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用 AVCaptureSession + AVCaptureMovieFileOutput 来录制视频,并通过AVAssetExportSeeion 手段来压缩视频并转换为 MP4 格
AVFoundation 介绍
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)。
那么建立视频拍摄的步骤如下 :
1.创建AVCaptureSession对象。
// 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]; }
2.使用AVCaptureDevice的静态方法获得需要使用的设备,例如拍照和录像就需要获得摄像头设备,录音就要获得麦克风设备。
// 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];
3.利用输入设备AVCaptureDevice初始化AVCaptureDeviceInput对象。
// 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; }
4.初始化输出数据管理对象,如果要拍照就初始化AVCaptureStillImageOutput对象;如果拍摄视频就初始化AVCaptureMovieFileOutput对象。
// 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];
5.将数据输入对象AVCaptureDeviceInput、数据输出对象AVCaptureOutput添加到媒体会话管理对象AVCaptureSession中。
// 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; } }
6.创建视频预览图层AVCaptureVideoPreviewLayer并指定媒体会话,添加图层到显示容器中,调用AVCaptureSession的startRuning方法开始捕获。
// 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];
7.将捕获的音频或视频数据输出到指定文件。
创建一个拍摄的按钮,当我们点击这个按钮就会触发视频录制,并将这个录制的视频放到 temp 文件夹中
- (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]; } }
当然我们录制的开始与结束都是有监听方法的,AVCaptureFileOutputRecordingDelegate 这个代理里面就有我们想要做的
- (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 ----"); }
到此,我们录制视频就结束了,那么是不是我们录制好了视频,就可以马上把这个视频上传给服务器分享给你的小伙伴们看了呢?
我们可以用如下方法测试一下我们录制出来的视频有多大 (m)
- (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; }
个人在这里做过测试,录制了 10s 的小视频得到的文件大小为 4.1M 左右,而且我用的分辨率还是640x480。。。很无语了是不是?
如果我们录制的视频,录制完成后要与服务器进行必要的上传,那么,我们肯定不能把这个刚刚录制出来的视频上传给服务器的,我们有必要对这个视频进行压缩了。那么我们的压缩方法,就要用到 AVAssetExportSeeion 这个类了。
// 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]]; }); } }]; } }
经过我们的压缩,这个时候10s 的 4M 视频就只剩下不够 1M 了。
以下是一些扩展:
- (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; }]; }
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原文地址:http://www.cnblogs.com/HJQ2016/p/5964368.html