iOS录音实践

在AVFoundation框架中AVAudioRecorder类专门处理录音操作，支持多种音频格式。下面是常用的属性和方法：

属性	说明
@property(readonly, getter=isRecording) BOOL recording;	是否正在录音，只读
@property(readonly) NSURL *url	录音文件地址，只读
@property(readonly) NSDictionary *settings	录音文件设置，只读
@property(readonly) NSTimeInterval currentTime	录音时长，只读，注意仅仅在录音状态可用
@property(readonly) NSTimeInterval deviceCurrentTime	输入设置的时间长度，只读，注意此属性一直可访问
@property(getter=isMeteringEnabled) BOOL meteringEnabled;	是否启用录音测量，如果启用录音测量可以获得录音分贝等数据信息
@property(nonatomic, copy) NSArray *channelAssignments	当前录音的通道
对象方法	说明
- (instancetype)initWithURL:(NSURL *)url settings:(NSDictionary *)settings error:(NSError **)outError	录音机对象初始化方法，注意其中的url必须是本地文件url，settings是录音格式、编码等设置
- (BOOL)prepareToRecord	准备录音，主要用于创建缓冲区，如果不手动调用，在调用record录音时也会自动调用
- (BOOL)record	开始录音
- (BOOL)recordAtTime:(NSTimeInterval)time	在指定的时间开始录音，一般用于录音暂停再恢复录音
- (BOOL)recordForDuration:(NSTimeInterval) duration	按指定的时长开始录音
- (BOOL)recordAtTime:(NSTimeInterval)time forDuration:(NSTimeInterval) duration	在指定的时间开始录音，并指定录音时长
- (void)pause;	暂停录音
- (void)stop;	停止录音
- (BOOL)deleteRecording;	删除录音，注意要删除录音此时录音机必须处于停止状态
- (void)updateMeters;	更新测量数据，注意只有meteringEnabled为YES此方法才可用
- (float)peakPowerForChannel:(NSUInteger)channelNumber;	指定通道的测量峰值，注意只有调用完updateMeters才有值
- (float)averagePowerForChannel:(NSUInteger)channelNumber	指定通道的测量平均值，注意只有调用完updateMeters才有值
代理方法	说明
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag	完成录音
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError *)error	录音编码发生错误

AVAudioRecorder创建录音机时除了指定路径外还必须指定录音设置信息，因为录音机必须知道录音文件的格式、采样率、通道数、每个采样点的位数等信息，通常只需要几个常用设置。关于录音设置详见帮助文档中的“AV Foundation Audio Settings Constants”。

以下代码实现录音，暂停，继续，取消，停止，播放功能。

#import "ViewController.h"

#import <AVFoundation/AVFoundation.h>

#define kAudioFileName @"test.caf"

@interface ViewController ()<AVAudioRecorderDelegate>

@property (nonatomic,strong) AVAudioRecorder *audioRecorder; //音频录音机
@property (nonatomic,strong) AVAudioPlayer *audioPlayer;     //音频播放器
@property (nonatomic,strong) NSTimer *timer;            //录音监控

@property (weak, nonatomic) IBOutlet UIProgressView *audioPower;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setAudioSession];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/**
 *  设置音频会话
 */
-(void)setAudioSession{
    AVAudioSession *audioSession=[AVAudioSession sharedInstance];
    //设置为播放和录音状态，以便可以在录制完之后播放录音
    [audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
    [audioSession setActive:YES error:nil];
}

/**
 *  录音文件设置
 *
 *  @return 返回录音设置
 */
- (NSDictionary *)getAudioSetting
{
    NSMutableDictionary *dic = [NSMutableDictionary dictionary];
    [dic setObject:@(kAudioFormatLinearPCM) forKey:AVFormatIDKey];  //设置录音格式
    [dic setObject:@(8000) forKey:AVSampleRateKey];                 //设置采样率
    [dic setObject:@(1) forKey:AVNumberOfChannelsKey];              //设置通道，这里采用单声道
    [dic setObject:@(8) forKey:AVLinearPCMBitDepthKey];             //每个采样点位数，分为8，16，24，32
    [dic setObject:@(YES) forKey:AVLinearPCMIsFloatKey];            //是否使用浮点数采样
    return dic;
}

/**
 *  录音存储路径
 *
 *  @return 返回存储路径
 */
- (NSURL *)getSavePath
{
    NSString *url = [NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask,YES) lastObject];
    url = [url stringByAppendingPathComponent:kAudioFileName];
    return [NSURL URLWithString:url];
}


- (NSTimer *)timer
{
    if (!_timer) {
        _timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(audioPowerChange) userInfo:nil repeats:YES];
    }
    return _timer;
}

- (AVAudioRecorder *)audioRecorder
{
    if (!_audioRecorder) {
        NSError *error = nil;
        _audioRecorder = [[AVAudioRecorder alloc] initWithURL:[self getSavePath] settings:[self getAudioSetting] error:&error];
        _audioRecorder.delegate = self;
        _audioRecorder.meteringEnabled = YES; //是否启用录音测量，如果启用录音测量可以获得录音分贝等数据信息
        if (error) {
            NSLog(@"创建录音机对象发生错误:%@",error.localizedDescription);
            return nil;
        }
    }
    return _audioRecorder;
}

- (AVAudioPlayer *)audioPlayer
{
    if (!_audioPlayer) {
        NSError *error = nil;
        _audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[self getSavePath] error:&error];
        if (error) {
            NSLog(@"创建音频播放器对象发生错误:%@",error.localizedDescription);
            return nil;
        }
    }
    return _audioPlayer;
}

#pragma mark - 
#pragma mark - AVAudioRecorderDelegate
//录音成功
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag
{
    if (![self.audioPlayer isPlaying]) {
        [self.audioPlayer play];
    }
}
//录音失败
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError *)error
{
    
}

#pragma mark - 
#pragma mark - Action

- (void)audioPowerChange{
    [self.audioRecorder updateMeters];  //更新测量值
    float power = [self.audioRecorder averagePowerForChannel:1]; //取得第一个通道的音频，注意音频强度范围时-160到0
    self.audioPower.progress = (1.0/160)*(power+160);
}

/**
 *  点击录音按钮
 *
 *  @param sender 录音按钮
 */
- (IBAction)startRecord:(id)sender {
    
    if (![self.audioRecorder isRecording]) {
        [self.audioRecorder record];
        self.timer.fireDate = [NSDate distantPast];
    }
}

/**
 *  点击取消录音按钮
 *
 *  @param sender 取消录音按钮
 */
- (IBAction)cancelRecord:(id)sender {
    self.audioRecorder.delegate = nil;
    if ([self.audioRecorder isRecording]) {
       [self.audioRecorder stop];
    }
    self.audioRecorder = nil;
}

/**
 *  点击暂定按钮
 *
 *  @param sender 暂停按钮
 */
- (IBAction)pause:(id)sender {
    if ([self.audioRecorder isRecording]) {
        [self.audioRecorder pause];
        self.timer.fireDate = [NSDate distantFuture];
    }
}

/**
 *  点击恢复按钮
 *  恢复录音只需要再次调用record，AVAudioSession会帮助你记录上次录音位置并追加录音
 *
 *  @param sender 恢复按钮
 */
- (IBAction)goon:(id)sender {
    [self startRecord:nil];
}

/**
 *  点击停止按钮
 *
 *  @param sender 停止按钮
 */
- (IBAction)stop:(id)sender {
    if ([self.audioRecorder isRecording]) {
        [self.audioRecorder stop];
        self.timer = [NSDate distantFuture];
    }
}

/**
 *  点击播放按钮
 *
 *  @param sender 播放按钮
 */
- (IBAction)play:(id)sender {
    
    if (![self.audioPlayer isPlaying]) {
        [self.audioPlayer play];
    }
}