我很难想出在任何 iOS 设备上可靠地复制 CVPixelBuffer 的代码。在我在 iPad Pro 上尝试之前,我的第一次尝试效果很好:
extension CVPixelBuffer {
func deepcopy() -> CVPixelBuffer? {
let width = CVPixelBufferGetWidth(self)
let height = CVPixelBufferGetHeight(self)
let format = CVPixelBufferGetPixelFormatType(self)
var pixelBufferCopyOptional:CVPixelBuffer?
CVPixelBufferCreate(nil, width, height, format, nil, &pixelBufferCopyOptional)
if let pixelBufferCopy = pixelBufferCopyOptional {
CVPixelBufferLockBaseAddress(self, kCVPixelBufferLock_ReadOnly)
CVPixelBufferLockBaseAddress(pixelBufferCopy, 0)
let baseAddress = CVPixelBufferGetBaseAddress(self)
let dataSize = CVPixelBufferGetDataSize(self)
let target = CVPixelBufferGetBaseAddress(pixelBufferCopy)
memcpy(target, baseAddress, dataSize)
CVPixelBufferUnlockBaseAddress(pixelBufferCopy, 0)
CVPixelBufferUnlockBaseAddress(self, kCVPixelBufferLock_ReadOnly)
}
return pixelBufferCopyOptional
}
}
以上在 iPad Pro 上崩溃是因为
CVPixelBufferGetDataSize(self)
略大于 CVPixelBufferGetDataSize(pixelBufferCopy)
,所以 memcpy 写入未分配的内存。所以我放弃了这个并尝试了这个:
func copy() -> CVPixelBuffer?
{
precondition(CFGetTypeID(self) == CVPixelBufferGetTypeID(), "copy() cannot be called on a non-CVPixelBuffer")
var _copy: CVPixelBuffer?
CVPixelBufferCreate(
nil,
CVPixelBufferGetWidth(self),
CVPixelBufferGetHeight(self),
CVPixelBufferGetPixelFormatType(self),
CVBufferGetAttachments(self, .shouldPropagate),
&_copy)
guard let copy = _copy else { return nil }
CVPixelBufferLockBaseAddress(self, .readOnly)
CVPixelBufferLockBaseAddress(copy, [])
defer
{
CVPixelBufferUnlockBaseAddress(copy, [])
CVPixelBufferUnlockBaseAddress(self, .readOnly)
}
for plane in 0 ..< CVPixelBufferGetPlaneCount(self)
{
let dest = CVPixelBufferGetBaseAddressOfPlane(copy, plane)
let source = CVPixelBufferGetBaseAddressOfPlane(self, plane)
let height = CVPixelBufferGetHeightOfPlane(self, plane)
let bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(self, plane)
memcpy(dest, source, height * bytesPerRow)
}
return copy
}
这在我的两个测试设备上都有效,但它刚刚接触到实际客户,结果它在 iPad 6 上崩溃了(到目前为止只有那个设备)。这是一个
EXC_BAD_ACCESS
调用memcpy()
再次。考虑到让它可靠地工作似乎有多困难,没有一个简单的 API 调用似乎很疯狂。还是我让它变得比需要的更难?感谢您的任何建议!
最佳答案
这个问答组合是纯金的。让我通过轻微的重构和一些控制流来增加值(value)以解释 CVPixelBuffers
没有飞机的。
public extension CVPixelBuffer {
func copy() throws -> CVPixelBuffer {
precondition(CFGetTypeID(self) == CVPixelBufferGetTypeID(), "copy() cannot be called on a non-CVPixelBuffer")
var _copy: CVPixelBuffer?
let width = CVPixelBufferGetWidth(self)
let height = CVPixelBufferGetHeight(self)
let formatType = CVPixelBufferGetPixelFormatType(self)
let attachments = CVBufferGetAttachments(self, .shouldPropagate)
CVPixelBufferCreate(nil, width, height, formatType, attachments, &_copy)
guard let copy = _copy else {
throw PixelBufferCopyError.allocationFailed
}
CVPixelBufferLockBaseAddress(self, .readOnly)
CVPixelBufferLockBaseAddress(copy, [])
defer {
CVPixelBufferUnlockBaseAddress(copy, [])
CVPixelBufferUnlockBaseAddress(self, .readOnly)
}
let pixelBufferPlaneCount: Int = CVPixelBufferGetPlaneCount(self)
if pixelBufferPlaneCount == 0 {
let dest = CVPixelBufferGetBaseAddress(copy)
let source = CVPixelBufferGetBaseAddress(self)
let height = CVPixelBufferGetHeight(self)
let bytesPerRowSrc = CVPixelBufferGetBytesPerRow(self)
let bytesPerRowDest = CVPixelBufferGetBytesPerRow(copy)
if bytesPerRowSrc == bytesPerRowDest {
memcpy(dest, source, height * bytesPerRowSrc)
}else {
var startOfRowSrc = source
var startOfRowDest = dest
for _ in 0..<height {
memcpy(startOfRowDest, startOfRowSrc, min(bytesPerRowSrc, bytesPerRowDest))
startOfRowSrc = startOfRowSrc?.advanced(by: bytesPerRowSrc)
startOfRowDest = startOfRowDest?.advanced(by: bytesPerRowDest)
}
}
}else {
for plane in 0 ..< pixelBufferPlaneCount {
let dest = CVPixelBufferGetBaseAddressOfPlane(copy, plane)
let source = CVPixelBufferGetBaseAddressOfPlane(self, plane)
let height = CVPixelBufferGetHeightOfPlane(self, plane)
let bytesPerRowSrc = CVPixelBufferGetBytesPerRowOfPlane(self, plane)
let bytesPerRowDest = CVPixelBufferGetBytesPerRowOfPlane(copy, plane)
if bytesPerRowSrc == bytesPerRowDest {
memcpy(dest, source, height * bytesPerRowSrc)
}else {
var startOfRowSrc = source
var startOfRowDest = dest
for _ in 0..<height {
memcpy(startOfRowDest, startOfRowSrc, min(bytesPerRowSrc, bytesPerRowDest))
startOfRowSrc = startOfRowSrc?.advanced(by: bytesPerRowSrc)
startOfRowDest = startOfRowDest?.advanced(by: bytesPerRowDest)
}
}
}
}
return copy
}
}
对 Swift 5 有效。提供更多背景知识...
AVCaptureVideoDataOutput
有很多格式.videoSettings
属性(property)可以拿。并非所有人都有飞机,尤其是 ML 模型可能需要的飞机。
关于ios - 在任何 iOS 设备上复制 CVPixelBuffer,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53132611/