Mac Support

[jaysonlane]

I've been working to add macOS support which basically amounts to changing out the CIContext in the VideoFilterExporter initializer from EAGLContext to MTLContext (as OpenGL ES is not available on mac):

let metalDevice = MTLCreateSystemDefaultDevice()!
let context = CIContext(MTLDevice: metalDevice, options: [kCIContextWorkingColorSpace : NSNull()])

This compiles and, I believe, is sufficient, however, I've noticed that the startVideoCompositionRequest on the custom compositor is never called [note: this is the only change]. When I run the export method a new video file is written but the filter is never applied. I saw that you ran into this issue when originally developing this for iOS from a StackOverflow question. I think this is the same issue, with the passthrough track ID causing the sole track to not have the filter applied and thus not calling the startVideoCompositionRequest. Do you have any insight into possible solutions?

[jojodmo]

I don't know what could be causing this, but here's some of my ideas

• Maybe it has to do with how certain objects are handled in iOS verses in macOS. For example, maybe something with the requiredSourceTrackIDs variable in the VideoFilterCompositionInstruction class - maybe a NSNumber isn't the expected NSValue. Maybe NSNumber isn't the expected Any in the requiredPixelBufferAttributesForRenderContext and sourcePixelBufferAttributes variables of the AVVideoCompositing class.
• Try cleaning the Build Folder (in Xcode, Command + Option [alt] + Shift + K)
• Try commenting out all of the code you have right now, and re-copying/downloading it all from here, and make sure that you only change the device, and nothing else.

Other than that, I don't really know what could be causing this - you may want to post a question on Stack Overflow. If I think of anything else, I'll be sure to let you know!

If you solve this, it would be awesome if you could post your solution here or propose a change to the files affected telling people about what you had to change.

Good luck!

[jojodmo]

Make sure that both the URL for file you're applying the filter to and the export URL end with .mp4 or .mov — I didn't have that in the README before, but I'm going to add it now.