如何创建样本缓冲区（CMSampleBufferRef）的实例？答案

【问题标题】：How to create instance of Sample Buffer (CMSampleBufferRef)?如何创建样本缓冲区（CMSampleBufferRef）的实例？
【发布时间】：2016-06-02 14:00:35
【问题描述】：

我尝试写ios相机，我拿了部分代码from apple：

- (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 >

}

我需要从程序中的任何位置调用此函数。但是因为它需要创建(CMSampleBufferRef) 的对象类型。怎么做？

我试着写这样的东西：

buf1 = [[CMSampleBufferRef alloc]init]

但这是错误的方式。

【问题讨论】：

在您的委托方法中，您不需要创建 CMSampleBuffer 的实例。您会获得对现有缓冲区的引用（sampleBuffer 参数）。
@stefos 恕我直言，调用方法需要转换成 3 个参数。还是我错了？
这是一个 AVCaptureVideoDataOutputSampleBufferDelegate 方法，在写入新视频帧时调用。您没有显式调用此方法。
正如@Xcoder 所说，您不要调用此方法。您只需使用 [captureOutput setSampleBufferDelegate: self queue:] 将控制器设置为委托。
@stefos 谢谢。我会考虑的

标签： ios objective-c camera cmsamplebufferref

【解决方案1】：

这是我目前用于在 swift3 中模拟 CMSampleBuffer 进行单元测试的 sn-p：

fileprivate func getCMSampleBuffer() -> CMSampleBuffer {
    var pixelBuffer : CVPixelBuffer? = nil
    CVPixelBufferCreate(kCFAllocatorDefault, 100, 100, kCVPixelFormatType_32BGRA, nil, &pixelBuffer)

    var info = CMSampleTimingInfo()
    info.presentationTimeStamp = kCMTimeZero
    info.duration = kCMTimeInvalid
    info.decodeTimeStamp = kCMTimeInvalid


    var formatDesc: CMFormatDescription? = nil
    CMVideoFormatDescriptionCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer!, &formatDesc)

    var sampleBuffer: CMSampleBuffer? = nil

    CMSampleBufferCreateReadyWithImageBuffer(kCFAllocatorDefault,
                                             pixelBuffer!,
                                             formatDesc!,
                                             &info,
                                             &sampleBuffer);

    return sampleBuffer!
}

【讨论】：

感谢您的回答。我已经不记得事情的本质了。

【解决方案2】：

@Rotem Tamir's Answer 的 Swift 5 版本

fileprivate func getCMSampleBuffer() -> CMSampleBuffer {
    var pixelBuffer: CVPixelBuffer?
    CVPixelBufferCreate(kCFAllocatorDefault, 100, 100, kCVPixelFormatType_32BGRA, nil, &pixelBuffer)

    var info = CMSampleTimingInfo()
    info.presentationTimeStamp = CMTime.zero
    info.duration = CMTime.invalid
    info.decodeTimeStamp = CMTime.invalid

    var formatDesc: CMFormatDescription?
    CMVideoFormatDescriptionCreateForImageBuffer(allocator: kCFAllocatorDefault,
                                                 imageBuffer: pixelBuffer!,
                                                 formatDescriptionOut: &formatDesc)

    var sampleBuffer: CMSampleBuffer?

    CMSampleBufferCreateReadyWithImageBuffer(allocator: kCFAllocatorDefault,
                                             imageBuffer: pixelBuffer!,
                                             formatDescription: formatDesc!,
                                             sampleTiming: &info,
                                             sampleBufferOut: &sampleBuffer)

    return sampleBuffer!
}

【讨论】：

【解决方案3】：

尝试所有这些（可能可行）：

UIImage *image = [self imageFromSampleBuffer:&sampleBuffer];
UIImage *image = [self imageFromSampleBuffer:(id)sampleBuffer];
UIImage *image = [self imageFromSampleBuffer:(__bridge CMSampleBufferRef)sampleBuffer];
UIImage *image = [self imageFromSampleBuffer:(__bridge id)sampleBuffer];

如果这些都不起作用，请创建对 CMSampleBuffer 的 CVImageBuffer 的引用，而不添加上述任何内容来替换 UIImage 方法中的 sampleBuffer：

CVImageBufferRef cvImageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

如果这不起作用，您可以创建一个单独的方法，将 CMSampleBuffer 转换为 UIImage，如下所示：

// 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);
}

此方法有效；事实上，这是我使用的那个。

【讨论】：