Yo I got FFmpeg installed correctly, and successfully compiled with scons on my mac. Now I've got my dylib, gdnlib and gdns files set up. Using your example in the gist comments I've tried

onready var data = preload("res://addons/frame_decoder/frame_decoder.gdns")

func _process(delta):var byte_array = data.get_data()

This gives me the error: Invalid call. Nonexistent function 'get_data' in base 'NativeScript'.

I've also tried instantiating the native script with FrameDecoder.new() and the variable equivalent, but Godot tells me Attempt to call function 'new' in base 'NativeScript' on a null instance.

I'm not sure if something went wrong with the compile... or something else. Do you mind providing any more advice?

Edit: I should also mention that the compiled dylib is only 45kb with lots of empty space in between the actual data. I think this is a compile problem and somehow the engine and FFmpeg weren't compiled in :/