AVCaptureSession：媒体（音、视频）捕获会话，负责把捕获的音视频数据输出到输出设备中。一个AVCaptureSession可以有多个输入输出。 AVCaptureDevice ：输入设备，包括麦克风、摄像头，通过该对象可以设置物理设备的一些属性（例如相机聚焦、白平衡等）。 AVCaptureDeviceInput ：设备输入数据管理对象，可以根据AVCaptureDevice创建对应的AVCaptureDeviceInput对象，该对象将会被添加到AVCaptureSession中管理。 AVCaptureVideoPreviewLayer ：相机拍摄预览图层，是CALayer的子类，使用该对象可以实时查看拍照或视频录制效果，创建该对象需要指定对应的 AVCaptureSession对象。 AVCaptureOutput ：输出数据管理对象，用于接收各类输出数据，通常使用对应的子类AVCaptureAudioDataOutput、AVCaptureStillImageOutput、 AVCaptureVideoDataOutput、AVCaptureFileOutput, 该对象将会被添加到AVCaptureSession中管理。 注意：前面几个对象的输出数据都是NSData类型，而AVCaptureFileOutput代表数据以文件形式输出，类似的，AVCcaptureFileOutput也不会直接创建使用，通常会使用其子类： AVCaptureAudioFileOutput、AVCaptureMovieFileOutput。当把一个输入或者输出添加到AVCaptureSession之后AVCaptureSession就会在所有相符的输入、输出设备之间 建立连接（AVCaptionConnection)。

// 创建会话 (AVCaptureSession) 对象。_captureSession = [[AVCaptureSession alloc] init];if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset640x480]) {    // 设置会话的 sessionPreset 属性, 这个属性影响视频的分辨率    [_captureSession setSessionPreset:AVCaptureSessionPreset640x480];}

// 获取摄像头输入设备， 创建 AVCaptureDeviceInput 对象// 在获取摄像头的时候，摄像头分为前后摄像头，我们创建了一个方法通过用摄像头的位置来获取摄像头 AVCaptureDevice *videoCaptureDevice = [self getCameraDeviceWithPosition:AVCaptureDevicePositionBack];if (!captureDevice) {    NSLog(@"---- 取得后置摄像头时出现问题---- ");    return;}// 添加一个音频输入设备// 直接可以拿数组中的数组中的第一个AVCaptureDevice *audioCaptureDevice = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio] firstObject];

// 视频输入对象// 根据输入设备初始化输入对象，用户获取输入数据_videoCaptureDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:captureDevice error:&error];if (error) {    NSLog(@"---- 取得设备输入对象时出错 ------ %@",error);    return;} //  音频输入对象//根据输入设备初始化设备输入对象，用于获得输入数据_audioCaptureDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:audioCaptureDevice error:&error];if (error) {    NSLog(@"取得设备输入对象时出错 ------ %@",error);    return;}

// 拍摄视频输出对象// 初始化输出设备对象，用户获取输出数据_caputureMovieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

// 将视频输入对象添加到会话 (AVCaptureSession) 中if ([_captureSession canAddInput:_videoCaptureDeviceInput]) {    [_captureSession addInput:_videoCaptureDeviceInput];}// 将音频输入对象添加到会话 (AVCaptureSession) 中if ([_captureSession canAddInput:_captureDeviceInput]) {    [_captureSession addInput:audioCaptureDeviceInput];    AVCaptureConnection *captureConnection = [_caputureMovieFileOutput connectionWithMediaType:AVMediaTypeVideo];    // 标识视频录入时稳定音频流的接受，我们这里设置为自动    if ([captureConnection isVideoStabilizationSupported]) {        captureConnection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;    }}

// 通过会话 (AVCaptureSession) 创建预览层_captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_captureSession];// 显示在视图表面的图层CALayer *layer = self.viewContrain.layer;layer.masksToBounds = true;_captureVideoPreviewLayer.frame = layer.bounds;_captureVideoPreviewLayer.masksToBounds = true;_captureVideoPreviewLayer.videoGravity=AVLayerVideoGravityResizeAspectFill;//填充模式[layer addSublayer:_captureVideoPreviewLayer];// 让会话（AVCaptureSession）勾搭好输入输出，然后把视图渲染到预览层上[_captureSession startRunning];

- (IBAction)takeMovie:(id)sender {[(UIButton *)sender setSelected:![(UIButton *)sender isSelected]];if ([(UIButton *)sender isSelected]) {     AVCaptureConnection *captureConnection=[self.caputureMovieFileOutput connectionWithMediaType:AVMediaTypeVideo];    // 开启视频防抖模式    AVCaptureVideoStabilizationMode stabilizationMode = AVCaptureVideoStabilizationModeCinematic;    if ([self.captureDeviceInput.device.activeFormat isVideoStabilizationModeSupported:stabilizationMode]) {        [captureConnection setPreferredVideoStabilizationMode:stabilizationMode];    }    //如果支持多任务则则开始多任务    if ([[UIDevice currentDevice] isMultitaskingSupported]) {       self.backgroundTaskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:nil];    }    // 预览图层和视频方向保持一致,这个属性设置很重要，如果不设置，那么出来的视频图像可以是倒向左边的。    captureConnection.videoOrientation=[self.captureVideoPreviewLayer connection].videoOrientation;   // 设置视频输出的文件路径，这里设置为 temp 文件    NSString *outputFielPath=[NSTemporaryDirectory() stringByAppendingString:MOVIEPATH];    // 路径转换成 URL 要用这个方法，用 NSBundle 方法转换成 URL 的话可能会出现读取不到路径的错误    NSURL *fileUrl=[NSURL fileURLWithPath:outputFielPath];   // 往路径的 URL 开始写入录像 Buffer ,边录边写    [self.caputureMovieFileOutput startRecordingToOutputFileURL:fileUrl recordingDelegate:self];}else {   // 取消视频拍摄    [self.caputureMovieFileOutput stopRecording];    [self.captureSession stopRunning];    [self completeHandle];}}

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didStartRecordingToOutputFileAtURL:(NSURL *)fileURL fromConnections:(NSArray *)connections{   NSLog(@"---- 开始录制 ----");}- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error{    NSLog(@"---- 录制结束 ----");}

- (CGFloat)getfileSize:(NSString *)path{    NSDictionary *outputFileAttributes = [[NSFileManager defaultManager] attributesOfItemAtPath:path error:nil];    NSLog (@"file size: %f", (unsigned long long)[outputFileAttributes fileSize]/1024.00 /1024.00);    return (CGFloat)[outputFileAttributes fileSize]/1024.00 /1024.00;}

// 这里我们创建一个按钮，当点击这个按钮，我们就会调用压缩视频的方法，然后再去重新计算大小，这样就会跟未被压缩前的大小有个明显的对比了// 压缩视频- (IBAction)compressVideo:(id)sender{    NSString *cachePath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];    NSString *savePath=[cachePath stringByAppendingPathComponent:MOVIEPATH];    NSURL *saveUrl=[NSURL fileURLWithPath:savePath];    // 通过文件的 url 获取到这个文件的资源    AVURLAsset *avAsset = [[AVURLAsset alloc] initWithURL:saveUrl options:nil];    // 用 AVAssetExportSession 这个类来导出资源中的属性    NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset];    // 压缩视频    if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality]) { // 导出属性是否包含低分辨率    // 通过资源（AVURLAsset）来定义 AVAssetExportSession，得到资源属性来重新打包资源 （AVURLAsset, 将某一些属性重新定义    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:avAsset presetName:AVAssetExportPresetLowQuality];    // 设置导出文件的存放路径    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];    [formatter setDateFormat:@"yyyy-MM-dd-HH:mm:ss"];    NSDate    *date = [[NSDate alloc] init];    NSString *outPutPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, true) lastObject] stringByAppendingPathComponent:[NSString stringWithFormat:@"output-%@.mp4",[formatter stringFromDate:date]]];    exportSession.outputURL = [NSURL fileURLWithPath:outPutPath];    // 是否对网络进行优化    exportSession.shouldOptimizeForNetworkUse = true;    // 转换成MP4格式    exportSession.outputFileType = AVFileTypeMPEG4;    // 开始导出,导出后执行完成的block    [exportSession exportAsynchronouslyWithCompletionHandler:^{        // 如果导出的状态为完成        if ([exportSession status] == AVAssetExportSessionStatusCompleted) {            dispatch_async(dispatch_get_main_queue(), ^{                // 更新一下显示包的大小                self.videoSize.text = [NSString stringWithFormat:@"%f MB",[self getfileSize:outPutPath]];            });        }    }];}}

- (IBAction)flashAutoClick:(UIButton *)sender {    [self setFlashMode:AVCaptureFlashModeAuto];    [self setFlashModeButtonStatus];}

- (IBAction)flashOnClick:(UIButton *)sender {    [self setFlashMode:AVCaptureFlashModeOn];    [self setFlashModeButtonStatus];}

- (IBAction)flashOffClick:(UIButton *)sender {    [self setFlashMode:AVCaptureFlashModeOff];    [self setFlashModeButtonStatus];}

/** *  给输入设备添加通知 */-(void)addNotificationToCaptureDevice:(AVCaptureDevice *)captureDevice{//注意添加区域改变捕获通知必须首先设置设备允许捕获[self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {    captureDevice.subjectAreaChangeMonitoringEnabled=YES;}];NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];//捕获区域发生改变[notificationCenter addObserver:self selector:@selector(areaChange:) name:AVCaptureDeviceSubjectAreaDidChangeNotification object:captureDevice];}-(void)removeNotificationFromCaptureDevice:(AVCaptureDevice *)captureDevice{NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];[notificationCenter removeObserver:self name:AVCaptureDeviceSubjectAreaDidChangeNotification object:captureDevice];}/** *  移除所有通知 */-(void)removeNotification{    NSNotificationCenter *notificationCenter= [NSNotificationCenter     defaultCenter];    [notificationCenter removeObserver:self];}-(void)addNotificationToCaptureSession:(AVCaptureSession *)captureSession{NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];//会话出错[notificationCenter addObserver:self selector:@selector(sessionRuntimeError:) name:AVCaptureSessionRuntimeErrorNotification object:captureSession];}/** *  设备连接成功 * *  @param notification 通知对象 */-(void)deviceConnected:(NSNotification *)notification{    NSLog(@"设备已连接...");}/** *  设备连接断开 * *  @param notification 通知对象 */-(void)deviceDisconnected:(NSNotification *)notification{NSLog(@"设备已断开.");}/** *  捕获区域改变 * *  @param notification 通知对象 */-(void)areaChange:(NSNotification *)notification{    NSLog(@"捕获区域改变...");}/** *  会话出错 * *  @param notification 通知对象 */-(void)sessionRuntimeError:(NSNotification *)notification{NSLog(@"会话发生错误.");}

/** *  取得指定位置的摄像头 * *  @param position 摄像头位置 * *  @return 摄像头设备 */-(AVCaptureDevice *)getCameraDeviceWithPosition:(AVCaptureDevicePosition )position{    NSArray *cameras= [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];    for (AVCaptureDevice *camera in cameras) {        if ([camera position]==position) {            return camera;        }    }    return nil;}/** *  改变设备属性的统一操作方法 * *  @param propertyChange 属性改变操作 */-(void)changeDeviceProperty:(PropertyChangeBlock)propertyChange{    AVCaptureDevice *captureDevice= [self.captureDeviceInput device];    NSError *error;    //注意改变设备属性前一定要首先调用lockForConfiguration:调用完之后使用unlockForConfiguration方法解锁    if ([captureDevice lockForConfiguration:&error]) {        propertyChange(captureDevice);        [captureDevice unlockForConfiguration];    }else{        NSLog(@"设置设备属性过程发生错误，错误信息：%@",error.localizedDescription);    }}/** *  设置闪光灯模式 * *  @param flashMode 闪光灯模式 */-(void)setFlashMode:(AVCaptureFlashMode )flashMode{    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {        if ([captureDevice isFlashModeSupported:flashMode]) {            [captureDevice setFlashMode:flashMode];        }    }];}/** *  设置聚焦模式 * *  @param focusMode 聚焦模式 */-(void)setFocusMode:(AVCaptureFocusMode )focusMode{    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {        if ([captureDevice isFocusModeSupported:focusMode]) {            [captureDevice setFocusMode:focusMode];        }    }];}/** *  设置曝光模式 * *  @param exposureMode 曝光模式 */-(void)setExposureMode:(AVCaptureExposureMode)exposureMode{    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {        if ([captureDevice isExposureModeSupported:exposureMode]) {            [captureDevice setExposureMode:exposureMode];        }    }];}/** *  设置聚焦点 * *  @param point 聚焦点 */-(void)focusWithMode:(AVCaptureFocusMode)focusMode exposureMode:(AVCaptureExposureMode)exposureMode atPoint:(CGPoint)point{    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {        if ([captureDevice isFocusModeSupported:focusMode]) {            [captureDevice setFocusMode:AVCaptureFocusModeAutoFocus];        }        if ([captureDevice isFocusPointOfInterestSupported]) {            [captureDevice setFocusPointOfInterest:point];        }        if ([captureDevice isExposureModeSupported:exposureMode]) {            [captureDevice setExposureMode:AVCaptureExposureModeAutoExpose];        }        if ([captureDevice isExposurePointOfInterestSupported]) {            [captureDevice setExposurePointOfInterest:point];        }    }];}/** *  添加点按手势，点按时聚焦 */-(void)addGenstureRecognizer{UITapGestureRecognizer *tapGesture=[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapScreen:)];    [self.viewContainer addGestureRecognizer:tapGesture];}-(void)tapScreen:(UITapGestureRecognizer *)tapGesture{    CGPoint point= [tapGesture locationInView:self.viewContainer];    //将UI坐标转化为摄像头坐标    CGPoint cameraPoint= [self.captureVideoPreviewLayer captureDevicePointOfInterestForPoint:point];    [self setFocusCursorWithPoint:point];    [self focusWithMode:AVCaptureFocusModeAutoFocus exposureMode:AVCaptureExposureModeAutoExpose atPoint:cameraPoint];}/** *  设置闪光灯按钮状态 */-(void)setFlashModeButtonStatus{    AVCaptureDevice *captureDevice=[self.captureDeviceInput device];    AVCaptureFlashMode flashMode=captureDevice.flashMode;    if([captureDevice isFlashAvailable]){        self.flashAutoButton.hidden=NO;    self.flashOnButton.hidden=NO;    self.flashOffButton.hidden=NO;    self.flashAutoButton.enabled=YES;    self.flashOnButton.enabled=YES;    self.flashOffButton.enabled=YES;    switch (flashMode) {        case AVCaptureFlashModeAuto:            self.flashAutoButton.enabled=NO;            break;        case AVCaptureFlashModeOn:            self.flashOnButton.enabled=NO;            break;        case AVCaptureFlashModeOff:            self.flashOffButton.enabled=NO;            break;        default:            break;    }}else{    self.flashAutoButton.hidden=YES;    self.flashOnButton.hidden=YES;    self.flashOffButton.hidden=YES;}}/** *  设置聚焦光标位置 * *  @param point 光标位置 */-(void)setFocusCursorWithPoint:(CGPoint)point{    self.focusCursor.center=point;    self.focusCursor.transform=CGAffineTransformMakeScale(1.5, 1.5);    self.focusCursor.alpha=1.0;    [UIView animateWithDuration:1.0 animations:^{        self.focusCursor.transform=CGAffineTransformIdentity;    } completion:^(BOOL finished) {        self.focusCursor.alpha=0;    }];}