How much difference does GPU speed make?

[JoeH]

I was wondering how much difference for DG-NV your GPU model makes. I have a 9500GT, about the slowest NVidia card which supports VP2, but it handles decoding HD streams without even hardly trying.

With DG-NV, how much of a difference does having a faster card make?

[Guest]

With DG-NV, how much of a difference does having a faster card make? If the card is 50% faster for decoding video and delivering the video, then the "how much of a difference" is 50%. :)

If you are really asking how much faster the higher end cards are for decoding and delivering video, then you need to compare the VP engine clock rate and the bus size.

[an3k]

There isn't a big difference If the older gfx can handle the source completely on the GPU.

I tested The Dark Knight on my GTX295 (VP2) and on my GT240 (VP5).
The GTX295 is faster than the GT240 but both cards need nearly the same time to decode the whole source.

The only notable difference is if you use source the older gfx cannot handle, thus using the CPU. For example VC-1 on VP2 vs. VP3/VP4/VP5.

VP2 cannot handle VC-1 completely on the GPU, so if features are used the gfx cannot handle, your CPU is used.
VP3+ can handle VC-1 completely on the GPU, thus cards with this VP-Version are faster.

[burfadel]

Isn't the decoder part separate from the actual GPU itself, meaning unless the decoder has changed between different spec models the speed will be very similar?

I believe the decoding isn't actually done using the pixel shaders etc?

[JoeH]

If the card is 50% faster for decoding video and delivering the video, then the "how much of a difference" is 50%. :)

The problem is that a 50% faster difference could mean a real speed difference of 0% faster, since the slower card can handle the video decoding already completely.

If I am encoding to X264 but using DG-NV to decode, for example, and the slowest NVidia GPU can handle 100% the decoding, there should be 0% speed difference between a 9500GT and a GTX295, because the GPU speed difference just doesn't matter anymore...

So, my question is - for DG-NV, how much, if any, of a noticeable difference is there between a slower and faster NVidia card. AN3k states there is none (except for additionaly VP support cases)... which makes perfect sense to me. Any one else have any experiences testing this?