Add C++ runtime for *streaming* faster conformer transducer from NeMo.

sherpa-onnx/csrc/CMakeLists.txt

@@ -74,6 +74,8 @@ set(sources
   online-transducer-model-config.cc
   online-transducer-model.cc
   online-transducer-modified-beam-search-decoder.cc
+  online-transducer-nemo-model.cc
+  online-transducer-greedy-search-nemo-decoder.cc
   online-wenet-ctc-model-config.cc
   online-wenet-ctc-model.cc
   online-zipformer-transducer-model.cc

sherpa-onnx/csrc/online-recognizer-impl.cc

@@ -7,13 +7,28 @@
 #include "sherpa-onnx/csrc/online-recognizer-ctc-impl.h"
 #include "sherpa-onnx/csrc/online-recognizer-paraformer-impl.h"
 #include "sherpa-onnx/csrc/online-recognizer-transducer-impl.h"
+#include "sherpa-onnx/csrc/online-recognizer-transducer-nemo-impl.h"
+#include "sherpa-onnx/csrc/onnx-utils.h"
 
 namespace sherpa_onnx {
 
 std::unique_ptr<OnlineRecognizerImpl> OnlineRecognizerImpl::Create(
     const OnlineRecognizerConfig &config) {
+
   if (!config.model_config.transducer.encoder.empty()) {
-    return std::make_unique<OnlineRecognizerTransducerImpl>(config);
+    Ort::Env env(ORT_LOGGING_LEVEL_WARNING);
+
+    auto decoder_model = ReadFile(config.model_config.transducer.decoder);
+    auto sess = std::make_unique<Ort::Session>(env, decoder_model.data(), decoder_model.size(), Ort::SessionOptions{});
+
+    size_t node_count = sess->GetOutputCount();
+
+    if (node_count == 1) {
+      return std::make_unique<OnlineRecognizerTransducerImpl>(config);
+    } else {
+      SHERPA_ONNX_LOGE("Running streaming Nemo transducer model");
+      return std::make_unique<OnlineRecognizerTransducerNeMoImpl>(config);
+    }
   }
 
   if (!config.model_config.paraformer.encoder.empty()) {
@@ -34,7 +49,18 @@ std::unique_ptr<OnlineRecognizerImpl> OnlineRecognizerImpl::Create(
 std::unique_ptr<OnlineRecognizerImpl> OnlineRecognizerImpl::Create(
     AAssetManager *mgr, const OnlineRecognizerConfig &config) {
   if (!config.model_config.transducer.encoder.empty()) {
-    return std::make_unique<OnlineRecognizerTransducerImpl>(mgr, config);
+    Ort::Env env(ORT_LOGGING_LEVEL_WARNING);
+
+    auto decoder_model = ReadFile(mgr, config.model_config.transducer.decoder);
+    auto sess = std::make_unique<Ort::Session>(env, decoder_model.data(), decoder_model.size(), Ort::SessionOptions{});
+
+    size_t node_count = sess->GetOutputCount();
+
+    if (node_count == 1) {
+      return std::make_unique<OnlineRecognizerTransducerImpl>(mgr, config);
+    } else {
+      return std::make_unique<OnlineRecognizerTransducerNeMoImpl>(mgr, config);
+    }
   }
 
   if (!config.model_config.paraformer.encoder.empty()) {

sherpa-onnx/csrc/online-recognizer-transducer-impl.h

@@ -46,6 +46,7 @@ static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
   r.timestamps.reserve(src.tokens.size());
 
   for (auto i : src.tokens) {
+    if (i == -1) continue;
     auto sym = sym_table[i];
 
     r.text.append(sym);

sherpa-onnx/csrc/online-recognizer-transducer-nemo-impl.h

@@ -0,0 +1,267 @@
+// sherpa-onnx/csrc/online-recognizer-transducer-nemo-impl.h
+//
+// Copyright (c)  2022-2024  Xiaomi Corporation
+// Copyright (c)  2024  Sangeet Sagar
+
+#ifndef SHERPA_ONNX_CSRC_ONLINE_RECOGNIZER_TRANSDUCER_NEMO_IMPL_H_
+#define SHERPA_ONNX_CSRC_ONLINE_RECOGNIZER_TRANSDUCER_NEMO_IMPL_H_
+
+#include <fstream>
+#include <ios>
+#include <memory>
+#include <regex>  // NOLINT
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/online-recognizer-impl.h"
+#include "sherpa-onnx/csrc/online-recognizer.h"
+#include "sherpa-onnx/csrc/online-transducer-greedy-search-nemo-decoder.h"
+#include "sherpa-onnx/csrc/online-transducer-nemo-model.h"
+#include "sherpa-onnx/csrc/symbol-table.h"
+#include "sherpa-onnx/csrc/transpose.h"
+#include "sherpa-onnx/csrc/utils.h"
+
+namespace sherpa_onnx {
+
+// defined in ./online-recognizer-transducer-impl.h
+// static may or may not be here? TODDOs
+static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
+                              const SymbolTable &sym_table,
+                              float frame_shift_ms,
+                              int32_t subsampling_factor,
+                              int32_t segment,
+                              int32_t frames_since_start);
+
+class OnlineRecognizerTransducerNeMoImpl : public OnlineRecognizerImpl {
+  public:
+  explicit OnlineRecognizerTransducerNeMoImpl(
+      const OnlineRecognizerConfig &config)
+      : config_(config),
+        symbol_table_(config.model_config.tokens),
+        endpoint_(config_.endpoint_config),
+        model_(std::make_unique<OnlineTransducerNeMoModel>(
+            config.model_config)) {
+    if (config.decoding_method == "greedy_search") {
+      decoder_ = std::make_unique<OnlineTransducerGreedySearchNeMoDecoder>(
+          model_.get(), config_.blank_penalty);
+    } else {
+      SHERPA_ONNX_LOGE("Unsupported decoding method: %s",
+                       config.decoding_method.c_str());
+      exit(-1);
+    }
+    PostInit();
+  }
+
+#if __ANDROID_API__ >= 9
+  explicit OnlineRecognizerTransducerNeMoImpl(
+      AAssetManager *mgr, const OnlineRecognizerConfig &config)
+      : config_(config),
+        symbol_table_(mgr, config.model_config.tokens),
+        endpoint_(mgrconfig_.endpoint_config),
+        model_(std::make_unique<OnlineTransducerNeMoModel>(
+            mgr, config.model_config)) {
+    if (config.decoding_method == "greedy_search") {
+      decoder_ = std::make_unique<OnlineTransducerGreedySearchNeMoDecoder>(
+          model_.get(), config_.blank_penalty);
+    } else {
+      SHERPA_ONNX_LOGE("Unsupported decoding method: %s",
+                      config.decoding_method.c_str());
+      exit(-1);
+    }
+
+    PostInit();
+  }
+#endif
+
+  std::unique_ptr<OnlineStream> CreateStream() const override {
+    auto stream = std::make_unique<OnlineStream>(config_.feat_config);
+    stream->SetStates(model_->GetInitStates());
+    InitOnlineStream(stream.get());
+    return stream;
+  }
+
+  bool IsReady(OnlineStream *s) const override {
+    return s->GetNumProcessedFrames() + model_->ChunkSize() <
+           s->NumFramesReady();
+  }
+
+  OnlineRecognizerResult GetResult(OnlineStream *s) const override {
+    OnlineTransducerDecoderResult decoder_result = s->GetResult();
+    decoder_->StripLeadingBlanks(&decoder_result);
+
+    // TODO(fangjun): Remember to change these constants if needed
+    int32_t frame_shift_ms = 10;
+    int32_t subsampling_factor = 8;
+    return Convert(decoder_result, symbol_table_, frame_shift_ms, subsampling_factor,
+                   s->GetCurrentSegment(), s->GetNumFramesSinceStart());
+  }
+
+  bool IsEndpoint(OnlineStream *s) const override {
+    if (!config_.enable_endpoint) {
+      return false;
+    }
+
+    int32_t num_processed_frames = s->GetNumProcessedFrames();
+
+    // frame shift is 10 milliseconds
+    float frame_shift_in_seconds = 0.01;
+
+    // subsampling factor is 8
+    int32_t trailing_silence_frames = s->GetResult().num_trailing_blanks * 8;
+
+    return endpoint_.IsEndpoint(num_processed_frames, trailing_silence_frames,
+                                frame_shift_in_seconds);
+  }
+
+  void Reset(OnlineStream *s) const override {
+    {
+      // segment is incremented only when the last
+      // result is not empty
+      const auto &r = s->GetResult();
+      if (!r.tokens.empty() && r.tokens.back() != 0) {
+        s->GetCurrentSegment() += 1;
+      }
+    }
+
+    // we keep the decoder_out
+    decoder_->UpdateDecoderOut(&s->GetResult());
+    Ort::Value decoder_out = std::move(s->GetResult().decoder_out);
+
+    auto r = decoder_->GetEmptyResult();
+
+    s->SetResult(r);
+    s->GetResult().decoder_out = std::move(decoder_out);
+
+    // Note: We only update counters. The underlying audio samples
+    // are not discarded.
+    s->Reset();
+  }
+
+  void DecodeStreams(OnlineStream **ss, int32_t n) const override {
+    int32_t chunk_size = model_->ChunkSize();
+    int32_t chunk_shift = model_->ChunkShift();
+
+    int32_t feature_dim = ss[0]->FeatureDim();
+
+    std::vector<OnlineTransducerDecoderResult> result(n);
+    std::vector<float> features_vec(n * chunk_size * feature_dim);
+    std::vector<std::vector<Ort::Value>> encoder_states(n);
+
+    for (int32_t i = 0; i != n; ++i) {
+      const auto num_processed_frames = ss[i]->GetNumProcessedFrames();
+      std::vector<float> features =
+          ss[i]->GetFrames(num_processed_frames, chunk_size);
+
+      // Question: should num_processed_frames include chunk_shift?
+      ss[i]->GetNumProcessedFrames() += chunk_shift;
+
+      std::copy(features.begin(), features.end(),
+                features_vec.data() + i * chunk_size * feature_dim);
+
+      result[i] = std::move(ss[i]->GetResult());
+      encoder_states[i] = std::move(ss[i]->GetStates());
+
+    }
+
+    auto memory_info =
+        Ort::MemoryInfo::CreateCpu(OrtDeviceAllocator, OrtMemTypeDefault);
+
+    std::array<int64_t, 3> x_shape{n, chunk_size, feature_dim};
+
+    Ort::Value x = Ort::Value::CreateTensor(memory_info, features_vec.data(),
+                                            features_vec.size(), x_shape.data(),
+                                            x_shape.size());
+
+    // Batch size is 1
+    auto states = std::move(encoder_states[0]);
+    int32_t num_states = states.size(); // num_states = 3
+    auto t = model_->RunEncoder(std::move(x), std::move(states));
+    // t[0] encoder_out, float tensor, (batch_size, dim, T)
+    // t[1] next states
+
+    std::vector<Ort::Value> out_states;
+    out_states.reserve(num_states);
+
+    for (int32_t k = 1; k != num_states + 1; ++k) {
+      out_states.push_back(std::move(t[k]));
+    }
+
+    Ort::Value encoder_out = Transpose12(model_->Allocator(), &t[0]);
+
+    // defined in online-transducer-greedy-search-nemo-decoder.h
+    // get intial states of decoder.
+    std::vector<Ort::Value> &decoder_states = ss[0]->GetNeMoDecoderStates();
+
+    // Subsequent decoder states (for each chunks) are updated inside the Decode method.
+    // This returns the decoder state from the LAST chunk. We probably dont need it. So we can discard it.
+    decoder_states = decoder_->Decode(std::move(encoder_out), 
+                                      std::move(decoder_states),
+                                      &result, ss, n);
+
+    ss[0]->SetResult(result[0]);
+
+    ss[0]->SetStates(std::move(out_states));
+  }
+
+  void InitOnlineStream(OnlineStream *stream) const {
+    auto r = decoder_->GetEmptyResult();
+
+    stream->SetResult(r);
+    stream->SetNeMoDecoderStates(model_->GetDecoderInitStates(1));
+  }
+
+ private:
+  void PostInit() {
+    config_.feat_config.nemo_normalize_type =
+        model_->FeatureNormalizationMethod();
+
+    config_.feat_config.low_freq = 0;
+    // config_.feat_config.high_freq = 8000;
+    config_.feat_config.is_librosa = true;
+    config_.feat_config.remove_dc_offset = false;
+    // config_.feat_config.window_type = "hann";
+    config_.feat_config.dither = 0;
+    config_.feat_config.nemo_normalize_type =
+        model_->FeatureNormalizationMethod();
+
+    int32_t vocab_size = model_->VocabSize();
+
+    // check the blank ID
+    if (!symbol_table_.Contains("<blk>")) {
+      SHERPA_ONNX_LOGE("tokens.txt does not include the blank token <blk>");
+      exit(-1);
+    }
+
+    if (symbol_table_["<blk>"] != vocab_size - 1) {
+      SHERPA_ONNX_LOGE("<blk> is not the last token!");
+      exit(-1);
+    }
+
+    if (symbol_table_.NumSymbols() != vocab_size) {
+      SHERPA_ONNX_LOGE("number of lines in tokens.txt %d != %d (vocab_size)",
+                       symbol_table_.NumSymbols(), vocab_size);
+      exit(-1);
+    }
+
+  }
+
+ private:
+  OnlineRecognizerConfig config_;
+  SymbolTable symbol_table_;
+  std::unique_ptr<OnlineTransducerNeMoModel> model_;
+  std::unique_ptr<OnlineTransducerGreedySearchNeMoDecoder> decoder_;
+  Endpoint endpoint_;
+
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_RECOGNIZER_TRANSDUCER_NEMO_IMPL_H_

sherpa-onnx/csrc/online-stream.cc

@@ -90,6 +90,12 @@ class OnlineStream::Impl {
 
   std::vector<Ort::Value> &GetStates() { return states_; }
 
+  void SetNeMoDecoderStates(std::vector<Ort::Value> decoder_states) {
+    decoder_states_ = std::move(decoder_states);
+  }
+
+  std::vector<Ort::Value> &GetNeMoDecoderStates() { return decoder_states_; }
+
   const ContextGraphPtr &GetContextGraph() const { return context_graph_; }
 
   std::vector<float> &GetParaformerFeatCache() {
@@ -129,6 +135,7 @@ class OnlineStream::Impl {
   TransducerKeywordResult empty_keyword_result_;
   OnlineCtcDecoderResult ctc_result_;
   std::vector<Ort::Value> states_;  // states for transducer or ctc models
+  std::vector<Ort::Value> decoder_states_;  // states for nemo transducer models
   std::vector<float> paraformer_feat_cache_;
   std::vector<float> paraformer_encoder_out_cache_;
   std::vector<float> paraformer_alpha_cache_;
@@ -218,6 +225,14 @@ std::vector<Ort::Value> &OnlineStream::GetStates() {
   return impl_->GetStates();
 }
 
+void OnlineStream::SetNeMoDecoderStates(std::vector<Ort::Value> decoder_states) {
+  return impl_->SetNeMoDecoderStates(std::move(decoder_states));
+}
+
+std::vector<Ort::Value> &OnlineStream::GetNeMoDecoderStates() {
+  return impl_->GetNeMoDecoderStates();
+}
+
 const ContextGraphPtr &OnlineStream::GetContextGraph() const {
   return impl_->GetContextGraph();
 }

sherpa-onnx/csrc/online-stream.h

@@ -91,6 +91,9 @@ class OnlineStream {
   void SetStates(std::vector<Ort::Value> states);
   std::vector<Ort::Value> &GetStates();
 
+  void SetNeMoDecoderStates(std::vector<Ort::Value> decoder_states); 
+  std::vector<Ort::Value> &GetNeMoDecoderStates(); 
+
   /**
    * Get the context graph corresponding to this stream.
    *