使用摄像头采集视频数据

AVCaptureSession

采集架构图

通过AVCaptureSession把 input和output关联起来。

输入设备

• Input
  • Mic
  • Camare

输出设备

• outPut
  • AVCaptureMovieFileOutput
  • AVCaptureStillImageOutput
  • AVCaptureVideoPreViewLayer

AVCaptureConnection 提供把输入和输出连接起来的功能

采集图二

AVCaptureSessionPreset

使用AVCaptureSessionPreset 指定摄像头采集的分辨率

AVCaptureVideoPreviewLayer

创建预览视图，可以直接将采集到的画面渲染出来。

关键代码参考

- (void) setupVideoCamareWithPosition:(AVCaptureDevicePosition) cameraPosition{
    
    // 1. get input device
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if (device.position == cameraPosition) {
            self.inputCamareDevice = device;
        }
    }
    // 2. captureSession
    BOOL enableApplicationSession  =  YES;
    if (enableApplicationSession) {
        self.captureSession.automaticallyConfiguresApplicationAudioSession = YES;
        self.captureSession.usesApplicationAudioSession = YES;
    }
    [self.captureSession beginConfiguration];
    
    //  3. add input
    NSError * error = nil;
    self.videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:_inputCamareDevice error:&error];
    if ([self.captureSession canAddInput:self.videoInput]) {
        [self.captureSession addInput:_videoInput];
    }
    
    // 4. add outPut
    [self.videoDataOutPut setSampleBufferDelegate:self queue:_cameraProcessingQueue];
    if ([self.captureSession canAddOutput:_videoDataOutPut]) {
        [self.captureSession addOutput:_videoDataOutPut];
    } else {
        NSLog(@"can't add video output");
    }
    if ([self.captureSession canSetSessionPreset:AVCaptureSessionPreset640x480]) {
        [self.captureSession setSessionPreset:AVCaptureSessionPreset640x480];
    }
    [self.captureSession commitConfiguration];
}
//   5. setupPreivew
- (void) setupPreviewWithView:(UIView *) view{
    if (!view) {
        return;
    }
    CALayer *layer = view.layer;
    layer.masksToBounds = YES;
    self.previewLayer.frame = layer.bounds;
    self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    [layer insertSublayer:self.previewLayer atIndex:0];
}
- (void) startCapture{
    if (![_captureSession isRunning]) {
        [_captureSession startRunning];
    }
}

demo 地址：https://github.com/zjunchao/streaming_tutorial/tree/master/tutorial01