CODEWITHSUNDEEP
swiftmemory-managementavcapturesessioncvpixelbuffer
Alvar
Alvar

Reputation: 539

Does Swift manage the memory of a CVPixelBuffer that I create from CVPixelBufferCreate?

Let's say I want to store a frame from camera output

let imageBuffer:CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
some_list.append(imageBuffer.copy())

And here is how the copy function is defined by extension to CVPixelBuffer:

extension CVPixelBuffer {
    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, CVAttachmentMode.shouldPropagate),
            &_copy)
        guard let copy = _copy else { fatalError() }
        CVPixelBufferLockBaseAddress(self, CVPixelBufferLockFlags.readOnly)
        CVPixelBufferLockBaseAddress(copy, CVPixelBufferLockFlags(rawValue: 0))
        let dest = CVPixelBufferGetBaseAddress(copy)
        let source = CVPixelBufferGetBaseAddress(self)
        let height = CVPixelBufferGetHeight(self)
        let bytesPerRow = CVPixelBufferGetBytesPerRow(self)
        memcpy(dest, source, height * bytesPerRow)
        CVPixelBufferUnlockBaseAddress(copy, CVPixelBufferLockFlags(rawValue: 0))
        CVPixelBufferUnlockBaseAddress(self, CVPixelBufferLockFlags.readOnly)
        return copy
    }
}

The question is: Do I need to explicitly manage the CVPixelBuffer copy I created? Or does Swift take care of it through reference count?

Upvotes: 1

Views: 1661

Answers (1)

pompopo
pompopo

Reputation: 969

Swift manages your buffer object, so you don't have to consider about releasing it.

Core Foundation objects returned from annotated APIs are automatically memory-managed in Swift—you don't need to invoke the CFRetain, CFRelease, or CFAutorelease functions yourself.

https://developer.apple.com/documentation/swift/imported_c_and_objective-c_apis/working_with_core_foundation_types#2994152

In fact, there is no Swift version of CVPixelBufferRelease function.

https://developer.apple.com/documentation/corevideo/1563589-cvpixelbufferrelease

Upvotes: 6

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