AVCaptureSession的简单使用,获取视频流,展示,录

使用步骤:
1.创建视频捕捉会话

    _session = [[AVCaptureSession alloc]init];
    _session.sessionPreset = AVCaptureSessionPresetHigh;//属性预设

2.设置会话输入

// 视频输入
    AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:error];
    if (videoInput) {
        if ([_session canAddInput:videoInput]){
            [_session addInput:videoInput];
        }
    }
    _deviceInput = videoInput;
    
    // 音频输入
    AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
    AVCaptureDeviceInput *audioIn = [[AVCaptureDeviceInput alloc] initWithDevice:audioDevice error:error];
    if ([_session canAddInput:audioIn]){
        [_session addInput:audioIn];
    }

3.设置会话输出(data或者file)
3.1:data输出

// 视频输出
        AVCaptureVideoDataOutput *videoOut = [[AVCaptureVideoDataOutput alloc] init];
        [videoOut setAlwaysDiscardsLateVideoFrames:YES];
        [videoOut setVideoSettings:@{(id)kCVPixelBufferPixelFormatTypeKey: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA]}];
            [videoOut setSampleBufferDelegate:self queue:captureQueue];
            if ([_session canAddOutput:videoOut]){
                [_session addOutput:videoOut];
        }
            _videoOutput = videoOut;
        _videoConnection = [videoOut connectionWithMediaType:AVMediaTypeVideo];
    
            // 音频输出
        AVCaptureAudioDataOutput *audioOut = [[AVCaptureAudioDataOutput alloc] init];
            [audioOut setSampleBufferDelegate:self queue:captureQueue];
        if ([_session canAddOutput:audioOut]){
                [_session addOutput:audioOut];
        }
            _audioConnection = [audioOut connectionWithMediaType:AVMediaTypeAudio];

        #pragma mark - delegate
        -(void)captureOutput:(AVCaptureOutput *)output didDropSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
        {
        //    NSLog(@"%@",sampleBuffer);
        }

        -(void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
        {
        //    NSLog(@"%@",sampleBuffer);
    
                @autoreleasepool {
        
            //视频
        //        if (connection == [_videoConnection connectionWithMediaType:AVMediaTypeVideo]) {
        //
        //
        //        }
        //
        //        //音频
        //        if (connection == [_audioConnection connectionWithMediaType:AVMediaTypeAudio]) {
        //
        //        }
    }
    
}

        // 静态图片输出
         AVCaptureStillImageOutput *imageOutput = [[AVCaptureStillImageOutput alloc] init];
          if (@available(iOS 11.0, *)) {
                imageOutput.outputSettings = @{AVVideoCodecKey:AVVideoCodecTypeJPEG};
        } else {
                imageOutput.outputSettings = @{AVVideoCodecKey:AVVideoCodecJPEG};
        }
            if ([_session canAddOutput:imageOutput]) {
                [_session addOutput:imageOutput];
        }
            _imageOutput = imageOutput;
        
        //视频流保存图片,拍照
        - (void)getVidioImage
        {
             AVCaptureConnection *connection = [_imageOutput connectionWithMediaType:AVMediaTypeVideo];
    
                [_imageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:^(CMSampleBufferRef _Nullable imageDataSampleBuffer, NSError * _Nullable error) {
                    if (error) {
                     return;
                    }
                    NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
                    UIImage *image = [[UIImage alloc]initWithData:imageData];
                    NSLog(@"%@",image);
                }];
        }

3.2: file输出

// 3.1初始化设备输出对象，用于获得输出数据
         FileOutput=[[AVCaptureMovieFileOutput alloc]init];
    
            // 3.2设置输出对象的一些属性
            AVCaptureConnection *captureConnection=[FileOutput connectionWithMediaType:AVMediaTypeVideo];
            //设置防抖
            //视频防抖 是在 iOS 6 和 iPhone 4S 发布时引入的功能。到了 iPhone 6，增加了更强劲和流畅的防抖模式，被称为影院级的视频防抖动。相关的 API 也有所改动 (目前为止并没有在文档中反映出来，不过可以查看头文件）。防抖并不是在捕获设备上配置的，而是在 AVCaptureConnection 上设置。由于不是所有的设备格式都支持全部的防抖模式，所以在实际应用中应事先确认具体的防抖模式是否支持：
            if ([captureConnection isVideoStabilizationSupported ]) {
             captureConnection.preferredVideoStabilizationMode=AVCaptureVideoStabilizationModeAuto;
            }
            //预览图层和视频方向保持一致
            captureConnection.videoOrientation = [previewLayer connection].videoOrientation;
    
            // 3.3将设备输出添加到会话中
            if ([_session canAddOutput:FileOutput]) {
                [_session addOutput:FileOutput];
            }

        // 3.4保存视频到本地
        [FileOutput startRecordingToOutputFileURL:videoUrl recordingDelegate:self];
        3.5保存视频的代理
            - (void)captureOutput:(AVCaptureFileOutput *)output didFinishRecordingToOutputFileAtURL:            (NSURL *)outputFileURL fromConnections:(NSArray<AVCaptureConnection *> *)connections                error:(nullable NSError *)error
            {
                ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
                [library writeVideoAtPathToSavedPhotosAlbum:outputFileURL completionBlock:^(NSURL *assetURL, NSError *error) {
                    if (error) {
                            NSLog(@"Save video fail:%@",error);
                    } else {
                            NSLog(@"Save video succeed.");
                    }
                }];
            }

            -(void)captureOutput:(AVCaptureFileOutput *)output didStartRecordingToOutputFileAtURL:(NSURL *)fileURL fromConnections:(NSArray<AVCaptureConnection *> *)connections{}

4.设置视频预览

previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:_session];
    UIView * aView = self.view;
    previewLayer.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
    [aView.layer addSublayer:previewLayer];
5.开始捕捉
    if (!_session.isRunning){
        [_session startRunning];
    }

6.其他

6.1//切换前后相机
    -(void)shiftCamera
    {
         _isCamenaBack = !_isCamenaBack;
        
            //切换至前置摄像头
            if(_isCamenaBack){
        
             AVCaptureDevice *device=nil;
             NSArray *devices=[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
             for(AVCaptureDevice *tmp in devices)
                {
                    if(tmp.position==AVCaptureDevicePositionFront)
                        device=tmp;
                }
             [_session beginConfiguration];
                [_session removeInput:_deviceInput];
              _deviceInput=nil;
              _deviceInput=[[AVCaptureDeviceInput alloc]initWithDevice:device error:nil];
             if([_session canAddInput:_deviceInput])
                    [_session addInput:_deviceInput];
             [_session commitConfiguration];
        
            }else{//切换至后置摄像头
        
            AVCaptureDevice *device=nil;
                NSArray *devices=[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
                for(AVCaptureDevice *tmp in devices)
                {
                    if(tmp.position==AVCaptureDevicePositionBack)
                device=tmp;
                }
                [_session beginConfiguration];
                [_session removeInput:_deviceInput];
                _deviceInput=nil;
                _deviceInput=[[AVCaptureDeviceInput alloc]initWithDevice:device error:nil];
                if([_session canAddInput:_deviceInput])
                    [_session addInput:_deviceInput];
                [_session commitConfiguration];
            }
    }

    6.2:闪光灯,对焦等等

demo:https://github.com/cckv/AVCaptureSession.git