diff --git a/sherpa-onnx/csrc/features.cc b/sherpa-onnx/csrc/features.cc
index 95c6f82a..82645849 100644
--- a/sherpa-onnx/csrc/features.cc
+++ b/sherpa-onnx/csrc/features.cc
@@ -60,6 +60,8 @@ class FeatureExtractor::Impl {
   explicit Impl(const FeatureExtractorConfig &config) : config_(config) {
     if (config_.is_mfcc) {
       InitMfcc();
+    } else if (config_.is_whisper) {
+      InitWhisper();
     } else {
       InitFbank();
     }
@@ -92,13 +94,9 @@ class FeatureExtractor::Impl {
 
       std::vector<float> samples;
       resampler_->Resample(waveform, n, false, &samples);
-      if (fbank_) {
-        fbank_->AcceptWaveform(config_.sampling_rate, samples.data(),
-                               samples.size());
-      } else {
-        mfcc_->AcceptWaveform(config_.sampling_rate, samples.data(),
-                              samples.size());
-      }
+
+      AcceptWaveformWrapper(config_.sampling_rate, samples.data(),
+                            samples.size());
       return;
     }
 
@@ -119,61 +117,81 @@ class FeatureExtractor::Impl {
 
       std::vector<float> samples;
       resampler_->Resample(waveform, n, false, &samples);
-      if (fbank_) {
-        fbank_->AcceptWaveform(config_.sampling_rate, samples.data(),
-                               samples.size());
-      } else {
-        mfcc_->AcceptWaveform(config_.sampling_rate, samples.data(),
-                              samples.size());
-      }
+
+      AcceptWaveformWrapper(config_.sampling_rate, samples.data(),
+                            samples.size());
+
       return;
     }
 
-    if (fbank_) {
-      fbank_->AcceptWaveform(sampling_rate, waveform, n);
-    } else {
-      mfcc_->AcceptWaveform(sampling_rate, waveform, n);
-    }
+    AcceptWaveformWrapper(sampling_rate, waveform, n);
   }
 
   void InputFinished() const {
     std::lock_guard<std::mutex> lock(mutex_);
-    fbank_->InputFinished();
+    if (fbank_) {
+      fbank_->InputFinished();
+    } else if (whisper_fbank_) {
+      whisper_fbank_->InputFinished();
+    } else if (mfcc_) {
+      mfcc_->InputFinished();
+    }
+
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
   }
 
   int32_t NumFramesReady() const {
-    std::lock_guard<std::mutex> lock(mutex_);
-    return fbank_->NumFramesReady();
+    if (fbank_) {
+      return fbank_->NumFramesReady();
+    } else if (whisper_fbank_) {
+      return whisper_fbank_->NumFramesReady();
+    } else if (mfcc_) {
+      return mfcc_->NumFramesReady();
+    }
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
+    return -1;
   }
 
   bool IsLastFrame(int32_t frame) const {
     std::lock_guard<std::mutex> lock(mutex_);
-    return fbank_->IsLastFrame(frame);
+    if (fbank_) {
+      return fbank_->IsLastFrame(frame);
+    } else if (whisper_fbank_) {
+      return whisper_fbank_->IsLastFrame(frame);
+    } else if (mfcc_) {
+      return mfcc_->IsLastFrame(frame);
+    }
+
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
+    return false;
   }
 
   std::vector<float> GetFrames(int32_t frame_index, int32_t n) {
     std::lock_guard<std::mutex> lock(mutex_);
-    if (frame_index + n > fbank_->NumFramesReady()) {
-      SHERPA_ONNX_LOGE("%d + %d > %d\n", frame_index, n,
-                       fbank_->NumFramesReady());
-      exit(-1);
+    if (frame_index + n > NumFramesReady()) {
+      SHERPA_ONNX_LOGE("%d + %d > %d\n", frame_index, n, NumFramesReady());
+      SHERPA_ONNX_EXIT(-1);
     }
 
     int32_t discard_num = frame_index - last_frame_index_;
     if (discard_num < 0) {
       SHERPA_ONNX_LOGE("last_frame_index_: %d, frame_index_: %d",
                        last_frame_index_, frame_index);
-      exit(-1);
+      SHERPA_ONNX_EXIT(-1);
     }
-    fbank_->Pop(discard_num);
 
-    int32_t feature_dim = fbank_->Dim();
+    PopWrapper(discard_num);
+
+    int32_t feature_dim = FeatureDim();
     std::vector<float> features(feature_dim * n);
 
     float *p = features.data();
 
     for (int32_t i = 0; i != n; ++i) {
-      const float *f = fbank_->GetFrame(i + frame_index);
+      const float *f = GetFrameWrapper(i + frame_index);
       std::copy(f, f + feature_dim, p);
       p += feature_dim;
     }
@@ -184,10 +202,65 @@ class FeatureExtractor::Impl {
   }
 
   int32_t FeatureDim() const {
-    return mfcc_ ? mfcc_opts_.num_ceps : opts_.mel_opts.num_bins;
+    if (fbank_ || whisper_fbank_) {
+      return opts_.mel_opts.num_bins;
+    } else if (mfcc_) {
+      return mfcc_opts_.num_ceps;
+    }
+
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
+    return -1;
   }
 
  private:
+  void AcceptWaveformWrapper(float sampling_rate, const float *waveform,
+                             int32_t n) const {
+    if (fbank_) {
+      fbank_->AcceptWaveform(sampling_rate, waveform, n);
+      return;
+    } else if (whisper_fbank_) {
+      whisper_fbank_->AcceptWaveform(sampling_rate, waveform, n);
+      return;
+    } else if (mfcc_) {
+      mfcc_->AcceptWaveform(sampling_rate, waveform, n);
+      return;
+    }
+
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
+  }
+
+  const float *GetFrameWrapper(int32_t frame_index) const {
+    if (fbank_) {
+      return fbank_->GetFrame(frame_index);
+    } else if (whisper_fbank_) {
+      return whisper_fbank_->GetFrame(frame_index);
+    } else if (mfcc_) {
+      return mfcc_->GetFrame(frame_index);
+    }
+
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
+    return nullptr;
+  }
+
+  void PopWrapper(int32_t discard_num) const {
+    if (fbank_) {
+      fbank_->Pop(discard_num);
+      return;
+    } else if (whisper_fbank_) {
+      whisper_fbank_->Pop(discard_num);
+      return;
+    } else if (mfcc_) {
+      mfcc_->Pop(discard_num);
+      return;
+    }
+
+    SHERPA_ONNX_LOGE("unreachable code");
+    SHERPA_ONNX_EXIT(-1);
+  }
+
   void InitFbank() {
     opts_.frame_opts.dither = config_.dither;
     opts_.frame_opts.snip_edges = config_.snip_edges;
@@ -208,6 +281,7 @@ class FeatureExtractor::Impl {
 
     fbank_ = std::make_unique<knf::OnlineFbank>(opts_);
   }
+
   void InitMfcc() {
     mfcc_opts_.frame_opts.dither = config_.dither;
     mfcc_opts_.frame_opts.snip_edges = config_.snip_edges;
@@ -232,9 +306,23 @@ class FeatureExtractor::Impl {
     mfcc_ = std::make_unique<knf::OnlineMfcc>(mfcc_opts_);
   }
 
+  void InitWhisper() {
+    config_.normalize_samples = true;
+    opts_.frame_opts.samp_freq = 16000;
+    opts_.mel_opts.num_bins = config_.feature_dim;
+
+    knf::WhisperFeatureOptions whisper_opts;
+    whisper_opts.frame_opts = opts_.frame_opts;
+    whisper_opts.dim = config_.feature_dim;
+
+    whisper_fbank_ = std::make_unique<knf::OnlineWhisperFbank>(whisper_opts);
+    config_.sampling_rate = opts_.frame_opts.samp_freq;
+  }
+
  private:
   std::unique_ptr<knf::OnlineFbank> fbank_;
   std::unique_ptr<knf::OnlineMfcc> mfcc_;
+  std::unique_ptr<knf::OnlineWhisperFbank> whisper_fbank_;
   knf::FbankOptions opts_;
   knf::MfccOptions mfcc_opts_;
   FeatureExtractorConfig config_;
diff --git a/sherpa-onnx/csrc/features.h b/sherpa-onnx/csrc/features.h
index d10b486b..b8e99320 100644
--- a/sherpa-onnx/csrc/features.h
+++ b/sherpa-onnx/csrc/features.h
@@ -79,6 +79,8 @@ struct FeatureExtractorConfig {
 
   bool is_mfcc = false;
 
+  bool is_whisper = false;
+
   bool round_to_power_of_two = true;
 
   std::string ToString() const;
diff --git a/sherpa-onnx/csrc/online-ctc-model.h b/sherpa-onnx/csrc/online-ctc-model.h
index bd01bc54..6886a3c6 100644
--- a/sherpa-onnx/csrc/online-ctc-model.h
+++ b/sherpa-onnx/csrc/online-ctc-model.h
@@ -77,6 +77,8 @@ class OnlineCtcModel {
 
   // Return true if the model supports batch size > 1
   virtual bool SupportBatchProcessing() const { return true; }
+
+  virtual bool UseWhisperFeature() const { return false; }
 };
 
 }  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/online-recognizer-ctc-impl.h b/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
index a675fd72..42b7fd25 100644
--- a/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
+++ b/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
@@ -15,6 +15,7 @@
 
 #include "sherpa-onnx/csrc/file-utils.h"
 #include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/offline-whisper-model.h"
 #include "sherpa-onnx/csrc/online-ctc-decoder.h"
 #include "sherpa-onnx/csrc/online-ctc-fst-decoder.h"
 #include "sherpa-onnx/csrc/online-ctc-greedy-search-decoder.h"
@@ -91,6 +92,10 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
       config_.feat_config.normalize_samples = false;
     }
 
+    if (model_->UseWhisperFeature()) {
+      config_.feat_config.is_whisper = true;
+    }
+
     InitDecoder();
   }
 
@@ -108,6 +113,10 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
       config_.feat_config.normalize_samples = false;
     }
 
+    if (model_->UseWhisperFeature()) {
+      config_.feat_config.is_whisper = true;
+    }
+
     InitDecoder();
   }
 
@@ -147,6 +156,10 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
       const auto num_processed_frames = ss[i]->GetNumProcessedFrames();
       std::vector<float> features =
           ss[i]->GetFrames(num_processed_frames, chunk_length);
+      if (config_.feat_config.is_whisper) {
+        OfflineWhisperModel::NormalizeFeatures(features.data(), chunk_length,
+                                               feat_dim);
+      }
 
       // Question: should num_processed_frames include chunk_shift?
       ss[i]->GetNumProcessedFrames() += chunk_shift;
@@ -287,6 +300,12 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
     const auto num_processed_frames = s->GetNumProcessedFrames();
     std::vector<float> frames =
         s->GetFrames(num_processed_frames, chunk_length);
+
+    if (config_.feat_config.is_whisper) {
+      OfflineWhisperModel::NormalizeFeatures(frames.data(), chunk_length,
+                                             feat_dim);
+    }
+
     s->GetNumProcessedFrames() += chunk_shift;
 
     auto memory_info =
diff --git a/sherpa-onnx/csrc/online-stream.cc b/sherpa-onnx/csrc/online-stream.cc
index 972133c7..f7abaa66 100644
--- a/sherpa-onnx/csrc/online-stream.cc
+++ b/sherpa-onnx/csrc/online-stream.cc
@@ -19,34 +19,51 @@ class OnlineStream::Impl {
       : feat_extractor_(config), context_graph_(std::move(context_graph)) {}
 
   void AcceptWaveform(int32_t sampling_rate, const float *waveform, int32_t n) {
+    std::lock_guard<std::mutex> lock(mutex_);
     feat_extractor_.AcceptWaveform(sampling_rate, waveform, n);
   }
 
-  void InputFinished() const { feat_extractor_.InputFinished(); }
+  void InputFinished() const {
+    std::lock_guard<std::mutex> lock(mutex_);
+    feat_extractor_.InputFinished();
+  }
 
   int32_t NumFramesReady() const {
+    std::lock_guard<std::mutex> lock(mutex_);
     return feat_extractor_.NumFramesReady() - start_frame_index_;
   }
 
   bool IsLastFrame(int32_t frame) const {
+    std::lock_guard<std::mutex> lock(mutex_);
     return feat_extractor_.IsLastFrame(frame);
   }
 
   std::vector<float> GetFrames(int32_t frame_index, int32_t n) const {
+    std::lock_guard<std::mutex> lock(mutex_);
     return feat_extractor_.GetFrames(frame_index + start_frame_index_, n);
   }
 
   void Reset() {
+    std::lock_guard<std::mutex> lock(mutex_);
     // we don't reset the feature extractor
     start_frame_index_ += num_processed_frames_;
     num_processed_frames_ = 0;
   }
 
-  int32_t &GetNumProcessedFrames() { return num_processed_frames_; }
+  int32_t &GetNumProcessedFrames() {
+    std::lock_guard<std::mutex> lock(mutex_);
+    return num_processed_frames_;
+  }
 
-  int32_t GetNumFramesSinceStart() const { return start_frame_index_; }
+  int32_t GetNumFramesSinceStart() const {
+    std::lock_guard<std::mutex> lock(mutex_);
+    return start_frame_index_;
+  }
 
-  int32_t &GetCurrentSegment() { return segment_; }
+  int32_t &GetCurrentSegment() {
+    std::lock_guard<std::mutex> lock(mutex_);
+    return segment_;
+  }
 
   void SetResult(const OnlineTransducerDecoderResult &r) { result_ = r; }
 
@@ -125,6 +142,7 @@ class OnlineStream::Impl {
 
  private:
   FeatureExtractor feat_extractor_;
+  mutable std::mutex mutex_;
   /// For contextual-biasing
   ContextGraphPtr context_graph_;
   int32_t num_processed_frames_ = 0;  // before subsampling
diff --git a/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc b/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
index 1cda9a62..f7cccc43 100644
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
@@ -74,6 +74,8 @@ class OnlineZipformer2CtcModel::Impl {
 
   int32_t ChunkShift() const { return decode_chunk_len_; }
 
+  bool UseWhisperFeature() const { return use_whisper_feature_; }
+
   OrtAllocator *Allocator() { return allocator_; }
 
   // Return a vector containing 3 tensors
@@ -278,6 +280,12 @@ class OnlineZipformer2CtcModel::Impl {
     SHERPA_ONNX_READ_META_DATA(T_, "T");
     SHERPA_ONNX_READ_META_DATA(decode_chunk_len_, "decode_chunk_len");
 
+    std::string feature_type;
+    SHERPA_ONNX_READ_META_DATA_STR_WITH_DEFAULT(feature_type, "feature", "");
+    if (feature_type == "whisper") {
+      use_whisper_feature_ = true;
+    }
+
     {
       auto shape =
           sess_->GetOutputTypeInfo(0).GetTensorTypeAndShapeInfo().GetShape();
@@ -417,6 +425,10 @@ class OnlineZipformer2CtcModel::Impl {
   int32_t T_ = 0;
   int32_t decode_chunk_len_ = 0;
   int32_t vocab_size_ = 0;
+
+  // for models from
+  // https://github.com/k2-fsa/icefall/blob/master/egs/multi_zh-hans/ASR/RESULTS.md#streaming-with-ctc-head
+  bool use_whisper_feature_ = false;
 };
 
 OnlineZipformer2CtcModel::OnlineZipformer2CtcModel(
@@ -447,6 +459,10 @@ int32_t OnlineZipformer2CtcModel::ChunkShift() const {
   return impl_->ChunkShift();
 }
 
+bool OnlineZipformer2CtcModel::UseWhisperFeature() const {
+  return impl_->UseWhisperFeature();
+}
+
 OrtAllocator *OnlineZipformer2CtcModel::Allocator() const {
   return impl_->Allocator();
 }
diff --git a/sherpa-onnx/csrc/online-zipformer2-ctc-model.h b/sherpa-onnx/csrc/online-zipformer2-ctc-model.h
index 32ddf212..3cbd4cc7 100644
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model.h
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model.h
@@ -64,6 +64,8 @@ class OnlineZipformer2CtcModel : public OnlineCtcModel {
   // before we process the next chunk.
   int32_t ChunkShift() const override;
 
+  bool UseWhisperFeature() const override;
+
  private:
   class Impl;
   std::unique_ptr<Impl> impl_;
diff --git a/sherpa-onnx/csrc/sherpa-onnx-microphone.cc b/sherpa-onnx/csrc/sherpa-onnx-microphone.cc
index a3c1294a..22f22124 100644
--- a/sherpa-onnx/csrc/sherpa-onnx-microphone.cc
+++ b/sherpa-onnx/csrc/sherpa-onnx-microphone.cc
@@ -130,7 +130,7 @@ for a list of pre-trained models to download.
   }
 
   if (!mic.OpenDevice(device_index, mic_sample_rate, 1, RecordCallback,
-                      nullptr /* user_data */)) {
+                      s.get())) {
     fprintf(stderr, "portaudio error: %d\n", device_index);
     exit(EXIT_FAILURE);
   }