Metal - Resize video buffer before passing to custom Kernel filter

Question

Within our iOS app, we are using custom filters using Metal (CIKernel/CIColorKernel wrappers).

Let\'s assume we have a 4K video and a custom video composition with a

Answer 1

As warrenm says, you could use a CILanczosScaleTransform filter to downsample the video frames before processing. However, this would still cause AVFoundation to allocate buffers in full resolution.

I assume you use a AVMutableVideoComposition to do the filtering? In this case you can just set the renderSize of the composition to the target size. From the docs:

The size at which the video composition should render.

This will tell AVFoundation to resample the frames (efficiently, fast) before handing them to your filter pipeline.