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 // Copyright (c) 2013 The Chromium Authors. All rights reserved.

 //

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 // this software without specific prior written permission.

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 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

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 #ifndef CONTENT_BROWSER_SPEECH_ENDPOINTER_ENDPOINTER_H_

 #define CONTENT_BROWSER_SPEECH_ENDPOINTER_ENDPOINTER_H_

 #include "energy_endpointer.h"

 namespace mozilla {

 struct AudioChunk;

 // A simple interface to the underlying energy-endpointer implementation, this

 // class lets callers provide audio as being recorded and let them poll to find

 // when the user has stopped speaking.

 //

 // There are two events that may trigger the end of speech:

 //

 // speechInputPossiblyComplete event:

 //

 // Signals that silence/noise has  been detected for a *short* amount of

 // time after some speech has been detected. It can be used for low latency

 // UI feedback. To disable it, set it to a large amount.

 //

 // speechInputComplete event:

 //

 // This event is intended to signal end of input and to stop recording.

 // The amount of time to wait after speech is set by

 // speech_input_complete_silence_length_ and optionally two other

 // parameters (see below).

 // This time can be held constant, or can change as more speech is detected.

 // In the latter case, the time changes after a set amount of time from the

 // *beginning* of speech.  This is motivated by the expectation that there

 // will be two distinct types of inputs: short search queries and longer

 // dictation style input.

 //

 // Three parameters are used to define the piecewise constant timeout function.

 // The timeout length is speech_input_complete_silence_length until

 // long_speech_length, when it changes to

 // long_speech_input_complete_silence_length.

 class Endpointer {

  public:

   explicit Endpointer(int sample_rate);

   // 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();

   // Process a segment of audio, which may be more than one frame.

   // The status of the last frame will be returned.

   EpStatus ProcessAudio(const AudioChunk& raw_audio, float* rms_out);

   // Get the status of the endpointer.

   EpStatus Status(int64_t *time_us);

   // Get the expected frame size for audio chunks. Audio chunks are expected

   // to contain a number of samples that is a multiple of this number, and extra

   // samples will be dropped.

   int32_t FrameSize() const {

     return frame_size_;

   }

   // Returns true if the endpointer detected reasonable audio levels above

   // background noise which could be user speech, false if not.

   bool DidStartReceivingSpeech() const {

     return speech_previously_detected_;

   }

   bool IsEstimatingEnvironment() const {

     return energy_endpointer_.estimating_environment();

   }

   void set_speech_input_complete_silence_length(int64_t time_us) {

     speech_input_complete_silence_length_us_ = time_us;

   }

   void set_long_speech_input_complete_silence_length(int64_t time_us) {

     long_speech_input_complete_silence_length_us_ = time_us;

   }

   void set_speech_input_possibly_complete_silence_length(int64_t time_us) {

     speech_input_possibly_complete_silence_length_us_ = time_us;

   }

   void set_long_speech_length(int64_t time_us) {

     long_speech_length_us_ = time_us;

   }

   bool speech_input_complete() const {

     return speech_input_complete_;

   }

   // RMS background noise level in dB.

   float NoiseLevelDb() const { return energy_endpointer_.GetNoiseLevelDb(); }

  private:

   // Reset internal states. Helper method common to initial input utterance

   // and following input utternaces.

   void Reset();

   // Minimum allowable length of speech input.

   int64_t speech_input_minimum_length_us_;

   // The speechInputPossiblyComplete event signals that silence/noise has been

   // detected for a *short* amount of time after some speech has been detected.

   // This proporty specifies the time period.

   int64_t speech_input_possibly_complete_silence_length_us_;

   // The speechInputComplete event signals that silence/noise has been

   // detected for a *long* amount of time after some speech has been detected.

   // This property specifies the time period.

   int64_t speech_input_complete_silence_length_us_;

   // Same as above, this specifies the required silence period after speech

   // detection. This period is used instead of

   // speech_input_complete_silence_length_ when the utterance is longer than

   // long_speech_length_. This parameter is optional.

   int64_t long_speech_input_complete_silence_length_us_;

   // The period of time after which the endpointer should consider

   // long_speech_input_complete_silence_length_ as a valid silence period

   // instead of speech_input_complete_silence_length_. This parameter is

   // optional.

   int64_t long_speech_length_us_;

   // First speech onset time, used in determination of speech complete timeout.

   int64_t speech_start_time_us_;

   // Most recent end time, used in determination of speech complete timeout.

   int64_t speech_end_time_us_;

   int64_t audio_frame_time_us_;

   EpStatus old_ep_status_;

   bool waiting_for_speech_possibly_complete_timeout_;

   bool waiting_for_speech_complete_timeout_;

   bool speech_previously_detected_;

   bool speech_input_complete_;

   EnergyEndpointer energy_endpointer_;

   int sample_rate_;

   int32_t frame_size_;

 };

 }  // namespace mozilla

 #endif  // CONTENT_BROWSER_SPEECH_ENDPOINTER_ENDPOINTER_H_