1 /*
2  * Copyright (C) 2011 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package android.media.audiofx;
18 
19 import android.util.Log;
20 
21 /**
22  * Acoustic Echo Canceler (AEC).
23  * <p>Acoustic Echo Canceler (AEC) is an audio pre-processing which removes the contribution of the
24  * signal received from the remote party from the captured audio signal.
25  * <p>AEC is used by voice communication applications (voice chat, video conferencing, SIP calls)
26  * where the presence of echo with significant delay in the signal received from the remote party
27  * is highly disturbing. AEC is often used in conjunction with noise suppression (NS).
28  * <p>An application creates an AcousticEchoCanceler object to instantiate and control an AEC
29  * engine in the audio capture path.
30  * <p>To attach the AcousticEchoCanceler to a particular {@link android.media.AudioRecord},
31  * specify the audio session ID of this AudioRecord when creating the AcousticEchoCanceler.
32  * The audio session is retrieved by calling
33  * {@link android.media.AudioRecord#getAudioSessionId()} on the AudioRecord instance.
34  * <p>On some devices, an AEC can be inserted by default in the capture path by the platform
35  * according to the {@link android.media.MediaRecorder.AudioSource} used. The application should
36  * call AcousticEchoCanceler.getEnable() after creating the AEC to check the default AEC activation
37  * state on a particular AudioRecord session.
38  * <p>See {@link android.media.audiofx.AudioEffect} class for more details on
39  * controlling audio effects.
40  */
41 
42 public class AcousticEchoCanceler extends AudioEffect {
43 
44     private final static String TAG = "AcousticEchoCanceler";
45 
46     /**
47      * Checks if the device implements acoustic echo cancellation.
48      * @return true if the device implements acoustic echo cancellation, false otherwise.
49      */
isAvailable()50     public static boolean isAvailable() {
51         return AudioEffect.isEffectTypeAvailable(AudioEffect.EFFECT_TYPE_AEC);
52     }
53 
54     /**
55      * Creates an AcousticEchoCanceler and attaches it to the AudioRecord on the audio
56      * session specified.
57      * @param audioSession system wide unique audio session identifier. The AcousticEchoCanceler
58      * will be applied to the AudioRecord with the same audio session.
59      * @return AcousticEchoCanceler created or null if the device does not implement AEC.
60      */
create(int audioSession)61     public static AcousticEchoCanceler create(int audioSession) {
62         AcousticEchoCanceler aec = null;
63         try {
64             aec = new AcousticEchoCanceler(audioSession);
65         } catch (IllegalArgumentException e) {
66             Log.w(TAG, "not implemented on this device"+ aec);
67         } catch (UnsupportedOperationException e) {
68             Log.w(TAG, "not enough resources");
69         } catch (RuntimeException e) {
70             Log.w(TAG, "not enough memory");
71         }
72         return aec;
73     }
74 
75     /**
76      * Class constructor.
77      * <p> The constructor is not guarantied to succeed and throws the following exceptions:
78      * <ul>
79      *  <li>IllegalArgumentException is thrown if the device does not implement an AEC</li>
80      *  <li>UnsupportedOperationException is thrown is the resources allocated to audio
81      *  pre-procesing are currently exceeded.</li>
82      *  <li>RuntimeException is thrown if a memory allocation error occurs.</li>
83      * </ul>
84      *
85      * @param audioSession system wide unique audio session identifier. The AcousticEchoCanceler
86      * will be applied to the AudioRecord with the same audio session.
87      *
88      * @throws java.lang.IllegalArgumentException
89      * @throws java.lang.UnsupportedOperationException
90      * @throws java.lang.RuntimeException
91      */
AcousticEchoCanceler(int audioSession)92     private AcousticEchoCanceler(int audioSession)
93             throws IllegalArgumentException, UnsupportedOperationException, RuntimeException {
94         super(EFFECT_TYPE_AEC, EFFECT_TYPE_NULL, 0, audioSession);
95     }
96 }
97