检查相机的iOS捕获分辨率

Question

我在iOS 7上使用OpenGL将前置摄像头视频捕获呈现到iPhone显示器（与iphone 5相同）上的UIView 。 我正在使用AVCaptureSessionPreset640x480并将其传递给AVCaptureSession方法

[captureSession setSessionPreset:AVCaptureSessionPreset640x480];

但是，渲染的视频似乎比上述设置的分辨率低，它似乎是AVCaptureSessionPreset352x288 。 实际上，无论我从这些常量中传递什么常量，分辨率都相同

NSString *const AVCaptureSessionPresetPhoto;
NSString *const AVCaptureSessionPresetHigh;
NSString *const AVCaptureSessionPresetMedium;
NSString *const AVCaptureSessionPresetLow;
NSString *const AVCaptureSessionPreset352x288;
NSString *const AVCaptureSessionPreset640x480;
NSString *const AVCaptureSessionPreset1280x720;
NSString *const AVCaptureSessionPreset1920x1080;
NSString *const AVCaptureSessionPresetiFrame960x540;
NSString *const AVCaptureSessionPresetiFrame1280x720;
NSString *const AVCaptureSessionPresetInputPriority;

如何检查相机实际拍摄的分辨率？

谢谢

Answer 1

读取捕获的缓冲区的尺寸，如下所示（对于AVCaptureSessionPresetPhoto您当然需要捕获静态图像，而不是读取视频帧...）：

- (void) captureOutput:(AVCaptureOutput *)captureOutput
       didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
              fromConnection:(AVCaptureConnection *)connection
  {
    CVPixelBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // "width" and "height" now hold your dimensions...

  }