Swift 我必须锁定AVCaptureVideoDataOutput生成的CVPixelBuffer吗
我有一个Swift 我必须锁定AVCaptureVideoDataOutput生成的CVPixelBuffer吗,swift,avfoundation,core-video,cvpixelbuffer,Swift,Avfoundation,Core Video,Cvpixelbuffer,我有一个AVCaptureVideoDataOutput生成CMSampleBuffer实例传递到我的AVCaptureVideoDataOutputSampleBufferDelegate函数中。我想高效地将像素缓冲区转换为CGImage实例，以便在我的应用程序的其他地方使用 我必须小心，不要保留对这些像素缓冲区的任何引用，否则捕获会话将开始删除帧，原因是OutOfBuffers。此外，如果转换时间过长，则帧将被丢弃，原因是FrameWasLate 之前，我尝试使用CIContext渲染CGI
AVCaptureVideoDataOutputCMSampleBufferAVCaptureVideoDataOutputSampleBufferDelegateCGImageOutOfBuffersFrameWasLateCIContextCGImageCGContextpublic func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
// Capture at 60 FPS but only process at 4 FPS, ignoring all other frames
let timestamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
guard timestamp - lastTimestamp >= CMTimeMake(value: 1, timescale: 4) else { return }
// Extract pixel buffer
guard let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
// Lock pixel buffer before accessing base address
guard kCVReturnSuccess == CVPixelBufferLockBaseAddress(imageBuffer, .readOnly) else { return }
defer { CVPixelBufferUnlockBaseAddress(imageBuffer, .readOnly) }
// Use CGContext to render CGImage from pixel buffer
guard let cgimage = CGContext(data: CVPixelBufferGetBaseAddress(imageBuffer),
width: CVPixelBufferGetWidth(imageBuffer),
height: CVPixelBufferGetHeight(imageBuffer),
bitsPerComponent: 8,
bytesPerRow: CVPixelBufferGetBytesPerRow(imageBuffer),
space: cgColorSpace,
bitmapInfo: cgBitmapInfo).makeImage() else { return }
// Do something with cgimage...
}
CVPixelBufferGetBaseAddressCVPixelBufferLockBaseAddressavcapturedevideodataoutput我可以跳过锁定这里的基址吗？如果在此特定场景中不锁定基址，最糟糕的情况是什么？根据您的描述，您根本不需要转换为
CGImageCIImage（cvPixelBuffer:）CIImageCIImageCIContextCVPixelBufferCVPixelBufferPoolCIContextCIImagecontext.writeHEIFRepresentation（of:…）只有到最后图像数据才会传输到CPU端。这个问题从一开始就没有根据，因为我忽略了测试跳过锁的实际图像结果。如问题中所述，当我在初始化CGContext之前锁定基址时，
makeImagemakeImageCVPixelBufferGetBaseAddressnilmakeImage现在我要想办法加快速度。我以60 FPS的速度捕获，这意味着我希望渲染时间尽可能少于16毫秒，以便在下一个到达之前删除CMSampleBuffer引用。我刚刚发现，这表明锁定像素缓冲区会迫使CPU参与，这可能是帧被删除的原因。通过避免锁，GPU被使用，这当然可以解释加速。现在我想知道为什么文档被更改了，不再说明这一点。出于好奇：你在以后用
cgmiagesAVCaptureDataOutput