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A library jar that provides APIs for Applications written for the Google Android Platform.

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/*
 * 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).
 * 

Noise suppression (NS) is an audio pre-processing 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. *

NS is mostly used by voice communication applications (voice chat, video conferencing, * SIP calls). *

An application creates a NoiseSuppressor object to instantiate and control an NS * engine in the audio framework. *

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. *

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. *

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"); } finally { return ns; } } /** * Class constructor. *

The constructor is not guarantied to succeed and throws the following exceptions: *

    *
  • IllegalArgumentException is thrown if the device does not implement an NS
  • *
  • UnsupportedOperationException is thrown is the resources allocated to audio * pre-procesing are currently exceeded.
  • *
  • RuntimeException is thrown if a memory allocation error occurs.
  • *
* * @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); } }




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