[mythtv-users] System specifications review...

Johnny jarpublic at gmail.com
Wed Nov 18 03:43:24 UTC 2009

> 1) What does VDPAU give me that I wouldn't get otherwise?  Yes I know
> that it does the MPEG decoding in the GPU, and it can do deinterlacing
> in the GPU, and it can do some nice OSD in the GPU, ... but can't I do
> all of that in the CPU?  Are the algorithms supplied by nVidia better
> than what is available for plain-old-CPU algorithms?

Yes the nvidia deinterlacers are superior to the software ones that
would be done in the CPU. Advanced 2x is doing motion compensation
deinterlacing. It is analyzing spacial movement within frames and
across adjacent frames. There isn't just one way to do this and it is
computationally intensive. This gives sharp full resolution images and
it preserves all of the temporal information. Either the algorithms
nvidia is using or because of some capabilities of the hardware it
does a better job than the software deinterlacers. Some people have
indicated that the hardware deinterlacers in their TVs do as good of a
job. But from what I have seen these are usually on the high end sets.
VDPAU also does a great job at scaling and denoising.

> 2) I think I may have read somewhere about the VDPAU MPEG decoder not
> being terribly tolerant of errors in the input stream.  Since I'm
> going to use this to decode OTA signals, and I live slightly further
> outside Boston than Jarod Wilson does, am I setting myself up for
> disappointment?

> 3) Why did nVidia make the GT220?  Or, to put it another way, why
> would one choose the GT220 over the GT8600 or the GT9500?

To make more money. These cards are made for more than HTPCs. The 2xx
processors are all based on nvidia's newest GPU architecture. The 28x
and 29x processors are significantly more capable than the 9xxx GPUs.
Then they just scale the architecture down to reach the various market
segments. They remove the number of shader units or run them at lower
clock frequencies etc. There are newer capabilities also, like DX11
support. For VDPAU the 2xx cards will support decoding of MPEG4 (aka
xvid/divx) whereas the earlier processors only hand MPEG2 and H264.
Also to answer your question more directly the 220 fits in more where
the 8400 or 9400 would fit. So it is more capable than its
predecessors in the same market segment.

If you don't care about xvid/divx, then just get the cheapest VDPAU
card that can do Advanced 2x. You are not likely to see much
difference visual as long as it is powerful enough to do the
deinterlacer you want to use. If you ask me you are over analyzing
this. Just try it out and make your own call.

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