捕获IOS 7.0及更高版本的视频帧示例代码

Question

我正在尝试为此Apple Q＆amp; A代码提供有关如何捕获视频帧的IOS 7代码：AppleQ&A1702

到目前为止，我认为我已经使用is code：

正确替换了已弃用的minFrameDuration

// If you wish to cap the frame rate to a known value, such as 2 fps, set minFrameDuration.
//output.minFrameDuration = CMTimeMake(1, 2); //deprecated
[device setActiveVideoMinFrameDuration:CMTimeMake(1, 2)];  //new in IOS7
[device setActiveVideoMaxFrameDuration:CMTimeMake(1, 2)];

但是，我无法运行代码，因为我收到了“No interface”错误＆＃39;对于此行的setSession：

// Assign session to an ivar.
[self setSession:session];

此外，我在此行收到了不兼容的类型警告：

[output setSampleBufferDelegate:self queue:queue];

我相信这个错误和警告有简单的答案，但经过大量的搜索，我感到难过。 有人可以帮我弄清楚为什么我直接从Apple示例代码中得到此错误和警告？谢谢卡门

[EDIT1]我不认为我已经完全放弃了我已弃用的​​minFrameDuration修复程序，而且可能不需要setSession方法。我正在尝试拼凑剪切和粘贴代码，以便以指定的帧速率从视频中捕获图像，而IOS7应用程序不需要在低于7.0的情况下运行。我暂时将捕获的图像放在我的故事板上的UIImageView中。

不应该这么难。

这是我到目前为止的整个代码部分，但是当我从viewDidLoad调用setupCaptureSession并且上面提到的不兼容类型警告仍然存在后仍然没有触发captureOutput方法，任何人都可以看到错误（我仍然是新手所以很好：）

// 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 resolution for video frames
    session.sessionPreset = AVCaptureSessionPresetHigh;

    // 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];
    [session addOutput:output];

    // Configure your output.
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
    [output setSampleBufferDelegate:self queue: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 2 fps, set
    // minFrameDuration.
    //output.minFrameDuration = CMTimeMake(1, 2); //deprecated


    //AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo];

    //if (conn.supportsVideoMinFrameDuration)  // these are deprecated in IOS7
    //  conn.videoMinFrameDuration = CMTimeMake(1,2);
    //if (conn.supportsVideoMaxFrameDuration)
    //  conn.videoMaxFrameDuration = CMTimeMake(1,2);

    NSError *error2;
    [device lockForConfiguration:&error2];
    if (error2 == nil) {
        if (device.activeFormat.videoSupportedFrameRateRanges){
            [device setActiveVideoMinFrameDuration:CMTimeMake(1, 2)];
            [device setActiveVideoMaxFrameDuration:CMTimeMake(1, 2)];
        }else{
            //handle condition
        }
    }else{
        // handle error2
    }
    [device unlockForConfiguration];


    // Start the session running to start the flow of data
    [session startRunning];

    // Assign session to an ivar.
    //[self setSession:session];  //not sure why need this, can't find code that works for it
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection
{
    NSLog(@"captureOutput: didOutputSampleBufferFromConnection");

    // Create a UIImage from the sample buffer data
    UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
    dispatch_async(dispatch_get_main_queue(), ^{
        //< Add your code here that uses the image >
        [self.imageView setImage:image];
        [self.view setNeedsDisplay];}
        );
}

// Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    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
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

    // 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();

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
                                                                bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Free up the context and color space
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    UIImage *image = [UIImage imageWithCGImage:quartzImage];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return (image);
} 

Answer 1

因此，这个问题的关键似乎是苹果指令“将会话分配给ivar＆＃39;然后调用他们没有提供代码的方法。

由于我是新手并且使用ARC，我希望不必了解合成/ ivars，我仍然没有。

但是，这里的代码是基本的捕获代码（我的整个viewController。）。基本上我必须在我的viewController.m

中的导入行之后声明会话

也许有人可以解释我的所作所为，但我现在正在考虑解决此问题（仍然不确定问题中提到的不兼容类型警告）：

#import "CJKViewController.h"

AVCaptureSession *session;

@interface CJKViewController ()

@end

@implementation CJKViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    // Create the session

    [self setupCaptureSession];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}







// Create and configure a capture session and start it running
- (void)setupCaptureSession
{
    NSError *error = nil;

//  AVCaptureSession *session = [[AVCaptureSession alloc] init];
    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 = AVCaptureSessionPresetHigh;

    // 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];
    [session addOutput:output];

    // Configure your output.
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
    [output setSampleBufferDelegate:self queue: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 2 fps, set
    // minFrameDuration.
    //output.minFrameDuration = CMTimeMake(1, 2); //deprecated


    //AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo];

    //if (conn.supportsVideoMinFrameDuration)
    //  conn.videoMinFrameDuration = CMTimeMake(1,2);
    //if (conn.supportsVideoMaxFrameDuration)
    //  conn.videoMaxFrameDuration = CMTimeMake(1,2);

    NSError *error2;
    [device lockForConfiguration:&error2];
    if (error2 == nil) {
        if (device.activeFormat.videoSupportedFrameRateRanges){
            [device setActiveVideoMinFrameDuration:CMTimeMake(1, 2)];
            [device setActiveVideoMaxFrameDuration:CMTimeMake(1, 2)];
        }
    }else{
        // handle error2
    }
    [device unlockForConfiguration];


    // Start the session running to start the flow of data
    [session startRunning];

    // Assign session to an ivar.
    //[self setSession:session];
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection
{
    NSLog(@"captureOutput: didOutputSampleBufferFromConnection");

    // Create a UIImage from the sample buffer data
    UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
    dispatch_async(dispatch_get_main_queue(), ^{
        //< Add your code here that uses the image >
        [self.imageView setImage:image];
        [self.view setNeedsDisplay];}
        );
}

// Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    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
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

    // 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();

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
                                                                bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Free up the context and color space
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    UIImage *image = [UIImage imageWithCGImage:quartzImage];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return (image);
}

@end