在任何 iOS 设备上复制 CVPixelBuffer
Copy a CVPixelBuffer on any iOS device
我很难想出在任何 iOS 设备上可靠地复制 CVPixelBuffer 的代码。我的第一次尝试效果很好,直到我在 iPad Pro 上尝试它:
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,因为 CVPixelBufferGetDataSize(self)
比 CVPixelBufferGetDataSize(pixelBufferCopy)
稍大,所以 memcpy 写入未分配的内存。
所以我放弃了,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
}
这适用于我的两台测试设备,但它刚刚到达实际客户,结果它在 iPad 6(目前只有该设备)上崩溃。这是 EXC_BAD_ACCESS
再次调用 memcpy()
。
似乎很疯狂,没有一个简单的 API 调用,因为要让它可靠地工作似乎是多么困难。还是我让它变得比需要的更难?感谢您的任何建议!
第二个实现看起来很可靠。我能想到的唯一问题是新像素缓冲区中的平面分配了不同的步长(每行字节数)。 stride length是根据width × (bytes per pixel) 然后以不指定的方式取整来达到最优的内存访问。
所以检查是否:
CVPixelBufferGetBytesPerRowOfPlane(self, plane) == CVPixelBufferGetBytesPerRowOfPlane(copy, plane
如果没有,逐行复制像素平面:
for plane in 0 ..< CVPixelBufferGetPlaneCount(self)
{
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 += bytesPerRowSrc
startOfRowDest += bytesPerRowDest
}
}
}
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程来增加价值,以解决 CVPixelBuffers
没有飞机的问题。
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
}
}
适用于 Swift 5. 提供更多背景知识... AVCaptureVideoDataOutput
.videoSettings
属性 可以采用多种格式。并非所有人都有飞机,尤其是 ML 模型可能需要的飞机。
我很难想出在任何 iOS 设备上可靠地复制 CVPixelBuffer 的代码。我的第一次尝试效果很好,直到我在 iPad Pro 上尝试它:
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,因为 CVPixelBufferGetDataSize(self)
比 CVPixelBufferGetDataSize(pixelBufferCopy)
稍大,所以 memcpy 写入未分配的内存。
所以我放弃了,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
}
这适用于我的两台测试设备,但它刚刚到达实际客户,结果它在 iPad 6(目前只有该设备)上崩溃。这是 EXC_BAD_ACCESS
再次调用 memcpy()
。
似乎很疯狂,没有一个简单的 API 调用,因为要让它可靠地工作似乎是多么困难。还是我让它变得比需要的更难?感谢您的任何建议!
第二个实现看起来很可靠。我能想到的唯一问题是新像素缓冲区中的平面分配了不同的步长(每行字节数)。 stride length是根据width × (bytes per pixel) 然后以不指定的方式取整来达到最优的内存访问。
所以检查是否:
CVPixelBufferGetBytesPerRowOfPlane(self, plane) == CVPixelBufferGetBytesPerRowOfPlane(copy, plane
如果没有,逐行复制像素平面:
for plane in 0 ..< CVPixelBufferGetPlaneCount(self)
{
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 += bytesPerRowSrc
startOfRowDest += bytesPerRowDest
}
}
}
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程来增加价值,以解决 CVPixelBuffers
没有飞机的问题。
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
}
}
适用于 Swift 5. 提供更多背景知识... AVCaptureVideoDataOutput
.videoSettings
属性 可以采用多种格式。并非所有人都有飞机,尤其是 ML 模型可能需要的飞机。