AVFoundation

• 照片/視頻捕捉功能
• 小視頻/直播
• 核心類在iOS和macOS上是一致的赊舶，macOS上提供了一個(gè)截屏功能

捕捉會(huì)話

• ????????捕捉會(huì)話: AVCaptureSession
• 捕捉設(shè)備????????: AVCaptureDevice.如麥克風(fēng)跳座、攝像頭
• ????????????????????????捕捉設(shè)備輸入: AVCaptureDeviceInput
• 捕捉設(shè)備輸出：AVCaptureOutput 抽象類
  • AVCaptureStillImageOutput 靜態(tài)圖片
  • AVCaptureMovieFileOutput 視頻文件
  • AVCaptureAudioDataOutput 音頻數(shù)據(jù)
  • AVCaptureVideoDataOutput 視頻數(shù)據(jù)
• 捕捉連接：AVCaptureConnection 根據(jù)捕捉的輸出設(shè)備的渲染媒體類型自動(dòng)建立連接
• 捕捉預(yù)覽： AVCaptureVideoPreviewLayer

視頻預(yù)覽圖層

//私有方法 用于支持該類定義的不同觸摸處理方法。 將屏幕坐標(biāo)系上的觸控點(diǎn)轉(zhuǎn)換為攝像頭上的坐標(biāo)系點(diǎn)
- (CGPoint)captureDevicePointForPoint:(CGPoint)point {
    AVCaptureVideoPreviewLayer *layer =
        (AVCaptureVideoPreviewLayer *)self.layer;
    return [layer captureDevicePointOfInterestForPoint:point];
    /*
     AVCaptureVideoPreviewLayer.定義了兩個(gè)方法，攝像頭/屏幕坐標(biāo)轉(zhuǎn)換躁愿；
     captureDevicePointOfInterestForPoint ：獲取屏幕坐標(biāo)系的CGPoint數(shù)據(jù)，返回轉(zhuǎn)換得到攝像頭設(shè)備坐標(biāo)系的CGPoint數(shù)據(jù)
     pointForCaptureDevicePointOfInterest : 獲取攝像頭坐標(biāo)系的CGPoint數(shù)據(jù)辫樱，返回轉(zhuǎn)換得到的屏幕坐標(biāo)系CGPoint數(shù)據(jù)
     */
}

視頻捕捉關(guān)于AVCaputureSession的配置

• ????設(shè)置Session
  • 初始化
  • 設(shè)置分辨率
  • 配置輸入設(shè)備(注意轉(zhuǎn)換為AVCaptureDeviceInput)
  • 配置輸入設(shè)備包括音頻輸入彭沼、視頻輸入
  • 配置輸出(靜態(tài)圖像輸出褐奴、視頻文件輸出)
  • 在為session添加輸入輸出時(shí)按脚，注意一定判斷是否能添加。(攝像頭并不隸屬于任何一個(gè)App它是公共設(shè)備)

- (BOOL)setupSession:(NSError **)error {

    
    //創(chuàng)建捕捉會(huì)話敦冬。AVCaptureSession 是捕捉場景的中心樞紐
    self.captureSession = [[AVCaptureSession alloc]init];
    
    /*
     AVCaptureSessionPresetHigh
     AVCaptureSessionPresetMedium
     AVCaptureSessionPresetLow
     AVCaptureSessionPreset640x480
     AVCaptureSessionPreset1280x720
     AVCaptureSessionPresetPhoto
     */
    //設(shè)置圖像的分辨率
    self.captureSession.sessionPreset = AVCaptureSessionPresetHigh;
    
    /** 添加視頻設(shè)備  */
    
    //拿到默認(rèn)視頻捕捉設(shè)備 iOS系統(tǒng)返回后置攝像頭
    AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    //將捕捉設(shè)備封裝成AVCaptureDeviceInput
    //注意：為會(huì)話添加捕捉設(shè)備辅搬，必須將設(shè)備封裝成AVCaptureDeviceInput對(duì)象
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:error];
    
    //判斷videoInput是否有效
    if (videoInput)
    {
        //canAddInput：測試是否能被添加到會(huì)話中。攝像頭是公共設(shè)備脖旱，不隸屬于任何一個(gè)app堪遂，可能其他app也在使用
        if ([self.captureSession canAddInput:videoInput])
        {
            //將videoInput 添加到 captureSession中
            [self.captureSession addInput:videoInput];
            //記錄當(dāng)前活躍設(shè)備
            self.activeVideoInput = videoInput;
        }
    }else
    {
        return NO;
    }
    
    /** 添加音頻設(shè)備  */
    
    //選擇默認(rèn)音頻捕捉設(shè)備 即返回一個(gè)內(nèi)置麥克風(fēng)
    AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
    
    //為這個(gè)設(shè)備創(chuàng)建一個(gè)捕捉設(shè)備輸入
    AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:error];
   
    //判斷audioInput是否有效
    if (audioInput) {
        
        //canAddInput：測試是否能被添加到會(huì)話中
        if ([self.captureSession canAddInput:audioInput])
        {
            //將audioInput 添加到 captureSession中
            [self.captureSession addInput:audioInput];
            //麥克風(fēng)就一個(gè)，無須記錄
        }
    }else
    {
        return NO;
    }

    /** 設(shè)置輸出：照片萌庆、視頻文件 */
    
    //AVCaptureStillImageOutput 實(shí)例 從攝像頭捕捉靜態(tài)圖片
    self.imageOutput = [[AVCaptureStillImageOutput alloc]init];
    
    //配置字典：希望捕捉到JPEG格式的圖片（存儲(chǔ)格式）
    self.imageOutput.outputSettings = @{AVVideoCodecKey:AVVideoCodecJPEG};
    
    //輸出連接 判斷是否可用溶褪，可用則添加到輸出連接中去
    if ([self.captureSession canAddOutput:self.imageOutput])
    {
        [self.captureSession addOutput:self.imageOutput];
        
    }
    
    
    //創(chuàng)建一個(gè)AVCaptureMovieFileOutput 實(shí)例，用于將Quick Time 電影錄制到文件系統(tǒng)
    self.movieOutput = [[AVCaptureMovieFileOutput alloc]init];
    
    //輸出連接 判斷是否可用踊兜，可用則添加到輸出連接中去
    if ([self.captureSession canAddOutput:self.movieOutput])
    {
        [self.captureSession addOutput:self.movieOutput];
    }
    
    //初始化視頻隊(duì)列
    self.videoQueue = dispatch_queue_create("bear.VideoQueue", NULL);
    
    return YES;
}

- (void)startSession {

    //檢查是否處于運(yùn)行狀態(tài),注意取反
    if (![self.captureSession isRunning])
    {
        //使用同步調(diào)用會(huì)損耗一定的時(shí)間竿滨，則用異步的方式處理
        dispatch_async(self.videoQueue, ^{
            [self.captureSession startRunning];
        });
        
    }
}

- (void)stopSession {
    
    //檢查是否處于運(yùn)行狀態(tài)
    if ([self.captureSession isRunning])
    {
        //使用異步方式，停止運(yùn)行
        dispatch_async(self.videoQueue, ^{
            [self.captureSession stopRunning];
        });
    }

}

實(shí)現(xiàn)前后攝像頭的改變

#pragma mark - Device Configuration   配置攝像頭支持的方法
//尋找指定的攝像頭設(shè)備
- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position {
    
    //獲取可用視頻設(shè)備
    NSArray *devicess = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    
    //遍歷可用的視頻設(shè)備 并返回position 參數(shù)值
    for (AVCaptureDevice *device in devicess)
    {
        if (device.position == position) {
            return device;
        }
    }
    return nil;
}

//獲取當(dāng)前活躍設(shè)備
- (AVCaptureDevice *)activeCamera {
    //返回當(dāng)前捕捉會(huì)話對(duì)應(yīng)的攝像頭的device 屬性
    return self.activeVideoInput.device;
}

//返回當(dāng)前未激活的攝像頭
- (AVCaptureDevice *)inactiveCamera {

    //通過查找當(dāng)前激活攝像頭的反向攝像頭獲得捏境，如果設(shè)備只有1個(gè)攝像頭于游，則返回nil
       AVCaptureDevice *device = nil;
      if (self.cameraCount > 1)
      {
          if ([self activeCamera].position == AVCaptureDevicePositionBack) {
               device = [self cameraWithPosition:AVCaptureDevicePositionFront];
         }else
         {
             device = [self cameraWithPosition:AVCaptureDevicePositionBack];
         }
     }

    return device;
}

//判斷是否有超過1個(gè)攝像頭可用
- (BOOL)canSwitchCameras {
    return self.cameraCount > 1;
}

//可用視頻捕捉設(shè)備的數(shù)量
- (NSUInteger)cameraCount {
     return [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];
}

//切換攝像頭
- (BOOL)switchCameras {

    //判斷是否有多個(gè)攝像頭
    if (![self canSwitchCameras])
    {
        return NO;
    }
    
    //獲取當(dāng)前設(shè)備的反向設(shè)備
    NSError *error;
    AVCaptureDevice *videoDevice = [self inactiveCamera];
    
    //將輸入設(shè)備封裝成AVCaptureDeviceInput
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
    
    //判斷videoInput 是否為nil
    if (videoInput)
    {
        //標(biāo)注原配置變化開始
        [self.captureSession beginConfiguration];
        
        //將捕捉會(huì)話中，原本的捕捉輸入設(shè)備移除
        [self.captureSession removeInput:self.activeVideoInput];
        //不加上面兩句會(huì)一直加入失敗
        //判斷新的設(shè)備是否能加入
        if ([self.captureSession canAddInput:videoInput])
        {
            //能加入成功垫言，則將videoInput 作為新的視頻捕捉設(shè)備
            [self.captureSession addInput:videoInput];
            
            //將獲得設(shè)備 改為 videoInput
            self.activeVideoInput = videoInput;
        }else
        {
            //如果新設(shè)備贰剥，無法加入。則將原本的視頻捕捉設(shè)備重新加入到捕捉會(huì)話中
            [self.captureSession addInput:self.activeVideoInput];
        }
        
        //配置完成后筷频，提交 AVCaptureSession commitConfiguration 會(huì)分批的將所有變更整合在一起蚌成。
        [self.captureSession commitConfiguration];
    }else
    {
        //設(shè)備添加錯(cuò)誤
        //創(chuàng)建AVCaptureDeviceInput 出現(xiàn)錯(cuò)誤，則通知委托來處理該錯(cuò)誤
        [self.delegate deviceConfigurationFailedWithError:error];
        return NO;
    }
    
    return YES;
}

實(shí)現(xiàn)攝像頭自動(dòng)聚焦功能

• 捕捉設(shè)備(聚焦/曝光)

• AVCapture Device 定義了很多方法凛捏，讓開發(fā)者控制ios設(shè)備上的攝像頭担忧。可以獨(dú)立調(diào)整和鎖定攝像頭的焦距坯癣、曝光瓶盛、白平衡。對(duì)焦和曝光可以基于特定的興趣點(diǎn)進(jìn)行設(shè)置示罗，使其在應(yīng)用中實(shí)現(xiàn)點(diǎn)擊對(duì)焦惩猫、點(diǎn)擊曝光的功能。還可以讓你控制設(shè)備的LED作為拍照的閃光燈或手電筒的使用

• 每當(dāng)修改攝像頭設(shè)備時(shí)蚜点，一定要先測試修改動(dòng)作是否能被設(shè)備支持轧房。并不是所有的攝像頭都支持所有功能，例如前置攝像頭就不支持對(duì)焦操作绍绘，因?yàn)樗湍繕?biāo)距離一般在一臂之長的距離奶镶。但大部分后置攝像頭是可以支持全尺寸對(duì)焦迟赃。嘗試應(yīng)用一個(gè)不被支持的動(dòng)作，會(huì)導(dǎo)致異常崩潰厂镇。所以修改攝像頭設(shè)備前捺氢，需要判斷是否支持

#pragma mark - Focus Methods 點(diǎn)擊聚焦方法的實(shí)現(xiàn)

- (BOOL)cameraSupportsTapToFocus {
    
    //詢問激活中的攝像頭是否支持興趣點(diǎn)對(duì)焦
    return [[self activeCamera]isFocusPointOfInterestSupported];
}

- (void)focusAtPoint:(CGPoint)point {
    
    AVCaptureDevice *device = [self activeCamera];
    
    //是否支持興趣點(diǎn)對(duì)焦 & 是否自動(dòng)對(duì)焦模式
    if (device.isFocusPointOfInterestSupported && [device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {
        
        NSError *error;
        //鎖定設(shè)備準(zhǔn)備配置，如果獲得了鎖
        //因?yàn)榕渲脮r(shí)剪撬，不能讓多個(gè)對(duì)象對(duì)他進(jìn)行更改，所以要對(duì)該過程上鎖
        if ([device lockForConfiguration:&error]) {
            
            //將focusPointOfInterest屬性設(shè)置CGPoint
            device.focusPointOfInterest = point;
            
            //focusMode 設(shè)置為AVCaptureFocusModeAutoFocus
            device.focusMode = AVCaptureFocusModeAutoFocus;
            
            //釋放該鎖定
            [device unlockForConfiguration];
        }else{
            //錯(cuò)誤時(shí)悠反，則返回給錯(cuò)誤處理代理
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

實(shí)現(xiàn)攝像頭自動(dòng)曝光以及鎖定曝光

#pragma mark - Exposure Methods   點(diǎn)擊曝光的方法實(shí)現(xiàn)

- (BOOL)cameraSupportsTapToExpose {
    
    //詢問設(shè)備是否支持對(duì)一個(gè)興趣點(diǎn)進(jìn)行曝光
    return [[self activeCamera] isExposurePointOfInterestSupported];
}

static const NSString *THCameraAdjustingExposureContext;

- (void)exposeAtPoint:(CGPoint)point {

    AVCaptureDevice *device = [self activeCamera];
    
    AVCaptureExposureMode exposureMode =AVCaptureExposureModeContinuousAutoExposure;
    
    //判斷是否支持 AVCaptureExposureModeContinuousAutoExposure 模式
    if (device.isExposurePointOfInterestSupported && [device isExposureModeSupported:exposureMode]) {
        
        [device isExposureModeSupported:exposureMode];
        
        NSError *error;
        
        //鎖定設(shè)備準(zhǔn)備配置
        if ([device lockForConfiguration:&error])
        {
            //配置期望值
            device.exposurePointOfInterest = point;
            device.exposureMode = exposureMode;
            
            //判斷設(shè)備是否支持鎖定曝光的模式残黑。
            if ([device isExposureModeSupported:AVCaptureExposureModeLocked]) {
                
                //支持，則使用kvo確定設(shè)備的adjustingExposure屬性的狀態(tài)斋否。
                [device addObserver:self forKeyPath:@"adjustingExposure" options:NSKeyValueObservingOptionNew context:&THCameraAdjustingExposureContext];
            }
            
            //釋放該鎖定
            [device unlockForConfiguration];
            
        }else
        {
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    //判斷context（上下文）是否為THCameraAdjustingExposureContext
    if (context == &THCameraAdjustingExposureContext) {
        
        //獲取device
        AVCaptureDevice *device = (AVCaptureDevice *)object;
        
        //判斷設(shè)備是否不再調(diào)整曝光等級(jí)梨水，確認(rèn)設(shè)備的exposureMode是否可以設(shè)置為AVCaptureExposureModeLocked
        if(!device.isAdjustingExposure && [device isExposureModeSupported:AVCaptureExposureModeLocked])
        {
            //移除作為adjustingExposure 的self，就不會(huì)得到后續(xù)變更的通知
            [object removeObserver:self forKeyPath:@"adjustingExposure" context:&THCameraAdjustingExposureContext];
            
            //異步方式調(diào)回主隊(duì)列茵臭，
            dispatch_async(dispatch_get_main_queue(), ^{
                NSError *error;
                if ([device lockForConfiguration:&error]) {
                    
                    //修改exposureMode
                    device.exposureMode = AVCaptureExposureModeLocked;
                    
                    //釋放該鎖定
                    [device unlockForConfiguration];
                    
                }else
                {
                    [self.delegate deviceConfigurationFailedWithError:error];
                }
            });
            
        }
        
    }else
    {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
    
    
}

//重新設(shè)置對(duì)焦&曝光
- (void)resetFocusAndExposureModes {

    AVCaptureDevice *device = [self activeCamera];
    AVCaptureFocusMode focusMode = AVCaptureFocusModeContinuousAutoFocus;
    
    //獲取對(duì)焦興趣點(diǎn) 和 連續(xù)自動(dòng)對(duì)焦模式 是否被支持
    BOOL canResetFocus = [device isFocusPointOfInterestSupported]&& [device isFocusModeSupported:focusMode];
    
    AVCaptureExposureMode exposureMode = AVCaptureExposureModeContinuousAutoExposure;
    
    //確認(rèn)曝光度可以被重設(shè)
    BOOL canResetExposure = [device isFocusPointOfInterestSupported] && [device isExposureModeSupported:exposureMode];
    
    //回顧一下疫诽，捕捉設(shè)備空間左上角（0，0）旦委，右下角（1奇徒，1） 中心點(diǎn)則（0.5，0.5）
    CGPoint centPoint = CGPointMake(0.5f, 0.5f);
    
    NSError *error;
    
    //鎖定設(shè)備缨硝，準(zhǔn)備配置
    if ([device lockForConfiguration:&error]) {
        
        //焦點(diǎn)可設(shè)摩钙，則修改
        if (canResetFocus) {
            device.focusMode = focusMode;
            device.focusPointOfInterest = centPoint;
        }
        
        //曝光度可設(shè)，則設(shè)置為期望的曝光模式
        if (canResetExposure) {
            device.exposureMode = exposureMode;
            device.exposurePointOfInterest = centPoint;
            
        }
        
        //釋放鎖定
        [device unlockForConfiguration];
        
    }else
    {
        [self.delegate deviceConfigurationFailedWithError:error];
    }
}

實(shí)現(xiàn)攝像頭手電筒和閃光燈模式的開啟關(guān)閉

#pragma mark - Flash and Torch Modes    閃光燈 & 手電筒

//判斷是否有閃光燈
- (BOOL)cameraHasFlash {
    return [[self activeCamera]hasFlash];
}

//閃光燈模式
- (AVCaptureFlashMode)flashMode {
    return [[self activeCamera]flashMode];
}

//設(shè)置閃光燈
- (void)setFlashMode:(AVCaptureFlashMode)flashMode {

    //獲取會(huì)話
    AVCaptureDevice *device = [self activeCamera];
    
    //判斷是否支持閃光燈模式
    if ([device isFlashModeSupported:flashMode]) {
    
        //如果支持查辩，則鎖定設(shè)備
        NSError *error;
        if ([device lockForConfiguration:&error]) {

            //修改閃光燈模式
            device.flashMode = flashMode;
            //修改完成胖笛，解鎖釋放設(shè)備
            [device unlockForConfiguration];
            
        }else
        {
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

//是否支持手電筒
- (BOOL)cameraHasTorch {
    return [[self activeCamera]hasTorch];
}

//手電筒模式
- (AVCaptureTorchMode)torchMode {
    return [[self activeCamera]torchMode];
}

//設(shè)置是否打開手電筒
- (void)setTorchMode:(AVCaptureTorchMode)torchMode {

    AVCaptureDevice *device = [self activeCamera];
    
    if ([device isTorchModeSupported:torchMode]) {
        
        NSError *error;
        if ([device lockForConfiguration:&error]) {
            
            device.torchMode = torchMode;
            [device unlockForConfiguration];
        }else
        {
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

靜態(tài)圖片的拍攝

#pragma mark - Image Capture Methods 拍攝靜態(tài)圖片
/*
    AVCaptureStillImageOutput 是AVCaptureOutput的子類。用于捕捉圖片
 */
- (void)captureStillImage {
    
    //獲取連接
    AVCaptureConnection *connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
    //程序只支持縱向宜岛，但是如果用戶橫向拍照時(shí)长踊，需要調(diào)整結(jié)果照片的方向
    //判斷是否支持設(shè)置視頻方向
    if (connection.isVideoOrientationSupported) {
        
        //獲取方向值
        connection.videoOrientation = [self currentVideoOrientation];
    }
    
    //定義一個(gè)handler 塊，會(huì)返回1個(gè)圖片的NSData數(shù)據(jù)（完成捕捉之后萍倡，我們要做的事情）
    id handler = ^(CMSampleBufferRef sampleBuffer,NSError *error){
                    if (sampleBuffer != NULL) {
                        //從緩沖區(qū)身弊，將緩沖數(shù)據(jù)轉(zhuǎn)換成靜態(tài)圖片
                        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:sampleBuffer];
                        UIImage *image = [[UIImage alloc]initWithData:imageData];
                        
                        //重點(diǎn)：捕捉圖片成功后，將圖片傳遞出去
                        [self writeImageToAssetsLibrary:image];
                    }else
                    {
                        NSLog(@"NULL sampleBuffer:%@",[error localizedDescription]);
                    }
                        
                };
    
    //捕捉靜態(tài)圖片
    [self.imageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:handler];
}

//獲取方向值
- (AVCaptureVideoOrientation)currentVideoOrientation {
    
    AVCaptureVideoOrientation orientation;
    
    //獲取UIDevice 的 orientation
    switch ([UIDevice currentDevice].orientation) {
        case UIDeviceOrientationPortrait:
            orientation = AVCaptureVideoOrientationPortrait;
            break;
        case UIDeviceOrientationLandscapeRight:
            orientation = AVCaptureVideoOrientationLandscapeLeft;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            orientation = AVCaptureVideoOrientationPortraitUpsideDown;
            break;
        default:
            orientation = AVCaptureVideoOrientationLandscapeRight;
            break;
    }
    
    return orientation;
}

/*
    Assets Library 框架 
    用來讓開發(fā)者通過代碼方式訪問iOS photo
    注意：會(huì)訪問到相冊(cè)遣铝，需要修改plist 權(quán)限佑刷。否則會(huì)導(dǎo)致項(xiàng)目崩潰
 */

- (void)writeImageToAssetsLibrary:(UIImage *)image {

    //創(chuàng)建ALAssetsLibrary  實(shí)例
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc]init];
    
    //參數(shù)1:圖片（參數(shù)為CGImageRef 所以image.CGImage）
    //參數(shù)2:方向參數(shù) 轉(zhuǎn)為NSUInteger
    //參數(shù)3:寫入成功、失敗處理
    [library writeImageToSavedPhotosAlbum:image.CGImage
                             orientation:(NSUInteger)image.imageOrientation
                         completionBlock:^(NSURL *assetURL, NSError *error) {
                             //成功后酿炸，發(fā)送捕捉圖片通知瘫絮。用于繪制程序的左下角的縮略圖
                             if (!error)
                             {
                                 //拍照時(shí)，左下角都有一個(gè)圖片縮略圖
                                 [self postThumbnailNotifification:image];
                             }else
                             {
                                 //失敗打印錯(cuò)誤信息
                                 id message = [error localizedDescription];
                                 NSLog(@"%@",message);
                             }
                         }];
}

//發(fā)送縮略圖通知
- (void)postThumbnailNotifification:(UIImage *)image {
    
    //回到主隊(duì)列
    dispatch_async(dispatch_get_main_queue(), ^{
        //發(fā)送請(qǐng)求
        NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
        [nc postNotificationName:THThumbnailCreatedNotification object:image];
    });
}

視頻錄制實(shí)現(xiàn)

• 關(guān)于QuckTime

  • 視頻內(nèi)容的捕捉：當(dāng)設(shè)置捕捉會(huì)話時(shí)填硕，添加一個(gè)名為AVCaptureMovieFileOutput的輸出麦萤。這個(gè)類定義了方法將QuckTime影片捕捉到磁盤鹿鳖。這個(gè)類大多數(shù)核心功能繼承于父類AVCaptureFileOutput。這個(gè)父類定義了許多實(shí)用功能壮莹，比如錄制到最長時(shí)限或錄制到特定文件大小時(shí)為止翅帜。還可以配置成保留最小可用的磁盤空間，這一點(diǎn)在存儲(chǔ)空間有限的移動(dòng)設(shè)備上錄制視頻時(shí)非常重要

  • 通常當(dāng)QuckTime影片準(zhǔn)備發(fā)布時(shí)命满，影片頭的元數(shù)據(jù)處于文件的開始位置涝滴。這樣可以讓那個(gè)視頻播放器快速讀取頭包含信息，來確定文件的內(nèi)容胶台、結(jié)構(gòu)和其包含的多個(gè)樣本的位置歼疮。不過，當(dāng)錄制一個(gè)QuckTime影片時(shí)诈唬，直到所有的樣片都完成捕捉后才能創(chuàng)建信息頭韩脏。當(dāng)錄制結(jié)束時(shí)，創(chuàng)建頭數(shù)據(jù)并將它附在文件結(jié)尾處铸磅。

• 將創(chuàng)建頭過程放在所有影片樣本完成捕捉之后存在一個(gè)問題赡矢，尤其是在移動(dòng)設(shè)備的情況下。如果遇到崩潰或者其他中斷阅仔，比如電話撥入吹散，則影片頭就不會(huì)被正確寫入，會(huì)在磁盤生成一個(gè)不可讀的影片文件霎槐。AVCaptureMovieFileOutput提供一個(gè)核心功能就是分段捕捉QuickTime影片送浊。

#pragma mark - Video Capture Methods 捕捉視頻

//判斷是否錄制狀態(tài)
- (BOOL)isRecording {
    return self.movieOutput.isRecording;
}

//開始錄制
- (void)startRecording {

    if (![self isRecording]) {
        
        //獲取當(dāng)前視頻捕捉連接信息，用于捕捉視頻數(shù)據(jù)配置一些核心屬性
        AVCaptureConnection * videoConnection = [self.movieOutput connectionWithMediaType:AVMediaTypeVideo];
        
        //判斷是否支持設(shè)置videoOrientation 屬性丘跌。
        if([videoConnection isVideoOrientationSupported])
        {
            //支持則修改當(dāng)前視頻的方向
            videoConnection.videoOrientation = [self currentVideoOrientation];
        }
        
        //判斷是否支持視頻穩(wěn)定 可以顯著提高視頻的質(zhì)量袭景。只會(huì)在錄制視頻文件涉及
        if([videoConnection isVideoStabilizationSupported])
        {
            videoConnection.enablesVideoStabilizationWhenAvailable = YES;
        }
        
        AVCaptureDevice *device = [self activeCamera];
        
        //攝像頭可以進(jìn)行平滑對(duì)焦模式操作。即減慢攝像頭鏡頭對(duì)焦速度闭树。當(dāng)用戶移動(dòng)拍攝時(shí)攝像頭會(huì)嘗試快速自動(dòng)對(duì)焦耸棒。
        if (device.isSmoothAutoFocusEnabled) {
            NSError *error;
            if ([device lockForConfiguration:&error]) {
                
                device.smoothAutoFocusEnabled = YES;
                [device unlockForConfiguration];
            }else
            {
                [self.delegate deviceConfigurationFailedWithError:error];
            }
        }
        
        //查找寫入捕捉視頻的唯一文件系統(tǒng)URL.
        self.outputURL = [self uniqueURL];
        
        //開始錄制。直播/小視頻 ---> 捕捉到視頻信息 ---> 壓縮(AAC/H264)
        //錄制成一個(gè)QuckTime視頻文件 --> 存儲(chǔ)到相冊(cè)报辱。(也涉及到編碼--硬編碼--由于AVFoundation已經(jīng)替你完成)
        //在捕捉輸出上調(diào)用方法 參數(shù)1:錄制保存路徑  參數(shù)2:代理
        [self.movieOutput startRecordingToOutputFileURL:self.outputURL recordingDelegate:self];
    }
}

- (CMTime)recordedDuration {
    
    return self.movieOutput.recordedDuration;
}


//寫入視頻唯一文件系統(tǒng)URL
- (NSURL *)uniqueURL {

    NSFileManager *fileManager = [NSFileManager defaultManager];
    
    //temporaryDirectoryWithTemplateString  可以將文件寫入的目的創(chuàng)建一個(gè)唯一命名的目錄与殃；
    //臨時(shí)文件，沒下載完成前是沒有后綴名的碍现，下載完成后才會(huì)變成正確的后綴名
    NSString *dirPath = [fileManager temporaryDirectoryWithTemplateString:@"kamera.XXXXXX"];
    
    if (dirPath) {
        //mov.視頻封裝的容器幅疼。和視頻編碼格式有區(qū)別
        NSString *filePath = [dirPath stringByAppendingPathComponent:@"kamera_movie.mov"];
        return  [NSURL fileURLWithPath:filePath];
        
    }
    
    return nil;
    
}

//停止錄制
- (void)stopRecording {

    //是否正在錄制
    if ([self isRecording]) {
        [self.movieOutput stopRecording];
    }
}

視頻拍攝縮略圖實(shí)現(xiàn)

#pragma mark - AVCaptureFileOutputRecordingDelegate 捕捉文件輸出

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error {

    //錯(cuò)誤
    if (error) {
        [self.delegate mediaCaptureFailedWithError:error];
    }else
    {
        //寫入
        [self writeVideoToAssetsLibrary:[self.outputURL copy]];
        
    }
    self.outputURL = nil;
}

//寫入捕捉到的視頻到相冊(cè)
- (void)writeVideoToAssetsLibrary:(NSURL *)videoURL {
    
    //ALAssetsLibrary 實(shí)例 提供寫入視頻的接口
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc]init];
    
    //寫資源庫寫入前，檢查視頻是否可被寫入 （寫入前盡量養(yǎng)成判斷的習(xí)慣）
    if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:videoURL]) {
        
        //創(chuàng)建block塊
        ALAssetsLibraryWriteVideoCompletionBlock completionBlock;
        completionBlock = ^(NSURL *assetURL,NSError *error)
        {
            if (error) {
                [self.delegate assetLibraryWriteFailedWithError:error];
            }else
            {
                //用于界面展示視頻縮略圖
                [self generateThumbnailForVideoAtURL:videoURL];
            }
            
        };
        
        //執(zhí)行實(shí)際寫入資源庫的動(dòng)作
        [library writeVideoAtPathToSavedPhotosAlbum:videoURL completionBlock:completionBlock];
    }
}

//獲取視頻左下角縮略圖
- (void)generateThumbnailForVideoAtURL:(NSURL *)videoURL {

    //在videoQueue 上昼接，
    dispatch_async(self.videoQueue, ^{
        
        //建立新的AVAsset & AVAssetImageGenerator
        AVAsset *asset = [AVAsset assetWithURL:videoURL];
        
        AVAssetImageGenerator *imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
        
        //設(shè)置maximumSize 寬為100爽篷，高為0 根據(jù)視頻的寬高比來計(jì)算圖片的高度
        imageGenerator.maximumSize = CGSizeMake(100.0f, 0.0f);
        
        //捕捉視頻縮略圖會(huì)考慮視頻的變化（如視頻的方向變化），如果不設(shè)置慢睡，縮略圖的方向可能出錯(cuò)
        imageGenerator.appliesPreferredTrackTransform = YES;
        
        //獲取CGImageRef圖片 注意需要自己管理它的創(chuàng)建和釋放
        CGImageRef imageRef = [imageGenerator copyCGImageAtTime:kCMTimeZero actualTime:NULL error:nil];
        
        //將圖片轉(zhuǎn)化為UIImage
        UIImage *image = [UIImage imageWithCGImage:imageRef];
        
        //釋放CGImageRef imageRef 防止內(nèi)存泄漏
        CGImageRelease(imageRef);
        
        //回到主線程
        dispatch_async(dispatch_get_main_queue(), ^{
            
            //發(fā)送通知逐工，傳遞最新的image
            [self postThumbnailNotifification:image];
        });
    });
}