/*
* 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-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.
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 AudioRecord, specify the audio session ID of this AudioRecord when creating the NoiseSuppressor. The audio session is retrieved by calling 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 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 AudioEffect class for more details on controlling audio effects.
/**
* 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.
Returns: true if the device implements noise suppression, false otherwise.
/**
* 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.
Params: - audioSession – system wide unique audio session identifier. The NoiseSuppressor
will be applied to the AudioRecord with the same audio session.
Returns: NoiseSuppressor created or null if the device does not implement noise
suppression.
/**
* 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.
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.
Params: - audioSession – system wide unique audio session identifier. The NoiseSuppressor
will be applied to the AudioRecord with the same audio session.
Throws:
/**
* 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);
}
}