AVFoundation 框架初探究（一）

// 简单的语音测试
-(void)speakHintMessage{

        // 这样子可以简单的播放一段语音
        AVSpeechSynthesizer * synthesizer = [[AVSpeechSynthesizer alloc]init];
        // Utterance 表达方式
        AVSpeechSynthesisVoice * voice  = [AVSpeechSynthesisVoice voiceWithLanguage:@"zh-CN"];
        AVSpeechUtterance  * utterance = [[AVSpeechUtterance alloc]initWithString:@"准备了猪，开始录制视频了"];
        utterance.rate  = 1.5; // 这个是播放速率 默认1.0
        utterance.voice = voice;
        utterance.pitchMultiplier = 0.8;        // 可在播放待定语句时候改变声调
        utterance.postUtteranceDelay = 0.1; // 语音合成器在播放下一条语句的时候有短暂的停顿  这个属性指定停顿的时间
        [synthesizer speakUtterance:utterance];
        
        /*
         "[AVSpeechSynthesisVoice 0x978a0b0] Language: th-TH",
         "[AVSpeechSynthesisVoice 0x977a450] Language: pt-BR",
         "[AVSpeechSynthesisVoice 0x977a480] Language: sk-SK",
         "[AVSpeechSynthesisVoice 0x978ad50] Language: fr-CA",
         "[AVSpeechSynthesisVoice 0x978ada0] Language: ro-RO",
         "[AVSpeechSynthesisVoice 0x97823f0] Language: no-NO",
         "[AVSpeechSynthesisVoice 0x978e7b0] Language: fi-FI",
         "[AVSpeechSynthesisVoice 0x978af50] Language: pl-PL",
         "[AVSpeechSynthesisVoice 0x978afa0] Language: de-DE",
         "[AVSpeechSynthesisVoice 0x978e390] Language: nl-NL",
         "[AVSpeechSynthesisVoice 0x978b030] Language: id-ID",
         "[AVSpeechSynthesisVoice 0x978b080] Language: tr-TR",
         "[AVSpeechSynthesisVoice 0x978b0d0] Language: it-IT",
         "[AVSpeechSynthesisVoice 0x978b120] Language: pt-PT",
         "[AVSpeechSynthesisVoice 0x978b170] Language: fr-FR",
         "[AVSpeechSynthesisVoice 0x978b1c0] Language: ru-RU",
         "[AVSpeechSynthesisVoice 0x978b210] Language: es-MX",
         "[AVSpeechSynthesisVoice 0x978b2d0] Language: zh-HK",
         "[AVSpeechSynthesisVoice 0x978b320] Language: sv-SE",
         "[AVSpeechSynthesisVoice 0x978b010] Language: hu-HU",
         "[AVSpeechSynthesisVoice 0x978b440] Language: zh-TW",
         "[AVSpeechSynthesisVoice 0x978b490] Language: es-ES",
         "[AVSpeechSynthesisVoice 0x978b4e0] Language: zh-CN",
         "[AVSpeechSynthesisVoice 0x978b530] Language: nl-BE",
         "[AVSpeechSynthesisVoice 0x978b580] Language: en-GB",
         "[AVSpeechSynthesisVoice 0x978b5d0] Language: ar-SA",
         "[AVSpeechSynthesisVoice 0x978b620] Language: ko-KR",
         "[AVSpeechSynthesisVoice 0x978b670] Language: cs-CZ",
         "[AVSpeechSynthesisVoice 0x978b6c0] Language: en-ZA",
         "[AVSpeechSynthesisVoice 0x978aed0] Language: en-AU",
         "[AVSpeechSynthesisVoice 0x978af20] Language: da-DK",
         "[AVSpeechSynthesisVoice 0x978b810] Language: en-US",
         "[AVSpeechSynthesisVoice 0x978b860] Language: en-IE",
         "[AVSpeechSynthesisVoice 0x978b8b0] Language: hi-IN", 
         "[AVSpeechSynthesisVoice 0x978b900] Language: el-GR",
         "[AVSpeechSynthesisVoice 0x978b950] Language: ja-JP" )
         */
        // 通过这个方法可以看到整个支持的会话的列表,信息如上输出
        NSLog(@"目前支持的语音列表:%@",[AVSpeechSynthesisVoice speechVoices]);
        
}

/*
 AVAudioPlayer 基本方法以及属性
 
 基本的初始化方法
 - (nullable instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError **)outError;
 - (nullable instancetype)initWithData:(NSData *)data error:(NSError **)outError;
 - (nullable instancetype)initWithContentsOfURL:(NSURL *)url fileTypeHint:(NSString * __nullable)utiString error:(NSError **)outError NS_AVAILABLE(10_9, 7_0);
 - (nullable instancetype)initWithData:(NSData *)data fileTypeHint:(NSString * __nullable)utiString error:(NSError **)outError NS_AVAILABLE(10_9, 7_0);
 
 // 准备播放，这个方法可以不执行，但执行的话可以降低播放器play方法和你听到声音之间的延时
 - (BOOL)prepareToPlay;
 
 // 播放
 - (BOOL)play;
 // play a sound some time in the future. time is an absolute time based on and greater than deviceCurrentTime.
 // 跳转到某一个时间点播放
 - (BOOL)playAtTime:(NSTimeInterval)time NS_AVAILABLE(10_7, 4_0);
 // 暂停 pauses  playback, but remains ready to play
 - (void)pause;
 // 停止
 // 它和上面的暂停的方法是在底层stop会撤销掉prepareToPlay时所作的设置，但是调用暂停不会
 - (void)stop;
 
 
 properties
 // 是否在播放
 @property(readonly, getter=isPlaying) BOOL playing
 // 音频声道数，只读
 @property(readonly) NSUInteger numberOfChannels
 // 音长
 @property(readonly) NSTimeInterval duration
 
 //the delegate will be sent messages from the AVAudioPlayerDelegate protocol
 @property(assign, nullable) id<AVAudioPlayerDelegate> delegate;
 
 // 下面两个是获取到的你初始化传入的相应的值
 @property(readonly, nullable) NSURL *url
 @property(readonly, nullable) NSData *data
 
 // set panning. -1.0 is left, 0.0 is center, 1.0 is right. NS_AVAILABLE(10_7, 4_0)
 // 允许使用立体声播放声音 如果为-1.0则完全左声道，如果0.0则左右声道平衡，如果为1.0则完全为右声道
 @property float pan
 
 // 音量 The volume for the sound. The nominal range is from 0.0 to 1.0.
 @property float volume
 
 // set音量逐渐减弱在时间间隔内
 - (void)setVolume:(float)volume fadeDuration:(NSTimeInterval)duration NS_AVAILABLE(10_12, 10_0);
 
 // 是否能设置rate属性，只有这个属性设置成YES了才能设置rate属性，并且这些属性都设置在prepareToPlay方法调用之前
 @property BOOL enableRate NS_AVAILABLE(10_8, 5_0);
 @property float rate NS_AVAILABLE(10_8, 5_0);
 
 // 当前播放的时间，利用定时器去观察这个属性可以读取到音频播放的时间点
    需要注意的是这个时间在你暂停播放之后是不会再改变的
 @property NSTimeInterval currentTime;
 
 // 输出设备播放音频的时间，注意如果播放中被暂停此时间也会继续累加
 @property(readonly) NSTimeInterval deviceCurrentTime NS_AVAILABLE(10_7, 4_0);
 
 // 这个属性实现循环播放， 设置一个大于0的数值，可以实现循环播放N次，要是设置-1，就会无限的循环播放
 @property NSInteger numberOfLoops;
 
 // 音频播放设置信息，只读
 @property(readonly) NSDictionary<NSString *, id> *settings NS_AVAILABLE(10_7, 4_0);
 
 // 10.0之后的属性
 @property(readonly) AVAudioFormat * format NS_AVAILABLE(10_12, 10_0);
 @property(getter=isMeteringEnabled) BOOL meteringEnabled;
 
 // 更新音频测量值，注意如果要更新音频测量值必须设置meteringEnabled为YES，通过音频测量值可以即时获得音频分贝等信息
 - (void)updateMeters
 
 // 获得指定声道的分贝峰值，注意如果要获得分贝峰值必须在此之前调用updateMeters方法
 - (float)peakPowerForChannel:(NSUInteger)channelNumber
 
 // 获得指定声道的分贝平均值，注意如果要获得分贝平均值必须在此之前调用updateMeters方法
 - (float)averagePowerForChannel:(NSUInteger)channelNumber
 
 @property(nonatomic, copy, nullable) NSArray<AVAudioSessionChannelDescription *> *channelAssignments
 
 
 AVAudioPlayerDelegate 播放代理
 @optional
 
 // 成功播放到结束
 - (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag;
 
 // if an error occurs while decoding it will be reported to the delegate.
 // 看上面的解释在音频解码出错的时候就会走这个方法
 - (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError * __nullable)error;
 
 
 // 注意下面的一行解释，下面的代理方法在8.0之后被弃用了，转用AVAudioSession来代替了
    AVAudioPlayer INTERRUPTION NOTIFICATIONS ARE DEPRECATED - Use AVAudioSession instead.

 // audioPlayerBeginInterruption: is called when the audio session has been interrupted while the player was playing. The player will have been paused.
 // Interruption 中断 声音播放被中断的时候就会进这个代理方法
 - (void)audioPlayerBeginInterruption:(AVAudioPlayer *)player NS_DEPRECATED_IOS(2_2, 8_0);
 
 // audioPlayerEndInterruption:withOptions: is called when the audio session interruption has ended and this player had been interrupted while playing.
 // 中断结束进这里代理
 - (void)audioPlayerEndInterruption:(AVAudioPlayer *)player withOptions:(NSUInteger)flags NS_DEPRECATED_IOS(6_0, 8_0);
 
 - (void)audioPlayerEndInterruption:(AVAudioPlayer *)player withFlags:(NSUInteger)flags NS_DEPRECATED_IOS(4_0, 6_0);
 
 // audioPlayerEndInterruption: is called when the preferred method, audioPlayerEndInterruption:withFlags:, is not implemented.
 - (void)audioPlayerEndInterruption:(AVAudioPlayer *)player NS_DEPRECATED_IOS(2_2, 6_0);
 
 */

/*
@interface AVAudioRecorder : NSObject {
 
// 私有的
@private
    void *_impl;
}

// 下面两个是初始化的方法，和我们前面说的AVAudioPlayer大致类似，我们不再解释
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;

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 format:(AVAudioFormat *)format error:(NSError **)outError API_AVAILABLE(macos(10.12), ios(10.0), watchos(4.0)) API_UNAVAILABLE(tvos);

// prepareToRecord 准备去记录，它的作用和前面AVAudioPlayer的也是类似的，可以看看前面的注释
methods that return BOOL return YES on success and NO on failure.
- (BOOL)prepareToRecord;  creates the file and gets ready to record. happens automatically on record.
 
// 开始记录 类似与AVAudioPlayer的play方法
- (BOOL)record;  start or resume recording to file.
 
 
// 在将来的某个特殊的你设置的时间点开始记录
- (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.

// 在某一段时间之后开始记录
- (BOOL)recordForDuration:(NSTimeInterval) duration;  record a file of a specified duration. the recorder will stop when it has recorded this length of audio

// 在某一个时间点的某一段时间之后开始记录
- (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.

// 下面是暂停和停止的方法，这两个比较好理解
- (void)pause;  pause recording
- (void)stop;   stops recording. closes the file.

// 删除记录，调用这个方法之前必须保证 recorder 是 stop 状态
- (BOOL)deleteRecording;  delete the recorded file. recorder must be stopped. returns NO on failure.

// 下面是一些属性
properties
// 是否在记录
@property(readonly, getter=isRecording) BOOL recording;  is it recording or not?
// 保存记录音频文件的URL
@property(readonly) NSURL *url;  URL of the recorded file
//
these settings are fully valid only when prepareToRecord has been called
@property(readonly) NSDictionary<NSString *, id> *settings;

//10.0之后的属性， AVAudioFormat 音频格式注意是只读
this object is fully valid only when prepareToRecord has been called
@property(readonly) AVAudioFormat *format API_AVAILABLE(macos(10.12), ios(10.0), watchos(4.0)) API_UNAVAILABLE(tvos);
// 代理
the delegate will be sent messages from the AVAudioRecorderDelegate protocol
@property(assign, nullable) id<AVAudioRecorderDelegate> delegate;

// 下面的currentTime和deviceCurrentTime在前面也是解释过，按照理解AVAudioPlayer的理解就没问题
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);


// meteringEnabled 也是和AVAudioPlayer相同
// 需要注意的前面也有提过，注意这个属性以及下面两个方法之间的必要关系。
   至于方法是干什么的我们不在解释，前面AVAudioPlayer也有
@property(getter=isMeteringEnabled) BOOL meteringEnabled;  turns level metering on or off. default is off.
- (void)updateMeters; call to refresh meter values
- (float)peakPowerForChannel:(NSUInteger)channelNumber; returns peak power in decibels for a given channel
- (float)averagePowerForChannel:(NSUInteger)channelNumber; returns average power in decibels for a given channel

The channels property lets you assign the output to record specific channels as described by AVAudioSession's channels property
This property is nil valued until set.
The array must have the same number of channels as returned by the numberOfChannels property.
@property(nonatomic, copy, nullable) NSArray<AVAudioSessionChannelDescription *> *channelAssignments NS_AVAILABLE(10_9, 7_0); Array of AVAudioSessionChannelDescription objects



// 代理  代理需要注意的地方我们不再说了。这个代理和前面AVAudioPlayer的完全类似
   注意点也是类似，有不理解的可以往前面翻
@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

// 下面的方法也是被AVAudioSession替换掉，这个我们在下面的介绍中会说AVAudioSession这个类
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);
*/

 /* returns singleton instance */
+ (AVAudioSession*)sharedInstance;

- (BOOL)setActive:(BOOL)active  error:(NSError * _Nullable *)outError;

- (BOOL)setActive:(BOOL)active withOptions:(AVAudioSessionSetActiveOptions)options error:(NSError **)outError

/* get session category. Examples: AVAudioSessionCategoryRecord, AVAudioSessionCategoryPlayAndRecord, etc. */
@property(readonly) NSString *category;

@property(readonly) NSArray<NSString *> *availableCategories;

/* set session category */
- (BOOL)setCategory:(NSString *)category error:(NSError **)outError;
/* set session category with options */
- (BOOL)setCategory:(NSString *)category withOptions:(AVAudioSessionCategoryOptions)options error:(NSError **)outError NS_AVAILABLE_IOS(6_0);
/* set session category and mode with options */
- (BOOL)setCategory:(NSString *)category mode:(NSString *)mode options:(AVAudioSessionCategoryOptions)options error:(NSError **)outError NS_AVAILABLE_IOS(10_0);

typedef NS_OPTIONS(NSUInteger, AVAudioSessionCategoryOptions)
{
	/* MixWithOthers is only valid with AVAudioSessionCategoryPlayAndRecord, AVAudioSessionCategoryPlayback, and  AVAudioSessionCategoryMultiRoute */
	AVAudioSessionCategoryOptionMixWithOthers			= 0x1,

	/* DuckOthers is only valid with AVAudioSessionCategoryAmbient, AVAudioSessionCategoryPlayAndRecord, AVAudioSessionCategoryPlayback, and AVAudioSessionCategoryMultiRoute */
	AVAudioSessionCategoryOptionDuckOthers				= 0x2
,
	/* AllowBluetooth is only valid with AVAudioSessionCategoryRecord and AVAudioSessionCategoryPlayAndRecord */
	AVAudioSessionCategoryOptionAllowBluetooth	__TVOS_PROHIBITED __WATCHOS_PROHIBITED		= 0x4,

	/* DefaultToSpeaker is only valid with AVAudioSessionCategoryPlayAndRecord */
	AVAudioSessionCategoryOptionDefaultToSpeaker __TVOS_PROHIBITED __WATCHOS_PROHIBITED		= 0x8,

	/* InterruptSpokenAudioAndMixWithOthers is only valid with AVAudioSessionCategoryPlayAndRecord, AVAudioSessionCategoryPlayback, and AVAudioSessionCategoryMultiRoute */
	AVAudioSessionCategoryOptionInterruptSpokenAudioAndMixWithOthers NS_AVAILABLE_IOS(9_0) 	= 0x11,

        /* AllowBluetoothA2DP is only valid with AVAudioSessionCategoryPlayAndRecord */
           AVAudioSessionCategoryOptionAllowBluetoothA2DP NS_AVAILABLE_IOS(10_0) = 0x20,

        /* AllowAirPlay is only valid with AVAudioSessionCategoryPlayAndRecord */
           AVAudioSessionCategoryOptionAllowAirPlay NS_AVAILABLE_IOS(10_0) __WATCHOS_PROHIBITED = 0x40,

} NS_AVAILABLE_IOS(6_0);

@property(readonly) NSArray<NSString *> *availableModes; 

- (BOOL)setMode:(NSString *)mode error:(NSError **)outError