一、前言

AVCaptureSession 是 AVFoundation 的核心类，用于管理捕获对象 AVCaptureInput 的视频和音频的输入，协调捕获的输出 AVCaptureOutput。

AVCaptureOutput 的输出有两种方法：

• 一种是直接以 movieFileUrl 方式输出；
• 一种是以原始数据流 data 的方式输出

流程对比图如下：

下面详细讲解两种录制视频的方案：

二、方案一：AVCaptureSession + AVCaptureMovieFileOutput

1.创建AVCaptureSession

//导入 AVFoundation.framework 
#import <AVFoundation/AVFoundation.h>

//声明属性
@property (nonatomic, strong) AVCaptureSession *captureSession;

//懒加载 AVCapturesession
- (AVCaptureSession *)captureSession {
    if (!_captureSession) {
        _captureSession = [[AVCaptureSession alloc] init];
        
        //设置分辨率
        if ([_captureSession canSetSessionPreset:AVCaptureSessionPresetHigh]) {
            [_captureSession setSessionPreset:AVCaptureSessionPresetHigh];
        }
    }
    return _captureSession;
}

注意：AVCaptureSession 的调用是会阻塞线程的，建议单独开辟子线程处理。

2.设置音频、视频输入

//声明属性
@property (nonatomic, strong) AVCaptureDeviceInput *videoInput;
@property (nonatomic, strong) AVCaptureDeviceInput *audioInput;


//设置视频，音频输入源
- (void)setCaptureDeviceInput {
    //1. 视频输入源
    //获取视频输入设备， 默认后置摄像头
    AVCaptureDevice *videoCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    NSError *error = nil;
    self.videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoCaptureDevice error:&error];
    
    if ([self.captureSession canAddInput:self.videoInput]) {
        [self.captureSession addInput:self.videoInput];
    }
    
    
    //2. 音频输入源
    AVCaptureDevice *audioCaptureDevice = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio] firstObject];
    self.audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&error];
    if ([self.captureSession canAddInput:self.audioInput]) {
        [self.captureSession addInput:self.audioInput];
    }
    
}

3.设置文件输出源

//声明属性
@property (nonatomic, strong) AVCaptureMovieFileOutput *movieFileOutput;
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *previewLayer;


//设置文件输出源
- (void)setDeviceFileOutput {
    
    //初始化文件输出对象
    self.movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
    
    //捕获会话中特定捕获输入对象和捕获输出对象之间的连接
    AVCaptureConnection *captureConnection = [self.movieFileOutput connectionWithMediaType:AVMediaTypeVideo];
    
    //设置防抖
    if ([captureConnection isVideoStabilizationSupported]) {
        captureConnection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
    }
    
    //预览图层和视频方向保持一致
    captureConnection.videoOrientation = [self.previewLayer connection].videoOrientation;
    
    //添加文件输出源
    if ([self.captureSession canAddOutput:self.movieFileOutput]) {
        [self.captureSession addOutput:self.movieFileOutput];
    }
    
}

4.添加视频预览层

- (void)setVideoPreviewLayer {
    self.previewLayer.frame = [UIScreen mainScreen].bounds;
    
    [self.superView.layer addSubLayer:self.previewLayer];
}


- (AVCaptureVideoPreviewLayer *)previewLayer {
    if (!_previewLayer) {
        _previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
        _previewLayer.masksToBounds = YES;
        _previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;//填充模式
    }
    return _previewLayer;
}

5. 开始采集

//声明属性
@property (nonatomic, strong) dispatch_queue_t sessionQueue;

//开始采集
- (void)startCapture {
	self.sessionQueue = dispatch_queue_create("com.capturesession.queue", DISPATCH_QUEUE_CONCURRENT);

    if (![self.captureSession isRunning]) {
        __weak __typeof(self) weakSelf = self;
        
        dispatch_async(self.sessionQueue, ^{
            [weakSelf.captureSession startRunning];
        });
        
    }
}

6. 开始录制

//开始录制
- (void)startRecord {
    
    [self.movieFileOutput startRecordingToOutputFileURL:[self createVideoPath] recordingDelegate:self];
}

当实际的录制开始或停止时，系统会有代理回调。当开始录制之后，这时可能还没有真正写入，真正开始写入会回调下面代理，停止录制也是如此，所以如果你需要对录制视频起始点操作，建议通过系统的回调代理：

//实现协议 <AVCaptureFileOutputRecordingDelegate>中的方法


#pragma mark _ AVCaptureFileOutputRecordingDelegate

//起始点 - 开始录制
- (void)captureOutput:(AVCaptureFileOutput *)output didStartRecordingToOutputFileAtURL:(NSURL *)fileURL fromConnections:(NSArray<AVCaptureConnection *> *)connections {
    
}

//结束录制
-(void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error
{
    NSLog(@"视频录制完成. 文件路径：%@",[outputFileURL absoluteString]);
}

7.停止录制

//停止录制
- (void)stopRecord {
    if ([self.movieFileOutput isRecording]) {
        [self.movieFileOutput stopRecording];
    }
}

8.停止采集

//停止采集
- (void)stopCapture {
    if ([self.captureSession isRunning]) {
        __weak __typeof(self) weakSelf = self;
        dispatch_async(self.sessionQueue, ^{
            [weakSelf.captureSession stopRunning];
            weakSelf.captureSession = nil;
        });
    }
}

三、方案二：AVCaptureSession + AVAssetWriter

方案二及更多内容，请访问： 基于AVFoundation实现视频录制的两种方式