iOS音视频学习10——AVFoundation录视频

视频录制

其实有了前面的拍照应用之后要在此基础上做视频录制功能并不复杂，程序只需要做如下修改：

1. 添加一个音频输入到会话（使用[[AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio] firstObject]获得输入设备，然后根据此输入设备创建一个设备输入对象），在拍照程序中已经添加了视频输入所以此时不需要添加视频输入。
2. 创建一个音乐播放文件输出对象AVCaptureMovieFileOutput取代原来的照片输出对象。
3. 将捕获到的视频数据写入到临时文件并在停止录制之后保存到相簿（通过AVCaptureMovieFileOutput的代理方法）。

相比拍照程序，程序的修改主要就是以上三点。当然为了让程序更加完善在下面的视频录制程序中加入了屏幕旋转视频、自动布局和后台保存任务等细节。下面是修改后的程序：

//
//  ViewController.m
//  AVFoundationCamera
//
//  Created by Kenshin Cui on 14/04/05.
//  Copyright (c) 2014年 cmjstudio. All rights reserved.
//  视频录制

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <AssetsLibrary/AssetsLibrary.h>
typedef void(^PropertyChangeBlock)(AVCaptureDevice *captureDevice);

@interface ViewController ()<AVCaptureFileOutputRecordingDelegate>//视频文件输出代理

@property (strong,nonatomic) AVCaptureSession *captureSession;//负责输入和输出设备之间的数据传递
@property (strong,nonatomic) AVCaptureDeviceInput *captureDeviceInput;//负责从AVCaptureDevice获得输入数据
@property (strong,nonatomic) AVCaptureMovieFileOutput *captureMovieFileOutput;//视频输出流
@property (strong,nonatomic) AVCaptureVideoPreviewLayer *captureVideoPreviewLayer;//相机拍摄预览图层
@property (assign,nonatomic) BOOL enableRotation;//是否允许旋转（注意在视频录制过程中禁止屏幕旋转）
@property (assign,nonatomic) CGRect *lastBounds;//旋转的前大小
@property (assign,nonatomic) UIBackgroundTaskIdentifier backgroundTaskIdentifier;//后台任务标识
@property (weak, nonatomic) IBOutlet UIView *viewContainer;
@property (weak, nonatomic) IBOutlet UIButton *takeButton;//拍照按钮
@property (weak, nonatomic) IBOutlet UIImageView *focusCursor; //聚焦光标


@end

@implementation ViewController

#pragma mark - 控制器视图方法
- (void)viewDidLoad {
    [super viewDidLoad];
}

-(void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    //初始化会话
    _captureSession=[[AVCaptureSession alloc]init];
    if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset1280x720]) {//设置分辨率
        _captureSession.sessionPreset=AVCaptureSessionPreset1280x720;
    }
    //获得输入设备
    AVCaptureDevice *captureDevice=[self getCameraDeviceWithPosition:AVCaptureDevicePositionBack];//取得后置摄像头
    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
    AVCaptureDevice *audioCaptureDevice=[[AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio] firstObject];
    
    
    NSError *error=nil;
    //根据输入设备初始化设备输入对象，用于获得输入数据
    _captureDeviceInput=[[AVCaptureDeviceInput alloc]initWithDevice:captureDevice error:&error];
    if (error) {
        NSLog(@"取得设备输入对象时出错，错误原因：%@",error.localizedDescription);
        return;
    }
    AVCaptureDeviceInput *audioCaptureDeviceInput=[[AVCaptureDeviceInput alloc]initWithDevice:audioCaptureDevice error:&error];
    if (error) {
        NSLog(@"取得设备输入对象时出错，错误原因：%@",error.localizedDescription);
        return;
    }
    //初始化设备输出对象，用于获得输出数据
    _captureMovieFileOutput=[[AVCaptureMovieFileOutput alloc]init];
    
    //将设备输入添加到会话中
    if ([_captureSession canAddInput:_captureDeviceInput]) {
        [_captureSession addInput:_captureDeviceInput];
        [_captureSession addInput:audioCaptureDeviceInput];
        AVCaptureConnection *captureConnection=[_captureMovieFileOutput connectionWithMediaType:AVMediaTypeVideo];
        if ([captureConnection isVideoStabilizationSupported ]) {
            captureConnection.preferredVideoStabilizationMode=AVCaptureVideoStabilizationModeAuto;
        }
    }
    
    //将设备输出添加到会话中
    if ([_captureSession canAddOutput:_captureMovieFileOutput]) {
        [_captureSession addOutput:_captureMovieFileOutput];
    }
    
    //创建视频预览层，用于实时展示摄像头状态
    _captureVideoPreviewLayer=[[AVCaptureVideoPreviewLayer alloc]initWithSession:self.captureSession];
    
    CALayer *layer=self.viewContainer.layer;
    layer.masksToBounds=YES;
    
    _captureVideoPreviewLayer.frame=layer.bounds;
    _captureVideoPreviewLayer.videoGravity=AVLayerVideoGravityResizeAspectFill;//填充模式
    //将视频预览层添加到界面中
    //[layer addSublayer:_captureVideoPreviewLayer];
    [layer insertSublayer:_captureVideoPreviewLayer below:self.focusCursor.layer];
    
    _enableRotation=YES;
    [self addNotificationToCaptureDevice:captureDevice];
    [self addGenstureRecognizer];
}

-(void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    [self.captureSession startRunning];
}

-(void)viewDidDisappear:(BOOL)animated{
    [super viewDidDisappear:animated];
    [self.captureSession stopRunning];
}

-(BOOL)shouldAutorotate{
    return self.enableRotation;
}

////屏幕旋转时调整视频预览图层的方向
//-(void)willTransitionToTraitCollection:(UITraitCollection *)newCollection withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator{
//    [super willTransitionToTraitCollection:newCollection withTransitionCoordinator:coordinator];
////    NSLog(@"%i,%i",newCollection.verticalSizeClass,newCollection.horizontalSizeClass);
//    UIInterfaceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation];
//    NSLog(@"%i",orientation);
//    AVCaptureConnection *captureConnection=[self.captureVideoPreviewLayer connection];
//    captureConnection.videoOrientation=orientation;
//
//}
//屏幕旋转时调整视频预览图层的方向
-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration{
    AVCaptureConnection *captureConnection=[self.captureVideoPreviewLayer connection];
    captureConnection.videoOrientation=(AVCaptureVideoOrientation)toInterfaceOrientation;
}
//旋转后重新设置大小
-(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation{
    _captureVideoPreviewLayer.frame=self.viewContainer.bounds;
}

-(void)dealloc{
    [self removeNotification];
}
#pragma mark - UI方法
#pragma mark 视频录制
- (IBAction)takeButtonClick:(UIButton *)sender {
    //根据设备输出获得连接
    AVCaptureConnection *captureConnection=[self.captureMovieFileOutput connectionWithMediaType:AVMediaTypeVideo];
    //根据连接取得设备输出的数据
    if (![self.captureMovieFileOutput isRecording]) {
        self.enableRotation=NO;
        //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
        captureConnection.videoOrientation=[self.captureVideoPreviewLayer connection].videoOrientation;
        NSString *outputFielPath=[NSTemporaryDirectory() stringByAppendingString:@"myMovie.mov"];
        NSLog(@"save path is :%@",outputFielPath);
        NSURL *fileUrl=[NSURL fileURLWithPath:outputFielPath];
        [self.captureMovieFileOutput startRecordingToOutputFileURL:fileUrl recordingDelegate:self];
    }
    else{
        [self.captureMovieFileOutput stopRecording];//停止录制
    }
}
#pragma mark 切换前后摄像头
- (IBAction)toggleButtonClick:(UIButton *)sender {
    AVCaptureDevice *currentDevice=[self.captureDeviceInput device];
    AVCaptureDevicePosition currentPosition=[currentDevice position];
    [self removeNotificationFromCaptureDevice:currentDevice];
    AVCaptureDevice *toChangeDevice;
    AVCaptureDevicePosition toChangePosition=AVCaptureDevicePositionFront;
    if (currentPosition==AVCaptureDevicePositionUnspecified||currentPosition==AVCaptureDevicePositionFront) {
        toChangePosition=AVCaptureDevicePositionBack;
    }
    toChangeDevice=[self getCameraDeviceWithPosition:toChangePosition];
    [self addNotificationToCaptureDevice:toChangeDevice];
    //获得要调整的设备输入对象
    AVCaptureDeviceInput *toChangeDeviceInput=[[AVCaptureDeviceInput alloc]initWithDevice:toChangeDevice error:nil];
    
    //改变会话的配置前一定要先开启配置，配置完成后提交配置改变
    [self.captureSession beginConfiguration];
    //移除原有输入对象
    [self.captureSession removeInput:self.captureDeviceInput];
    //添加新的输入对象
    if ([self.captureSession canAddInput:toChangeDeviceInput]) {
        [self.captureSession addInput:toChangeDeviceInput];
        self.captureDeviceInput=toChangeDeviceInput;
    }
    //提交会话配置
    [self.captureSession commitConfiguration];
    
}

#pragma mark - 视频输出代理
-(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(@"视频录制完成.");
    //视频录入完成之后在后台将视频存储到相簿
    self.enableRotation=YES;
    UIBackgroundTaskIdentifier lastBackgroundTaskIdentifier=self.backgroundTaskIdentifier;
    self.backgroundTaskIdentifier=UIBackgroundTaskInvalid;
    ALAssetsLibrary *assetsLibrary=[[ALAssetsLibrary alloc]init];
    [assetsLibrary writeVideoAtPathToSavedPhotosAlbum:outputFileURL completionBlock:^(NSURL *assetURL, NSError *error) {
        if (error) {
            NSLog(@"保存视频到相簿过程中发生错误，错误信息：%@",error.localizedDescription);
        }
        if (lastBackgroundTaskIdentifier!=UIBackgroundTaskInvalid) {
            [[UIApplication sharedApplication] endBackgroundTask:lastBackgroundTaskIdentifier];
        }
        NSLog(@"成功保存视频到相簿.");
    }];
    
}

#pragma mark - 通知
/**
 *  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.");
}

#pragma mark - 私有方法

/**
 *  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;
        
    }];
}
@end