前言

在AV Foundation中使用AVAudioRecorder類添加音頻錄制功能和使用AVAudioPlayer一樣簡(jiǎn)單, 都是在Audio Queue Server上層構(gòu)建的.同時(shí)支持macOS和iOS平臺(tái).可以從內(nèi)置麥克風(fēng)錄制音頻,也可以支持?jǐn)?shù)字音頻接口或USB外接麥克風(fēng)錄制.

主要內(nèi)容如下:

如何創(chuàng)建AVAudioRecorder  
    1\. 音頻格式
    2\. 采樣率
    3\. 通道數(shù)
創(chuàng)建Demo
    1\. 配置音頻會(huì)話
    2\. 實(shí)現(xiàn)錄音功能
    3\. 使用Audio Metering實(shí)現(xiàn)聲波視覺(jué)顯示

創(chuàng)建AVAudioRecorder之前先了解一下它的方法和成員變量

@property (readonly, getter=isRecording) BOOL recording;//是否正在錄音
@property (readonly) NSDictionary<NSString *, id> *settings;//錄音配置：采樣率、音頻格式、通道數(shù)...
@property (readonly) NSURL *url;//錄音文件存放URL
@property (readonly) NSTimeInterval currentTime;//錄音時(shí)長(zhǎng)
@property (getter=isMeteringEnabled) BOOL meteringEnabled;//是否監(jiān)控聲波

AVAudioRecorder的實(shí)例方法:

- (BOOL)prepareToRecord;//為錄音準(zhǔn)備緩沖區(qū)
- (BOOL)record;//錄音開(kāi)始亿絮，暫停后調(diào)用會(huì)恢復(fù)錄音
- (BOOL)recordAtTime:(NSTimeInterval)time;//在指定時(shí)間后開(kāi)始錄音
- (BOOL)recordForDuration:(NSTimeInterval) duration;//按指定時(shí)長(zhǎng)錄音
- (BOOL)recordAtTime:(NSTimeInterval)time 
         forDuration:(NSTimeInterval)duration;//上面2個(gè)的合體
- (void)pause; //暫停錄音
- (void)stop; //停止錄音
- (BOOL)deleteRecording;//刪除錄音往枷，必須先停止錄音再刪除

AVAudioRecorder的代理方法:

//錄音完成后調(diào)用
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder 
                           successfully:(BOOL)flag;
//錄音編碼發(fā)生錯(cuò)誤時(shí)調(diào)用
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder 
                                   error:(NSError *)error;

如何創(chuàng)建AVAudioRecorder

創(chuàng)建AVAudioRecorder對(duì)象所需要的參數(shù)如下:

• 音頻流錄制時(shí)寫(xiě)入到本地的路徑URL
• settings錄音配置：采樣率、音頻格式缓呛、通道數(shù)…等鍵值參數(shù)字典
• 發(fā)生錯(cuò)誤的NSError指針

如下代碼:

/**
 創(chuàng)建錄音器
 */
- (void)createRecorder {
    NSString *directory = NSTemporaryDirectory();
    NSString *filePath = [directory stringByAppendingPathComponent:@"voice1.m4a"];
    NSURL *url = [NSURL fileURLWithPath:filePath];

    NSDictionary *setting = @{AVFormatIDKey : @(kAudioFormatMPEG4AAC),
                              AVSampleRateKey: @22050.0f,
                              AVNumberOfChannelsKey: @1};
    NSError *error;
    self.recorder = [[AVAudioRecorder alloc] initWithURL:url
                                                settings:setting
                                                   error:&error];
    if (self.recorder) {
        [self.recorder prepareToRecord];
    } else {
        NSLog(@"Recorder Create Error: %@", [error localizedDescription]);
    }
}

這里的建議調(diào)用[self.recorder prepareToRecord]方法對(duì)錄音實(shí)例進(jìn)行預(yù)設(shè)就像上一章創(chuàng)建AVAudioPlayer類似.都是為了執(zhí)行底層Audio Queue初始化的必要過(guò)程.這個(gè)prepareToRecord方法還在給定的URL參數(shù)指定的位置創(chuàng)建一個(gè)文件，這樣就減少了錄制啟動(dòng)時(shí)的延時(shí)

音頻格式

AVFormatIDKeykey指定錄制格式,這里的除了kAudioFormatMPEG4AAC格式還有下面這些:

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'
};

這里的kAudioFormatLinearPCM會(huì)將為壓縮的音頻流寫(xiě)入到文件中,這就是原始數(shù)據(jù),保真度最高,當(dāng)然文件也最大, 選擇ACCkAudioFormatMPEG4AAC或者AppleIMA4kAudioFormatAppleLossless等格式會(huì)顯著縮小文件，還能保證音頻質(zhì)量.

注意：
指定的音頻格式一定要和文件寫(xiě)入的URL文件類型保持一致捎泻。如果錄制xxx.wav文件格式 是 Waveform Audio File Format(WAVE)的格式要求,即 低字節(jié)序、 LinePCM埋哟。 如果AVFormatIDKey指定的值不是kAudioFormatLinearPCM則會(huì)發(fā)生錯(cuò)誤笆豁。NSError 會(huì)返回如下錯(cuò)誤
The operation couldn’t be completed. (OSState error 1718449215.)

采樣率

上邊的代碼里AVSampleRateKey用于定義錄音器的采樣率. 采樣率定義了對(duì)輸入的模擬音頻信號(hào)每一秒內(nèi)的采樣數(shù). 如果使用低采樣率 比如8kHz,會(huì)導(dǎo)致粗粒度、AM廣播類型的錄制效果, 不過(guò)文件會(huì)比較小; 使用44.1kHz的采樣率(CD質(zhì)量的采樣率)會(huì)得到非常高質(zhì)量的內(nèi)容, 不過(guò)文件比較大. 至于使用什么樣的采樣率沒(méi)有明確的定義. 不過(guò)開(kāi)發(fā)者應(yīng)該盡量使用標(biāo)準(zhǔn)的采樣率赤赊，比如: 8000Hz闯狱、16 000Hz(16kHz)、22050Hz(22.05kHz)或 44100Hz(44.1kHz)砍鸠、當(dāng)然還有48000Hz和96000Hz ,(kHz代表千赫),超過(guò)48000或96000的采樣對(duì)人耳已經(jīng)沒(méi)有意義.最終是我們的耳朵在進(jìn)行判斷.（上一章說(shuō)了 人耳所能聽(tīng)到的聲音扩氢，最低的頻率是從20Hz起一直到最高頻率20kHz,錄音最好采用 x 2 倍的頻率）

通道數(shù)

AVNumberOfChannelsKey用于定義記錄音頻內(nèi)容的通道數(shù)。指定默認(rèn)值1 意味著使用單聲道錄制爷辱、設(shè)置2意味著使用立體聲錄制录豺。除非使用外部硬件進(jìn)行錄制遍尺，否則同窗應(yīng)該創(chuàng)建單聲道錄音牵现。 這里的通道數(shù)是指 錄制設(shè)備的輸入數(shù)量 可以理解為 麥克風(fēng) 內(nèi)置 或者外接麥克風(fēng)錄制比如 插入Apple耳機(jī) 里面的麥克風(fēng)。

以上是全面AVAudioRecorder的部分概念,AVAudioRecorder支持無(wú)限時(shí)長(zhǎng)錄制,還可以設(shè)置從未來(lái)某一時(shí)間點(diǎn)開(kāi)始錄制或指定時(shí)長(zhǎng)錄制

網(wǎng)絡(luò)流媒體處理

AVAudioPlayer音頻播放器只能播放本地文件五续，并且是一次性加載所有的音頻數(shù)據(jù)弟断，但我們有時(shí)候需要邊下載邊聽(tīng)怎么辦咏花？
AVAudioPlayer是不支持這種網(wǎng)絡(luò)流媒體形式的音頻播放，要播放這種網(wǎng)絡(luò)流媒體，我們需要使用AudioToolbox框架的音頻隊(duì)列服務(wù)Audio Queue Services昏翰。

音頻隊(duì)列服務(wù)分為3個(gè)部分:

• 3個(gè)緩沖器
• 1個(gè)緩沖隊(duì)列
• 1個(gè)回調(diào)

1. 下面是錄音的音頻隊(duì)列服務(wù)的工作原理:

2. 下面是播放音頻的音頻隊(duì)列服務(wù)的工作原理;

當(dāng)然處理這些不需要我們自己去寫(xiě)C語(yǔ)言函數(shù)實(shí)現(xiàn) 有個(gè)開(kāi)源庫(kù)FreeStreamer

FreeStreamer使用

#import <FreeStreamer/FreeStreamer.h>
- (void)viewDidLoad {
    [super viewDidLoad];
    [self initAudioStream];
    //播放網(wǎng)絡(luò)流媒體音頻
    [self.audioStream play];
}
/* 初始化網(wǎng)絡(luò)流媒體對(duì)象 */
- (void)initAudioStream{
    NSString *urlStr = @"http://sc1.111ttt.com/2016/1/02/24/195242042236.mp3";
    NSURL *url = [NSURL URLWithString:urlStr];
    //創(chuàng)建FSAudioStream對(duì)象
    self.audioStream = [[FSAudioStream alloc] initWithUrl:url];
    //設(shè)置播放錯(cuò)誤回調(diào)Block
    self.audioStream.onFailure = ^(FSAudioStreamError error, NSString *description){
          NSLog(@"播放過(guò)程中發(fā)生錯(cuò)誤苍匆，錯(cuò)誤信息：%@",description);
    };
    //設(shè)置播放完成回調(diào)Block
    self.audioStream.onCompletion = ^(){
          NSLog(@"播放完成!");
    };
    [self.audioStream setVolume:0.5];//設(shè)置聲音大小
}

有點(diǎn)跑遠(yuǎn)了 回到正題 本章將不會(huì)把這個(gè)寫(xiě)到demo中 請(qǐng)諒解

下面我們來(lái)寫(xiě)個(gè)AVAudioRecorder的Demo 完成上述功能

配置會(huì)話

首先創(chuàng)建以一個(gè)AVAudioRecorderDemo工程iOS平臺(tái)這些相信大家非常熟練了.

在AppDelegate里面導(dǎo)入#import <AVFoundation/AVFoundation.h>
寫(xiě)上設(shè)置如下代碼

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    AVAudioSession *session = [AVAudioSession sharedInstance];
    NSError *error;
    if (![session setCategory:AVAudioSessionCategoryPlayAndRecord error:&error]) {
        NSLog(@"Category Error: %@",[error localizedDescription]);
    }

    //激活會(huì)話
    if (![session setActive:YES error:&error]) {
        NSLog(@"Activation Error: %@",[error localizedDescription]);
    }
    return YES;
}

這AVAudioSessionCategoryPlayAndRecord是上一章說(shuō)的那幾種Category,我們需要錄音+播放功能

下一步 配置 plist文件訪問(wèn)權(quán)限信息

然后選擇SourceCode

填寫(xiě)上

<!-- ?? Microphone -->
<key>NSMicrophoneUsageDescription</key>
<string>$(PRODUCT_NAME) microphone use</string>

上邊這些是為了訪問(wèn)本地授權(quán), 記得授權(quán)如果第一次被拒就必須讓用戶手動(dòng) 到通用-設(shè)置里面去配置否則將永遠(yuǎn)不好使哈。如果不寫(xiě)這種本地授權(quán) 程序應(yīng)該會(huì) crash

錄音代碼實(shí)現(xiàn)

首先我們來(lái)封裝一個(gè)類起名叫BDRecoder吧. 這里類我們讓它負(fù)責(zé)所有 音頻錄制棚菊、暫停錄制浸踩、保存錄制文件等功能 并有回調(diào)函數(shù)等block. BDRecoder.h看起來(lái)像下面這樣, 這里后續(xù)完善的話可以加個(gè)代理 表示錄制過(guò)程中意外中斷或者線路切換等邏輯.

//
//  BDRecorder.h
//  AVAudioRecorderDemo
//
//  Created by sunyazhou on 2017/3/29.
//  Copyright ? 2017年 Baidu, Inc. All rights reserved.
//
#import <Foundation/Foundation.h>
#import <AVFoundation/AVFoundation.h>
@class MemoModel;
//錄音停止的回調(diào)
typedef void (^BDRecordingStopCompletionHanlder)(BOOL);
//保存錄音文件完成的回調(diào)
typedef void (^BDRecordingSaveCompletionHanlder)(BOOL, id);
@interface BDRecorder : NSObject
/**
 * 外部獲取當(dāng)前錄制的時(shí)間
 * 小時(shí):分鐘:秒  當(dāng)然后續(xù)可以加微秒和毫秒哈就是格式字符串 00:03:02 這樣
 */
@property (nonatomic, readonly) NSString *formattedCurrentTime;
- (BOOL)record; //開(kāi)始錄音
- (void)pause;  //暫停錄音
- (void)stopWithCompletionHandler:(BDRecordingStopCompletionHanlder)handler;
- (void)saveRecordingWithName:(NSString *)name
            completionHandler:(BDRecordingSaveCompletionHanlder)handler;
/**
 回放錄制的文件
 @param memo 備忘錄文件model 放著當(dāng)前播放的model
 @return 是否播放成功
 */
- (BOOL)playbackURL:(MemoModel *)memo;
@end

BDRecoder.m

//
//  BDRecorder.m
//  AVAudioRecorderDemo
//
//  Created by sunyazhou on 2017/3/29.
//  Copyright ? 2017年 Baidu, Inc. All rights reserved.
//
#import "BDRecorder.h"
#import "MemoModel.h"
@interface BDRecorder () <AVAudioRecorderDelegate>
@property (nonatomic, strong) AVAudioPlayer *player;
@property (nonatomic, strong) AVAudioRecorder *recorder;
@property (nonatomic, strong) BDRecordingStopCompletionHanlder completionHandler;
@end
@implementation BDRecorder
- (instancetype)init {
    self = [super init];
    if (self) {
        NSString *temDir = NSTemporaryDirectory();
        NSString *filePath = [temDir stringByAppendingPathComponent:@"test1.caf"];
        NSURL *fileURL = [NSURL fileURLWithPath:filePath];
        NSDictionary *setting = @{AVFormatIDKey: @(kAudioFormatAppleIMA4),
                                  AVSampleRateKey: @44100.0f,
                                  AVNumberOfChannelsKey: @1,
                                  AVEncoderBitDepthHintKey: @16,
                                  AVEncoderAudioQualityKey: @(AVAudioQualityMedium)
                                  };
        NSError *error;
        self.recorder = [[AVAudioRecorder alloc] initWithURL:fileURL settings:setting error:&error];
        if (self.recorder) {
            self.recorder.delegate = self;
            [self.recorder prepareToRecord];
        } else {
            NSLog(@"Create Recorder Error: %@",[error localizedDescription]);
        } 
    }
    return self;
}
- (BOOL)record {
    return [self.recorder record];
}
- (void)pause {
    [self.recorder pause];
}
- (void)stopWithCompletionHandler:(BDRecordingStopCompletionHanlder)handler {
    self.completionHandler = handler;
    [self.recorder stop];
}
- (void)saveRecordingWithName:(NSString *)name
            completionHandler:(BDRecordingSaveCompletionHanlder)handler {
    NSTimeInterval timestamp = [NSDate timeIntervalSinceReferenceDate];
    NSString *filename = [NSString stringWithFormat:@"%@-%f.caf", name, timestamp];
    NSString *docDir = [self documentsDirectory];
    NSString *destPath = [docDir stringByAppendingPathComponent:filename];
    NSURL *srcURL = self.recorder.url;
    NSURL *destURL = [NSURL fileURLWithPath:destPath];
    NSError *error;
    BOOL success = [[NSFileManager defaultManager] copyItemAtURL:srcURL toURL:destURL error:&error];
    if (success) {
        MemoModel *model = [MemoModel memoWithTitle:name url:destURL];
        handler(YES, model);
    }

}
- (NSString *)documentsDirectory {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [paths objectAtIndex:0];
}
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder
                           successfully:(BOOL)flag {
    if (self.completionHandler) { self.completionHandler(flag); }
}
@end

這里的self.completionHandler當(dāng)外部調(diào)用stopWithCompletionHandler的時(shí)候暫存一下block是為了錄音完成時(shí)告訴外部通知一下以便于可以彈出一個(gè)UIAlertView去顯示保存等操作

當(dāng)停止錄音, 進(jìn)入語(yǔ)音備忘階段命名階段時(shí) 讓外部調(diào)用saveRecordingWithName:completionHandler傳入文件的命名,然后我們通過(guò)self.recorder.url獲取到URL并且copy到tmp里面是目錄并命名

下一步要實(shí)現(xiàn)playbackURL: 這里面有個(gè)MemoModel參數(shù)的對(duì)象,
這個(gè)MemoModel是一個(gè)對(duì)象model放著 文件name、url…

#import <Foundation/Foundation.h>
@interface MemoModel : NSObject <NSCopying>
@property (copy, nonatomic, readonly) NSString *title;
@property (strong, nonatomic, readonly) NSURL *url;
@property (copy, nonatomic, readonly) NSString *dateString;
@property (copy, nonatomic, readonly) NSString *timeString;
+ (instancetype)memoWithTitle:(NSString *)title url:(NSURL *)url;
- (BOOL)deleteMemo;
@end
//具體實(shí)現(xiàn)請(qǐng)參考我的最終demo

實(shí)現(xiàn)播放部分需要?jiǎng)?chuàng)建播放器 這里就簡(jiǎn)單創(chuàng)建一下AVAudioPlayer

/**
 回放錄制的文件

 @param memo 備忘錄文件model 放著當(dāng)前播放的model
 @return 是否播放成功
 */
- (BOOL)playbackURL:(MemoModel *)memo {
    [self.player stop];
    self.player = [[AVAudioPlayer alloc] initWithContentsOfURL:memo.url error:nil];
    if (self.player) {
        [self.player prepareToPlay];
        return YES;
    }
    return NO;
}

這里通過(guò)memo.url 給當(dāng)前播放器播放, 這里就簡(jiǎn)單實(shí)現(xiàn)一下 如果需要復(fù)雜實(shí)現(xiàn)可以參考我上一章講解的AVAudioPlayer

最后把顯示事件部分的代碼加上

/**
 * 外部獲取當(dāng)前錄制的時(shí)間
 * 小時(shí):分鐘:秒  當(dāng)然后續(xù)可以加微秒和毫秒哈就是格式字符串 00:03:02 這樣
 */
@property (nonatomic, readonly) NSString *formattedCurrentTime;

這里我們需要復(fù)寫(xiě)formattedCurrentTimeget方法獲取時(shí)間格式例如: 00:00:00

/**
 返回當(dāng)前錄制的時(shí)間格式 HH:mm:ss
 @return 返回組裝好的字符串
 */
- (NSString *)formattedCurrentTime {
    NSUInteger time = (NSUInteger)self.recorder.currentTime;
    NSInteger hours = (time / 3600);
    NSInteger minutes = (time / 60) % 60;
    NSInteger seconds = time % 60;

    NSString *format = @"%02i:%02i:%02i";
    return [NSString stringWithFormat:format, hours, minutes, seconds];
}

上邊大致是封裝BDRecorder的過(guò)程

下面是對(duì)ViewControllerUI的設(shè)置, 設(shè)置好時(shí)間格式 我們需要在ViewController里 自己搞個(gè)定時(shí)器去更新錄制的時(shí)間在UI上的顯示, 因?yàn)?code>self.recorder.currentTime是只讀熟悉 沒(méi)提供set方法 所以我們也無(wú)法用KVO監(jiān)聽(tīng)recorder的屬性變化.

代碼如下:

//
//  ViewController.m
//  AVAudioRecorderDemo
//
//  Created by sunyazhou on 2017/3/28.
//  Copyright ? 2017年 Baidu, Inc. All rights reserved.
//
#import "ViewController.h"
#import <Masonry/Masonry.h>
#import <AVFoundation/AVFoundation.h>
#import "BDRecorder.h"
#import "LevelMeterView.h"
#import "MemoModel.h"
#import "MemoCell.h"
#import "LevelPair.h"
#define MEMOS_ARCHIVE    @"memos.archive"
@interface ViewController () <UITableViewDelegate, UITableViewDataSource>
@property (nonatomic, strong) NSMutableArray <MemoModel *>*memos;
@property (nonatomic, strong) BDRecorder *recorder;
@property (nonatomic, strong) NSTimer *timer;
@property (nonatomic, strong) CADisplayLink *levelTimer;
@property (weak, nonatomic) IBOutlet UIView *containerView;
@property (weak, nonatomic) IBOutlet UIButton *recordButton;
@property (weak, nonatomic) IBOutlet UIButton *stopButton;
@property (weak, nonatomic) IBOutlet UILabel *timeLabel;
@property (weak, nonatomic) IBOutlet LevelMeterView *levelMeterView;
@property (weak, nonatomic) IBOutlet UITableView *tableview;
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];

    self.recorder = [[BDRecorder alloc] init];
    self.memos = [NSMutableArray array];
    self.stopButton.enabled = NO;

    UIImage *recordImage = [[UIImage imageNamed:@"record"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    UIImage *pauseImage = [[UIImage imageNamed:@"pause"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    UIImage *stopImage = [[UIImage imageNamed:@"stop"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    [self.recordButton setImage:recordImage forState:UIControlStateNormal];
    [self.recordButton setImage:pauseImage forState:UIControlStateSelected];
    [self.stopButton setImage:stopImage forState:UIControlStateNormal];

    NSData *data = [NSData dataWithContentsOfURL:[self archiveURL]];
    if (!data) {
        _memos = [NSMutableArray array];
    } else {
        _memos = [NSKeyedUnarchiver unarchiveObjectWithData:data];
    }

    [self.tableview registerNib:[UINib nibWithNibName:@"MemoCell" bundle:[NSBundle mainBundle]] forCellReuseIdentifier:@"MemoCell"];

    [self layoutSubveiws];
}

- (void)layoutSubveiws{
    [self.containerView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view.mas_top).offset(30);
        make.left.equalTo(self.view.mas_left).offset(20);
        make.right.equalTo(self.view.mas_right).offset(-20);
        make.centerX.equalTo(self.view.mas_centerX);
        make.bottom.equalTo(self.tableview.mas_top).offset(-50);
    }];

    [self.tableview mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.right.bottom.equalTo(self.view);
        make.top.equalTo(self.view.mas_top).offset(200);
    }];

    [self.timeLabel mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.left.right.equalTo(self.containerView);
        make.centerX.equalTo(self.containerView.mas_centerX);
        make.height.equalTo(@25);
    }];

    [self.recordButton mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.equalTo(self.containerView.mas_left);
        make.bottom.equalTo(self.containerView.mas_bottom);
        make.width.height.equalTo(@71);
    }];

    [self.stopButton mas_makeConstraints:^(MASConstraintMaker *make) {
        make.right.equalTo(self.containerView.mas_right);
        make.bottom.equalTo(self.containerView.mas_bottom);
        make.width.height.equalTo(@71);
    }];

    [self.levelMeterView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.right.equalTo(self.view);
        make.height.equalTo(@30);
        make.bottom.equalTo(self.tableview.mas_top);
    }];
}
- (void)startTimer {
    [self.timer invalidate];
    self.timer = [NSTimer timerWithTimeInterval:0.5
                                         target:self
                                     selector:@selector(updateTimeDisplay)
                                       userInfo:nil
                                        repeats:YES];
    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}
- (void)stopTimer {
    [self.timer invalidate];
    self.timer = nil;
}
- (void)updateTimeDisplay {
    self.timeLabel.text = self.recorder.formattedCurrentTime;
}
- (void)startMeterTimer {
    [self.levelTimer invalidate];
    self.levelTimer = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateMeter)];
//    if ([self.levelTimer respondsToSelector:@selector(setPreferredFramesPerSecond:)]) {
//        self.levelTimer.preferredFramesPerSecond = 5;
//    } else {
    self.levelTimer.frameInterval = 5;
//    }
    [self.levelTimer addToRunLoop:[NSRunLoop currentRunLoop]
                          forMode:NSRunLoopCommonModes];

}
- (void)stopMeterTimer {
    [self.levelTimer invalidate];
    self.levelTimer = nil;
    [self.levelMeterView resetLevelMeter];
}
- (void)updateMeter {
    LevelPair *levels = [self.recorder levels];
    self.levelMeterView.level = levels.level;
    self.levelMeterView.peakLevel = levels.peakLevel;
    [self.levelMeterView setNeedsDisplay];

}
#pragma mark -
#pragma mark - UITableViewDelegate
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.memos.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    MemoCell *cell = [tableView dequeueReusableCellWithIdentifier:@"MemoCell"];
    cell.model = self.memos[indexPath.row];
    return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    MemoModel *model = self.memos[indexPath.row];
    [self.recorder playbackURL:model];
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
    return YES;
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        MemoModel *memo = self.memos[indexPath.row];
        [memo deleteMemo];
        [self.memos removeObjectAtIndex:indexPath.row];
        [self saveMemos];
        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
    }
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return 80;
}
#pragma mark - event response 所有觸發(fā)的事件響應(yīng) 按鈕统求、通知检碗、分段控件等
- (IBAction)record:(UIButton *)sender {
    self.stopButton.enabled = YES;
    if ([sender isSelected]) {
        [self stopMeterTimer];
        [self stopTimer];
        [self.recorder pause];
    } else {
        [self startMeterTimer];
        [self startTimer];
        [self.recorder record];
    }
    [sender setSelected:![sender isSelected]];
}
- (IBAction)stopRecording:(UIButton *)sender {
    [self stopMeterTimer];
    self.recordButton.selected = NO;
    self.stopButton.enabled = NO;
    [self.recorder stopWithCompletionHandler:^(BOOL result) {
        double delayInSeconds = 0.01;
        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t) (delayInSeconds * NSEC_PER_SEC));
        dispatch_after(popTime, dispatch_get_main_queue(), ^{
            [self showSaveDialog];
        });
    }];
}
- (void)showSaveDialog {
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"保存錄音" message:@"輸入名稱" preferredStyle:UIAlertControllerStyleAlert];
    [alertController addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
       textField.placeholder = @"我的錄音";
    }];
    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil];
    UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        NSString *filename = [alertController.textFields.firstObject text];
        [self.recorder saveRecordingWithName:filename completionHandler:^(BOOL success, id object) {
            if (success) {
                [self.memos insertObject:object atIndex:0];
                [self saveMemos];
                [self.tableview reloadData];
            } else {
                NSLog(@"Error saving file: %@", [object localizedDescription]);
            }
        }];
    }];
    [alertController addAction:cancelAction];
    [alertController addAction:okAction];

    [self presentViewController:alertController animated:YES completion:nil];
}
#pragma mark - Memo Archiving
//保存?zhèn)渫沵odel  這里簡(jiǎn)單用歸檔的方式存儲(chǔ)一下
- (void)saveMemos {
    NSData *fileData = [NSKeyedArchiver archivedDataWithRootObject:self.memos];
    [fileData writeToURL:[self archiveURL] atomically:YES];
}
//存儲(chǔ)歸檔的路徑
- (NSURL *)archiveURL {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsDir = [paths objectAtIndex:0];
    NSString *archivePath = [docsDir stringByAppendingPathComponent:MEMOS_ARCHIVE];
    return [NSURL fileURLWithPath:archivePath];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

代碼稍稍有點(diǎn)長(zhǎng) 我簡(jiǎn)單說(shuō)一下 大家可以參照最終的demo

文章最終的Demo獲取：加iOS高級(jí)技術(shù)交流群：624212887码邻，獲取Demo

@property (nonatomic, strong) NSMutableArray <MemoModel *>*memos;
@property (nonatomic, strong) BDRecorder *recorder;

聲明一個(gè)數(shù)組 存放需要播放的model對(duì)象信息 名稱 文件url折剃、日期等

@property (nonatomic, strong) NSTimer *timer;
@property (nonatomic, strong) CADisplayLink *levelTimer;

一個(gè)timer用于 刷新錄制時(shí)間
levelTimer用于刷新錄制的視波圖也叫Audio Metering對(duì)音頻進(jìn)行計(jì)量

在BDRecorder中增加了

- (LevelPair *)levels {
    [self.recorder updateMeters];
    float avgPower = [self.recorder averagePowerForChannel:0];
    float peakPower = [self.recorder peakPowerForChannel:0];
    float linearLevel = [self.meterTable valueForPower:avgPower];
    float linearPeak = [self.meterTable valueForPower:peakPower];
    return [LevelPair levelsWithLevel:linearLevel peakLevel:linearPeak];
}

這兩個(gè)方法

1\. averagePowerForChannel取出波谷平均值
2\. peakPowerForChannel取出波峰 

兩個(gè)方法都會(huì)返回一個(gè)用于表示聲音分貝(dB)等級(jí)的浮點(diǎn)值. 這個(gè)值的表示范圍0dB(fullscale) ~ -160dB 0dB最大 -160dB最小

開(kāi)啟音頻計(jì)量 (需要在BDRecorder中開(kāi)啟, 如下代碼) 會(huì)帶來(lái)很多額外的開(kāi)銷，但我覺(jué)得還是很劃算的 畢竟要顯示視覺(jué)效果才是王道.
如果meteringEnabled開(kāi)啟則音頻錄音器就會(huì)對(duì)捕捉到的音頻樣本進(jìn)行分貝計(jì)算像屋。

開(kāi)啟音頻計(jì)量(Audio Metering)方法:

self.recorder.meteringEnabled = YES;

更新前調(diào)用了如下代碼

- (LevelPair *)levels {
    [self.recorder updateMeters];
    ...
}

每當(dāng)讀取值之前需要調(diào)用[self.recorder updateMeters]方法才能獲取到最新值怕犁，否則可能獲取的不夠精確

然后 使用MeterTable類 聲明的函數(shù)valueForPower: 把上邊兩個(gè)閥值 轉(zhuǎn)成線性運(yùn)算

就是分貝值從對(duì)數(shù)形式的-160 ~ 0范圍轉(zhuǎn)換為線性0到1的形式.

//
//  MeterTable.m
//  AVAudioRecorderDemo
//
//  Created by sunyazhou on 2017/4/5.
//  Copyright ? 2017年 Baidu, Inc. All rights reserved.
//
#import "MeterTable.h"
#define MIN_DB -60.0f
#define TABLE_SIZE 300
@implementation MeterTable {
    float _scaleFactor;
    NSMutableArray *_meterTable;
}
- (id)init {
    self = [super init];
    if (self) {
        float dbResolution = MIN_DB / (TABLE_SIZE - 1);

        _meterTable = [NSMutableArray arrayWithCapacity:TABLE_SIZE];
        _scaleFactor = 1.0f / dbResolution;

        float minAmp = dbToAmp(MIN_DB);
        float ampRange = 1.0 - minAmp;
        float invAmpRange = 1.0 / ampRange;

        for (int i = 0; i < TABLE_SIZE; i++) {
            float decibels = i * dbResolution;
            float amp = dbToAmp(decibels);
            float adjAmp = (amp - minAmp) * invAmpRange;
            _meterTable[i] = @(adjAmp);
        }
    }
    return self;
}
float dbToAmp(float dB) {
    return powf(10.0f, 0.05f * dB);
}
- (float)valueForPower:(float)power {
    if (power < MIN_DB) {
        return 0.0f;
    } else if (power >= 0.0f) {
        return 1.0f;
    } else {
        int index = (int) (power * _scaleFactor);
        return [_meterTable[index] floatValue];
    }
}
@end

這個(gè)類創(chuàng)建了一個(gè)數(shù)組_meterTable保存從計(jì)算前的分貝數(shù)到使用一定級(jí)別分貝解析之后的轉(zhuǎn)換結(jié)果, 這里使用的解析率-0.2dB, 解析等級(jí)可以通過(guò)MIN_DB TABLE_SIZE這兩個(gè)宏的值來(lái)修改,每個(gè)分貝值都調(diào)用dbToAmp:函數(shù)轉(zhuǎn)換為線性范圍內(nèi)的值,使其處于0(-60dB) ~ 1()范圍內(nèi), 之后由這些范圍內(nèi)的值構(gòu)成平行曲線,開(kāi)平方計(jì)算并保存到內(nèi)部查找表格中. 然后如果外部需要可以調(diào)用valueForPower:來(lái)獲取.

然后保存到LevelPair的實(shí)例對(duì)象返回 這個(gè)實(shí)例很簡(jiǎn)單存放兩個(gè)值一個(gè)level一個(gè)peakLevel

@interface LevelPair : NSObject
@property (nonatomic, readonly) float level;
@property (nonatomic, readonly) float peakLevel;
+ (instancetype)levelsWithLevel:(float)level peakLevel:(float)peakLevel;
- (instancetype)initWithLevel:(float)level peakLevel:(float)peakLevel;
@end

在ViewController中顯示相關(guān)的UI

- (void)startTimer {
    [self.timer invalidate];
    self.timer = [NSTimer timerWithTimeInterval:0.5
                                         target:self
                                     selector:@selector(updateTimeDisplay)
                                       userInfo:nil
                                        repeats:YES];
    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}
- (void)stopTimer {
    [self.timer invalidate];
    self.timer = nil;
}
- (void)updateTimeDisplay {
    self.timeLabel.text = self.recorder.formattedCurrentTime;
}
- (void)startMeterTimer {
    [self.levelTimer invalidate];
    self.levelTimer = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateMeter)];
//    if ([self.levelTimer respondsToSelector:@selector(setPreferredFramesPerSecond:)]) {
//        self.levelTimer.preferredFramesPerSecond = 5;
//    } else {
    self.levelTimer.frameInterval = 5;
//    }
    [self.levelTimer addToRunLoop:[NSRunLoop currentRunLoop]
                          forMode:NSRunLoopCommonModes];

}
- (void)stopMeterTimer {
    [self.levelTimer invalidate];
    self.levelTimer = nil;
    [self.levelMeterView resetLevelMeter];
}
- (void)updateMeter {
    LevelPair *levels = [self.recorder levels];
    self.levelMeterView.level = levels.level;
    self.levelMeterView.peakLevel = levels.peakLevel;
    [self.levelMeterView setNeedsDisplay];
}

用于定時(shí)器的處理

事件的相關(guān)響應(yīng)

#pragma mark - event response 所有觸發(fā)的事件響應(yīng) 按鈕、通知开睡、分段控件等
- (IBAction)record:(UIButton *)sender {
    self.stopButton.enabled = YES;
    if ([sender isSelected]) {
        [self stopMeterTimer];
        [self stopTimer];
        [self.recorder pause];
    } else {
        [self startMeterTimer];
        [self startTimer];
        [self.recorder record];
    }
    [sender setSelected:![sender isSelected]];
}
- (IBAction)stopRecording:(UIButton *)sender {
    [self stopMeterTimer];
    self.recordButton.selected = NO;
    self.stopButton.enabled = NO;
    [self.recorder stopWithCompletionHandler:^(BOOL result) {
        double delayInSeconds = 0.01;
        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t) (delayInSeconds * NSEC_PER_SEC));
        dispatch_after(popTime, dispatch_get_main_queue(), ^{
            [self showSaveDialog];
        });
    }];
}

這里保存數(shù)據(jù)使用的是歸檔方式

BDRecorder沒(méi)有 處理意外中斷等情況 比如外接麥克風(fēng) 和音頻意外來(lái)電等因苹，如果需要處理 就可以在BDRecorder中聲明幾個(gè)代理監(jiān)聽(tīng)音頻回話的那幾個(gè)通知就可以了 這里出于學(xué)習(xí)為目的就簡(jiǎn)單寫(xiě)到這里吧，如果大家需求強(qiáng)烈我可以回頭補(bǔ)上并開(kāi)源篇恒。

很多人糾結(jié)如何根據(jù)波形繪制更好的圖 我這里是借助本書(shū)作者的demo完成相關(guān)波形處理的視圖扶檐。

#import "LevelMeterView.h"
#import "LevelMeterColorThreshold.h"
@interface LevelMeterView ()
@property (nonatomic) NSUInteger ledCount;
@property (strong, nonatomic) UIColor *ledBackgroundColor;
@property (strong, nonatomic) UIColor *ledBorderColor;
@property (nonatomic, strong) NSArray *colorThresholds;
@end
@implementation LevelMeterView
- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self setupView];
    }
    return self;
}
- (id)initWithCoder:(NSCoder *)coder {
    self = [super initWithCoder:coder];
    if (self) {
        [self setupView];
    }
    return self;
}
- (void)setupView {

    self.backgroundColor = [UIColor clearColor];

    _ledCount = 20;

    _ledBackgroundColor = [UIColor colorWithWhite:0.0f alpha:0.35f];
    _ledBorderColor = [UIColor blackColor];

    UIColor *greenColor = [UIColor colorWithRed:0.458 green:1.000 blue:0.396 alpha:1.000];
    UIColor *yellowColor = [UIColor colorWithRed:1.000 green:0.930 blue:0.315 alpha:1.000];
    UIColor *redColor = [UIColor colorWithRed:1.000 green:0.325 blue:0.329 alpha:1.000];

    _colorThresholds = @[[LevelMeterColorThreshold colorThresholdWithMaxValue:0.5 color:greenColor name:@"green"],
                         [LevelMeterColorThreshold colorThresholdWithMaxValue:0.8 color:yellowColor name:@"yellow"],
                         [LevelMeterColorThreshold colorThresholdWithMaxValue:1.0 color:redColor name:@"red"]];
}

- (void)drawRect:(CGRect)rect {

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextTranslateCTM(context, 0, CGRectGetHeight(self.bounds));
    CGContextRotateCTM(context, (CGFloat) -M_PI_2);
    CGRect bounds = CGRectMake(0., 0., [self bounds].size.height, [self bounds].size.width);

    CGFloat lightMinValue = 0.0f;

    NSInteger peakLED = -1;

    if (self.peakLevel > 0.0f) {
        peakLED = self.peakLevel * self.ledCount;
        if (peakLED >= self.ledCount) {
            peakLED = self.ledCount - 1;
        }
    }

    for (int ledIndex = 0; ledIndex < self.ledCount; ledIndex++) {

        UIColor *ledColor = [self.colorThresholds[0] color];

        CGFloat ledMaxValue = (CGFloat) (ledIndex + 1) / self.ledCount;

        for (int colorIndex = 0; colorIndex < self.colorThresholds.count - 1; colorIndex++) {
            LevelMeterColorThreshold *currThreshold = self.colorThresholds[colorIndex];
            LevelMeterColorThreshold *nextThreshold = self.colorThresholds[colorIndex + 1];
            if (currThreshold.maxValue <= ledMaxValue) {
                ledColor = nextThreshold.color;
            }
        }

        CGFloat height = CGRectGetHeight(bounds);
        CGFloat width = CGRectGetWidth(bounds);

        CGRect ledRect = CGRectMake(0.0f, height * ((CGFloat) ledIndex / self.ledCount), width, height * (1.0f / self.ledCount));

        // Fill background color
        CGContextSetFillColorWithColor(context, self.ledBackgroundColor.CGColor);
        CGContextFillRect(context, ledRect);

        // Draw Light
        CGFloat lightIntensity;
        if (ledIndex == peakLED) {
            lightIntensity = 1.0f;
        } else {
            lightIntensity = clamp((self.level - lightMinValue) / (ledMaxValue - lightMinValue));
        }

        UIColor *fillColor = nil;
        if (lightIntensity == 1.0f) {
            fillColor = ledColor;
        } else if (lightIntensity > 0.0f) {
            CGColorRef color = CGColorCreateCopyWithAlpha([ledColor CGColor], lightIntensity);
            fillColor = [UIColor colorWithCGColor:color];
            CGColorRelease(color);
        }

        CGContextSetFillColorWithColor(context, fillColor.CGColor);
        UIBezierPath *fillPath = [UIBezierPath bezierPathWithRoundedRect:ledRect cornerRadius:2.0f];
        CGContextAddPath(context, fillPath.CGPath);

        // Stroke border
        CGContextSetStrokeColorWithColor(context, self.ledBorderColor.CGColor);
        UIBezierPath *strokePath = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(ledRect, 0.5, 0.5) cornerRadius:2.0f];
        CGContextAddPath(context, strokePath.CGPath);

        CGContextDrawPath(context, kCGPathFillStroke);

        lightMinValue = ledMaxValue;
    }
}

CGFloat clamp(CGFloat intensity) {
    if (intensity < 0.0f) {
        return 0.0f;
    } else if (intensity >= 1.0) {
        return 1.0f;
    } else {
        return intensity;
    }
}

- (void)resetLevelMeter {
    self.level = 0.0f;
    self.peakLevel = 0.0f;
    [self setNeedsDisplay];
}
@end

這里給出了level和peak的閥值 有很多第三方開(kāi)源的view大家可以自行研究一下 很簡(jiǎn)單 就是把相關(guān)閥值量化的過(guò)程。

總結(jié)

AVAudioRecorder 的學(xué)習(xí)還算完整的搞完了,隨時(shí)記錄一下學(xué)習(xí)內(nèi)容和技術(shù)知識(shí)胁艰。

文章最終的Demo獲瓤钪：加iOS高級(jí)技術(shù)交流群：624212887，獲取Demo,以及更多iOS學(xué)習(xí)資料

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