Add an endpointer for detecting end of speech.

chrome/browser/speech/endpointer/endpointer.cc

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/speech/endpointer/endpointer.h"
+#include "base/time.h"
+
+using base::Time;
+
+namespace {
+static const int kFrameRate = 50;  // 1 frame = 20ms of audio.
+}
+
+namespace speech_input {
+
+Endpointer::Endpointer(int sample_rate)
+    : speech_input_possibly_complete_silence_length_us_(-1),
+      speech_input_complete_silence_length_us_(-1),
+      audio_frame_time_us_(0),
+      sample_rate_(sample_rate),
+      frame_size_(0) {
+  Reset();
+
+  frame_size_ = static_cast<int>(sample_rate / static_cast<float>(kFrameRate));
+
+  speech_input_minimum_length_us_ =
+      static_cast<int64>(1.7 * Time::kMicrosecondsPerSecond);
+  speech_input_complete_silence_length_us_ =
+      static_cast<int64>(0.5 * Time::kMicrosecondsPerSecond);
+  long_speech_input_complete_silence_length_us_ = -1;
+  long_speech_length_us_ = -1;
+  speech_input_possibly_complete_silence_length_us_ =
+      1 * Time::kMicrosecondsPerSecond;
+
+  // Set the default configuration for Push To Talk mode.
+  EnergyEndpointerParams ep_config;
+  ep_config.set_frame_period(1.0f / static_cast<float>(kFrameRate));
+  ep_config.set_frame_duration(1.0f / static_cast<float>(kFrameRate));
+  ep_config.set_endpoint_margin(0.2f);
+  ep_config.set_onset_window(0.15f);
+  ep_config.set_speech_on_window(0.4f);
+  ep_config.set_offset_window(0.15f);
+  ep_config.set_onset_detect_dur(0.09f);
+  ep_config.set_onset_confirm_dur(0.075f);
+  ep_config.set_on_maintain_dur(0.10f);
+  ep_config.set_offset_confirm_dur(0.12f);
+  ep_config.set_decision_threshold(1000.0f);
+  ep_config.set_min_decision_threshold(50.0f);
+  ep_config.set_fast_update_dur(0.2f);
+  ep_config.set_sample_rate(static_cast<float>(sample_rate));
+  ep_config.set_min_fundamental_frequency(57.143f);
+  ep_config.set_max_fundamental_frequency(400.0f);
+  ep_config.set_contamination_rejection_period(0.25f);
+  energy_endpointer_.Init(ep_config);
+}
+
+void Endpointer::Reset() {
+  old_ep_status_ = EP_PRE_SPEECH;
+  waiting_for_speech_possibly_complete_timeout_ = false;
+  waiting_for_speech_complete_timeout_ = false;
+  speech_previously_detected_ = false;
+  speech_input_complete_ = false;
+  audio_frame_time_us_ = 0; // Reset time for packets sent to endpointer.
+  speech_end_time_us_ = -1;
+  speech_start_time_us_ = -1;
+}
+
+void Endpointer::StartSession() {
+  Reset();
+  energy_endpointer_.StartSession();
+}
+
+void Endpointer::EndSession() {
+  energy_endpointer_.EndSession();
+}
+
+void Endpointer::SetEnvironmentEstimationMode() {
+  Reset();
+  energy_endpointer_.SetEnvironmentEstimationMode();
+}
+
+void Endpointer::SetUserInputMode() {
+  energy_endpointer_.SetUserInputMode();
+}
+
+EpStatus Endpointer::Status(int64 *time) {
+  return energy_endpointer_.Status(time);
+}
+
+EpStatus Endpointer::ProcessAudio(const int16* audio_data, int num_samples) {
+  EpStatus ep_status = EP_PRE_SPEECH;
+
+  // Process the input data in blocks of frame_size_, dropping any incomplete
+  // frames at the end (which is ok since typically the caller will be recording
+  // audio in multiples of our frame size).
+  int sample_index = 0;
+  while (sample_index + frame_size_ <= num_samples) {
+    // Have the endpointer process the frame.
+    energy_endpointer_.ProcessAudioFrame(audio_frame_time_us_,
+                                         audio_data + sample_index,
+                                         frame_size_);
+    sample_index += frame_size_;
+    audio_frame_time_us_ += (frame_size_ * Time::kMicrosecondsPerSecond) /
+                         sample_rate_;
+
+    // Get the status of the endpointer.
+    int64 ep_time;
+    ep_status = energy_endpointer_.Status(&ep_time);
+
+    // Handle state changes.
+    if ((EP_SPEECH_PRESENT == ep_status) &&
+        (EP_POSSIBLE_ONSET == old_ep_status_)) {
+      speech_end_time_us_ = -1;
+      waiting_for_speech_possibly_complete_timeout_ = false;
+      waiting_for_speech_complete_timeout_ = false;
+      // Trigger SpeechInputDidStart event on first detection.
+      if (false == speech_previously_detected_) {
+        speech_previously_detected_ = true;
+        speech_start_time_us_ = ep_time;
+      }
+    }
+    if ((EP_PRE_SPEECH == ep_status) &&
+        (EP_POSSIBLE_OFFSET == old_ep_status_)) {
+      speech_end_time_us_ = ep_time;
+      waiting_for_speech_possibly_complete_timeout_ = true;
+      waiting_for_speech_complete_timeout_ = true;
+    }
+    if (ep_time > speech_input_minimum_length_us_) {
+      // Speech possibly complete timeout.
+      if ((waiting_for_speech_possibly_complete_timeout_) &&
+          (ep_time - speech_end_time_us_ >
+              speech_input_possibly_complete_silence_length_us_)) {
+        waiting_for_speech_possibly_complete_timeout_ = false;
+      }
+      if (waiting_for_speech_complete_timeout_) {
+        // The length of the silence timeout period can be held constant, or it
+        // can be changed after a fixed amount of time from the beginning of
+        // speech.
+        bool has_stepped_silence =
+            (long_speech_length_us_ > 0) &&
+            (long_speech_input_complete_silence_length_us_ > 0);
+        int64 requested_silence_length;
+        if (has_stepped_silence &&
+            (ep_time - speech_start_time_us_) > long_speech_length_us_) {
+          requested_silence_length =
+              long_speech_input_complete_silence_length_us_;
+        } else {
+          requested_silence_length =
+              speech_input_complete_silence_length_us_;
+        }
+
+        // Speech complete timeout.
+        if ((ep_time - speech_end_time_us_) > requested_silence_length) {
+          waiting_for_speech_complete_timeout_ = false;
+          speech_input_complete_ = true;
+        }
+      }
+    }
+    old_ep_status_ = ep_status;
+  }
+  return ep_status;
+}
+
+}  // namespace speech