That doesn't change the fact that Dirac doesn't calculate filters with the microcontroller of the device.Any algorithm can be implemented on a microprocessor as long as the processor speed and its accessible memory are enough for it. It doesn’t matter if Dirac runs on a PC, because you can interpret any code to run on any appropriate programmable processor which is when firmware updates come into the picture to reprogram the microcontroller. Actually, it might even run faster on the device than your PC, since your PC is doing a lot of background tasks to service GUI, file system interrupts, complicated multi core memory management and allocations, and … to name a few.
A firmware upgrade to the device itself doesn't make the code which runs in PC executable with the microcontroller of the device. But it could contain the code modified so that it can be executed with that microcontroller.
AV devices are prone to low performance microcontrollers. Menus and operations are slow. Rarely does a modern PC struggle with these issues even if its under higher load. But yes, if the device would have a powerful microcontroller then it could be even faster in some operations.
Fortunately the DSP chips in these devices are cabable of applying filters (doing arithmetic calculations) fast enough.