音频录制

原生音视频编码  https://github.com/loyinglin/LearnVideoToolBox/tree/master

基于 AVFoundation 进行音频录制

@interface ViewController ()<AVAudioRecorderDelegate>
{
    AVAudioRecorder *recorder;
    AVAudioPlayer *player;
}

@property (weak, nonatomic) IBOutlet UILabel *label;
 
@end


- (IBAction)record:(id)sender {
    
    if (recorder == nil) {
//        路径拼接
        NSString *filePath =
        [NSString stringWithFormat:@"%@/rec_audio.caf", [self documentsDirectory]];
//        构建URL
        NSURL *fileUrl = [NSURL fileURLWithPath:filePath];
        
        NSError *error = nil;
//        AVAudioSession类提供了Audio Session服务，Audio Session是指定应用于音频系统如何交互。AVAudioSession通过指定一个音频类别实现的，音频类别描述了应用使用音频的方式
//        下面是设置音频回话类别
//        AVAudioSessionCategoryRecord代表只能输入音频，即录制音频，其效果是停止其他音频播放，开始录制音频，         AVAudioSessionCategoryPlayback代表只能输出音频，即进行音频播放。
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord
                                               error:&error];
//        设置是否“活跃”，这会把系统的任何声音关闭
        [[AVAudioSession sharedInstance] setActive:YES error:&error];
//        设置settings参数
        NSMutableDictionary *settings = [NSMutableDictionary dictionary];
//        AVFormatIDKey键是设置录制音频编码格式，kAudioFormatLinearPCM代表线性PCM编码格式，PCM（pulse code modulation）线性脉冲编码调制，它是一种非压缩格式。
//        注意：编码格式与文件格式不同，例如WAV是音频文件格式，它采用线性PCM音频编码
        [settings setValue:[NSNumber numberWithInt:kAudioFormatLinearPCM]
                    forKey:AVFormatIDKey];
//        AVSampleRateKey键是设置音频采样频率，44100.0是音频CD，VCD，SVCD和MP3所用的采样频率。
        [settings setValue:[NSNumber numberWithFloat:44100.0]
                    forKey:AVSampleRateKey];
//        AVNumberOfChannelsKey设置声道数量，值为1或者2
        [settings setValue:[NSNumber numberWithInt:1]
                    forKey:AVNumberOfChannelsKey];
//        AVLinearPCMBitDepthKey这是采样位数，取值为8，16，24，32，16是默认值
        [settings setValue:[NSNumber numberWithInt:16]
                    forKey:AVLinearPCMBitDepthKey];
//        AVLinearPCMIsBigEndianKey设置音频解码是大字节序还是小字节序，大字节序，YES，否则为NO
        [settings setValue:[NSNumber numberWithBool:NO]
                    forKey:AVLinearPCMIsBigEndianKey];
//        AVLinearPCMIsFloatKey设置音频解码是否为浮点数，如果是则设置为YES，否则为NO
        [settings setValue:[NSNumber numberWithBool:NO]
                    forKey:AVLinearPCMIsFloatKey];
//        实例化recorder对象
        recorder = [[AVAudioRecorder alloc]
                    initWithURL:fileUrl
                    settings:settings
                    error:&error];
//        设置代理
        recorder.delegate = self;
    }
    
//    如果正在录制，return
    if(recorder.isRecording) {
        return;
    }
//如果正在播放，停止
    if(player && player.isPlaying) {
        [player stop];
    }
//    开始录制
    [recorder record];
    
    self.label.text = @"录制中...";
}

- (IBAction)stop:(id)sender {
    self.label.text = @"停止...";
//    是否正在录制
    if(recorder.isRecording) {
        [recorder stop];//停止
        recorder.delegate = nil;
        recorder = nil;
    }
    if(player.isPlaying) {
        [player stop];
    }
}

- (IBAction)play:(id)sender {
    
    if(recorder.isRecording) {
        [recorder stop];
        recorder.delegate = nil;
        recorder = nil;
    }
    if(player.isPlaying) {
        [player stop];
    }
    
    NSString *filePath =
    [NSString stringWithFormat:@"%@/rec_audio.caf", [self documentsDirectory]];
    NSURL *fileUrl = [NSURL fileURLWithPath:filePath];
    
    NSError *error = nil;
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback
                                           error:&error];
    [[AVAudioSession sharedInstance] setActive:YES error:&error];
    player = [[AVAudioPlayer alloc] initWithContentsOfURL:fileUrl error:&error];
    
    if(error) {
        NSLog(@"%@",[error description]);
    } else {
        [player play];
        self.label.text = @"播放...";
    }
    
}
-(NSString *)documentsDirectory{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                         NSUserDomainMask, YES);
    return [paths objectAtIndex:0];
}

#pragma mark--实现AVAudioRecorderDelegate协议方法
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag{   
    NSLog(@"录制完成。");
}
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError *)error{
    NSLog(@"录制错误发生: %@", [error localizedDescription]);
}
- (void)audioRecorderBeginInterruption:(AVAudioRecorder *)recorder{
    NSLog(@"播放中断。");
}
- (void)audioRecorderEndInterruption:(AVAudioRecorder *)recorder withOptions:(NSUInteger)flags{
    NSLog(@"中断返回。");
}