Android音频采集

Android的多媒体框架包括了对各种通用音频格式进行采集和编码的支持，因此你能够容易的把音频集成到你的应用程序中。如果设备硬件支持，你还能够使用MediaRecorder API来记录音频。

本文向你展示如何编写从设备的麦克中采集音频、保存并播放它的应用程序。

注意：Android模拟器没有采集音频的能力，但是实际的设备可能提供这种能力。

执行音频采集

从设备上采集音频比音视频播放要复杂一些，但依然相当简单：

1.创建一个新的android.media.MediaRecorder类的实例；

2.使用MediaRecorder.setAudioSource()方法设置音频源。你可能还想使用MediaRecorder.AudioSource.MIC;

3.使用MediaRecorder.setOutputFormat()方法设置输出文件格式；

4.使用MediaRecorder.setOutputFile()方法设置输出文件名；

5.使用MediaRecorder.setAudioEncoder()方法设置音频编码；

6.调用MediaRecorder实例上的MediaRecorder.prepare()方法；

7.调用MediaRecorder.start()方法启动音频采集；

8.调用MediaRecorder.stop()方法终止音频采集；

9.使用完MediaRecorder实例后，调用它的MediaRecorder.release()方法。要始终调用这个方法来立即释放资源。

示例：录音和播放录音

这个例子的类演示了如何建立、启动和终止音频采集，并且播放录音文件。

* The application needs to have the permission to write to external storage

* if the output file is written to the external storage, and also the

* permission to record audio. These permissions must be set in the

* application's AndroidManifest.xml file, with something like:

* <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

* <uses-permission android:name="android.permission.RECORD_AUDIO" />

package com.android.audiorecordtest;

import android.app.Activity;

import android.widget.LinearLayout;

import android.os.Bundle;

import android.os.Environment;

import android.view.ViewGroup;

import android.widget.Button;

import android.view.View;

import android.view.View.OnClickListener;

import android.content.Context;

import android.util.Log;

import android.media.MediaRecorder;

import android.media.MediaPlayer;

import java.io.IOException;

public class AudioRecordTest extends Activity

{

private static final String LOG_TAG = "AudioRecordTest";

private static String mFileName = null;

private RecordButton mRecordButton = null;

private MediaRecorder mRecorder = null;

private PlayButton mPlayButton = null;

private MediaPlayer mPlayer = null;

private void onRecord(boolean start) {

if (start) {

startRecording();

} else {

stopRecording();

}

private void onPlay(boolean start) {

if (start) {

startPlaying();

} else {

stopPlaying();

}

private void startPlaying() {

mPlayer = new MediaPlayer();

try {

mPlayer.setDataSource(mFileName);

mPlayer.prepare();

mPlayer.start();

} catch (IOException e) {

Log.e(LOG_TAG, "prepare() failed");

}

private void stopPlaying() {

mPlayer.release();

mPlayer = null;

}

private void startRecording() {

mRecorder = new MediaRecorder();

mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);

mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);

mRecorder.setOutputFile(mFileName);

mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

try {

mRecorder.prepare();

} catch (IOException e) {

Log.e(LOG_TAG, "prepare() failed");

}

mRecorder.start();

}

private void stopRecording() {

mRecorder.stop();

mRecorder.release();

mRecorder = null;

}

class RecordButton extends Button {

boolean mStartRecording = true;

OnClickListener clicker = new OnClickListener() {

public void onClick(View v) {

onRecord(mStartRecording);

if (mStartRecording) {

setText("Stop recording");

} else {

setText("Start recording");

}

mStartRecording = !mStartRecording;

}

};

public RecordButton(Context ctx) {

super(ctx);

setText("Start recording");

setOnClickListener(clicker);

}

class PlayButton extends Button {

boolean mStartPlaying = true;

OnClickListener clicker = new OnClickListener() {

public void onClick(View v) {

onPlay(mStartPlaying);

if (mStartPlaying) {

setText("Stop playing");

} else {

setText("Start playing");

}

mStartPlaying = !mStartPlaying;

}

};

public PlayButton(Context ctx) {

super(ctx);

setText("Start playing");

setOnClickListener(clicker);

}

public AudioRecordTest() {

mFileName = Environment.getExternalStorageDirectory().getAbsolutePath();

mFileName += "/audiorecordtest.3gp";

}

@Override

public void onCreate(Bundle icicle) {

super.onCreate(icicle);

LinearLayout ll = new LinearLayout(this);

mRecordButton = new RecordButton(this);

ll.addView(mRecordButton,

new LinearLayout.LayoutParams(

ViewGroup.LayoutParams.WRAP_CONTENT,

0));

mPlayButton = new PlayButton(this);

ll.addView(mPlayButton,

new LinearLayout.LayoutParams(

ViewGroup.LayoutParams.WRAP_CONTENT,

0));

setContentView(ll);

}

@Override

public void onPause() {

super.onPause();

if (mRecorder != null) {

mRecorder.release();

mRecorder = null;

}

if (mPlayer != null) {

mPlayer.release();

mPlayer = null;

}

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