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GTX 560 > 7950: slower render times?
About 4 months ago, I replaced my GTX 560 with a Radeon HD 7950, primarily for gaming. I understand that the 7950 is a very fast compute card, so I figured Vegas’s OpenCL rendering might take advantage of that. Little did I know that, compared to CUDA, it was [i]much[/i] slower. I’ve been using CPU for all of my rendering. In most cases, I can render at about 0.8x speed, whereas with the GTX 560, it was [i]at least[/i] twice as fast (I don’t remember its exact speed). OpenCL rendering is at least half the speed as CPU.
Full specs:
– Intel Core i7-2600K @ 4.0GHz
– MSI Z68A-GD80 motherboard
– 8GB DDR3 1600MHz RAM
– SAPPHIRE Radeon HD 7950 (OCed to 1150 (core), 1600 (memory), 1250 (VDDC)Is what I’m experiencing normal? I read that either Vegas or the Catalyst drivers could be to blame.
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7 Replies
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Main Concept AVC OpenCL does not support AMD graphics core next cards. AKA 7xxx series cards which includes your 7950.
Sony AVC does support GCN cards but Sony AVC is only partially GPU accelerated.
Sony Vegas itself (video prefs tab) does support the AMD GCN cards, but this usage all depends on what effects and such you use. Only the effects and transitions support GPU acceleration.
I also have a 7950. I previously had a 5850 and the Main Concept AVC OpenCL encoder really flew under the 5850.
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Main Concept for me is the slowest of the two, GPU or CPU, more so when selecting the GPU. It usually gets around 25FPS, and after about 3 seconds worth of rendering, it’ll pause for a few more before continuing on, etc.
Sony AVC is what I’ve been using (GPU).
Regardless, render times are much slower than when I have a GTX 560. It’s not a deal breaker, but it’s had me considering Adobe Premiere, although I heard that that’s noticeably slower than Vegas in most areas. My videos are simple and don’t need anything hardcore, so I’ll probably just stick with Vegas and hope that they figure out a better way to take advantage of these cards.
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I simply just stick to what works best and stay away
from this Card confusing mess for now….lol, lol.Steve Rhoden
(Cow Leader)
Film Editor & Compositor.
Filmex Creative Media.
https://www.facebook.com/FilmexCreativeMedia
1-876-461-9019 -
Even though my specific Radeon was listed as compatible with Vegas’ GPU acceleration when that premiered with Vegas 11, Vegas didn’t even recognize it. So now I have an nvidia GTS 450, which works with Vegas.
There’s all kinds of problems with Vegas and GPU acceleration (I can’t even upgrade my nvidia drivers or it’ll completely mess with Vegas), so you just have to go with what works.
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When Vegas 11 came out, first version of Vegas to use OpenCL rather than CUDA (well, CUDA-proprietary; as nVidia will tell you, CUDA is also OpenCL compliant these days, but when one speaks of CUDA, that’s usually to indicate the CUDA-only support, which was limited to the small bit of acceleration in Vegas 10 and maybe a few earlier version, just in the CODECs themselves), I did a comparison. I ran a GTX 570 against a Radeon HD6970. The HD6970 was as fast or faster at everything, so I kept it.
A couple of things. Back then anyway, I had to track down the better OpenCL drivers; the one that came bundled in the generic ATi/AMD install package didn’t work. Back then, the nVidia driver was buggy… didn’t see it fail on Vegas, but it did fail on a few sections of a few OpenCL benchmark programs.
I haven’t run benchmarks on my new system, but I’m pretty convinced that the level of acceleration in Vegas is limited to helping out slower PCs only. There’s always some time wasted in compiling OpenCL programs, transferring them to the GPU, transferring data to/from the GPU, etc, the CPU waiting on the GPU to finish, etc. So despite the fact that your GPU may be 25x faster than your CPU on paper, only some of that speed gets tapped, and a faster CPU eliminates the advantage. That’s of course implementation-dependent; if Vegas managed to run the GPU stuff asynchronously and pipeline processing, keeping the CPU at around 100% and maybe the GPU a bit more used, we might see a big win from the GPU. But that’s probably a huge change to the way Vegas works right now.
I’d be surprised if Vegas didn’t work right with the newer GPUs, unless there’s something rotten in their OpenGL implementation. One of the main premises of OpenGL is that it make the actual hardware a non-issue, as long as its capable of supporting the needed OpenGL ops. AMD actually has a driver that lets you run OpenGL on an AMD CPU… not necessarily what you want, but it does work.
-Dave
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So I switched from MP4 to MPEG-2 rendering, and it’s much faster, rendering at about 75FPS for a 1920×1080 29.97FPS video at 50Mbps.
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That’s to be expected. H.264/AVC/MPEG-4 Part 10 delivers about twice the coding efficiency of MPEG-2. You would expect H.264 at 25Mb/s to be about the same quality as MPEG-2 at 50Mb/s.
More or less. This comes from many times the encoding and decoding complexity. I recall when PCs got fast enough to do DVD decoding plus upscaling in software… on a Pentium at 133MHz. Back in the early 1990s. A buddy of mine worked for one of the companies doing DVD hardware decoders for PCs, and they had just released a software product that, for the first time, looked better than the hardware decoders.
My laptop, a 2.4GHz Core 2 Duo, was just enough CPU to decode HD quality AVC in without jerking around. And it actually did depend on the right decoder… the freebie in VLC didn’t make it. This was around the time they started using GPUs for decoding acceleration in players. With the accelerated player, the same video went from about 90-95% CPU to about 12% CPU.
But keep that in mind: just decoding AVC on two CPUs used them up. Imagine encoding from AVC back to AVC… it’s going to take a really long time on this computer. I do recall renders that ran 24 hours, back when I actually did rendering on this PC. MPEG-2, on the other hand, was no big deal for this computer.
-Dave
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