/*
* 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;
/**
* Acoustic Echo Canceler (AEC).
* <p>Acoustic Echo Canceler (AEC) is an audio pre-processing which removes the contribution of the
* signal received from the remote party from the captured audio signal.
* <p>AEC is used by voice communication applications (voice chat, video conferencing, SIP calls)
* where the presence of echo with significant delay in the signal received from the remote party
* is highly disturbing. AEC is often used in conjunction with noise suppression (NS).
* <p>An application creates an AcousticEchoCanceler object to instantiate and control an AEC
* engine in the audio capture path.
* <p>To attach the AcousticEchoCanceler to a particular {@link android.media.AudioRecord},
* specify the audio session ID of this AudioRecord when creating the AcousticEchoCanceler.
* The audio session is retrieved by calling
* {@link android.media.AudioRecord#getAudioSessionId()} on the AudioRecord instance.
* <p>On some devices, an AEC 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 AcousticEchoCanceler.getEnable() after creating the AEC to check the default AEC activation
* state on a particular AudioRecord session.
* <p>See {@link android.media.audiofx.AudioEffect} class for more details on
* controlling audio effects.
*/
public class AcousticEchoCanceler extends AudioEffect {
private final static String TAG = "AcousticEchoCanceler";
/**
* Checks if the device implements acoustic echo cancellation.
* @return true if the device implements acoustic echo cancellation, false otherwise.
*/
public static boolean isAvailable() {
return AudioEffect.isEffectTypeAvailable(AudioEffect.EFFECT_TYPE_AEC);
}
/**
* Creates an AcousticEchoCanceler and attaches it to the AudioRecord on the audio
* session specified.
* @param audioSession system wide unique audio session identifier. The AcousticEchoCanceler
* will be applied to the AudioRecord with the same audio session.
* @return AcousticEchoCanceler created or null if the device does not implement AEC.
*/
public static AcousticEchoCanceler create(int audioSession) {
AcousticEchoCanceler aec = null;
try {
aec = new AcousticEchoCanceler(audioSession);
} catch (IllegalArgumentException e) {
Log.w(TAG, "not implemented on this device"+ aec);
} catch (UnsupportedOperationException e) {
Log.w(TAG, "not enough resources");
} catch (RuntimeException e) {
Log.w(TAG, "not enough memory");
}
return aec;
}
/**
* 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 AEC</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 AcousticEchoCanceler
* will be applied to the AudioRecord with the same audio session.
*
* @throws java.lang.IllegalArgumentException
* @throws java.lang.UnsupportedOperationException
* @throws java.lang.RuntimeException
*/
private AcousticEchoCanceler(int audioSession)
throws IllegalArgumentException, UnsupportedOperationException, RuntimeException {
super(EFFECT_TYPE_AEC, EFFECT_TYPE_NULL, 0, audioSession);
}
}