The Tor Browser: comparison content/media/webspeech/recognition/energy

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+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// The EnergyEndpointer class finds likely speech onset and offset points.
+//
+// The implementation described here is about the simplest possible.
+// It is based on timings of threshold crossings for overall signal
+// RMS. It is suitable for light weight applications.
+//
+// As written, the basic idea is that one specifies intervals that
+// must be occupied by super- and sub-threshold energy levels, and
+// defers decisions re onset and offset times until these
+// specifications have been met.  Three basic intervals are tested: an
+// onset window, a speech-on window, and an offset window.  We require
+// super-threshold to exceed some mimimum total durations in the onset
+// and speech-on windows before declaring the speech onset time, and
+// we specify a required sub-threshold residency in the offset window
+// before declaring speech offset. As the various residency requirements are
+// met, the EnergyEndpointer instance assumes various states, and can return the
+// ID of these states to the client (see EpStatus below).
+//
+// The levels of the speech and background noise are continuously updated. It is
+// important that the background noise level be estimated initially for
+// robustness in noisy conditions. The first frames are assumed to be background
+// noise and a fast update rate is used for the noise level. The duration for
+// fast update is controlled by the fast_update_dur_ paramter.
+//
+// If used in noisy conditions, the endpointer should be started and run in the
+// EnvironmentEstimation mode, for at least 200ms, before switching to
+// UserInputMode.
+// Audio feedback contamination can appear in the input audio, if not cut
+// out or handled by echo cancellation. Audio feedback can trigger a false
+// accept. The false accepts can be ignored by setting
+// ep_contamination_rejection_period.
+#ifndef CONTENT_BROWSER_SPEECH_ENDPOINTER_ENERGY_ENDPOINTER_H_
+#define CONTENT_BROWSER_SPEECH_ENDPOINTER_ENERGY_ENDPOINTER_H_
+#include <vector>
+#include "nsAutoPtr.h"
+#include "energy_endpointer_params.h"
+namespace mozilla {
+// Endpointer status codes
+enum EpStatus {
+EP_PRE_SPEECH = 10,
+EP_POSSIBLE_ONSET,
+EP_SPEECH_PRESENT,
+EP_POSSIBLE_OFFSET,
+EP_POST_SPEECH,
+};
+class EnergyEndpointer {
+public:
+// The default construction MUST be followed by Init(), before any
+// other use can be made of the instance.
+EnergyEndpointer();
+virtual ~EnergyEndpointer();
+void Init(const EnergyEndpointerParams& params);
+// Start the endpointer. This should be called at the beginning of a session.
+void StartSession();
+// Stop the endpointer.
+void EndSession();
+// Start environment estimation. Audio will be used for environment estimation
+// i.e. noise level estimation.
+void SetEnvironmentEstimationMode();
+// Start user input. This should be called when the user indicates start of
+// input, e.g. by pressing a button.
+void SetUserInputMode();
+// Computes the next input frame and modifies EnergyEndpointer status as
+// appropriate based on the computation.
+void ProcessAudioFrame(int64_t time_us,
+const int16_t* samples, int num_samples,
+float* rms_out);
+// Returns the current state of the EnergyEndpointer and the time
+// corresponding to the most recently computed frame.
+EpStatus Status(int64_t* status_time_us) const;
+bool estimating_environment() const {
+return estimating_environment_;
+}
+// Returns estimated noise level in dB.
+float GetNoiseLevelDb() const;
+private:
+class HistoryRing;
+// Resets the endpointer internal state.  If reset_threshold is true, the
+// state will be reset completely, including adaptive thresholds and the
+// removal of all history information.
+void Restart(bool reset_threshold);
+// Update internal speech and noise levels.
+void UpdateLevels(float rms);
+// Returns the number of frames (or frame number) corresponding to
+// the 'time' (in seconds).
+int TimeToFrame(float time) const;
+EpStatus status_;  // The current state of this instance.
+float offset_confirm_dur_sec_;  // max on time allowed to confirm POST_SPEECH
+int64_t endpointer_time_us_;  // Time of the most recently received audio frame.
+int64_t fast_update_frames_; // Number of frames for initial level adaptation.
+int64_t frame_counter_;  // Number of frames seen. Used for initial adaptation.
+float max_window_dur_;  // Largest search window size (seconds)
+float sample_rate_;  // Sampling rate.
+// Ring buffers to hold the speech activity history.
+nsAutoPtr<HistoryRing> history_;
+// Configuration parameters.
+EnergyEndpointerParams params_;
+// RMS which must be exceeded to conclude frame is speech.
+float decision_threshold_;
+// Flag to indicate that audio should be used to estimate environment, prior
+// to receiving user input.
+bool estimating_environment_;
+// Estimate of the background noise level. Used externally for UI feedback.
+float noise_level_;
+// An adaptive threshold used to update decision_threshold_ when appropriate.
+float rms_adapt_;
+// Start lag corresponds to the highest fundamental frequency.
+int start_lag_;
+// End lag corresponds to the lowest fundamental frequency.
+int end_lag_;
+// Time when mode switched from environment estimation to user input. This
+// is used to time forced rejection of audio feedback contamination.
+int64_t user_input_start_time_us_;
+// prevent copy constructor and assignment
+EnergyEndpointer(const EnergyEndpointer&);
+void operator=(const EnergyEndpointer&);
+};
+}  // namespace mozilla
+#endif  // CONTENT_BROWSER_SPEECH_ENDPOINTER_ENERGY_ENDPOINTER_H_

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comparison: content/media/webspeech/recognition/energy_endpointer.h

content/media/webspeech/recognition/energy_endpointer.h