录音 `AVAudioRecorder`

初始化方法

/* The file type to create can be set through the corresponding settings key. If not set, it will be inferred from the file extension. Will overwrite a file at the specified url if a file exists. */
- (nullable instancetype)initWithURL:(NSURL *)url settings:(NSDictionary<NSString *, id> *)settings error:(NSError **)outError;

// 录音文件的url
@property(readonly) NSURL *url; /* URL of the recorded file */

// 录音文件的设置信息
/* these settings are fully valid only when prepareToRecord has been called */
@property(readonly) NSDictionary<NSString *, id> *settings;

url: 录音文件保存的位置，一般都是保存到沙盒中

注意：
url一般使用[NSURL fileURLWithPath:_filePath]进行初始化，使用URLWithString:方法初始化会初始化失败；原因就是URL的格式，需要scheme，fileURLWithPath会添加file://，但是URLWithString不会做任何处理

settings: 录音的配置信息，取值如下:

例子:

设置:
    _settings = @{
                  AVFormatIDKey: @(kAudioFormatMPEG4AAC),
                  AVSampleRateKey: @(_sampleRate),
                  AVNumberOfChannelsKey: @2,
                  AVLinearPCMBitDepthKey: @16,
                  AVEncoderAudioQualityKey: @(AVAudioQualityHigh)
                  };

// 打印结果:
_audioRecorder.settings: {
    AVAudioFileTypeKey = 1633973363;
    AVEncoderBitDepthHintKey = 0; // 默认的
    AVEncoderBitRateKey = 40000; // 默认的
    AVEncoderQualityKey = 96;
    AVFormatIDKey = 1633772320;
    AVNumberOfChannelsKey = 2;
    AVSampleRateKey = 11025;
}

注意，对于录音音量比较小的问题，需要添加下面的代码

 // 音量控制，否则声音很小
    NSError *volumError = nil;
    [[AVAudioSession sharedInstance] overrideOutputAudioPort:AVAudioSessionPortOverrideSpeaker error:&volumError];
    if (volumError) {
        NSLog(@"音量控制失败 --- ");
        NSLog(@"%@", volumError);
    }

`AVFormatIDKey`

录音的文件格式

CF_ENUM(AudioFormatID)
{
    kAudioFormatLinearPCM               = 'lpcm',
    kAudioFormatAC3                     = 'ac-3',
    kAudioFormat60958AC3                = 'cac3',
    kAudioFormatAppleIMA4               = 'ima4',
    kAudioFormatMPEG4AAC                = 'aac ',
    kAudioFormatMPEG4CELP               = 'celp',
    kAudioFormatMPEG4HVXC               = 'hvxc',
    kAudioFormatMPEG4TwinVQ             = 'twvq',
    kAudioFormatMACE3                   = 'MAC3',
    kAudioFormatMACE6                   = 'MAC6',
    kAudioFormatULaw                    = 'ulaw',
    kAudioFormatALaw                    = 'alaw',
    kAudioFormatQDesign                 = 'QDMC',
    kAudioFormatQDesign2                = 'QDM2',
    kAudioFormatQUALCOMM                = 'Qclp',
    kAudioFormatMPEGLayer1              = '.mp1',
    kAudioFormatMPEGLayer2              = '.mp2',
    kAudioFormatMPEGLayer3              = '.mp3',
    kAudioFormatTimeCode                = 'time',
    kAudioFormatMIDIStream              = 'midi',
    kAudioFormatParameterValueStream    = 'apvs',
    kAudioFormatAppleLossless           = 'alac',
    kAudioFormatMPEG4AAC_HE             = 'aach',
    kAudioFormatMPEG4AAC_LD             = 'aacl',
    kAudioFormatMPEG4AAC_ELD            = 'aace',
    kAudioFormatMPEG4AAC_ELD_SBR        = 'aacf',
    kAudioFormatMPEG4AAC_ELD_V2         = 'aacg',    
    kAudioFormatMPEG4AAC_HE_V2          = 'aacp',
    kAudioFormatMPEG4AAC_Spatial        = 'aacs',
    kAudioFormatAMR                     = 'samr',
    kAudioFormatAMR_WB                  = 'sawb',
    kAudioFormatAudible                 = 'AUDB',
    kAudioFormatiLBC                    = 'ilbc',
    kAudioFormatDVIIntelIMA             = 0x6D730011,
    kAudioFormatMicrosoftGSM            = 0x6D730031,
    kAudioFormatAES3                    = 'aes3',
    kAudioFormatEnhancedAC3             = 'ec-3',
    kAudioFormatFLAC                    = 'flac',
    kAudioFormatOpus                    = 'opus'
};

kAudioFormatLinearPCM: 音频的原始文件（caf）
kAudioFormatMPEG4AAC: aac文件格式的音频

注意
文件格式不可以直接.mp3格式，会报错

`AVSampleRateKey`

采用率（赫兹）“

常用的有

8,000 Hz: 电话所用采样率, 对于人的说话已经足够
11,025 Hz: 说话

参考文章：

https://baike.baidu.com/item/%E9%9F%B3%E9%A2%91%E9%87%87%E6%A0%B7%E7%8E%87/9023551

`AVNumberOfChannelsKey`

采用通道数，一般有:

1: 单声道
2: 双声道

`linear PCM keys`

`AVLinearPCMBitDepthKey`

采样深度，影响声音质量，比如从caf转mp3，如果设置为8的话，声音可能会失真，需要设置更高一点(比如16)

取值有: 8, 16, 24, 32

`AVLinearPCMIsBigEndianKey`

YES: 大端模式
NO: 小端模式

参考文章:

https://blog.csdn.net/chivalrousli/article/details/38419995

`AVLinearPCMIsFloatKey`

是否支持浮点处理

`AVLinearPCMIsNonInterleaved`

交叉的

`audio file type key` 11.0 之后

`AVAudioFileTypeKey`

AudioFile.h文件中可以查看具体的

`encoder property keys`

编码属性

`AVEncoderAudioQualityKey`

编码质量

取值有:

typedef NS_ENUM(NSInteger, AVAudioQuality) {
    AVAudioQualityMin    = 0,
    AVAudioQualityLow    = 0x20,
    AVAudioQualityMedium = 0x40,
    AVAudioQualityHigh   = 0x60,
    AVAudioQualityMax    = 0x7F
};

`AVEncoderAudioQualityForVBRKey`

动态比特率，取值是 AVAudioQuality，只和AVAudioBitRateStrategy_Variable有关

`AVEncoderBitRateKey`

编码比特率

注意
AVEncoderBitRateKey和AVEncoderBitRatePerChannelKey只需要设置一个；only one of AVEncoderBitRateKey and AVEncoderBitRatePerChannelKey should be provided.

`AVEncoderBitRatePerChannelKey`

每个声道的比特率

`AVEncoderBitRateStrategyKey`

编码比特率的策略

取值有:

/* values for AVEncoderBitRateStrategyKey */
AVF_EXPORT NSString *const AVAudioBitRateStrategy_Constant              NS_AVAILABLE(10_9, 7_0);
AVF_EXPORT NSString *const AVAudioBitRateStrategy_LongTermAverage       NS_AVAILABLE(10_9, 7_0);
AVF_EXPORT NSString *const AVAudioBitRateStrategy_VariableConstrained   NS_AVAILABLE(10_9, 7_0);
AVF_EXPORT NSString *const AVAudioBitRateStrategy_Variable              NS_AVAILABLE(10_9, 7_0);

`AVEncoderBitDepthHintKey`

取值 8 to 32

控制方法

// 准备录音
- (BOOL)prepareToRecord; /* creates the file and gets ready to record. happens automatically on record. */

// 开始录音
- (BOOL)record; /* start or resume recording to file. */

// 在设定的时间time开始录音
- (BOOL)recordAtTime:(NSTimeInterval)time NS_AVAILABLE_IOS(6_0); /* start recording at specified time in the future. time is an absolute time based on and greater than deviceCurrentTime. */

// 录音时间为 duration 秒，超过会自动停止
- (BOOL)recordForDuration:(NSTimeInterval) duration; /* record a file of a specified duration. the recorder will stop when it has recorded this length of audio */

// 在设定的时间time开始录音，录音最大时间长为 duration
- (BOOL)recordAtTime:(NSTimeInterval)time forDuration:(NSTimeInterval) duration NS_AVAILABLE_IOS(6_0); /* record a file of a specified duration starting at specified time. time is an absolute time based on and greater than deviceCurrentTime. */

// 暂停
- (void)pause; /* pause recording */

// 停止
- (void)stop; /* stops recording. closes the file. */

// 删除录音
- (BOOL)deleteRecording; /* delete the recorded file. recorder must be stopped. returns NO on failure. */

// 是否正在录音中
@property(readonly, getter=isRecording) BOOL recording; /* is it recording or not? */

代理

/* the delegate will be sent messages from the AVAudioRecorderDelegate protocol */ 
@property(assign, nullable) id<AVAudioRecorderDelegate> delegate;

@protocol AVAudioRecorderDelegate <NSObject>
@optional 

/* audioRecorderDidFinishRecording:successfully: is called when a recording has been finished or stopped. This method is NOT called if the recorder is stopped due to an interruption. */
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag;

/* if an error occurs while encoding it will be reported to the delegate. */
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError * __nullable)error;

#if TARGET_OS_IPHONE

/* AVAudioRecorder INTERRUPTION NOTIFICATIONS ARE DEPRECATED - Use AVAudioSession instead. */

/* audioRecorderBeginInterruption: is called when the audio session has been interrupted while the recorder was recording. The recorded file will be closed. */
- (void)audioRecorderBeginInterruption:(AVAudioRecorder *)recorder NS_DEPRECATED_IOS(2_2, 8_0);

/* audioRecorderEndInterruption:withOptions: is called when the audio session interruption has ended and this recorder had been interrupted while recording. */
/* Currently the only flag is AVAudioSessionInterruptionFlags_ShouldResume. */
- (void)audioRecorderEndInterruption:(AVAudioRecorder *)recorder withOptions:(NSUInteger)flags NS_DEPRECATED_IOS(6_0, 8_0);

- (void)audioRecorderEndInterruption:(AVAudioRecorder *)recorder withFlags:(NSUInteger)flags NS_DEPRECATED_IOS(4_0, 6_0);

/* audioRecorderEndInterruption: is called when the preferred method, audioRecorderEndInterruption:withFlags:, is not implemented. */
- (void)audioRecorderEndInterruption:(AVAudioRecorder *)recorder NS_DEPRECATED_IOS(2_2, 6_0);

#endif // TARGET_OS_IPHONE

@end

录音时间

/* get the current time of the recording - only valid while recording */
@property(readonly) NSTimeInterval currentTime;
/* get the device current time - always valid */
@property(readonly) NSTimeInterval deviceCurrentTime NS_AVAILABLE_IOS(6_0);

currentTime: 当前的录音时间，录音时有效；停止录音的时候为0
deviceCurrentTime: 当前的设备时间

录音时间的处理：

record时记录deviceCurrentTime为_recorderBeginTime
录音完成的代理方法audioRecorderDidFinishRecording记录结束时间为_recorderEndTime
_recorderEndTime减去_recorderBeginTime就得到了录音时间长，不过这只是一个大概的，不是很准确，aac格式会有误差；

注意
1、使用caf格式录音时，时间是准确的，设置recordForDuration:方法也是有效的、准确的；
2、使用aac格式录音时，设置recordForDuration:方法也是不准确的，有误差1秒多

录音最大时间的处理:

1、设置最大时间的方法:

BOOL result = [_audioRecorder recordAtTime:_audioRecorder.deviceCurrentTime forDuration:_maxDuration]

2、开启定时器进行处理

注：在定时器方法中也需要处理最大时间，aac文件格式录音时间是不准确的

- (void)timerFire {
    // 主线程执行
    dispatch_async(dispatch_get_main_queue(), ^{
        BOOL result = _audioRecorder.isRecording;
        NSTimeInterval time = result ? _audioRecorder.currentTime : _audioPlayer.currentTime;
        NSLog(@"currentTime: %f", _audioRecorder.currentTime);
        NSLog(@"deviceCurrentTime: %f", _audioRecorder.deviceCurrentTime);
        NSLog(@"_recorderBeginTime: %f", _recorderBeginTime);
        NSLog(@"duration: %f", _audioRecorder.deviceCurrentTime - _recorderBeginTime);
        // 录音的最大时间处理: (aac格式时间不准确，caf准确)
        if (result) {
            if (time > _maxDuration) {
                [self stop];
                return;
            }
        }
        [self notifyToDelegateDidRecordingOrPalying:result currentTime:time];
    });
}

补充

/* get the current time of the recording - only valid while recording */
@property(readonly) NSTimeInterval currentTime;
/* get the device current time - always valid */
@property(readonly) NSTimeInterval deviceCurrentTime NS_AVAILABLE_IOS(6_0);

currentTime: 当前时间，录音时有效，停止录音的时候为0
deviceCurrentTime: 一直有效，有值

代码：

NSLog(@"_audioRecorder 初始化完成");
[self _logRecordTime];

/// ------

- (BOOL)record {
   NSLog(@"_audioRecorder 准备");
   [self _logRecordTime];

    BOOL result = [_audioRecorder recordAtTime:_audioRecorder.deviceCurrentTime forDuration:_maxDuration];
   if (result) {
       NSLog(@"_audioRecorder 开始");
       [self _logRecordTime];
       _recorderBeginTime = _audioRecorder.deviceCurrentTime;
   } else {
       [self notifyToDelegateRecorderInitFailed];
   }
   return result;
}

2018-08-22 18:06:38.177723+0800 HaiZiGuoParents[42414:12224854] _audioRecorder 初始化完成
2018-08-22 18:06:38.177745+0800 HaiZiGuoParents[42414:12224854] _audioRecorder.deviceCurrentTime: 1388447.325438
2018-08-22 18:06:38.177769+0800 HaiZiGuoParents[42414:12224854] _audioRecorder.currentTime: 0.000000
2018-08-22 18:06:38.177798+0800 HaiZiGuoParents[42414:12224854] _audioRecorder 准备
2018-08-22 18:06:38.177950+0800 HaiZiGuoParents[42414:12224854] _audioRecorder.deviceCurrentTime: 1388447.325647
2018-08-22 18:06:38.177971+0800 HaiZiGuoParents[42414:12224854] _audioRecorder.currentTime: 0.000000
2018-08-22 18:06:38.394655+0800 HaiZiGuoParents[42414:12224854] _audioRecorder 开始
2018-08-22 18:06:38.394743+0800 HaiZiGuoParents[42414:12224854] _audioRecorder.deviceCurrentTime: 1388447.542438
2018-08-22 18:06:38.394961+0800 HaiZiGuoParents[42414:12224854] _audioRecorder.currentTime: 0.026122

1388447.542438 - 1388447.325647 = 0.216791 可以看到以录音deviceCurrentTime作为标准计算时间为 0.216791，实际上currentTime为0.026122，差了一些

分贝

// 是否开启分贝检测
@property(getter=isMeteringEnabled) BOOL meteringEnabled; /* turns level metering on or off. default is off. */

// 更新，在调用下面��两个方法之前需要先调用这个方法
- (void)updateMeters; /* call to refresh meter values */

// 当前分贝
- (float)peakPowerForChannel:(NSUInteger)channelNumber; /* returns peak power in decibels for a given channel */

// 平均分贝
- (float)averagePowerForChannel:(NSUInteger)channelNumber; /* returns average power in decibels for a given channel */

备注

采样率:

11025.0: 5分钟1.5M

iOS音频开发相关（二）录音 `AVAudioRecorder`

录音 `AVAudioRecorder`

初始化方法

`AVFormatIDKey`

`AVSampleRateKey`

`AVNumberOfChannelsKey`

`linear PCM keys`

`AVLinearPCMBitDepthKey`

`AVLinearPCMIsBigEndianKey`

`AVLinearPCMIsFloatKey`

`AVLinearPCMIsNonInterleaved`

`audio file type key` 11.0 之后

`AVAudioFileTypeKey`

`encoder property keys`

`AVEncoderAudioQualityKey`

`AVEncoderAudioQualityForVBRKey`

`AVEncoderBitRateKey`

`AVEncoderBitRatePerChannelKey`

`AVEncoderBitRateStrategyKey`

`AVEncoderBitDepthHintKey`

控制方法

代理

录音时间

分贝

备注

猜你喜欢

iOS音频开发相关（二）录音 `AVAudioRecorder`

录音 AVAudioRecorder

初始化方法

AVFormatIDKey

AVSampleRateKey

AVNumberOfChannelsKey

linear PCM keys

AVLinearPCMBitDepthKey

AVLinearPCMIsBigEndianKey

AVLinearPCMIsFloatKey

AVLinearPCMIsNonInterleaved

audio file type key 11.0 之后

AVAudioFileTypeKey

encoder property keys

AVEncoderAudioQualityKey

AVEncoderAudioQualityForVBRKey

AVEncoderBitRateKey

AVEncoderBitRatePerChannelKey

AVEncoderBitRateStrategyKey

AVEncoderBitDepthHintKey

控制方法

代理

录音时间

分贝

备注

猜你喜欢

录音 `AVAudioRecorder`

`AVFormatIDKey`

`AVSampleRateKey`

`AVNumberOfChannelsKey`

`linear PCM keys`

`AVLinearPCMBitDepthKey`

`AVLinearPCMIsBigEndianKey`

`AVLinearPCMIsFloatKey`

`AVLinearPCMIsNonInterleaved`

`audio file type key` 11.0 之后

`AVAudioFileTypeKey`

`encoder property keys`

`AVEncoderAudioQualityKey`

`AVEncoderAudioQualityForVBRKey`

`AVEncoderBitRateKey`

`AVEncoderBitRatePerChannelKey`

`AVEncoderBitRateStrategyKey`

`AVEncoderBitDepthHintKey`