content: /*
   * Copyright (C) 2011 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.media.audiofx;
  
  import android.util.Log;
  
  /**
   * Noise Suppressor (NS).
   * <p>Noise suppression (NS) is an audio pre-processor which removes background noise from the
   * captured signal. The component of the signal considered as noise can be either stationary
   * (car/airplane engine, AC system) or non-stationary (other peoples conversations, car horn) for
   * more advanced implementations.
   * <p>NS is mostly used by voice communication applications (voice chat, video conferencing,
   * SIP calls).
   * <p>An application creates a NoiseSuppressor object to instantiate and control an NS
   * engine in the audio framework.
   * <p>To attach the NoiseSuppressor to a particular {@link android.media.AudioRecord},
   * specify the audio session ID of this AudioRecord when creating the NoiseSuppressor.
   * The audio session is retrieved by calling
   * {@link android.media.AudioRecord#getAudioSessionId()} on the AudioRecord instance.
   * <p>On some devices, NS can be inserted by default in the capture path by the platform
   * according to the {@link android.media.MediaRecorder.AudioSource} used. The application should
   * call NoiseSuppressor.getEnable() after creating the NS to check the default NS activation
   * state on a particular AudioRecord session.
   * <p>See {@link android.media.audiofx.AudioEffect} class for more details on
   * controlling audio effects.
   */
  
  public class NoiseSuppressor extends AudioEffect {
  
      private final static String TAG = "NoiseSuppressor";
  
      /**
       * Checks if the device implements noise suppression.
       * @return true if the device implements noise suppression, false otherwise.
       */
      public static boolean isAvailable() {
          return AudioEffect.isEffectTypeAvailable(AudioEffect.EFFECT_TYPE_NS);
      }
  
      /**
       * Creates a NoiseSuppressor and attaches it to the AudioRecord on the audio
       * session specified.
       * @param audioSession system wide unique audio session identifier. The NoiseSuppressor
       * will be applied to the AudioRecord with the same audio session.
       * @return NoiseSuppressor created or null if the device does not implement noise
       * suppression.
       */
      public static NoiseSuppressor create(int audioSession) {
          NoiseSuppressor ns = null;
          try {
              ns = new NoiseSuppressor(audioSession);
          } catch (IllegalArgumentException e) {
              Log.w(TAG, "not implemented on this device "+ns);
          } catch (UnsupportedOperationException e) {
              Log.w(TAG, "not enough resources");
          } catch (RuntimeException e) {
              Log.w(TAG, "not enough memory");
          }
          return ns;
      }
  
      /**
       * Class constructor.
       * <p> The constructor is not guarantied to succeed and throws the following exceptions:
       * <ul>
       *  <li>IllegalArgumentException is thrown if the device does not implement an NS</li>
       *  <li>UnsupportedOperationException is thrown is the resources allocated to audio
       *  pre-procesing are currently exceeded.</li>
       *  <li>RuntimeException is thrown if a memory allocation error occurs.</li>
       * </ul>
       *
       * @param audioSession system wide unique audio session identifier. The NoiseSuppressor
       * will be applied to the AudioRecord with the same audio session.
       *
       * @throws java.lang.IllegalArgumentException
       * @throws java.lang.UnsupportedOperationException
       * @throws java.lang.RuntimeException
       */
      private NoiseSuppressor(int audioSession)
              throws IllegalArgumentException, UnsupportedOperationException, RuntimeException {
          super(EFFECT_TYPE_NS, EFFECT_TYPE_NULL, 0, audioSession);
      }
  }
  