I mostly found forum posts complaining that FFmpeg isn’t effectively leveraging however many n cores someone’s turbo-charged machine happens to present to the OS, as demonstrated by their CPU monitoring tool. I also did some Googling regarding multithreaded FFmpeg. Now, how to take advantage of FFmpeg’s threading API (which supports POSIX threads, Win32 threads, BeOS threads, and even OS/2 threads)? Would it surprise you to learn that this aspect is not extensively documented? Time to reverse engineer the API. As briefly mentioned in my last Theora post, I think FFmpeg’s Theora decoder can exploit multiple CPUs in a few ways: 1) Perform all of the DC prediction reversals in a separate thread while the main thread is busy decoding the AC coefficients (meanwhile, I have committed an optimization where the reversal occurs immediately after DC decoding in order to exploit CPU cache) 2) create n separate threads and assign each (num_slices / n) slices to decode (where a slice is a row of the image that is 16 pixels high).

Ffmpeg av1 multithread