好的,这是一个更完整的答案.首先,设置捕获：

// Create capture session
self.captureSession = [[AVCaptureSession alloc] init];

[self.captureSession setSessionPreset:AVCaptureSessionPresetPhoto];

// Setup capture input
self.inputDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput *captureInput = [AVCaptureDeviceInput deviceInputWithDevice:self.inputDevice
                                                                           error:nil];
[self.captureSession addInput:captureInput];

// Setup video processing (capture output)
AVCaptureVideoDataOutput *captureOutput = [[AVCaptureVideoDataOutput alloc] init];
// Don't add frames to the queue if frames are already processing
captureOutput.alwaysDiscardsLateVideoFrames = YES;

// Create a serial queue to handle processing of frames
_videoQueue = dispatch_queue_create("cameraQueue",NULL);
[captureOutput setSampleBufferDelegate:self queue:_videoQueue];

// Set the video output to store frame in YUV
NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;

NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange];
NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
[captureOutput setVideoSettings:videoSettings];
[self.captureSession addOutput:captureOutput];

现在好了委托/回调的实现：

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
   fromConnection:(AVCaptureConnection *)connection
{

// Create autorelease pool because we are not in the main_queue
@autoreleasepool {

    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

    //Lock the imagebuffer
    CVPixelBufferLockBaseAddress(imageBuffer,0);

    // Get information about the image
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);

    //    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);

    CVPlanarPixelBufferInfo_YCbCrBiPlanar *bufferInfo = (CVPlanarPixelBufferInfo_YCbCrBiPlanar *)baseAddress;

    // This just moved the pointer past the offset
    baseAddress = (uint8_t *)CVPixelBufferGetBaseAddressOfPlane(imageBuffer,0);


    // convert the image
    _prefImageView.image = [self makeUIImage:baseAddress bufferInfo:bufferInfo width:width height:height bytesPerRow:bytesPerRow];

    // Update the display with the captured image for DEBUG purposes
    dispatch_async(dispatch_get_main_queue(),^{
        [_myMainView.yUVImage setImage:_prefImageView.image];
    });        
}

最后这里是从YUV转换为UIImage的方法

- (UIImage *)makeUIImage:(uint8_t *)inBaseAddress bufferInfo:(CVPlanarPixelBufferInfo_YCbCrBiPlanar *)inBufferInfo width:(size_t)inWidth height:(size_t)inHeight bytesPerRow:(size_t)inBytesPerRow {

NSUInteger yPitch = EndianU32_BtoN(inBufferInfo->componentInfoY.rowBytes);

uint8_t *rgbBuffer = (uint8_t *)malloc(inWidth * inHeight * 4);
uint8_t *yBuffer = (uint8_t *)inBaseAddress;
uint8_t val;
int bytesPerPixel = 4;

// for each byte in the input buffer,fill in the output buffer with four bytes
// the first byte is the Alpha channel,then the next three contain the same
// value of the input buffer
for(int y = 0; y < inHeight*inWidth; y++)
{
    val = yBuffer[y];
    // Alpha channel
    rgbBuffer[(y*bytesPerPixel)] = 0xff;

    // next three bytes same as input
    rgbBuffer[(y*bytesPerPixel)+1] = rgbBuffer[(y*bytesPerPixel)+2] =  rgbBuffer[y*bytesPerPixel+3] = val;
}

// Create a device-dependent RGB color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

CGContextRef context = CGBitmapContextCreate(rgbBuffer,yPitch,inHeight,8,yPitch*bytesPerPixel,colorSpace,kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);

CGImageRef quartzImage = CGBitmapContextCreateImage(context);

CGContextRelease(context);
CGColorSpaceRelease(colorSpace);

UIImage *image = [UIImage imageWithCGImage:quartzImage];

CGImageRelease(quartzImage);
free(rgbBuffer);
return  image;
}

你还需要#import“Endian.h”

请注意,对CGBitmapContextCreate的调用比我预期的要复杂得多.我对视频处理并不是很精明,但是这个电话让我感到困惑了一段时间.然后,当它最终起作用时,它就像魔术一样.