CoreAudio实现录音播音和扬声器听筒模式的切换

本例子使用Core Audio实现类似于微信的音频对讲功能，可以录音和播放并且实现了听筒模式和扬声器模式的切换。录音主要使用AVAudioRecorder类来实现录音功能，播放则使用AVAudioPlayer类来实现播放音频功能，扬声器和听筒模式的切换是通过设置AVAudioSession类的属性值来实现切换效果。

- (void)viewDidLoad
{
[super viewDidLoad];
//创建录音按钮
UIButton* recorderB = [[[UIButton alloc]initWithFrame:CGRectMake(20, 220, 60, 40)]autorelease];
[recorderB setTitle:@"record" forState:UIControlStateNormal];
[recorderB setBackgroundColor:[UIColor grayColor]];
[recorderB addTarget:self action:@selector(prerecord:) forControlEvents:UIControlEventTouchDown];
[recorderB addTarget:self action:@selector(startrecord:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:recorderB];

//创建播放按钮
UIButton* play = [[[UIButton alloc]initWithFrame:CGRectMake(230, 220, 60, 40)]autorelease];
[play setTitle:@"play" forState:UIControlStateNormal];
[play setBackgroundColor:[UIColor grayColor]];
[play addTarget:self action:@selector(play:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:play];

//创建听筒模式和扬声器模式切换按钮
change = [[[UISwitch alloc]initWithFrame:CGRectMake(120, 225, 40, 40)]autorelease];
//默认设置为没有打开，则用听筒模式
[change setOn:NO];
[change addTarget:self action:@selector(change:) forControlEvents:UIControlEventValueChanged];
[self.view addSubview:change];

}

//切换按钮事件
-(void)change:(UISwitch*)sender{
NSLog(@"%@",NSStringFromSelector(_cmd));
//录音的时候因为设置的音频会话是录音模式，所以录音完成后要把音频会话设置回听筒模式或者扬声器模式，根据切换器的值判断,kAudioSessionOverrideAudioRoute_None为听筒模式，kAudioSessionOverrideAudioRoute_Speaker为扬声器模式
UInt32 audioRouteOverride = ![sender isOn] ?kAudioSessionOverrideAudioRoute_None:kAudioSessionOverrideAudioRoute_Speaker;
AudioSessionSetProperty(kAudioSessionProperty_OverrideAudioRoute, sizeof(audioRouteOverride), &audioRouteOverride);
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setActive:YES error:nil];
}

//录音事件
-(void)record:(id)sender{
//获取当前应用的AudioSession,每个应用都有自己唯一的声频会话
AVAudioSession * audioSession = [AVAudioSession sharedInstance];
NSError* error1;
//设置当前应用的声频会话为录音模式
/*
Use this category for background sounds such as rain, car engine noise, etc.
Mixes with other music.

AVF_EXPORT NSString *const AVAudioSessionCategoryAmbient;

Use this category for background sounds. Other music will stop playing. AVF_EXPORT NSString *const AVAudioSessionCategorySoloAmbient;

Use this category for music tracks.

AVF_EXPORT NSString *const AVAudioSessionCategoryPlayback;

Use this category when recording audio.

AVF_EXPORT NSString *const AVAudioSessionCategoryRecord;

Use this category when recording and playing back audio.

AVF_EXPORT NSString *const AVAudioSessionCategoryPlayAndRecord;

Use this category when using a hardware codec or signal processor while
not playing or recording audio.

AVF_EXPORT NSString *const AVAudioSessionCategoryAudioProcessing;
*/
[audioSession setCategory:AVAudioSessionCategoryRecord error: &error1];
//激活音频会话
[audioSession setActive:YES error: &error1];
NSLog(@"record...");
//创建录音的文件保存位置
NSString* filepath = [DOCUMENT_PATH stringByAppendingPathComponent:@"test.caf"];
url = [[NSURL fileURLWithPath:filepath]retain];
NSLog(@"path:%@",filepath);
//设置录音的相关属性
NSMutableDictionary *settings = [[NSMutableDictionary alloc] init];
//设置音频格式
[settings
setValue:[NSNumber numberWithInteger:kAudioFormatLinearPCM] forKey:AVFormatIDKey];
//设置采用率
[settings
setValue:[NSNumber numberWithFloat:44100.0f] forKey:AVSampleRateKey];
//设置频道
[settings
setValue:[NSNumber numberWithInteger:2] forKey:AVNumberOfChannelsKey];
//设置录音质量
[settings
setValue:[NSNumber numberWithInteger:AVAudioQualityHigh] forKey:AVEncoderAudioQualityKey];
NSError* error;
recorder = [[AVAudioRecorder alloc]initWithURL:url settings:settings error:&error];
recorder.delegate = self;
//录音准备，会为建立录音文件做好需要的准备
BOOL isrecord = [recorder prepareToRecord];
NSLog(@"isrecord:%d",isrecord);
//正式开始录音
[recorder record];
NSLog(@"record begin...");

}
//手指离开点击录音按钮的事件
-(void)startrecord:(id)sender{

NSLog(@"%@",NSStringFromSelector(_cmd));
NSTimeInterval now = [[NSDate date]timeIntervalSince1970];
//获取长按录音按钮的时间
NSTimeInterval offset = now - starttime;
NSLog(@"offset:%f",offset);
//如果长按的时间少于1秒，则不录音
if (offset<=1) {
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(record:) object:self];
}else{
//超过一秒，则完成录音，停止继续录音
[self stoprecorder:recorder];
}
}
//手指点击录音按钮时间
-(void)prerecord:(id)sender{
NSLog(@"%@",NSStringFromSelector(_cmd));
//获取点击的时间
starttime = [[NSDate date]timeIntervalSince1970];
NSLog(@"starttime:%f",starttime);
//点击超过一秒后才正式录音
[self performSelector:@selector(record:) withObject:self afterDelay:1];
}

//停止录音的事件
-(void)stoprecorder:(AVAudioRecorder*)sender{
NSLog(@"%@",NSStringFromSelector(_cmd));
//判断是否还在录音，如果是就停止
if ([recorder isRecording]) {
[recorder stop];
}

}
//播放事件
-(void)play:(id)sender{

NSLog(@"%@",NSStringFromSelector(_cmd));
NSError* error;
NSLog(@"url:%@",url);
//通过AVAudioPlayer打开刚才录音的文件
AVAudioPlayer* player = [[AVAudioPlayer alloc]initWithData:[NSData dataWithContentsOfURL:url] error:&error];
//AVAudioPlayer预处理，为需要播放做好准备
BOOL isplay = [player prepareToPlay];
NSLog(@"isplay:%d",isplay);
// player.volume = 1;
player.delegate = self;
//正式播放
[player play];
}
- (void)didReceiveMemoryWarning
{

[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
//录音完成后的回调事件
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag{
NSLog(@"%@",NSStringFromSelector(_cmd));
//录音完成后关闭释放资源
if ([recorder isRecording]) {
[recorder stop];
}
[recorder release];
//录音的时候因为设置的音频会话是录音模式，所以录音完成后要把音频会话设置回听筒模式或者扬声器模式，根据切换器的值判断,kAudioSessionOverrideAudioRoute_None为听筒模式，kAudioSessionOverrideAudioRoute_Speaker为扬声器模式
UInt32 audioRouteOverride = ![change isOn] ?kAudioSessionOverrideAudioRoute_None:kAudioSessionOverrideAudioRoute_Speaker;
AudioSessionSetProperty(kAudioSessionProperty_OverrideAudioRoute, sizeof(audioRouteOverride), &audioRouteOverride);
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
//类别要AVAudioSessionCategoryPlayAndRecord，才有效
[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
[audioSession setActive:YES error:nil];

}

//录音编码出错的回调
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError *)error{
NSLog(@"%@",NSStringFromSelector(_cmd));
[recorder release];
}
//播放音频完成后的回调
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag{
NSLog(@"%@",NSStringFromSelector(_cmd));
//成功播放完音频后释放资源
if ([player isPlaying]) {
[player stop];
}
[player release];
}

//音频播放解码出错的回调
- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error{
NSLog(@"%@",NSStringFromSelector(_cmd));
[player release];
}