AviSynth and VirtualDub – speed improvement

Recently my old video card die… it is (was) a GeForce GTL 7600 (a custom made version by Sony, the same specs of a GT 7600, but a bit slower and with a very good pipe cooling system). It was the default video card in my Sony HTPC PC – a VGX-XL202 – and I never thought to replace it because, even if it was slow and old and with only 256MB, it was capable to play Blu-ray without stuttering (with some codecs and setting tweaks) and because AviSynth and VirtualDub use only CPU for their processing…

Or, at least, it was what I thought!

Just today I replaced it with a brand new Sapphire (AMD) Radeon HD 5450; a low profile 1GB DDR3 “honest” video card. I chose to buy this because I need a video card ASAP, it’s cheap and, as I have other two PCs, I’ll buy a better one later when I’ll upgrade another CPU.

Well, as I was working onto one of my project the day the card died, I promptly re-run the conversion, and I noted one thing: conversion speed is improved, A LOT! Now it runs at about double speed!

So, it seems that AviSynth and/or VirtualDub DO USE GPU power too, or the old GPU simply slowed down the CPU speed?

If it’s true that GPU power is important for conversion speed as the CPU, my next upgrade (CPU from Core 2 Duo E6300 1.86GHz to Core 2 Quad Q6700 2.67GHz, and GPU from GeForce GTL 7600 256MB to AMD Radeon HD7750 1/2GB) will improve speed up to 2.5x/3x thanks only to CPU; how much the video card will improve speed is to be discovered…

If someone had some similar experience, please post here… if only I knew this, I would have replaced my old video card before… years before!