Even an old Sempron will probably decode most AVIs (MPEG-4 ASP?) with low CPU load; shuffling things to and from the GPU probably won't buy you much and in this case probably costs you overhead. Compressing to MPEG is also probably being done in software and not on the GPU; I'm not aware if there is any Linux support for GPGPU-accelerated encoding even with VAAPI. 

On 18 Jul 2011, at 1529, Andrew Z wrote:

> I spent some silly amount of time trying to get all three to perform together.
> Finally i guess i succeeded, but the results are nowhere to be excited about.
> 
> It takes about 40 minutes to transcode of ~800MB avi to mpeg on my ancient Sempron system with 2GB and GT240(512MB) with GPU enabled and ~30minutes w/o GPU. The CPU load is ~80% (GPU enabled) and ~99% (no GPU involved).
> 
> I posted results on vlc forum, wondering, pretty much "why bother with vaapi", but i guess the question won't be answered.
> 
> Yet, i'm curios what's your experience and thoughts on the matter? 
> 
> Andrew