add endpointing for online websocket server (#294)

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

@@ -26,7 +26,8 @@ namespace sherpa_onnx {
 static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
                                       const SymbolTable &sym_table,
                                       int32_t frame_shift_ms,
-                                      int32_t subsampling_factor) {
+                                      int32_t subsampling_factor,
+                                      int32_t segment) {
   OnlineRecognizerResult r;
   r.tokens.reserve(src.tokens.size());
   r.timestamps.reserve(src.tokens.size());
@@ -44,6 +45,8 @@ static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
     r.timestamps.push_back(time);
   }
 
+  r.segment = segment;
+
   return r;
 }
 
@@ -192,7 +195,8 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
     // TODO(fangjun): Remember to change these constants if needed
     int32_t frame_shift_ms = 10;
     int32_t subsampling_factor = 4;
-    return Convert(decoder_result, sym_, frame_shift_ms, subsampling_factor);
+    return Convert(decoder_result, sym_, frame_shift_ms, subsampling_factor,
+                   s->GetCurrentSegment());
   }
 
   bool IsEndpoint(OnlineStream *s) const override {
@@ -213,6 +217,15 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
   }
 
   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);

sherpa-onnx/csrc/online-stream.cc

@@ -43,6 +43,8 @@ class OnlineStream::Impl {
 
   int32_t &GetNumProcessedFrames() { return num_processed_frames_; }
 
+  int32_t &GetCurrentSegment() { return segment_; }
+
   void SetResult(const OnlineTransducerDecoderResult &r) { result_ = r; }
 
   OnlineTransducerDecoderResult &GetResult() { return result_; }
@@ -83,6 +85,7 @@ class OnlineStream::Impl {
   ContextGraphPtr context_graph_;
   int32_t num_processed_frames_ = 0;  // before subsampling
   int32_t start_frame_index_ = 0;     // never reset
+  int32_t segment_ = 0;
   OnlineTransducerDecoderResult result_;
   std::vector<Ort::Value> states_;
   std::vector<float> paraformer_feat_cache_;
@@ -123,6 +126,10 @@ int32_t &OnlineStream::GetNumProcessedFrames() {
   return impl_->GetNumProcessedFrames();
 }
 
+int32_t &OnlineStream::GetCurrentSegment() {
+  return impl_->GetCurrentSegment();
+}
+
 void OnlineStream::SetResult(const OnlineTransducerDecoderResult &r) {
   impl_->SetResult(r);
 }

sherpa-onnx/csrc/online-stream.h

@@ -68,6 +68,8 @@ class OnlineStream {
   // The returned reference is valid as long as this object is alive.
   int32_t &GetNumProcessedFrames();
 
+  int32_t &GetCurrentSegment();
+
   void SetResult(const OnlineTransducerDecoderResult &r);
   OnlineTransducerDecoderResult &GetResult();
 

sherpa-onnx/csrc/online-websocket-server-impl.cc

@@ -194,6 +194,9 @@ void OnlineWebsocketDecoder::Decode() {
 
   for (auto c : c_vec) {
     auto result = recognizer_->GetResult(c->s.get());
+    if (recognizer_->IsEndpoint(c->s.get())) {
+      recognizer_->Reset(c->s.get());
+    }
 
     asio::post(server_->GetConnectionContext(),
                [this, hdl = c->hdl, str = result.AsJsonString()]() {