在Swift 2.0中创建CMSampleBuffer的副本

Question

This has been asked before, but something must have changed in Swift since it was asked. I am trying to store CMSampleBuffer objects returned from an AVCaptureSession to be processed later. After some experimentation I discovered that AVCaptureSession must be reusing its CMSampleBuffer references. When I try to keep more than 15 the session hangs. So I thought I would make copies of the sample buffers. But I can't seem to get it to work. Here is what I have written:

var allocator: Unmanaged<CFAllocator>! = CFAllocatorGetDefault()
var bufferCopy: UnsafeMutablePointer<CMSampleBuffer?>
let err = CMSampleBufferCreateCopy(allocator.takeRetainedValue(), sampleBuffer, bufferCopy)
if err == noErr {
    bufferArray.append(bufferCopy.memory!)
} else {
    NSLog("Failed to copy buffer. Error: \(err)")
}

This won't compile because it says that Variable 'bufferCopy' used before being initialized . I've looked at many examples and they'll either compile and not work or they won't compile.

Anyone see what I'm doing wrong here?

Answer 1

You can simply pass a CMSampleBuffer? variable (which, as an optional, is implicitly initialized with nil ) as inout argument with & :

var bufferCopy : CMSampleBuffer?
let err = CMSampleBufferCreateCopy(kCFAllocatorDefault, buffer, &bufferCopy)
if err == noErr {
    // ...
}

Answer 2

Literally you're attempting to use the variable bufferCopy before it is initialized.

You've declared a type for it, but haven't allocated the memory it's pointing to.

You should instead create CMSampleBuffers using the following call https://developer.apple.com/library/tvos/documentation/CoreMedia/Reference/CMSampleBuffer/index.html#//apple_ref/c/func/CMSampleBufferCreate

You should be able to copy the buffer into this then (as long as the format of the buffer matches the one you're copying from).