diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6e573162..41a12718 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -174,8 +174,6 @@ if(SHERPA_ONNX_ENABLE_WEBSOCKET)
   include(asio)
 endif()
 
-include(json)
-
 add_subdirectory(sherpa-onnx)
 
 if(SHERPA_ONNX_ENABLE_C_API)
diff --git a/cmake/json.cmake b/cmake/json.cmake
deleted file mode 100644
index b1da43a9..00000000
--- a/cmake/json.cmake
+++ /dev/null
@@ -1,45 +0,0 @@
-function(download_json)
-  include(FetchContent)
-
-  set(json_URL  "https://github.com/nlohmann/json/archive/refs/tags/v3.11.2.tar.gz")
-  set(json_URL2 "https://huggingface.co/csukuangfj/sherpa-cmake-deps/resolve/main/json-3.11.2.tar.gz")
-  set(json_HASH "SHA256=d69f9deb6a75e2580465c6c4c5111b89c4dc2fa94e3a85fcd2ffcd9a143d9273")
-
-  # If you don't have access to the Internet,
-  # please pre-download json
-  set(possible_file_locations
-    $ENV{HOME}/Downloads/json-3.11.2.tar.gz
-    ${PROJECT_SOURCE_DIR}/json-3.11.2.tar.gz
-    ${PROJECT_BINARY_DIR}/json-3.11.2.tar.gz
-    /tmp/json-3.11.2.tar.gz
-    /star-fj/fangjun/download/github/json-3.11.2.tar.gz
-  )
-
-  foreach(f IN LISTS possible_file_locations)
-    if(EXISTS ${f})
-      set(json_URL  "${f}")
-      file(TO_CMAKE_PATH "${json_URL}" json_URL)
-      message(STATUS "Found local downloaded json: ${json_URL}")
-      set(json_URL2)
-      break()
-    endif()
-  endforeach()
-
-  FetchContent_Declare(json
-    URL
-      ${json_URL}
-      ${json_URL2}
-    URL_HASH          ${json_HASH}
-  )
-
-  FetchContent_GetProperties(json)
-  if(NOT json_POPULATED)
-    message(STATUS "Downloading json from ${json_URL}")
-    FetchContent_Populate(json)
-  endif()
-  message(STATUS "json is downloaded to ${json_SOURCE_DIR}")
-  include_directories(${json_SOURCE_DIR}/include)
-  # Use #include "nlohmann/json.hpp"
-endfunction()
-
-download_json()
diff --git a/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h b/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h
index 8f2f31df..d6dedd5b 100644
--- a/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h
+++ b/sherpa-onnx/csrc/offline-recognizer-whisper-impl.h
@@ -28,197 +28,6 @@
 
 namespace sherpa_onnx {
 
-static std::string FixInvalidUtf8(const std::string &s) {
-  int32_t s_size = s.size();
-
-  std::string ans;
-  ans.reserve(s_size);
-
-  for (int32_t i = 0; i < s_size;) {
-    uint8_t c = s[i];
-    if (c < 0x80) {
-      // valid
-      ans.append(1, c);
-      ++i;
-      continue;
-    } else if ((c >= 0xc0) && (c < 0xe0)) {
-      // beginning of two bytes
-      if ((i + 1) > (s_size - 1)) {
-        // no subsequent byte. invalid!
-        i += 1;
-        continue;
-      }
-      uint8_t next = s[i + 1];
-      if (!(next >= 0x80 && next < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-      // valid 2-byte utf-8
-      ans.append(1, c);
-      ans.append(1, next);
-      i += 2;
-      continue;
-    } else if ((c >= 0xe0) && (c < 0xf0)) {
-      // beginning of 3 bytes
-      if ((i + 2) > (s_size - 1)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next = s[i + 1];
-      if (!(next >= 0x80 && next < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next2 = s[i + 2];
-      if (!(next2 >= 0x80 && next2 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      ans.append(1, c);
-      ans.append(1, next);
-      ans.append(1, next2);
-      i += 3;
-      continue;
-    } else if ((c >= 0xf0) && (c < 0xf8)) {
-      // 4 bytes
-      if ((i + 3) > (s_size - 1)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next = s[i + 1];
-      if (!(next >= 0x80 && next < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next2 = s[i + 2];
-      if (!(next2 >= 0x80 && next2 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next3 = s[i + 3];
-      if (!(next3 >= 0x80 && next3 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-      ans.append(1, c);
-      ans.append(1, next);
-      ans.append(1, next2);
-      ans.append(1, next3);
-      i += 4;
-      continue;
-    } else if ((c >= 0xf8) && (c < 0xfc)) {
-      // 5 bytes
-      if ((i + 4) > (s_size - 1)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next = s[i + 1];
-      if (!(next >= 0x80 && next < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next2 = s[i + 2];
-      if (!(next2 >= 0x80 && next2 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next3 = s[i + 3];
-      if (!(next3 >= 0x80 && next3 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next4 = s[i + 4];
-      if (!(next4 >= 0x80 && next4 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-      ans.append(1, c);
-      ans.append(1, next);
-      ans.append(1, next2);
-      ans.append(1, next3);
-      ans.append(1, next4);
-      i += 5;
-      continue;
-    } else if ((c >= 0xfc) && (c < 0xfe)) {
-      // 6 bytes
-      if ((i + 5) > (s_size - 1)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next = s[i + 1];
-      if (!(next >= 0x80 && next < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next2 = s[i + 2];
-      if (!(next2 >= 0x80 && next2 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next3 = s[i + 3];
-      if (!(next3 >= 0x80 && next3 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next4 = s[i + 4];
-      if (!(next4 >= 0x80 && next4 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-
-      uint8_t next5 = s[i + 5];
-      if (!(next5 >= 0x80 && next5 < 0xc0)) {
-        // invalid
-        i += 1;
-        continue;
-      }
-      ans.append(1, c);
-      ans.append(1, next);
-      ans.append(1, next2);
-      ans.append(1, next3);
-      ans.append(1, next4);
-      ans.append(1, next5);
-      i += 6;
-      continue;
-    } else {
-      i += 1;
-    }
-  }
-  return ans;
-}
-
 static OfflineRecognitionResult Convert(const OfflineWhisperDecoderResult &src,
                                         const SymbolTable &sym_table) {
   OfflineRecognitionResult r;
@@ -235,19 +44,7 @@ static OfflineRecognitionResult Convert(const OfflineWhisperDecoderResult &src,
     r.tokens.push_back(s);
   }
 
-  // TODO(fangjun): Fix the following error in offline-stream.cc
-  //
-  //      j["text"] = text;
-
-  // libc++abi: terminating with uncaught exception of type
-  // nlohmann::json_abi_v3_11_2::detail::type_error:
-  // [json.exception.type_error.316] incomplete UTF-8 string; last byte: 0x86
-
-#if 0
-  r.text = FixInvalidUtf8(text);
-#else
   r.text = text;
-#endif
 
   return r;
 }
diff --git a/sherpa-onnx/csrc/offline-stream.cc b/sherpa-onnx/csrc/offline-stream.cc
index cf7ca341..3cb463b4 100644
--- a/sherpa-onnx/csrc/offline-stream.cc
+++ b/sherpa-onnx/csrc/offline-stream.cc
@@ -267,14 +267,14 @@ std::string OfflineRecognitionResult::AsJsonString() const {
      << "timestamps"
      << "\""
      << ": ";
-  os << "\"[";
+  os << "[";
 
   std::string sep = "";
   for (auto t : timestamps) {
     os << sep << std::fixed << std::setprecision(2) << t;
     sep = ", ";
   }
-  os << "]\", ";
+  os << "], ";
 
   os << "\""
      << "tokens"
diff --git a/sherpa-onnx/csrc/online-recognizer-transducer-impl.h b/sherpa-onnx/csrc/online-recognizer-transducer-impl.h
index 9af9a780..31d54fe8 100644
--- a/sherpa-onnx/csrc/online-recognizer-transducer-impl.h
+++ b/sherpa-onnx/csrc/online-recognizer-transducer-impl.h
@@ -28,9 +28,10 @@ namespace sherpa_onnx {
 
 static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
                                       const SymbolTable &sym_table,
-                                      int32_t frame_shift_ms,
+                                      float frame_shift_ms,
                                       int32_t subsampling_factor,
-                                      int32_t segment) {
+                                      int32_t segment,
+                                      int32_t frames_since_start) {
   OnlineRecognizerResult r;
   r.tokens.reserve(src.tokens.size());
   r.timestamps.reserve(src.tokens.size());
@@ -49,6 +50,7 @@ static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
   }
 
   r.segment = segment;
+  r.start_time = frames_since_start * frame_shift_ms / 1000.;
 
   return r;
 }
@@ -216,7 +218,7 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
     int32_t frame_shift_ms = 10;
     int32_t subsampling_factor = 4;
     return Convert(decoder_result, sym_, frame_shift_ms, subsampling_factor,
-                   s->GetCurrentSegment());
+                   s->GetCurrentSegment(), s->GetNumFramesSinceStart());
   }
 
   bool IsEndpoint(OnlineStream *s) const override {
diff --git a/sherpa-onnx/csrc/online-recognizer.cc b/sherpa-onnx/csrc/online-recognizer.cc
index c3b18766..687b0211 100644
--- a/sherpa-onnx/csrc/online-recognizer.cc
+++ b/sherpa-onnx/csrc/online-recognizer.cc
@@ -14,37 +14,61 @@
 #include <utility>
 #include <vector>
 
-#include "nlohmann/json.hpp"
 #include "sherpa-onnx/csrc/online-recognizer-impl.h"
 
 namespace sherpa_onnx {
 
 std::string OnlineRecognizerResult::AsJsonString() const {
-  using json = nlohmann::json;
-  json j;
-  j["text"] = text;
-  j["tokens"] = tokens;
-  j["start_time"] = start_time;
-#if 1
-  // This branch chooses number of decimal points to keep in
-  // the return json string
   std::ostringstream os;
+  os << "{";
+  os << "\"is_final\":" << (is_final ? "true" : "false") << ", ";
+  os << "\"segment\":" << segment << ", ";
+  os << "\"start_time\":" << std::fixed << std::setprecision(2) << start_time
+     << ", ";
+
+  os << "\"text\""
+     << ": ";
+  os << "\"" << text << "\""
+     << ", ";
+
+  os << "\""
+     << "timestamps"
+     << "\""
+     << ": ";
   os << "[";
+
   std::string sep = "";
   for (auto t : timestamps) {
     os << sep << std::fixed << std::setprecision(2) << t;
     sep = ", ";
   }
+  os << "], ";
+
+  os << "\""
+     << "tokens"
+     << "\""
+     << ":";
+  os << "[";
+
+  sep = "";
+  auto oldFlags = os.flags();
+  for (const auto &t : tokens) {
+    if (t.size() == 1 && static_cast<uint8_t>(t[0]) > 0x7f) {
+      const uint8_t *p = reinterpret_cast<const uint8_t *>(t.c_str());
+      os << sep << "\""
+         << "<0x" << std::hex << std::uppercase << static_cast<uint32_t>(p[0])
+         << ">"
+         << "\"";
+      os.flags(oldFlags);
+    } else {
+      os << sep << "\"" << t << "\"";
+    }
+    sep = ", ";
+  }
   os << "]";
-  j["timestamps"] = os.str();
-#else
-  j["timestamps"] = timestamps;
-#endif
+  os << "}";
 
-  j["segment"] = segment;
-  j["is_final"] = is_final;
-
-  return j.dump();
+  return os.str();
 }
 
 void OnlineRecognizerConfig::Register(ParseOptions *po) {
diff --git a/sherpa-onnx/csrc/online-recognizer.h b/sherpa-onnx/csrc/online-recognizer.h
index 3aa83802..3be7a046 100644
--- a/sherpa-onnx/csrc/online-recognizer.h
+++ b/sherpa-onnx/csrc/online-recognizer.h
@@ -44,11 +44,11 @@ struct OnlineRecognizerResult {
   /// When an endpoint is detected, it is incremented
   int32_t segment = 0;
 
-  /// Starting frame of this segment.
+  /// Starting time of this segment.
   /// When an endpoint is detected, it will change
   float start_time = 0;
 
-  /// True if this is the last segment.
+  /// True if the end of this segment is reached
   bool is_final = false;
 
   /** Return a json string.
diff --git a/sherpa-onnx/csrc/online-stream.cc b/sherpa-onnx/csrc/online-stream.cc
index 39dfd796..8cec219b 100644
--- a/sherpa-onnx/csrc/online-stream.cc
+++ b/sherpa-onnx/csrc/online-stream.cc
@@ -43,6 +43,8 @@ class OnlineStream::Impl {
 
   int32_t &GetNumProcessedFrames() { return num_processed_frames_; }
 
+  int32_t GetNumFramesSinceStart() const { return start_frame_index_; }
+
   int32_t &GetCurrentSegment() { return segment_; }
 
   void SetResult(const OnlineTransducerDecoderResult &r) { result_ = r; }
@@ -126,6 +128,10 @@ int32_t &OnlineStream::GetNumProcessedFrames() {
   return impl_->GetNumProcessedFrames();
 }
 
+int32_t OnlineStream::GetNumFramesSinceStart() const {
+  return impl_->GetNumFramesSinceStart();
+}
+
 int32_t &OnlineStream::GetCurrentSegment() {
   return impl_->GetCurrentSegment();
 }
diff --git a/sherpa-onnx/csrc/online-stream.h b/sherpa-onnx/csrc/online-stream.h
index 6b7a96c4..b9214b1d 100644
--- a/sherpa-onnx/csrc/online-stream.h
+++ b/sherpa-onnx/csrc/online-stream.h
@@ -66,7 +66,9 @@ class OnlineStream {
   // Initially, it is 0. It is always less than NumFramesReady().
   //
   // The returned reference is valid as long as this object is alive.
-  int32_t &GetNumProcessedFrames();
+  int32_t &GetNumProcessedFrames();  // It's reset after calling Reset()
+
+  int32_t GetNumFramesSinceStart() const;
 
   int32_t &GetCurrentSegment();
 
diff --git a/sherpa-onnx/csrc/online-websocket-server-impl.cc b/sherpa-onnx/csrc/online-websocket-server-impl.cc
index 9c265de8..eaf65cfa 100644
--- a/sherpa-onnx/csrc/online-websocket-server-impl.cc
+++ b/sherpa-onnx/csrc/online-websocket-server-impl.cc
@@ -195,9 +195,14 @@ void OnlineWebsocketDecoder::Decode() {
   for (auto c : c_vec) {
     auto result = recognizer_->GetResult(c->s.get());
     if (recognizer_->IsEndpoint(c->s.get())) {
+      result.is_final = true;
       recognizer_->Reset(c->s.get());
     }
 
+    if (!recognizer_->IsReady(c->s.get()) && c->eof) {
+      result.is_final = true;
+    }
+
     asio::post(server_->GetConnectionContext(),
                [this, hdl = c->hdl, str = result.AsJsonString()]() {
                  server_->Send(hdl, str);