iphone ios4 视频捕捉

要注意：初始化摄像头的时候，设置采集格式是rgb的，

numberWithInt:kCVPixelFormatType_32BGRA

所以，输出的时候可以用以下方法生成NSImage

见http://stackoverflow.com/questions/3152259/how-to-convert-a-cvimagebufferref-to-uiimage

第一步：初始化AVCaptureSession，添加输入，输出源 

#import <AVFoundation/AVFoundation.h>  
  
// Create and configure a capture session and start it running  
- (void)setupCaptureSession   
{  
    NSError *error = nil;  
  
    // Create the session  
    AVCaptureSession *session = [[AVCaptureSession alloc] init];  
  
    // Configure the session to produce lower resolution video frames, if your   
    // processing algorithm can cope. We'll specify medium quality for the  
    // chosen device.  
    session.sessionPreset = AVCaptureSessionPresetMedium;  
  
    // Find a suitable AVCaptureDevice  
    AVCaptureDevice *device = [AVCaptureDevice  
                             defaultDeviceWithMediaType:AVMediaTypeVideo];  
  
    // Create a device input with the device and add it to the session.  
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device   
                                                                    error:&error];  
    if (!input) {  
        // Handling the error appropriately.  
    }  
    [session addInput:input];  
  
    // Create a VideoDataOutput and add it to the session  
    AVCaptureVideoDataOutput *output = [[[AVCaptureVideoDataOutput alloc] init] autorelease];  
    [session addOutput:output];  
  
    // Configure your output.  
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);  
    [output setSampleBufferDelegate:self queue:queue];  
    dispatch_release(queue);  
  
    // Specify the pixel format  
    output.videoSettings =   
                [NSDictionary dictionaryWithObject:  
                    [NSNumber numberWithInt:kCVPixelFormatType_32BGRA]   
                    forKey:(id)kCVPixelBufferPixelFormatTypeKey];  
  
  
    // If you wish to cap the frame rate to a known value, such as 15 fps, set   
    // minFrameDuration.  
    output.minFrameDuration = CMTimeMake(1, 15);  
  
    // Start the session running to start the flow of data  
    [session startRunning];  
  
    // Assign session to an ivar.  
    [self setSession:session];  
}  

第二步：实现AVCaptureVideoDataOutputSampleBufferDelegate协议方法 

// Delegate routine that is called when a sample buffer was written  
- (void)captureOutput:(AVCaptureOutput *)captureOutput   
         didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer   
         fromConnection:(AVCaptureConnection *)connection  
{   
    // Create a UIImage from the sample buffer data  
    UIImage *image = [self imageFromSampleBuffer:sampleBuffer];  
  
     < Add your code here that uses the image >  
  
}  
  
// Create a UIImage from sample buffer data  
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer   
{  
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);  
    // Lock the base address of the pixel buffer  
    CVPixelBufferLockBaseAddress(imageBuffer,0);  
  
    // Get the number of bytes per row for the pixel buffer  
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);   
    // Get the pixel buffer width and height  
    size_t width = CVPixelBufferGetWidth(imageBuffer);   
    size_t height = CVPixelBufferGetHeight(imageBuffer);   
  
    // Create a device-dependent RGB color space  
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();   
    if (!colorSpace)   
    {  
        NSLog(@"CGColorSpaceCreateDeviceRGB failure");  
        return nil;  
    }  
  
    // Get the base address of the pixel buffer  
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);  
    // Get the data size for contiguous planes of the pixel buffer.  
    size_t bufferSize = CVPixelBufferGetDataSize(imageBuffer);   
  
    // Create a Quartz direct-access data provider that uses data we supply  
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, baseAddress, bufferSize,   
                                                            NULL);  
    // Create a bitmap image from data supplied by our data provider  
    CGImageRef cgImage =   
        CGImageCreate(width,  
                        height,  
                        8,  
                        32,  
                        bytesPerRow,  
                        colorSpace,  
                        kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Little,  
                        provider,  
                        NULL,  
                        true,  
                        kCGRenderingIntentDefault);  
    CGDataProviderRelease(provider);  
    CGColorSpaceRelease(colorSpace);  
  
    // Create and return an image object representing the specified Quartz image  
    UIImage *image = [UIImage imageWithCGImage:cgImage];  
    CGImageRelease(cgImage);  
  
    CVPixelBufferUnlockBaseAddress(imageBuffer, 0);  
  
    return image;  
}  

好了，现在就可以自由的显示和分析获取的UIImage了，再也不用使用私有API了