如何在库中设置 AVCaptureVideoDataOutput

Question

我正在尝试为 iPhone 创建一个库，因此我正在尝试通过调用来初始化相机。 当我在此声明中调用“self”时，问题就出现了：

"[captureOutput setSampleBufferDelegate:self queue:queue];"

因为编译器说：“在此范围内未声明 self”，我需要做什么才能将同一类设置为“AVCaptureVideoDataOutputSampleBufferDelegate”？至少给我指出正确的方向：P。

谢谢 ！！！

这是完整的功能：

bool VideoCamera_Init(){


    //Init Capute from the camera and show the camera


    /*We setup the input*/
    AVCaptureDeviceInput *captureInput = [AVCaptureDeviceInput 
                                          deviceInputWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] 
                                          error:nil];
    /*We setupt the output*/
    AVCaptureVideoDataOutput *captureOutput = [[AVCaptureVideoDataOutput alloc] init];
    /*While a frame is processes in -captureOutput:didOutputSampleBuffer:fromConnection: delegate methods no other frames are added in the queue.
     If you don't want this behaviour set the property to NO */
    captureOutput.alwaysDiscardsLateVideoFrames = YES; 
    /*We specify a minimum duration for each frame (play with this settings to avoid having too many frames waiting
     in the queue because it can cause memory issues). It is similar to the inverse of the maximum framerate.
     In this example we set a min frame duration of 1/10 seconds so a maximum framerate of 10fps. We say that
     we are not able to process more than 10 frames per second.*/
    captureOutput.minFrameDuration = CMTimeMake(1, 20);

    /*We create a serial queue to handle the processing of our frames*/
    dispatch_queue_t queue;
    queue = dispatch_queue_create("cameraQueue", NULL);
    variableconnombrealeatorio= [[VideoCameraThread alloc] init];
    [captureOutput setSampleBufferDelegate:self queue:queue];


    dispatch_release(queue);
    // Set the video output to store frame in BGRA (It is supposed to be faster)
    NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey; 
    NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA]; 
    NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key]; 
    [captureOutput setVideoSettings:videoSettings]; 
    /*And we create a capture session*/
    AVCaptureSession * captureSession = [[AVCaptureSession alloc] init];
    captureSession.sessionPreset= AVCaptureSessionPresetMedium;
    /*We add input and output*/
    [captureSession addInput:captureInput];
    [captureSession addOutput:captureOutput];
    /*We start the capture*/
    [captureSession startRunning];


    return TRUE;
}

我也做了下一堂课，但缓冲区是空的：

"

#import "VideoCameraThread.h"

CMSampleBufferRef bufferCamara;

@implementation VideoCameraThread

• (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)连接 { bufferCamera=sampleBuffer;

  } “

Answer 1

您正在编写一个 C 函数，它没有 Objective C 类、对象或 self 标识符的概念。您将需要修改您的函数以接受一个参数来接受您想要使用的sampleBufferDelegate：

bool VideoCamera_Init(id<AVCaptureAudioDataOutputSampleBufferDelegate> sampleBufferDelegate) {
    ...
    [captureOutput setSampleBufferDelegate:sampleBufferDelegate queue:queue];
    ...
}

或者您可以使用 Objective C 面向对象的接口而不是 C 风格的接口来编写您的库。

此函数中的内存管理也存在问题。例如，您正在分配 AVCaptureSession 并将其分配给局部变量。此函数返回后，您将无法检索该 AVCaptureSession 以便释放它。