Android音頻采集
Android的多媒體框架包括了對各種通用音頻格式進行采集和編碼的支持，因此你能夠容易的把音頻集成到你的應用程序中。如果設備硬件支持，你還能夠使用MediaRecorder API來記錄音頻。
本文向你展示如何編寫從設備的麥克中采集音頻、保存并播放它的應用程序。
注意：Android模擬器沒有采集音頻的能力，但是實際的設備可能提供這種能力。
執行音頻采集
從設備上采集音頻比音視頻播放要復雜一些，但依然相當簡單：
1. 創建一個新的android.media.MediaRecorder類的實例；
2. 使用MediaRecorder.setAudioSource()方法設置音頻源。你可能還想使用MediaRecorder.AudioSource.MIC;
3. 使用MediaRecorder.setOutputFormat()方法設置輸出文件格式；
4. 使用MediaRecorder.setOutputFile()方法設置輸出文件名；
5. 使用MediaRecorder.setAudioEncoder()方法設置音頻編碼；
6. 調用MediaRecorder實例上的MediaRecorder.prepare()方法；
7. 調用MediaRecorder.start()方法啟動音頻采集；
8. 調用MediaRecorder.stop()方法終止音頻采集；
9. 使用完MediaRecorder實例后，調用它的MediaRecorder.release()方法。要始終調用這個方法來立即釋放資源。
示例：錄音和播放錄音
這個例子的類演示了如何建立、啟動和終止音頻采集，并且播放錄音文件。
/*
* 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;
}
}
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