh
index a1b06205..e5cdbc08 100755
--- a/build-swift-macos.sh
+++ b/build-swift-macos.sh
@@ -29,4 +29,7 @@ libtool -static -o ./install/lib/libsherpa-onnx.a \
   ./install/lib/libkaldi-native-fbank-core.a \
   ./install/lib/libsherpa-onnx-fst.a \
   ./install/lib/libsherpa-onnx-kaldifst-core.a \
-  ./install/lib/libkaldi-decoder-core.a
+  ./install/lib/libkaldi-decoder-core.a \
+  ./install/lib/libucd.a \
+  ./install/lib/libpiper_phonemize.a \
+  ./install/lib/libespeak-ng.a
diff --git a/c-api-examples/offline-tts-c-api.c b/c-api-examples/offline-tts-c-api.c
index c4e9be62..7fbdb004 100644
--- a/c-api-examples/offline-tts-c-api.c
+++ b/c-api-examples/offline-tts-c-api.c
@@ -65,6 +65,29 @@ static struct cag_option options[] = {
      .identifier = 'a',
      .description =
          "Filename to save the generated audio. Default to ./generated.wav"},
+
+    {.access_name = "tts-rule-fsts",
+     .value_name = "/path/to/rule.fst",
+     .identifier = 'b',
+     .description = "It not empty, it contains a list of rule FST filenames."
+                    "Multiple filenames are separated by a comma and they are "
+                    "applied from left to right. An example value: "
+                    "rule1.fst,rule2,fst,rule3.fst"},
+
+    {.access_name = "max-num-sentences",
+     .value_name = "2",
+     .identifier = 'c',
+     .description = "Maximum number of sentences that we process at a time. "
+                    "This is to avoid OOM for very long input text. "
+                    "If you set it to -1, then we process all sentences in a "
+                    "single batch."},
+
+    {.access_name = "vits-data-dir",
+     .value_name = "/path/to/espeak-ng-data",
+     .identifier = 'd',
+     .description =
+         "Path to espeak-ng-data. If it is given, --vits-lexicon is ignored"},
+
 };
 
 static void ShowUsage() {
@@ -163,15 +186,38 @@ int32_t main(int32_t argc, char *argv[]) {
         free((void *)filename);
         filename = strdup(value);
         break;
+      case 'b':
+        config.rule_fsts = value;
+        break;
+      case 'c':
+        config.max_num_sentences = atoi(value);
+        break;
+      case 'd':
+        config.model.vits.data_dir = value;
+        break;
+      case '?':
+        fprintf(stderr, "Unknown option\n");
+        // fall through
       case 'h':
         // fall through
       default:
         ShowUsage();
     }
   }
+  fprintf(stderr, "here\n");
 
-  if (!config.model.vits.model || !config.model.vits.lexicon ||
-      !config.model.vits.tokens) {
+  if (!config.model.vits.model) {
+    fprintf(stderr, "Please provide --vits-model\n");
+    ShowUsage();
+  }
+
+  if (!config.model.vits.tokens) {
+    fprintf(stderr, "Please provide --vits-tokens\n");
+    ShowUsage();
+  }
+
+  if (!config.model.vits.data_dir && !config.model.vits.lexicon) {
+    fprintf(stderr, "Please provide --vits-data-dir or --vits-lexicon\n");
     ShowUsage();
   }
 
diff --git a/cmake/cmake_extension.py b/cmake/cmake_extension.py
index c67abc50..008dbd67 100644
--- a/cmake/cmake_extension.py
+++ b/cmake/cmake_extension.py
@@ -73,6 +73,10 @@ class BuildExtension(build_ext):
 
         extra_cmake_args = f" -DCMAKE_INSTALL_PREFIX={install_dir} "
         extra_cmake_args += " -DBUILD_SHARED_LIBS=ON "
+        extra_cmake_args += " -DBUILD_PIPER_PHONMIZE_EXE=OFF "
+        extra_cmake_args += " -DBUILD_PIPER_PHONMIZE_TESTS=OFF "
+        extra_cmake_args += " -DBUILD_ESPEAK_NG_EXE=OFF "
+        extra_cmake_args += " -DBUILD_ESPEAK_NG_TESTS=OFF "
 
         extra_cmake_args += " -DSHERPA_ONNX_ENABLE_CHECK=OFF "
         extra_cmake_args += " -DSHERPA_ONNX_ENABLE_PYTHON=ON "
@@ -146,6 +150,9 @@ class BuildExtension(build_ext):
             binaries += ["sherpa-onnx-core.dll"]
             binaries += ["sherpa-onnx-portaudio.dll"]
             binaries += ["onnxruntime.dll"]
+            binaries += ["piper_phonemize.dll"]
+            binaries += ["espeak-ng.dll"]
+            binaries += ["ucd.dll"]
             binaries += ["kaldi-decoder-core.dll"]
             binaries += ["sherpa-onnx-fst.lib"]
             binaries += ["sherpa-onnx-kaldifst-core.lib"]
@@ -161,5 +168,8 @@ class BuildExtension(build_ext):
             shutil.copy(f"{src_file}", f"{out_bin_dir}/")
 
         shutil.rmtree(f"{install_dir}/bin")
+        shutil.rmtree(f"{install_dir}/share")
+        shutil.rmtree(f"{install_dir}/lib/pkgconfig")
+
         if is_windows():
             shutil.rmtree(f"{install_dir}/lib")
diff --git a/cmake/espeak-ng-for-piper.cmake b/cmake/espeak-ng-for-piper.cmake
index e1dfb2fc..38f3fa55 100644
--- a/cmake/espeak-ng-for-piper.cmake
+++ b/cmake/espeak-ng-for-piper.cmake
@@ -86,7 +86,7 @@ function(download_espeak_ng_for_piper)
       -Wno-unused-result
       -Wno-format-overflow
       -Wno-format-truncation
-      -Wno-maybe-uninitialized
+      -Wno-uninitialized
       -Wno-format
     )
 
diff --git a/cmake/sherpa-onnx.pc.in b/cmake/sherpa-onnx.pc.in
index 1d38622e..b9c5af9c 100644
--- a/cmake/sherpa-onnx.pc.in
+++ b/cmake/sherpa-onnx.pc.in
@@ -13,4 +13,4 @@ Cflags: -I"${includedir}"
 # Note: -lcargs is required only for the following file
 # https://github.com/k2-fsa/sherpa-onnx/blob/master/c-api-examples/decode-file-c-api.c
 # We add it here so that users don't need to specify -lcargs when compiling decode-file-c-api.c
-Libs: -L"${libdir}" -lsherpa-onnx-c-api -lsherpa-onnx-core -lonnxruntime -lkaldi-decoder-core -lsherpa-onnx-kaldifst-core -lsherpa-onnx-fst -lkaldi-native-fbank-core -lcargs -Wl,-rpath,${libdir} @SHERPA_ONNX_PKG_CONFIG_EXTRA_LIBS@
+Libs: -L"${libdir}" -lsherpa-onnx-c-api -lsherpa-onnx-core -lonnxruntime -lkaldi-decoder-core -lsherpa-onnx-kaldifst-core -lsherpa-onnx-fst -lkaldi-native-fbank-core -lpiper_phonemize -lespeak-ng -lucd -lcargs -Wl,-rpath,${libdir} @SHERPA_ONNX_PKG_CONFIG_EXTRA_LIBS@
diff --git a/ios-swift/SherpaOnnx/SherpaOnnx.xcodeproj/project.pbxproj b/ios-swift/SherpaOnnx/SherpaOnnx.xcodeproj/project.pbxproj
index f74b87f4..0d3be225 100644
--- a/ios-swift/SherpaOnnx/SherpaOnnx.xcodeproj/project.pbxproj
+++ b/ios-swift/SherpaOnnx/SherpaOnnx.xcodeproj/project.pbxproj
@@ -40,7 +40,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
-		C93989AF2A89FE33009AB859 /* onnxruntime.xcframework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.xcframework; name = onnxruntime.xcframework; path = "../../build-ios/ios-onnxruntime/1.16.0/onnxruntime.xcframework"; sourceTree = "<group>"; };
+		C93989AF2A89FE33009AB859 /* onnxruntime.xcframework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.xcframework; name = onnxruntime.xcframework; path = "../../build-ios/ios-onnxruntime/1.16.3/onnxruntime.xcframework"; sourceTree = "<group>"; };
 		C93989B12A89FF78009AB859 /* decoder.int8.onnx */ = {isa = PBXFileReference; lastKnownFileType = file; name = decoder.int8.onnx; path = "../../../icefall-models/sherpa-onnx-streaming-paraformer-bilingual-zh-en/decoder.int8.onnx"; sourceTree = "<group>"; };
 		C93989B22A89FF78009AB859 /* encoder.int8.onnx */ = {isa = PBXFileReference; lastKnownFileType = file; name = encoder.int8.onnx; path = "../../../icefall-models/sherpa-onnx-streaming-paraformer-bilingual-zh-en/encoder.int8.onnx"; sourceTree = "<group>"; };
 		C93989B32A89FF78009AB859 /* tokens.txt */ = {isa = PBXFileReference; lastKnownFileType = text; name = tokens.txt; path = "../../../icefall-models/sherpa-onnx-streaming-paraformer-bilingual-zh-en/tokens.txt"; sourceTree = "<group>"; };
diff --git a/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ContentView.swift b/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ContentView.swift
index debc8cb5..fca8db7b 100644
--- a/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ContentView.swift
+++ b/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ContentView.swift
@@ -65,7 +65,7 @@ struct ContentView: View {
                         self.filename = tempDirectoryURL.appendingPathComponent("test.wav")
                     }
 
-                    let ret = audio.save(filename: filename.path)
+                    let _ = audio.save(filename: filename.path)
 
                     self.audioPlayer = try! AVAudioPlayer(contentsOf: filename)
                     self.audioPlayer.play()
diff --git a/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ViewModel.swift b/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ViewModel.swift
index a42ecc78..f29de9e8 100644
--- a/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ViewModel.swift
+++ b/ios-swiftui/SherpaOnnxTts/SherpaOnnxTts/ViewModel.swift
@@ -7,6 +7,12 @@
 
 import Foundation
 
+
+// used to get the path to espeak-ng-data
+func resourceURL(to path: String) -> String {
+    return URL(string: path, relativeTo: Bundle.main.resourceURL)!.path
+}
+
 func getResource(_ forResource: String, _ ofType: String) -> String {
   let path = Bundle.main.path(forResource: forResource, ofType: ofType)
   precondition(
@@ -59,8 +65,30 @@ func getTtsForAishell3() -> SherpaOnnxOfflineTtsWrapper {
   return SherpaOnnxOfflineTtsWrapper(config: &config)
 }
 
+// https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
+func getTtsFor_en_US_amy_low() -> SherpaOnnxOfflineTtsWrapper {
+  // please see  https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+
+  // vits-vctk.onnx
+  let model = getResource("en_US-amy-low", "onnx")
+
+  // tokens.txt
+  let tokens = getResource("tokens", "txt")
+
+  // in this case, we don't need lexicon.txt
+  let dataDir = resourceURL(to: "espeak-ng-data")
+
+  let vits = sherpaOnnxOfflineTtsVitsModelConfig(model: model, lexicon: "", tokens: tokens, dataDir: dataDir)
+  let modelConfig = sherpaOnnxOfflineTtsModelConfig(vits: vits)
+  var config = sherpaOnnxOfflineTtsConfig(model: modelConfig)
+
+  return SherpaOnnxOfflineTtsWrapper(config: &config)
+}
+
 func createOfflineTts() -> SherpaOnnxOfflineTtsWrapper {
-  return getTtsForVCTK()
+  return getTtsFor_en_US_amy_low()
+
+  // return getTtsForVCTK()
 
   // return getTtsForAishell3()
 
diff --git a/kotlin-api-examples/Main.kt b/kotlin-api-examples/Main.kt
index 69c41dfd..4d7b5ff6 100644
--- a/kotlin-api-examples/Main.kt
+++ b/kotlin-api-examples/Main.kt
@@ -8,20 +8,22 @@ fun main() {
 }
 
 fun testTts() {
+  // see https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
+  // https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
   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",
+        model="./vits-piper-en_US-amy-low/en_US-amy-low.onnx",
+        tokens="./vits-piper-en_US-amy-low/tokens.txt",
+        dataDir="./vits-piper-en_US-amy-low/espeak-ng-data",
       ),
       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")
+  val audio = tts.generate(text="“Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.”")
+  audio.save(filename="test-en.wav")
 }
 
 fun testAsr() {
diff --git a/kotlin-api-examples/run.sh b/kotlin-api-examples/run.sh
index 21e36430..499221e7 100755
--- a/kotlin-api-examples/run.sh
+++ b/kotlin-api-examples/run.sh
@@ -34,9 +34,10 @@ 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
 
-if [ ! -f ./vits-zh-aishell3/tokens.txt ]; then
-  git lfs install
-  git clone https://huggingface.co/csukuangfj/vits-zh-aishell3
+if [ ! -f ./vits-piper-en_US-amy-low/en_US-amy-low.onnx ]; then
+  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+  tar xf vits-piper-en_US-amy-low.tar.bz2
+  rm vits-piper-en_US-amy-low.tar.bz2
 fi
 
 kotlinc-jvm -include-runtime -d main.jar Main.kt WaveReader.kt SherpaOnnx.kt faked-asset-manager.kt Tts.kt
diff --git a/nodejs-examples/.gitignore b/nodejs-examples/.gitignore
index d5f19d89..1c2d5f33 100644
--- a/nodejs-examples/.gitignore
+++ b/nodejs-examples/.gitignore
@@ -1,2 +1,3 @@
 node_modules
+lib
 package-lock.json
diff --git a/nodejs-examples/README.md b/nodejs-examples/README.md
index 1ee665e3..647609a2 100644
--- a/nodejs-examples/README.md
+++ b/nodejs-examples/README.md
@@ -42,15 +42,14 @@ In the following, we demonstrate how to run text-to-speech.
 ## ./test-offline-tts-en.js
 
 [./test-offline-tts-en.js](./test-offline-tts-en.js) shows how to use
-a VITS pretrained model
-[VCTK](https://k2-fsa.github.io/sherpa/onnx/tts/pretrained_models/vits.html#vctk-english-multi-speaker-109-speakers)
+[vits-piper-en_US-amy-low.tar.bz2](https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2)
 for text-to-speech.
 
 You can use the following command to run it:
 
 ```bash
-wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-vctk.tar.bz2
-tar xvf vits-vctk.tar.bz2
+wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+tar xvf vits-piper-en_US-amy-low.tar.bz2
 node ./test-offline-tts-en.js
 ```
 
diff --git a/nodejs-examples/test-offline-tts-en.js b/nodejs-examples/test-offline-tts-en.js
index e44e1a55..8f0e0c02 100644
--- a/nodejs-examples/test-offline-tts-en.js
+++ b/nodejs-examples/test-offline-tts-en.js
@@ -4,9 +4,9 @@ const sherpa_onnx = require('sherpa-onnx');
 
 function createOfflineTts() {
   const vits = new sherpa_onnx.OfflineTtsVitsModelConfig();
-  vits.model = './vits-vctk/vits-vctk.onnx';
-  vits.lexicon = './vits-vctk/lexicon.txt';
-  vits.tokens = './vits-vctk/tokens.txt';
+  vits.model = 'vits-piper-en_US-amy-low/en_US-amy-low.onnx'
+  vits.tokens = './vits-piper-en_US-amy-low/tokens.txt';
+  vits.dataDir = './vits-piper-en_US-amy-low/espeak-ng-data'
 
   const modelConfig = new sherpa_onnx.OfflineTtsModelConfig();
   modelConfig.vits = vits;
@@ -18,10 +18,11 @@ function createOfflineTts() {
 }
 
 const tts = createOfflineTts();
-const speakerId = 99;
+const speakerId = 0;
 const speed = 1.0;
-const audio =
-    tts.generate('Good morning. How are you doing?', speakerId, speed);
+const audio = tts.generate(
+    '“Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.”',
+    speakerId, speed);
 audio.save('./test-en.wav');
 console.log('Saved to test-en.wav successfully.');
 tts.free();
diff --git a/python-api-examples/offline-tts.py b/python-api-examples/offline-tts.py
index c05cde1e..c806ce4c 100755
--- a/python-api-examples/offline-tts.py
+++ b/python-api-examples/offline-tts.py
@@ -63,15 +63,25 @@ def get_args():
     parser.add_argument(
         "--vits-lexicon",
         type=str,
+        default="",
         help="Path to lexicon.txt",
     )
 
     parser.add_argument(
         "--vits-tokens",
         type=str,
+        default="",
         help="Path to tokens.txt",
     )
 
+    parser.add_argument(
+        "--vits-data-dir",
+        type=str,
+        default="",
+        help="""Path to the dict director of espeak-ng. If it is specified,
+        --vits-lexicon and --vits-tokens are ignored""",
+    )
+
     parser.add_argument(
         "--tts-rule-fsts",
         type=str,
@@ -79,6 +89,17 @@ def get_args():
         help="Path to rule.fst",
     )
 
+    parser.add_argument(
+        "--max-num-sentences",
+        type=int,
+        default=2,
+        help="""Max number of sentences in a batch to avoid OOM if the input
+        text is very long. Set it to -1 to process all the sentences in a
+        single batch. A smaller value does not mean it is slower compared
+        to a larger one on CPU.
+        """,
+    )
+
     parser.add_argument(
         "--output-filename",
         type=str,
@@ -142,14 +163,19 @@ def main():
             vits=sherpa_onnx.OfflineTtsVitsModelConfig(
                 model=args.vits_model,
                 lexicon=args.vits_lexicon,
+                data_dir=args.vits_data_dir,
                 tokens=args.vits_tokens,
             ),
             provider=args.provider,
             debug=args.debug,
             num_threads=args.num_threads,
         ),
-        rule_fsts=args.tts_rule_fsts
+        rule_fsts=args.tts_rule_fsts,
+        max_num_sentences=args.max_num_sentences,
     )
+    if not tts_config.validate():
+        raise ValueError("Please check your config")
+
     tts = sherpa_onnx.OfflineTts(tts_config)
 
     start = time.time()
diff --git a/scripts/apk/build-apk-tts.sh.in b/scripts/apk/build-apk-tts.sh.in
index e6c87357..779bb797 100644
--- a/scripts/apk/build-apk-tts.sh.in
+++ b/scripts/apk/build-apk-tts.sh.in
@@ -37,13 +37,9 @@ model_dir={{ tts_model.model_dir }}
 model_name={{ tts_model.model_name }}
 lang={{ tts_model.lang }}
 
-mkdir $model_dir
-cd $model_dir
-wget -qq https://huggingface.co/csukuangfj/$model_dir/resolve/main/$model_name
-wget -qq https://huggingface.co/csukuangfj/$model_dir/resolve/main/lexicon.txt
-wget -qq https://huggingface.co/csukuangfj/$model_dir/resolve/main/tokens.txt
-wget -qq https://huggingface.co/csukuangfj/$model_dir/resolve/main/MODEL_CARD 2>/dev/null || true
-wget -qq https://huggingface.co/csukuangfj/$model_dir/resolve/main/rule.fst 2>/dev/null || true
+wget -qq https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/$model_dir.tar.bz2
+tar xf $model_dir.tar.bz2
+rm $model_dir.tar.bz2
 
 popd
 # Now we are at the project root directory
@@ -52,11 +48,19 @@ git checkout .
 pushd android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx
 sed -i.bak s/"modelDir = null"/"modelDir = \"$model_dir\""/ ./MainActivity.kt
 sed -i.bak s/"modelName = null"/"modelName = \"$model_name\""/ ./MainActivity.kt
+
 {% if tts_model.rule_fsts %}
   rule_fsts={{ tts_model.rule_fsts }}
   sed -i.bak s%"ruleFsts = null"%"ruleFsts = \"$rule_fsts\""% ./MainActivity.kt
 {% endif %}
 
+{% if tts_model.data_dir %}
+  data_dir={{ tts_model.data_dir }}
+  sed -i.bak s%"dataDir = null"%"dataDir = \"$data_dir\""% ./MainActivity.kt
+{% else %}
+  sed -i.bak s/"lexicon = null"/"lexicon = \"lexicon.txt\""/ ./MainActivity.kt
+{% endif %}
+
 git diff
 popd
 
diff --git a/scripts/apk/generate-tts-apk-script.py b/scripts/apk/generate-tts-apk-script.py
index a9f94ae6..958f5547 100755
--- a/scripts/apk/generate-tts-apk-script.py
+++ b/scripts/apk/generate-tts-apk-script.py
@@ -27,9 +27,122 @@ def get_args():
 @dataclass
 class TtsModel:
     model_dir: str
-    model_name: str
-    lang: str  # en, zh, fr, de, etc.
+    model_name: str = ""
+    lang: str = ""  # en, zh, fr, de, etc.
     rule_fsts: Optional[List[str]] = None
+    data_dir: Optional[str] = None
+
+
+def get_piper_models() -> List[TtsModel]:
+    models = [
+        TtsModel(model_dir="vits-piper-ar_JO-kareem-low"),
+        TtsModel(model_dir="vits-piper-ar_JO-kareem-medium"),
+        TtsModel(model_dir="vits-piper-ca_ES-upc_ona-medium"),
+        TtsModel(model_dir="vits-piper-ca_ES-upc_ona-x_low"),
+        TtsModel(model_dir="vits-piper-ca_ES-upc_pau-x_low"),
+        TtsModel(model_dir="vits-piper-ca_ES-upc_pau-x_low"),
+        TtsModel(model_dir="vits-piper-cs_CZ-jirka-medium"),
+        TtsModel(model_dir="vits-piper-da_DK-talesyntese-medium"),
+        TtsModel(model_dir="vits-piper-de_DE-eva_k-x_low"),
+        TtsModel(model_dir="vits-piper-de_DE-karlsson-low"),
+        TtsModel(model_dir="vits-piper-de_DE-kerstin-low"),
+        TtsModel(model_dir="vits-piper-de_DE-pavoque-low"),
+        TtsModel(model_dir="vits-piper-de_DE-ramona-low"),
+        TtsModel(model_dir="vits-piper-de_DE-thorsten-high"),
+        TtsModel(model_dir="vits-piper-de_DE-thorsten-low"),
+        TtsModel(model_dir="vits-piper-de_DE-thorsten-medium"),
+        TtsModel(model_dir="vits-piper-de_DE-thorsten_emotional-medium"),
+        TtsModel(model_dir="vits-piper-el_GR-rapunzelina-low"),
+        TtsModel(model_dir="vits-piper-en_GB-alan-low"),
+        TtsModel(model_dir="vits-piper-en_GB-alan-medium"),
+        TtsModel(model_dir="vits-piper-en_GB-alba-medium"),
+        TtsModel(model_dir="vits-piper-en_GB-jenny_dioco-medium"),
+        TtsModel(model_dir="vits-piper-en_GB-northern_english_male-medium"),
+        TtsModel(model_dir="vits-piper-en_GB-semaine-medium"),
+        TtsModel(model_dir="vits-piper-en_GB-southern_english_female-low"),
+        TtsModel(model_dir="vits-piper-en_GB-sweetbbak-amy"),
+        TtsModel(model_dir="vits-piper-en_GB-vctk-medium"),
+        TtsModel(model_dir="vits-piper-en_US-amy-low"),
+        TtsModel(model_dir="vits-piper-en_US-amy-medium"),
+        TtsModel(model_dir="vits-piper-en_US-arctic-medium"),
+        TtsModel(model_dir="vits-piper-en_US-danny-low"),
+        TtsModel(model_dir="vits-piper-en_US-hfc_male-medium"),
+        TtsModel(model_dir="vits-piper-en_US-joe-medium"),
+        TtsModel(model_dir="vits-piper-en_US-kathleen-low"),
+        TtsModel(model_dir="vits-piper-en_US-kusal-medium"),
+        TtsModel(model_dir="vits-piper-en_US-l2arctic-medium"),
+        TtsModel(model_dir="vits-piper-en_US-lessac-high"),
+        TtsModel(model_dir="vits-piper-en_US-lessac-low"),
+        TtsModel(model_dir="vits-piper-en_US-lessac-medium"),
+        TtsModel(model_dir="vits-piper-en_US-libritts-high"),
+        TtsModel(model_dir="vits-piper-en_US-libritts_r-medium"),
+        TtsModel(model_dir="vits-piper-en_US-ryan-high"),
+        TtsModel(model_dir="vits-piper-en_US-ryan-low"),
+        TtsModel(model_dir="vits-piper-en_US-ryan-medium"),
+        TtsModel(model_dir="vits-piper-es_ES-carlfm-x_low"),
+        TtsModel(model_dir="vits-piper-es_ES-davefx-medium"),
+        TtsModel(model_dir="vits-piper-es_ES-mls_10246-low"),
+        TtsModel(model_dir="vits-piper-es_ES-mls_9972-low"),
+        TtsModel(model_dir="vits-piper-es_ES-sharvard-medium"),
+        TtsModel(model_dir="vits-piper-es_MX-ald-medium"),
+        TtsModel(model_dir="vits-piper-fi_FI-harri-low"),
+        TtsModel(model_dir="vits-piper-fi_FI-harri-medium"),
+        TtsModel(model_dir="vits-piper-fr_FR-siwis-low"),
+        TtsModel(model_dir="vits-piper-fr_FR-siwis-medium"),
+        TtsModel(model_dir="vits-piper-fr_FR-upmc-medium"),
+        TtsModel(model_dir="vits-piper-hu_HU-anna-medium"),
+        TtsModel(model_dir="vits-piper-hu_HU-berta-medium"),
+        TtsModel(model_dir="vits-piper-hu_HU-imre-medium"),
+        TtsModel(model_dir="vits-piper-is_IS-bui-medium"),
+        TtsModel(model_dir="vits-piper-is_IS-salka-medium"),
+        TtsModel(model_dir="vits-piper-is_IS-steinn-medium"),
+        TtsModel(model_dir="vits-piper-is_IS-ugla-medium"),
+        TtsModel(model_dir="vits-piper-it_IT-riccardo-x_low"),
+        TtsModel(model_dir="vits-piper-ka_GE-natia-medium"),
+        TtsModel(model_dir="vits-piper-kk_KZ-iseke-x_low"),
+        TtsModel(model_dir="vits-piper-kk_KZ-issai-high"),
+        TtsModel(model_dir="vits-piper-kk_KZ-raya-x_low"),
+        TtsModel(model_dir="vits-piper-lb_LU-marylux-medium"),
+        TtsModel(model_dir="vits-piper-ne_NP-google-medium"),
+        TtsModel(model_dir="vits-piper-ne_NP-google-x_low"),
+        TtsModel(model_dir="vits-piper-nl_BE-nathalie-medium"),
+        TtsModel(model_dir="vits-piper-nl_BE-nathalie-x_low"),
+        TtsModel(model_dir="vits-piper-nl_BE-rdh-medium"),
+        TtsModel(model_dir="vits-piper-nl_BE-rdh-x_low"),
+        TtsModel(model_dir="vits-piper-nl_NL-mls_5809-low"),
+        TtsModel(model_dir="vits-piper-nl_NL-mls_7432-low"),
+        TtsModel(model_dir="vits-piper-no_NO-talesyntese-medium"),
+        TtsModel(model_dir="vits-piper-pl_PL-darkman-medium"),
+        TtsModel(model_dir="vits-piper-pl_PL-gosia-medium"),
+        TtsModel(model_dir="vits-piper-pl_PL-mc_speech-medium"),
+        TtsModel(model_dir="vits-piper-pl_PL-mls_6892-low"),
+        TtsModel(model_dir="vits-piper-pt_BR-edresson-low"),
+        TtsModel(model_dir="vits-piper-pt_BR-faber-medium"),
+        TtsModel(model_dir="vits-piper-pt_PT-tugao-medium"),
+        TtsModel(model_dir="vits-piper-ro_RO-mihai-medium"),
+        TtsModel(model_dir="vits-piper-ru_RU-denis-medium"),
+        TtsModel(model_dir="vits-piper-ru_RU-dmitri-medium"),
+        TtsModel(model_dir="vits-piper-ru_RU-irina-medium"),
+        TtsModel(model_dir="vits-piper-ru_RU-ruslan-medium"),
+        TtsModel(model_dir="vits-piper-sk_SK-lili-medium"),
+        TtsModel(model_dir="vits-piper-sr_RS-serbski_institut-medium"),
+        TtsModel(model_dir="vits-piper-sv_SE-nst-medium"),
+        TtsModel(model_dir="vits-piper-sw_CD-lanfrica-medium"),
+        TtsModel(model_dir="vits-piper-tr_TR-dfki-medium"),
+        TtsModel(model_dir="vits-piper-tr_TR-fahrettin-medium"),
+        TtsModel(model_dir="vits-piper-uk_UA-lada-x_low"),
+        TtsModel(model_dir="vits-piper-uk_UA-ukrainian_tts-medium"),
+        TtsModel(model_dir="vits-piper-vi_VN-25hours_single-low"),
+        TtsModel(model_dir="vits-piper-vi_VN-vais1000-medium"),
+        TtsModel(model_dir="vits-piper-vi_VN-vivos-x_low"),
+        TtsModel(model_dir="vits-piper-zh_CN-huayan-medium"),
+    ]
+    for m in models:
+        m.data_dir = m.model_dir + "/" + "espeak-ng-data"
+        m.model_name = m.model_dir[len("vits-piper-") :] + ".onnx"
+        m.lang = "en"
+
+    return models
 
 
 def get_all_models() -> List[TtsModel]:
@@ -98,56 +211,6 @@ def get_all_models() -> List[TtsModel]:
         # English (US)
         TtsModel(model_dir="vits-vctk", model_name="vits-vctk.onnx", lang="en"),
         TtsModel(model_dir="vits-ljs", model_name="vits-ljs.onnx", lang="en"),
-        TtsModel(model_dir="vits-piper-en_US-amy-low", model_name="en_US-amy-low.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-amy-medium", model_name="en_US-amy-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-arctic-medium", model_name="en_US-arctic-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-danny-low", model_name="en_US-danny-low.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-hfc_male-medium", model_name="en_US-hfc_male-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-joe-medium", model_name="en_US-joe-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-kathleen-low", model_name="en_US-kathleen-low.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-kusal-medium", model_name="en_US-kusal-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-l2arctic-medium", model_name="en_US-l2arctic-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-lessac-low", model_name="en_US-lessac-low.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-lessac-medium", model_name="en_US-lessac-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-lessac-high", model_name="en_US-lessac-high.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-libritts-high", model_name="en_US-libritts-high.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-libritts_r-medium", model_name="en_US-libritts_r-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-ryan-low", model_name="en_US-ryan-low.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-ryan-medium", model_name="en_US-ryan-medium.onnx", lang="en",),
-        TtsModel(model_dir="vits-piper-en_US-ryan-high", model_name="en_US-ryan-high.onnx", lang="en",),
-        # English (GB)
-        TtsModel(model_dir="vits-piper-en_GB-alan-low", model_name="en_GB-alan-low.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-alan-medium", model_name="en_GB-alan-medium.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-alba-medium", model_name="en_GB-alba-medium.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-jenny_dioco-medium", model_name="en_GB-jenny_dioco-medium.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-northern_english_male-medium", model_name="en_GB-northern_english_male-medium.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-semaine-medium", model_name="en_GB-semaine-medium.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-southern_english_female-low", model_name="en_GB-southern_english_female-low.onnx",lang="en",),
-        TtsModel(model_dir="vits-piper-en_GB-vctk-medium", model_name="en_GB-vctk-medium.onnx",lang="en",),
-        # German (DE)
-        TtsModel(model_dir="vits-piper-de_DE-eva_k-x_low", model_name="de_DE-eva_k-x_low.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-karlsson-low", model_name="de_DE-karlsson-low.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-kerstin-low", model_name="de_DE-kerstin-low.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-pavoque-low", model_name="de_DE-pavoque-low.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-ramona-low", model_name="de_DE-ramona-low.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-thorsten-low", model_name="de_DE-thorsten-low.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-thorsten-medium", model_name="de_DE-thorsten-medium.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-thorsten-high", model_name="de_DE-thorsten-high.onnx",lang="de",),
-        TtsModel(model_dir="vits-piper-de_DE-thorsten_emotional-medium", model_name="de_DE-thorsten_emotional-medium.onnx",lang="de",),
-        # French (FR)
-        TtsModel(model_dir="vits-piper-fr_FR-upmc-medium", model_name="fr_FR-upmc-medium.onnx",lang="fr",),
-        TtsModel(model_dir="vits-piper-fr_FR-siwis-low", model_name="fr_FR-siwis-low.onnx",lang="fr",),
-        TtsModel(model_dir="vits-piper-fr_FR-siwis-medium", model_name="fr_FR-siwis-medium.onnx",lang="fr",),
-
-        # Spanish (ES)
-        TtsModel(model_dir="vits-piper-es_ES-carlfm-x_low", model_name="es_ES-carlfm-x_low.onnx",lang="es",),
-        TtsModel(model_dir="vits-piper-es_ES-davefx-medium", model_name="es_ES-davefx-medium.onnx",lang="es",),
-        TtsModel(model_dir="vits-piper-es_ES-mls_10246-low", model_name="es_ES-mls_10246-low.onnx",lang="es",),
-        TtsModel(model_dir="vits-piper-es_ES-mls_9972-low", model_name="es_ES-mls_9972-low.onnx",lang="es",),
-        TtsModel(model_dir="vits-piper-es_ES-sharvard-medium", model_name="es_ES-sharvard-medium.onnx",lang="es",),
-
-        # Spanish (MX)
-        TtsModel(model_dir="vits-piper-es_MX-ald-medium", model_name="es_MX-ald-medium.onnx",lang="es",),
         # fmt: on
     ]
 
@@ -162,7 +225,8 @@ def main():
         s = f.read()
     template = environment.from_string(s)
     d = dict()
-    all_model_list = get_all_models()
+    #  all_model_list = get_all_models()
+    all_model_list = get_piper_models()
     num_models = len(all_model_list)
 
     num_per_runner = num_models // total
diff --git a/scripts/nodejs/index.js b/scripts/nodejs/index.js
index ac77ae4a..b61f2955 100644
--- a/scripts/nodejs/index.js
+++ b/scripts/nodejs/index.js
@@ -186,6 +186,7 @@ const SherpaOnnxOfflineTtsVitsModelConfig = StructType({
   "model" : cstring,
   "lexicon" : cstring,
   "tokens" : cstring,
+  "dataDir" : cstring,
   "noiseScale" : float,
   "noiseScaleW" : float,
   "lengthScale" : float,
@@ -201,6 +202,7 @@ const SherpaOnnxOfflineTtsModelConfig = StructType({
 const SherpaOnnxOfflineTtsConfig = StructType({
   "model" : SherpaOnnxOfflineTtsModelConfig,
   "ruleFsts" : cstring,
+  "maxNumSentences" : int32_t,
 });
 
 const SherpaOnnxGeneratedAudio = StructType({
diff --git a/setup.py b/setup.py
index 7b21311b..88071293 100644
--- a/setup.py
+++ b/setup.py
@@ -65,6 +65,9 @@ def get_binaries_to_install():
         binaries += ["sherpa-onnx-core.dll"]
         binaries += ["sherpa-onnx-portaudio.dll"]
         binaries += ["onnxruntime.dll"]
+        binaries += ["piper_phonemize.dll"]
+        binaries += ["espeak-ng.dll"]
+        binaries += ["ucd.dll"]
         binaries += ["kaldi-decoder-core.dll"]
         binaries += ["sherpa-onnx-fst.lib"]
         binaries += ["sherpa-onnx-kaldifst-core.lib"]
diff --git a/sherpa-onnx/c-api/c-api.cc b/sherpa-onnx/c-api/c-api.cc
index a88063de..9c796cd4 100644
--- a/sherpa-onnx/c-api/c-api.cc
+++ b/sherpa-onnx/c-api/c-api.cc
@@ -547,6 +547,8 @@ SherpaOnnxOfflineTts *SherpaOnnxCreateOfflineTts(
   tts_config.model.vits.lexicon =
       SHERPA_ONNX_OR(config->model.vits.lexicon, "");
   tts_config.model.vits.tokens = SHERPA_ONNX_OR(config->model.vits.tokens, "");
+  tts_config.model.vits.data_dir =
+      SHERPA_ONNX_OR(config->model.vits.data_dir, "");
   tts_config.model.vits.noise_scale =
       SHERPA_ONNX_OR(config->model.vits.noise_scale, 0.667);
   tts_config.model.vits.noise_scale_w =
@@ -558,6 +560,7 @@ SherpaOnnxOfflineTts *SherpaOnnxCreateOfflineTts(
   tts_config.model.debug = config->model.debug;
   tts_config.model.provider = SHERPA_ONNX_OR(config->model.provider, "cpu");
   tts_config.rule_fsts = SHERPA_ONNX_OR(config->rule_fsts, "");
+  tts_config.max_num_sentences = SHERPA_ONNX_OR(config->max_num_sentences, 2);
 
   if (tts_config.model.debug) {
     fprintf(stderr, "%s\n", tts_config.ToString().c_str());
diff --git a/sherpa-onnx/c-api/c-api.h b/sherpa-onnx/c-api/c-api.h
index 9fd48afd..66d7669e 100644
--- a/sherpa-onnx/c-api/c-api.h
+++ b/sherpa-onnx/c-api/c-api.h
@@ -607,6 +607,7 @@ SHERPA_ONNX_API typedef struct SherpaOnnxOfflineTtsVitsModelConfig {
   const char *model;
   const char *lexicon;
   const char *tokens;
+  const char *data_dir;
 
   float noise_scale;
   float noise_scale_w;
@@ -623,6 +624,7 @@ SHERPA_ONNX_API typedef struct SherpaOnnxOfflineTtsModelConfig {
 SHERPA_ONNX_API typedef struct SherpaOnnxOfflineTtsConfig {
   SherpaOnnxOfflineTtsModelConfig model;
   const char *rule_fsts;
+  int32_t max_num_sentences;
 } SherpaOnnxOfflineTtsConfig;
 
 SHERPA_ONNX_API typedef struct SherpaOnnxGeneratedAudio {
diff --git a/sherpa-onnx/csrc/CMakeLists.txt b/sherpa-onnx/csrc/CMakeLists.txt
index 02ec56c0..304a1867 100644
--- a/sherpa-onnx/csrc/CMakeLists.txt
+++ b/sherpa-onnx/csrc/CMakeLists.txt
@@ -74,6 +74,7 @@ set(sources
   packed-sequence.cc
   pad-sequence.cc
   parse-options.cc
+  piper-phonemize-lexicon.cc
   provider.cc
   resample.cc
   session.cc
diff --git a/sherpa-onnx/csrc/lexicon.cc b/sherpa-onnx/csrc/lexicon.cc
index e53320b5..0b57e3f4 100644
--- a/sherpa-onnx/csrc/lexicon.cc
+++ b/sherpa-onnx/csrc/lexicon.cc
@@ -129,8 +129,8 @@ Lexicon::Lexicon(AAssetManager *mgr, const std::string &lexicon,
 }
 #endif
 
-std::vector<int64_t> Lexicon::ConvertTextToTokenIds(
-    const std::string &text) const {
+std::vector<std::vector<int64_t>> Lexicon::ConvertTextToTokenIds(
+    const std::string &text, const std::string & /*voice*/ /*= ""*/) const {
   switch (language_) {
     case Language::kEnglish:
       return ConvertTextToTokenIdsEnglish(text);
@@ -150,7 +150,7 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIds(
   return {};
 }
 
-std::vector<int64_t> Lexicon::ConvertTextToTokenIdsChinese(
+std::vector<std::vector<int64_t>> Lexicon::ConvertTextToTokenIdsChinese(
     const std::string &text) const {
   std::vector<std::string> words;
   if (pattern_) {
@@ -245,10 +245,10 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsChinese(
     ans.push_back(eos);
   }
 
-  return ans;
+  return {ans};
 }
 
-std::vector<int64_t> Lexicon::ConvertTextToTokenIdsEnglish(
+std::vector<std::vector<int64_t>> Lexicon::ConvertTextToTokenIdsEnglish(
     const std::string &_text) const {
   std::string text(_text);
   ToLowerCase(&text);
@@ -301,7 +301,7 @@ std::vector<int64_t> Lexicon::ConvertTextToTokenIdsEnglish(
     ans.push_back(token2id_.at("$"));  // eos
   }
 
-  return ans;
+  return {ans};
 }
 
 void Lexicon::InitTokens(std::istream &is) { token2id_ = ReadTokens(is); }
diff --git a/sherpa-onnx/csrc/lexicon.h b/sherpa-onnx/csrc/lexicon.h
index c79ac11a..197b0afe 100644
--- a/sherpa-onnx/csrc/lexicon.h
+++ b/sherpa-onnx/csrc/lexicon.h
@@ -18,11 +18,15 @@
 #include "android/asset_manager_jni.h"
 #endif
 
+#include "sherpa-onnx/csrc/offline-tts-frontend.h"
+
 namespace sherpa_onnx {
 
-// TODO(fangjun): Refactor it to an abstract class
-class Lexicon {
+class Lexicon : public OfflineTtsFrontend {
  public:
+  Lexicon() = default;  // for subclasses
+                        //
+  // Note: for models from piper, we won't use this class.
   Lexicon(const std::string &lexicon, const std::string &tokens,
           const std::string &punctuations, const std::string &language,
           bool debug = false, bool is_piper = false);
@@ -34,28 +38,29 @@ class Lexicon {
           bool is_piper = false);
 #endif
 
-  std::vector<int64_t> ConvertTextToTokenIds(const std::string &text) const;
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIds(
+      const std::string &text, const std::string &voice = "") const override;
 
  private:
-  std::vector<int64_t> ConvertTextToTokenIdsGerman(
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIdsGerman(
       const std::string &text) const {
     return ConvertTextToTokenIdsEnglish(text);
   }
 
-  std::vector<int64_t> ConvertTextToTokenIdsSpanish(
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIdsSpanish(
       const std::string &text) const {
     return ConvertTextToTokenIdsEnglish(text);
   }
 
-  std::vector<int64_t> ConvertTextToTokenIdsFrench(
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIdsFrench(
       const std::string &text) const {
     return ConvertTextToTokenIdsEnglish(text);
   }
 
-  std::vector<int64_t> ConvertTextToTokenIdsEnglish(
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIdsEnglish(
       const std::string &text) const;
 
-  std::vector<int64_t> ConvertTextToTokenIdsChinese(
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIdsChinese(
       const std::string &text) const;
 
   void InitLanguage(const std::string &lang);
diff --git a/sherpa-onnx/csrc/macros.h b/sherpa-onnx/csrc/macros.h
index fae92dc6..39a2146c 100644
--- a/sherpa-onnx/csrc/macros.h
+++ b/sherpa-onnx/csrc/macros.h
@@ -43,6 +43,21 @@
     }                                                                   \
   } while (0)
 
+#define SHERPA_ONNX_READ_META_DATA_WITH_DEFAULT(dst, src_key, default_value) \
+  do {                                                                       \
+    auto value =                                                             \
+        meta_data.LookupCustomMetadataMapAllocated(src_key, allocator);      \
+    if (!value) {                                                            \
+      dst = default_value;                                                   \
+    } else {                                                                 \
+      dst = atoi(value.get());                                               \
+      if (dst < 0) {                                                         \
+        SHERPA_ONNX_LOGE("Invalid value %d for %s", dst, src_key);           \
+        exit(-1);                                                            \
+      }                                                                      \
+    }                                                                        \
+  } while (0)
+
 // read a vector of integers
 #define SHERPA_ONNX_READ_META_DATA_VEC(dst, src_key)                     \
   do {                                                                   \
@@ -112,4 +127,20 @@
     }                                                                   \
   } while (0)
 
+#define SHERPA_ONNX_READ_META_DATA_STR_WITH_DEFAULT(dst, src_key,       \
+                                                    default_value)      \
+  do {                                                                  \
+    auto value =                                                        \
+        meta_data.LookupCustomMetadataMapAllocated(src_key, allocator); \
+    if (!value) {                                                       \
+      dst = default_value;                                              \
+    } else {                                                            \
+      dst = value.get();                                                \
+      if (dst.empty()) {                                                \
+        SHERPA_ONNX_LOGE("Invalid value for %s\n", src_key);            \
+        exit(-1);                                                       \
+      }                                                                 \
+    }                                                                   \
+  } while (0)
+
 #endif  // SHERPA_ONNX_CSRC_MACROS_H_
diff --git a/sherpa-onnx/csrc/offline-tts-frontend.h b/sherpa-onnx/csrc/offline-tts-frontend.h
new file mode 100644
index 00000000..9f116f12
--- /dev/null
+++ b/sherpa-onnx/csrc/offline-tts-frontend.h
@@ -0,0 +1,35 @@
+// sherpa-onnx/csrc/offline-tts-frontend.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_OFFLINE_TTS_FRONTEND_H_
+#define SHERPA_ONNX_CSRC_OFFLINE_TTS_FRONTEND_H_
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace sherpa_onnx {
+
+class OfflineTtsFrontend {
+ public:
+  virtual ~OfflineTtsFrontend() = default;
+
+  /** Convert a string to token IDs.
+   *
+   * @param text The input text.
+   *             Example 1: "This is the first sample sentence; this is the
+   *             second one." Example 2: "这是第一句。这是第二句。"
+   * @param voice Optional. It is for espeak-ng.
+   *
+   * @return Return a vector-of-vector of token IDs. Each subvector contains
+   *         a sentence that can be processed independently.
+   *         If a frontend does not support splitting the text into sentences,
+   *         the resulting vector contains only one subvector.
+   */
+  virtual std::vector<std::vector<int64_t>> ConvertTextToTokenIds(
+      const std::string &text, const std::string &voice = "") const = 0;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_OFFLINE_TTS_FRONTEND_H_
diff --git a/sherpa-onnx/csrc/offline-tts-vits-impl.h b/sherpa-onnx/csrc/offline-tts-vits-impl.h
index da5435af..49208bc9 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-impl.h
+++ b/sherpa-onnx/csrc/offline-tts-vits-impl.h
@@ -18,9 +18,11 @@
 #include "kaldifst/csrc/text-normalizer.h"
 #include "sherpa-onnx/csrc/lexicon.h"
 #include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/offline-tts-frontend.h"
 #include "sherpa-onnx/csrc/offline-tts-impl.h"
 #include "sherpa-onnx/csrc/offline-tts-vits-model.h"
 #include "sherpa-onnx/csrc/onnx-utils.h"
+#include "sherpa-onnx/csrc/piper-phonemize-lexicon.h"
 #include "sherpa-onnx/csrc/text-utils.h"
 
 namespace sherpa_onnx {
@@ -29,10 +31,9 @@ class OfflineTtsVitsImpl : public OfflineTtsImpl {
  public:
   explicit OfflineTtsVitsImpl(const OfflineTtsConfig &config)
       : config_(config),
-        model_(std::make_unique<OfflineTtsVitsModel>(config.model)),
-        lexicon_(config.model.vits.lexicon, config.model.vits.tokens,
-                 model_->Punctuations(), model_->Language(), config.model.debug,
-                 model_->IsPiper()) {
+        model_(std::make_unique<OfflineTtsVitsModel>(config.model)) {
+    InitFrontend();
+
     if (!config.rule_fsts.empty()) {
       std::vector<std::string> files;
       SplitStringToVector(config.rule_fsts, ",", false, &files);
@@ -49,10 +50,9 @@ class OfflineTtsVitsImpl : public OfflineTtsImpl {
 #if __ANDROID_API__ >= 9
   OfflineTtsVitsImpl(AAssetManager *mgr, const OfflineTtsConfig &config)
       : config_(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,
-                 model_->IsPiper()) {
+        model_(std::make_unique<OfflineTtsVitsModel>(mgr, config.model)) {
+    InitFrontend(mgr);
+
     if (!config.rule_fsts.empty()) {
       std::vector<std::string> files;
       SplitStringToVector(config.rule_fsts, ",", false, &files);
@@ -101,20 +101,119 @@ class OfflineTtsVitsImpl : public OfflineTtsImpl {
       }
     }
 
-    std::vector<int64_t> x = lexicon_.ConvertTextToTokenIds(text);
-    if (x.empty()) {
+    std::vector<std::vector<int64_t>> x =
+        frontend_->ConvertTextToTokenIds(text, model_->Voice());
+
+    if (x.empty() || (x.size() == 1 && x[0].empty())) {
       SHERPA_ONNX_LOGE("Failed to convert %s to token IDs", text.c_str());
       return {};
     }
 
-    if (model_->AddBlank()) {
-      std::vector<int64_t> buffer(x.size() * 2 + 1);
-      int32_t i = 1;
-      for (auto k : x) {
-        buffer[i] = k;
-        i += 2;
+    if (model_->AddBlank() && config_.model.vits.data_dir.empty()) {
+      for (auto &k : x) {
+        k = AddBlank(k);
       }
-      x = std::move(buffer);
+    }
+
+    int32_t x_size = static_cast<int32_t>(x.size());
+
+    if (config_.max_num_sentences <= 0 || x_size <= config_.max_num_sentences) {
+      return Process(x, sid, speed);
+    }
+
+    // the input text is too long, we process sentences within it in batches
+    // to avoid OOM. Batch size is config_.max_num_sentences
+    std::vector<std::vector<int64_t>> batch;
+    int32_t batch_size = config_.max_num_sentences;
+    batch.reserve(config_.max_num_sentences);
+    int32_t num_batches = x_size / batch_size;
+
+    if (config_.model.debug) {
+      SHERPA_ONNX_LOGE(
+          "Text is too long. Split it into %d batches. batch size: %d. Number "
+          "of sentences: %d",
+          num_batches, batch_size, x_size);
+    }
+
+    GeneratedAudio ans;
+
+    int32_t k = 0;
+
+    for (int32_t b = 0; b != num_batches; ++b) {
+      batch.clear();
+      for (int32_t i = 0; i != batch_size; ++i, ++k) {
+        batch.push_back(std::move(x[k]));
+      }
+
+      auto audio = Process(batch, sid, speed);
+      ans.sample_rate = audio.sample_rate;
+      ans.samples.insert(ans.samples.end(), audio.samples.begin(),
+                         audio.samples.end());
+    }
+
+    batch.clear();
+    while (k < x.size()) {
+      batch.push_back(std::move(x[k]));
+      ++k;
+    }
+
+    if (!batch.empty()) {
+      auto audio = Process(batch, sid, speed);
+      ans.sample_rate = audio.sample_rate;
+      ans.samples.insert(ans.samples.end(), audio.samples.begin(),
+                         audio.samples.end());
+    }
+
+    return ans;
+  }
+
+ private:
+  void InitFrontend(AAssetManager *mgr) {
+    if (model_->IsPiper() && !config_.model.vits.data_dir.empty()) {
+      frontend_ = std::make_unique<PiperPhonemizeLexicon>(
+          mgr, config_.model.vits.tokens, config_.model.vits.data_dir);
+    } else {
+      frontend_ = std::make_unique<Lexicon>(
+          mgr, config_.model.vits.lexicon, config_.model.vits.tokens,
+          model_->Punctuations(), model_->Language(), config_.model.debug,
+          model_->IsPiper());
+    }
+  }
+
+  void InitFrontend() {
+    if (model_->IsPiper() && !config_.model.vits.data_dir.empty()) {
+      frontend_ = std::make_unique<PiperPhonemizeLexicon>(
+          config_.model.vits.tokens, config_.model.vits.data_dir);
+    } else {
+      frontend_ = std::make_unique<Lexicon>(
+          config_.model.vits.lexicon, config_.model.vits.tokens,
+          model_->Punctuations(), model_->Language(), config_.model.debug,
+          model_->IsPiper());
+    }
+  }
+
+  std::vector<int64_t> AddBlank(const std::vector<int64_t> &x) const {
+    // we assume the blank ID is 0
+    std::vector<int64_t> buffer(x.size() * 2 + 1);
+    int32_t i = 1;
+    for (auto k : x) {
+      buffer[i] = k;
+      i += 2;
+    }
+    return buffer;
+  }
+
+  GeneratedAudio Process(const std::vector<std::vector<int64_t>> &tokens,
+                         int32_t sid, float speed) const {
+    int32_t num_tokens = 0;
+    for (const auto &k : tokens) {
+      num_tokens += k.size();
+    }
+
+    std::vector<int64_t> x;
+    x.reserve(num_tokens);
+    for (const auto &k : tokens) {
+      x.insert(x.end(), k.begin(), k.end());
     }
 
     auto memory_info =
@@ -147,7 +246,7 @@ class OfflineTtsVitsImpl : public OfflineTtsImpl {
   OfflineTtsConfig config_;
   std::unique_ptr<OfflineTtsVitsModel> model_;
   std::vector<std::unique_ptr<kaldifst::TextNormalizer>> tn_list_;
-  Lexicon lexicon_;
+  std::unique_ptr<OfflineTtsFrontend> frontend_;
 };
 
 }  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/offline-tts-vits-model-config.cc b/sherpa-onnx/csrc/offline-tts-vits-model-config.cc
index 71c19e57..b9fce0f6 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-model-config.cc
+++ b/sherpa-onnx/csrc/offline-tts-vits-model-config.cc
@@ -13,6 +13,9 @@ void OfflineTtsVitsModelConfig::Register(ParseOptions *po) {
   po->Register("vits-model", &model, "Path to VITS model");
   po->Register("vits-lexicon", &lexicon, "Path to lexicon.txt for VITS models");
   po->Register("vits-tokens", &tokens, "Path to tokens.txt for VITS models");
+  po->Register("vits-data-dir", &data_dir,
+               "Path to the directory containing dict for espeak-ng. If it is "
+               "given, --vits-lexicon is ignored.");
   po->Register("vits-noise-scale", &noise_scale, "noise_scale for VITS models");
   po->Register("vits-noise-scale-w", &noise_scale_w,
                "noise_scale_w for VITS models");
@@ -31,16 +34,6 @@ bool OfflineTtsVitsModelConfig::Validate() const {
     return false;
   }
 
-  if (lexicon.empty()) {
-    SHERPA_ONNX_LOGE("Please provide --vits-lexicon");
-    return false;
-  }
-
-  if (!FileExists(lexicon)) {
-    SHERPA_ONNX_LOGE("--vits-lexicon: %s does not exist", lexicon.c_str());
-    return false;
-  }
-
   if (tokens.empty()) {
     SHERPA_ONNX_LOGE("Please provide --vits-tokens");
     return false;
@@ -51,6 +44,43 @@ bool OfflineTtsVitsModelConfig::Validate() const {
     return false;
   }
 
+  if (data_dir.empty()) {
+    if (lexicon.empty()) {
+      SHERPA_ONNX_LOGE("Please provide --vits-lexicon");
+      return false;
+    }
+
+    if (!FileExists(lexicon)) {
+      SHERPA_ONNX_LOGE("--vits-lexicon: %s does not exist", lexicon.c_str());
+      return false;
+    }
+
+  } else {
+    if (!FileExists(data_dir + "/phontab")) {
+      SHERPA_ONNX_LOGE("%s/phontab does not exist. Skipping test",
+                       data_dir.c_str());
+      return false;
+    }
+
+    if (!FileExists(data_dir + "/phonindex")) {
+      SHERPA_ONNX_LOGE("%s/phonindex does not exist. Skipping test",
+                       data_dir.c_str());
+      return false;
+    }
+
+    if (!FileExists(data_dir + "/phondata")) {
+      SHERPA_ONNX_LOGE("%s/phondata does not exist. Skipping test",
+                       data_dir.c_str());
+      return false;
+    }
+
+    if (!FileExists(data_dir + "/intonations")) {
+      SHERPA_ONNX_LOGE("%s/intonations does not exist. Skipping test",
+                       data_dir.c_str());
+      return false;
+    }
+  }
+
   return true;
 }
 
@@ -61,6 +91,7 @@ std::string OfflineTtsVitsModelConfig::ToString() const {
   os << "model=\"" << model << "\", ";
   os << "lexicon=\"" << lexicon << "\", ";
   os << "tokens=\"" << tokens << "\", ";
+  os << "data_dir=\"" << data_dir << "\", ";
   os << "noise_scale=" << noise_scale << ", ";
   os << "noise_scale_w=" << noise_scale_w << ", ";
   os << "length_scale=" << length_scale << ")";
diff --git a/sherpa-onnx/csrc/offline-tts-vits-model-config.h b/sherpa-onnx/csrc/offline-tts-vits-model-config.h
index 62bc566b..cde8b392 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-model-config.h
+++ b/sherpa-onnx/csrc/offline-tts-vits-model-config.h
@@ -16,6 +16,10 @@ struct OfflineTtsVitsModelConfig {
   std::string lexicon;
   std::string tokens;
 
+  // If data_dir is given, lexicon is ignored
+  // data_dir is for piper-phonemize, which uses espeak-ng
+  std::string data_dir;
+
   float noise_scale = 0.667;
   float noise_scale_w = 0.8;
   float length_scale = 1;
@@ -28,11 +32,13 @@ struct OfflineTtsVitsModelConfig {
   OfflineTtsVitsModelConfig(const std::string &model,
                             const std::string &lexicon,
                             const std::string &tokens,
+                            const std::string &data_dir,
                             float noise_scale = 0.667,
                             float noise_scale_w = 0.8, float length_scale = 1)
       : model(model),
         lexicon(lexicon),
         tokens(tokens),
+        data_dir(data_dir),
         noise_scale(noise_scale),
         noise_scale_w(noise_scale_w),
         length_scale(length_scale) {}
diff --git a/sherpa-onnx/csrc/offline-tts-vits-model.cc b/sherpa-onnx/csrc/offline-tts-vits-model.cc
index dafe5052..31e3a7c3 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-model.cc
+++ b/sherpa-onnx/csrc/offline-tts-vits-model.cc
@@ -51,6 +51,7 @@ class OfflineTtsVitsModel::Impl {
 
   std::string Punctuations() const { return punctuations_; }
   std::string Language() const { return language_; }
+  std::string Voice() const { return voice_; }
   bool IsPiper() const { return is_piper_; }
   int32_t NumSpeakers() const { return num_speakers_; }
 
@@ -74,10 +75,12 @@ class OfflineTtsVitsModel::Impl {
 
     Ort::AllocatorWithDefaultOptions allocator;  // used in the macro below
     SHERPA_ONNX_READ_META_DATA(sample_rate_, "sample_rate");
-    SHERPA_ONNX_READ_META_DATA(add_blank_, "add_blank");
+    SHERPA_ONNX_READ_META_DATA_WITH_DEFAULT(add_blank_, "add_blank", 0);
     SHERPA_ONNX_READ_META_DATA(num_speakers_, "n_speakers");
-    SHERPA_ONNX_READ_META_DATA_STR(punctuations_, "punctuation");
+    SHERPA_ONNX_READ_META_DATA_STR_WITH_DEFAULT(punctuations_, "punctuation",
+                                                "");
     SHERPA_ONNX_READ_META_DATA_STR(language_, "language");
+    SHERPA_ONNX_READ_META_DATA_STR_WITH_DEFAULT(voice_, "voice", "");
 
     std::string comment;
     SHERPA_ONNX_READ_META_DATA_STR(comment, "comment");
@@ -215,6 +218,7 @@ class OfflineTtsVitsModel::Impl {
   int32_t num_speakers_;
   std::string punctuations_;
   std::string language_;
+  std::string voice_;
 
   bool is_piper_ = false;
 };
@@ -244,6 +248,7 @@ std::string OfflineTtsVitsModel::Punctuations() const {
 }
 
 std::string OfflineTtsVitsModel::Language() const { return impl_->Language(); }
+std::string OfflineTtsVitsModel::Voice() const { return impl_->Voice(); }
 
 bool OfflineTtsVitsModel::IsPiper() const { return impl_->IsPiper(); }
 
diff --git a/sherpa-onnx/csrc/offline-tts-vits-model.h b/sherpa-onnx/csrc/offline-tts-vits-model.h
index 1cf9ad2e..7708144c 100644
--- a/sherpa-onnx/csrc/offline-tts-vits-model.h
+++ b/sherpa-onnx/csrc/offline-tts-vits-model.h
@@ -46,7 +46,8 @@ class OfflineTtsVitsModel {
   bool AddBlank() const;
 
   std::string Punctuations() const;
-  std::string Language() const;
+  std::string Language() const;  // e.g., Chinese, English, German, etc.
+  std::string Voice() const;     // e.g., en-us, for espeak-ng
   bool IsPiper() const;
   int32_t NumSpeakers() const;
 
diff --git a/sherpa-onnx/csrc/offline-tts.cc b/sherpa-onnx/csrc/offline-tts.cc
index b8536e26..aaaf22fb 100644
--- a/sherpa-onnx/csrc/offline-tts.cc
+++ b/sherpa-onnx/csrc/offline-tts.cc
@@ -21,6 +21,12 @@ void OfflineTtsConfig::Register(ParseOptions *po) {
                "Multiple filenames are separated by a comma and they are "
                "applied from left to right. An example value: "
                "rule1.fst,rule2,fst,rule3.fst");
+
+  po->Register(
+      "tts-max-num-sentences", &max_num_sentences,
+      "Maximum number of sentences that we process at a time. "
+      "This is to avoid OOM for very long input text. "
+      "If you set it to -1, then we process all sentences in a single batch.");
 }
 
 bool OfflineTtsConfig::Validate() const {
@@ -43,7 +49,8 @@ std::string OfflineTtsConfig::ToString() const {
 
   os << "OfflineTtsConfig(";
   os << "model=" << model.ToString() << ", ";
-  os << "rule_fsts=\"" << rule_fsts << "\")";
+  os << "rule_fsts=\"" << rule_fsts << "\", ";
+  os << "max_num_sentences=" << max_num_sentences << ")";
 
   return os.str();
 }
diff --git a/sherpa-onnx/csrc/offline-tts.h b/sherpa-onnx/csrc/offline-tts.h
index f581ea04..20a86913 100644
--- a/sherpa-onnx/csrc/offline-tts.h
+++ b/sherpa-onnx/csrc/offline-tts.h
@@ -28,10 +28,17 @@ struct OfflineTtsConfig {
   // If there are multiple rules, they are applied from left to right.
   std::string rule_fsts;
 
+  // Maximum number of sentences that we process at a time.
+  // This is to avoid OOM for very long input text.
+  // If you set it to -1, then we process all sentences in a single batch.
+  int32_t max_num_sentences = 2;
+
   OfflineTtsConfig() = default;
   OfflineTtsConfig(const OfflineTtsModelConfig &model,
-                   const std::string &rule_fsts)
-      : model(model), rule_fsts(rule_fsts) {}
+                   const std::string &rule_fsts, int32_t max_num_sentences)
+      : model(model),
+        rule_fsts(rule_fsts),
+        max_num_sentences(max_num_sentences) {}
 
   void Register(ParseOptions *po);
   bool Validate() const;
diff --git a/sherpa-onnx/csrc/piper-phonemize-lexicon.cc b/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
new file mode 100644
index 00000000..4ad6374c
--- /dev/null
+++ b/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
@@ -0,0 +1,170 @@
+// sherpa-onnx/csrc/piper-phonemize-lexicon.cc
+//
+// Copyright (c)  2022-2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/piper-phonemize-lexicon.h"
+
+#include <codecvt>
+#include <fstream>
+#include <locale>
+#include <map>
+#include <mutex>  // NOLINT
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include <strstream>
+
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "espeak-ng/speak_lib.h"
+#include "phoneme_ids.hpp"
+#include "phonemize.hpp"
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/onnx-utils.h"
+
+namespace sherpa_onnx {
+
+static std::unordered_map<char32_t, int32_t> ReadTokens(std::istream &is) {
+  std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> conv;
+  std::unordered_map<char32_t, int32_t> token2id;
+
+  std::string line;
+
+  std::string sym;
+  std::u32string s;
+  int32_t id;
+  while (std::getline(is, line)) {
+    std::istringstream iss(line);
+    iss >> sym;
+    if (iss.eof()) {
+      id = atoi(sym.c_str());
+      sym = " ";
+    } else {
+      iss >> id;
+    }
+
+    // eat the trailing \r\n on windows
+    iss >> std::ws;
+    if (!iss.eof()) {
+      SHERPA_ONNX_LOGE("Error when reading tokens: %s", line.c_str());
+      exit(-1);
+    }
+
+    s = conv.from_bytes(sym);
+    if (s.size() != 1) {
+      SHERPA_ONNX_LOGE("Error when reading tokens at Line %s. size: %d",
+                       line.c_str(), static_cast<int32_t>(s.size()));
+      exit(-1);
+    }
+    char32_t c = s[0];
+
+    if (token2id.count(c)) {
+      SHERPA_ONNX_LOGE("Duplicated token %s. Line %s. Existing ID: %d",
+                       sym.c_str(), line.c_str(), token2id.at(c));
+      exit(-1);
+    }
+
+    token2id.insert({c, id});
+  }
+
+  return token2id;
+}
+
+// see the function "phonemes_to_ids" from
+// https://github.com/rhasspy/piper/blob/master/notebooks/piper_inference_(ONNX).ipynb
+static std::vector<int64_t> PhonemesToIds(
+    const std::unordered_map<char32_t, int32_t> &token2id,
+    const std::vector<piper::Phoneme> &phonemes) {
+  // see
+  // https://github.com/rhasspy/piper-phonemize/blob/master/src/phoneme_ids.hpp#L17
+  int32_t pad = token2id.at(U'_');
+  int32_t bos = token2id.at(U'^');
+  int32_t eos = token2id.at(U'$');
+
+  std::vector<int64_t> ans;
+  ans.reserve(phonemes.size());
+
+  ans.push_back(bos);
+  for (auto p : phonemes) {
+    if (token2id.count(p)) {
+      ans.push_back(token2id.at(p));
+      ans.push_back(pad);
+    } else {
+      SHERPA_ONNX_LOGE("Skip unkown phonemes. Unicode codepoint: \\U+%04x.", p);
+    }
+  }
+  ans.push_back(eos);
+
+  return ans;
+}
+
+void InitEspeak(const std::string &data_dir) {
+  static std::once_flag init_flag;
+  std::call_once(init_flag, [data_dir]() {
+    int32_t result =
+        espeak_Initialize(AUDIO_OUTPUT_SYNCHRONOUS, 0, data_dir.c_str(), 0);
+    if (result != 22050) {
+      SHERPA_ONNX_LOGE(
+          "Failed to initialize espeak-ng with data dir: %s. Return code is: "
+          "%d",
+          data_dir.c_str(), result);
+      exit(-1);
+    }
+  });
+}
+
+PiperPhonemizeLexicon::PiperPhonemizeLexicon(const std::string &tokens,
+                                             const std::string &data_dir)
+    : data_dir_(data_dir) {
+  {
+    std::ifstream is(tokens);
+    token2id_ = ReadTokens(is);
+  }
+
+  InitEspeak(data_dir_);
+}
+
+#if __ANDROID_API__ >= 9
+PiperPhonemizeLexicon::PiperPhonemizeLexicon(AAssetManager *mgr,
+                                             const std::string &tokens,
+                                             const std::string &data_dir) {
+  {
+    auto buf = ReadFile(mgr, tokens);
+    std::istrstream is(buf.data(), buf.size());
+    token2id_ = ReadTokens(is);
+  }
+
+  // We should copy the directory of espeak-ng-data from the asset to
+  // some internal or external storage and then pass the directory to data_dir.
+  InitEspeak(data_dir_);
+}
+#endif
+
+std::vector<std::vector<int64_t>> PiperPhonemizeLexicon::ConvertTextToTokenIds(
+    const std::string &text, const std::string &voice /*= ""*/) const {
+  piper::eSpeakPhonemeConfig config;
+
+  // ./bin/espeak-ng-bin --path  ./install/share/espeak-ng-data/ --voices
+  // to list available voices
+  config.voice = voice;  // e.g., voice is en-us
+
+  std::vector<std::vector<piper::Phoneme>> phonemes;
+  piper::phonemize_eSpeak(text, config, phonemes);
+
+  std::vector<std::vector<int64_t>> ans;
+
+  std::vector<int64_t> phoneme_ids;
+  for (const auto &p : phonemes) {
+    phoneme_ids = PhonemesToIds(token2id_, p);
+    ans.push_back(std::move(phoneme_ids));
+  }
+
+  return ans;
+}
+
+}  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/piper-phonemize-lexicon.h b/sherpa-onnx/csrc/piper-phonemize-lexicon.h
new file mode 100644
index 00000000..d2cdad2a
--- /dev/null
+++ b/sherpa-onnx/csrc/piper-phonemize-lexicon.h
@@ -0,0 +1,41 @@
+// sherpa-onnx/csrc/piper-phonemize-lexicon.h
+//
+// Copyright (c)  2022-2023  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_PIPER_PHONEMIZE_LEXICON_H_
+#define SHERPA_ONNX_CSRC_PIPER_PHONEMIZE_LEXICON_H_
+
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "sherpa-onnx/csrc/offline-tts-frontend.h"
+
+namespace sherpa_onnx {
+
+class PiperPhonemizeLexicon : public OfflineTtsFrontend {
+ public:
+  PiperPhonemizeLexicon(const std::string &tokens, const std::string &data_dir);
+
+#if __ANDROID_API__ >= 9
+  PiperPhonemizeLexicon(AAssetManager *mgr, const std::string &tokens,
+                        const std::string &data_dir);
+#endif
+
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIds(
+      const std::string &text, const std::string &voice = "") const override;
+
+ private:
+  std::string data_dir_;
+  // map unicode codepoint to an integer ID
+  std::unordered_map<char32_t, int32_t> token2id_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_PIPER_PHONEMIZE_LEXICON_H_
diff --git a/sherpa-onnx/csrc/piper-phonemize-test.cc b/sherpa-onnx/csrc/piper-phonemize-test.cc
index b1d0790a..47e2c57b 100644
--- a/sherpa-onnx/csrc/piper-phonemize-test.cc
+++ b/sherpa-onnx/csrc/piper-phonemize-test.cc
@@ -48,7 +48,7 @@ TEST(PiperPhonemize, Case1) {
 
   piper::eSpeakPhonemeConfig config;
 
-  // ./bin/espeak-ng --path  ./install/share/espeak-ng-data/ --voices
+  // ./bin/espeak-ng-bin --path  ./install/share/espeak-ng-data/ --voices
   // to list available voices
   config.voice = "en-us";
 
@@ -61,15 +61,15 @@ TEST(PiperPhonemize, Case1) {
   }
   std::cout << "\n";
 
-  std::vector<piper::PhonemeId> phonemeIds;
-  std::map<piper::Phoneme, std::size_t> missingPhonemes;
+  std::vector<piper::PhonemeId> phoneme_ids;
+  std::map<piper::Phoneme, std::size_t> missing_phonemes;
 
   {
     piper::PhonemeIdConfig config;
-    phonemes_to_ids(phonemes[0], config, phonemeIds, missingPhonemes);
+    phonemes_to_ids(phonemes[0], config, phoneme_ids, missing_phonemes);
   }
 
-  for (int32_t p : phonemeIds) {
+  for (int32_t p : phoneme_ids) {
     std::cout << p << " ";
   }
   std::cout << "\n";
diff --git a/sherpa-onnx/jni/jni.cc b/sherpa-onnx/jni/jni.cc
index 0a039f64..a3c7952c 100644
--- a/sherpa-onnx/jni/jni.cc
+++ b/sherpa-onnx/jni/jni.cc
@@ -545,6 +545,12 @@ static OfflineTtsConfig GetOfflineTtsConfig(JNIEnv *env, jobject config) {
   ans.model.vits.tokens = p;
   env->ReleaseStringUTFChars(s, p);
 
+  fid = env->GetFieldID(vits_cls, "dataDir", "Ljava/lang/String;");
+  s = (jstring)env->GetObjectField(vits, fid);
+  p = env->GetStringUTFChars(s, nullptr);
+  ans.model.vits.data_dir = p;
+  env->ReleaseStringUTFChars(s, p);
+
   fid = env->GetFieldID(vits_cls, "noiseScale", "F");
   ans.model.vits.noise_scale = env->GetFloatField(vits, fid);
 
@@ -573,6 +579,9 @@ static OfflineTtsConfig GetOfflineTtsConfig(JNIEnv *env, jobject config) {
   ans.rule_fsts = p;
   env->ReleaseStringUTFChars(s, p);
 
+  fid = env->GetFieldID(cls, "maxNumSentences", "I");
+  ans.max_num_sentences = env->GetIntField(config, fid);
+
   return ans;
 }
 
@@ -589,6 +598,11 @@ JNIEXPORT jlong JNICALL Java_com_k2fsa_sherpa_onnx_OfflineTts_new(
 #endif
   auto config = sherpa_onnx::GetOfflineTtsConfig(env, _config);
   SHERPA_ONNX_LOGE("config:\n%s", config.ToString().c_str());
+
+  if (!config.Validate()) {
+    SHERPA_ONNX_LOGE("Erros found in config!");
+  }
+
   auto tts = new sherpa_onnx::SherpaOnnxOfflineTts(
 #if __ANDROID_API__ >= 9
       mgr,
diff --git a/sherpa-onnx/python/csrc/offline-tts-vits-model-config.cc b/sherpa-onnx/python/csrc/offline-tts-vits-model-config.cc
index 60521ef9..6e016715 100644
--- a/sherpa-onnx/python/csrc/offline-tts-vits-model-config.cc
+++ b/sherpa-onnx/python/csrc/offline-tts-vits-model-config.cc
@@ -16,17 +16,20 @@ void PybindOfflineTtsVitsModelConfig(py::module *m) {
   py::class_<PyClass>(*m, "OfflineTtsVitsModelConfig")
       .def(py::init<>())
       .def(py::init<const std::string &, const std::string &,
-                    const std::string &, float, float, float>(),
+                    const std::string &, const std::string, float, float,
+                    float>(),
            py::arg("model"), py::arg("lexicon"), py::arg("tokens"),
-           py::arg("noise_scale") = 0.667, py::arg("noise_scale_w") = 0.8,
-           py::arg("length_scale") = 1.0)
+           py::arg("data_dir") = "", py::arg("noise_scale") = 0.667,
+           py::arg("noise_scale_w") = 0.8, py::arg("length_scale") = 1.0)
       .def_readwrite("model", &PyClass::model)
       .def_readwrite("lexicon", &PyClass::lexicon)
       .def_readwrite("tokens", &PyClass::tokens)
+      .def_readwrite("data_dir", &PyClass::data_dir)
       .def_readwrite("noise_scale", &PyClass::noise_scale)
       .def_readwrite("noise_scale_w", &PyClass::noise_scale_w)
       .def_readwrite("length_scale", &PyClass::length_scale)
-      .def("__str__", &PyClass::ToString);
+      .def("__str__", &PyClass::ToString)
+      .def("validate", &PyClass::Validate);
 }
 
 }  // namespace sherpa_onnx
diff --git a/sherpa-onnx/python/csrc/offline-tts.cc b/sherpa-onnx/python/csrc/offline-tts.cc
index 538cecee..e191c081 100644
--- a/sherpa-onnx/python/csrc/offline-tts.cc
+++ b/sherpa-onnx/python/csrc/offline-tts.cc
@@ -30,10 +30,14 @@ static void PybindOfflineTtsConfig(py::module *m) {
   using PyClass = OfflineTtsConfig;
   py::class_<PyClass>(*m, "OfflineTtsConfig")
       .def(py::init<>())
-      .def(py::init<const OfflineTtsModelConfig &, const std::string &>(),
-           py::arg("model"), py::arg("rule_fsts") = "")
+      .def(py::init<const OfflineTtsModelConfig &, const std::string &,
+                    int32_t>(),
+           py::arg("model"), py::arg("rule_fsts") = "",
+           py::arg("max_num_sentences") = 2)
       .def_readwrite("model", &PyClass::model)
       .def_readwrite("rule_fsts", &PyClass::rule_fsts)
+      .def_readwrite("max_num_sentences", &PyClass::max_num_sentences)
+      .def("validate", &PyClass::Validate)
       .def("__str__", &PyClass::ToString);
 }
 
diff --git a/swift-api-examples/SherpaOnnx.swift b/swift-api-examples/SherpaOnnx.swift
index 2b310b03..cf7e69aa 100644
--- a/swift-api-examples/SherpaOnnx.swift
+++ b/swift-api-examples/SherpaOnnx.swift
@@ -578,6 +578,7 @@ func sherpaOnnxOfflineTtsVitsModelConfig(
   model: String,
   lexicon: String,
   tokens: String,
+  dataDir: String = "",
   noiseScale: Float = 0.667,
   noiseScaleW: Float = 0.8,
   lengthScale: Float = 1.0
@@ -586,6 +587,7 @@ func sherpaOnnxOfflineTtsVitsModelConfig(
     model: toCPointer(model),
     lexicon: toCPointer(lexicon),
     tokens: toCPointer(tokens),
+    data_dir: toCPointer(dataDir),
     noise_scale: noiseScale,
     noise_scale_w: noiseScaleW,
     length_scale: lengthScale)
@@ -607,11 +609,13 @@ func sherpaOnnxOfflineTtsModelConfig(
 
 func sherpaOnnxOfflineTtsConfig(
   model: SherpaOnnxOfflineTtsModelConfig,
-  ruleFsts: String = ""
+  ruleFsts: String = "",
+  maxNumSenetences: Int = 2
 ) -> SherpaOnnxOfflineTtsConfig {
   return SherpaOnnxOfflineTtsConfig(
     model: model,
-    rule_fsts: toCPointer(ruleFsts)
+    rule_fsts: toCPointer(ruleFsts),
+    max_num_sentences: Int32(maxNumSenetences)
   )
 }
 
diff --git a/swift-api-examples/run-tts.sh b/swift-api-examples/run-tts.sh
index 2bfcc3e7..5604a43a 100755
--- a/swift-api-examples/run-tts.sh
+++ b/swift-api-examples/run-tts.sh
@@ -7,17 +7,12 @@ if [ ! -d ../build-swift-macos ]; then
   exit 1
 fi
 
-if [ ! -d ./vits-vctk ]; then
-  echo "Please download the pre-trained model for testing."
-  echo "You can refer to"
-  echo ""
-  echo "https://k2-fsa.github.io/sherpa/onnx/tts/pretrained_models/vits.html#vctk-english-multi-speaker-109-speakers"
-  echo ""
-  echo "for help"
+if [ ! -d ./vits-piper-en_US-amy-low ]; then
+  echo "Download a pre-trained model for testing."
 
-  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-vctk.tar.bz2
-  tar xvf vits-vctk.tar.bz2
-  rm vits-vctk.tar.bz2
+  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
+  tar xf vits-piper-en_US-amy-low.tar.bz2
+  rm vits-piper-en_US-amy-low.tar.bz2
 fi
 
 if [ ! -e ./tts ]; then
diff --git a/swift-api-examples/tts.swift b/swift-api-examples/tts.swift
index 28819646..61c68bce 100644
--- a/swift-api-examples/tts.swift
+++ b/swift-api-examples/tts.swift
@@ -1,18 +1,20 @@
 func run() {
-  let model = "./vits-vctk/vits-vctk.onnx"
-  let lexicon = "./vits-vctk/lexicon.txt"
-  let tokens = "./vits-vctk/tokens.txt"
+  let model = "./vits-piper-en_US-amy-low/en_US-amy-low.onnx"
+  let tokens = "./vits-piper-en_US-amy-low/tokens.txt"
+  let dataDir = "./vits-piper-en_US-amy-low/espeak-ng-data"
   let vits = sherpaOnnxOfflineTtsVitsModelConfig(
     model: model,
-    lexicon: lexicon,
-    tokens: tokens
+    lexicon: "",
+    tokens: tokens,
+    dataDir: dataDir
   )
   let modelConfig = sherpaOnnxOfflineTtsModelConfig(vits: vits)
   var ttsConfig = sherpaOnnxOfflineTtsConfig(model: modelConfig)
 
   let tts = SherpaOnnxOfflineTtsWrapper(config: &ttsConfig)
 
-  let text = "How are you doing? Fantastic!"
+  let text =
+    "“Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.”"
   let sid = 99
   let speed: Float = 1.0