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,

               ViewGroup.LayoutParams.WRAP_CONTENT,

               0));

       mPlayButton = new PlayButton(this);

       ll.addView(mPlayButton,

           new LinearLayout.LayoutParams(

               ViewGroup.LayoutParams.WRAP_CONTENT,

               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;

       }

   }

}