一 音頻會(huì)話

音頻會(huì)話:音頻會(huì)話在應(yīng)用程序中扮演中間人的角色,可以通過(guò)音頻會(huì)話來(lái)控制音頻的操作
所有的應(yīng)用程序都有音頻會(huì)話,無(wú)論是否使用

• 音頻會(huì)話分類(Category):
  AVFoundaation定義了七種分類來(lái)描述應(yīng)用程序所使用的音頻行為
  (O:可選,Y:支持, N: 不支持)

• 設(shè)置音頻會(huì)話分類

//1. 取得音頻會(huì)話單例
    AVAudioSession *session = [AVAudioSession sharedInstance];
    NSError *error;
    //2. 設(shè)置音頻會(huì)話分類
    if (![session setCategory:AVAudioSessionCategoryPlayback error:&error]) {
        NSLog(@"設(shè)置音頻會(huì)話分類失敗%@",[error localizedDescription]);
    }
    //3. 激活會(huì)話
    if([session setActive:YES error:&error]){
        NSLog(@"音頻會(huì)話激活失敗%@",[error localizedDescription]);
    }

• 使用AVAudioPlayer 播放音頻:AVAudioPlayer 只能播放本地文件

  NSURL *filePath = [[NSBundle mainBundle]URLForResource:@"aaa" withExtension:@"mp3"];
    AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:filePath error:nil];
    if (audioPlayer) {
      [audioPlayer prepareToPlay];//調(diào)用 play 方法的時(shí)候會(huì)自動(dòng)調(diào)用一次
    }
    [audioPlayer play];//開(kāi)始播放
    [audioPlayer pause];//暫停
    [audioPlayer stop];//停止

    audioPlayer.pan = 0.0; // -1.0 ~ 1.0 立體聲播放
    audioPlayer.volume = 0.5; //音量 0.0 ~ 1.0
    audioPlayer.numberOfLoops = -1; //循環(huán)播放次數(shù),-1 無(wú)限輪播

pause和stop都會(huì)停止播放,再次調(diào)用play都會(huì)繼續(xù)播放,區(qū)別在于stop會(huì)撤銷prepareToPlay方法所做的設(shè)置,而pause不會(huì)

• 中斷處理
  當(dāng)正在播放音頻的時(shí)候,有電話撥入會(huì)導(dǎo)致中斷,中斷發(fā)生的時(shí)候需要對(duì)相應(yīng)狀態(tài)做一些處理

- (void)audioInterruptionNotiSet {
    NSNotificationCenter  *notiCenter = [NSNotificationCenter defaultCenter];
    [notiCenter addObserver:self selector:@selector(handleInterruption:) name:AVAudioSessionInterruptionNotification object:[AVAudioSession sharedInstance]];
}

- (void)handleInterruption:(NSNotification *)noti {
    NSDictionary *info = noti.userInfo;
    AVAudioSessionInterruptionType type = [info[AVAudioSessionInterruptionTypeKey] unsignedIntegerValue];
    if (type  == AVAudioSessionInterruptionTypeBegan) {
        //中斷開(kāi)始時(shí)的處理 正在播放的音頻停止 需要對(duì) UI 設(shè)置停止?fàn)顟B(tài)
    }
    if (type  == AVAudioSessionInterruptionTypeEnded) {
        // 中斷結(jié)束的時(shí)候處理, 因?yàn)橹袛嘟Y(jié)束后 原先停止的音頻不會(huì)自動(dòng)恢復(fù) 需要在結(jié)束的時(shí)候設(shè)置
    }
}

• 路線改變的處理

iOS 設(shè)置上音頻輸出設(shè)備一般包括麥克風(fēng)和耳機(jī),麥克風(fēng)正在播放音頻的時(shí)候插入耳機(jī).音頻會(huì)改為耳機(jī)輸出,當(dāng)拔出耳機(jī)的時(shí)候,需要暫停音頻播放

- (void)audioRouteChangeNotiSet {
    NSNotificationCenter  *notiCenter = [NSNotificationCenter defaultCenter];
    [notiCenter addObserver:self selector:@selector(handleInterruption:) name:AVAudioSessionRouteChangeNotification object:[AVAudioSession sharedInstance]];
}
- (void)handRountChange:(NSNotification *)noti {
    NSDictionary *info = noti.userInfo;
    AVAudioSessionRouteChangeReason reasion = [info[AVAudioSessionRouteChangeReasonKey] unsignedIntegerValue];
    if (reasion  == AVAudioSessionRouteChangeReasonOldDeviceUnavailable) {
        // 當(dāng)輸出路徑改變的時(shí)候,舊有的路徑設(shè)備不可用 的時(shí)候做處理
        AVAudioSessionRouteDescription *routeDescription = info[AVAudioSessionRouteChangePreviousRouteKey];
        AVAudioSessionPortDescription *portDescription = routeDescription.outputs[0];
        NSString *portType = portDescription.portType;
        if ([portType isEqualToString:AVAudioSessionPortHeadphones]) {
            // 當(dāng)耳機(jī)不可用的時(shí)候,說(shuō)明是拔出耳機(jī) 此時(shí)需要做的處理
        }
    }
}

• 音頻錄制
  音頻錄制需要設(shè)置音頻會(huì)話分類為Record或者PlayAndRecord,需要對(duì)音頻格式進(jìn)行正確設(shè)置匹配輸出文件的后綴名.

NSURL *filePath ; //輸出文件路徑,需指定后綴名
    NSDictionary *recordSetting = @{
                                    AVFormatIDKey : @(kAudioFormatMPEG4AAC),
                                    AVSampleRateKey : @(22050.0f),
                                    AVEncoderBitRateKey : @(16),
                                    AVNumberOfChannelsKey : @(1),
                                    AVVideoQualityKey : @(AVAudioQualityMedium)
                                    };
    NSError *error;
    AVAudioRecorder *audioRecorder = [[AVAudioRecorder alloc]initWithURL:filePath settings:recordSetting error:&error];
    [audioRecorder prepareToRecord];
    
    [audioRecorder record];//開(kāi)始錄制
    [audioRecorder stop];// 停止錄制
    [audioRecorder pause];//暫停

//獲取音頻音量信息
    audioRecorder.meteringEnabled = YES;
    [audioRecorder updateMeters];
    float avgpower = [audioRecorder averagePowerForChannel:0];
    float peakpower = [audioRecorder peakPowerForChannel:0];