Slow rendering using OpenCL

[Norman Black]

You said you were using the Sony AVC encoder, yet you said you used CUDA and he OpenCL. Only the Main Concept AVC encoder has separate CUDA and OpenCL options listed. Sony AVC says nothing about GPU specifics. Anyway, from my experience, Sony AVC only uses the GPU lightly and is more dependent on CPU performance. Not much difference in encode time CPU only to GPU support encode time.

Main Concept AVC would load the GPU more and you would see a very large difference in CPU only to GPU encode times. Also, difference in visual quality as the OpenCL/CUDA encoders are completely different algorithms from the CPU only encoder. This only really showed when pusing bitrates really low.

[Marius Dalangauskas]

Ahh yes, pardon me. Indeed we tried the MainConcept AVC encoder, but again, for a graphics card as good as his (considered a high-end card) the render time is still very slow (18 minutes/10 minute file). Same goes with Sony AVC encoder. We’ve read some thing about OpenCL working way slower in 13.1-13.3 Catalyst drivers than 12.1, thinking that might be the problem. While we try out the older drivers, could someone suggest something else?

[Thayalan Paramasawam]

yes that probleum comes from catalyst drivers…..i have same probleum…..so need to update the latset version.

After i update this version i have probleum (Crash) when rendering mpeg 2 for dvd,so i need to off open cl but its working for 1920×1080.

[Norman Black]

Sorry I don’t have specific numbers but I remember the Main Concept OpenCL encoder running at greater than real time with my old 5850 card on 1080p30 files. This on a core i7 860 machine and driver 13.1.

Unfortunately, after I upgraded my video card to a 7950, the MC AVC OpenCL encoder no longer thinks OpenCL is available since it runs in CPU only mode. Everything else works fine, just a problem with Main Concept. Otherwise I could give you numbers from my 7950.

[Marius Dalangauskas]

It’s not a huge problem for us, but saving 12 minutes from each rendered video does add up in the end. I forgot to mention that our videos are recorder with the MPEG-1 codec. Small in size and good in quality. We’re thinking that could be the problem.

[Norman Black]

I put my old 5850 back into my computer. Main Concept OpenCL now works again. I did not change the driver or anything. No need to.

I my machine it encodes at real time or better speed for 1080p30 files. Input files are GoPro Hero 3 Black (H.264 20Mbps) or Contour camera H.264 files.

One thing to test. Are you sure that OpenCL is being use with your 7950 card? It does not want to work with mine. Encode a 1 minute section CPU only and then OpenCL if available and compare times.

The 7950 is a GCN (graphic core next) design. Precompiled OpenCL code for AMD will not work on it. You need source or pseudo code to be compiled at runtime if you don’t have precompiled code for that architecture. The Main Concept OpenCL encoder in Vegas 12 may not, and stupidly not have included code that can be JIT compiled.

[Marius Dalangauskas]

I wish to ask really quick. Is it possible that AMD will release a patch for this?

[Norman Black]

Who is to say it is an AMD problem. Just as likely to be a Main Concept problem.

I found posts with problems with the 7950 card rendering with MC AVC OpenCL going back to VP11. Those got error messages. In VP12 is just falls to CPU only in my case.

Given that nothing else has a problem with the 7950, I am leaning towards it being a Main Concept problem. MC may have issues with anything in AMD’s graphic core next line of cards (79xx).

Sony support has been sitting on my support request for some time on this. Maybe they are waiting for Main Concept to get back to them.

[Lee Ray]

Norm,

After all these months, did Sony ever get back to you on your 7950 issue?

For the past 3 weeks, I’ve had a ticket open with Sony on my 7870. My older card, an XFX Radeon HD 6950, worked fine utilizing the GPU under Main Concept. I picked up the 7870 because I wanted to improve my render times and the price was right. Now I’m having the same problem as every other 7xxx owner – NO accelerated GPU rendering times. It takes over 3 minutes to render a 1 minute video. The 6950 was doing it in 40 seconds.

I’ll probably go back to the 6950 unless SOMEONE out there has come up with a solution to get the 7xxx card to work. Anyone?

[Lee Ray]

Update:

Finally got a response from Sony Tech Support tonight but his reply was unbelievable.

In a nutshell, I was told: “My video does not contain enough effects or graphics to require the GPU to be utilized.” He said I needed to add more effects and increase the bit-rate of the final clip before I would see a difference. What?? There’s a friggin’ switch that says “USE GPU”…but they forgot to add “if it feels like being used”.

The whole purpose of buying a newer, high-end video card was to reduce the rendering time. I now have a video card that takes 3X longer than my old one. Sony doesn’t seem to have a problem with this.

It has been an awful past 3 weeks for me and this pushed me over the edge tonight. I’m tossing up my hands, going with Norm’s comment that “ATI Radeon HD 7xxx series cards don’t work with Vegas”, and returning the card tomorrow. I’ll live with my HD 6950 until I can find a card out there that will work EVERY time I render…and hopefully at 70-90 frames per second.

Is someone out there using an ATI Radeon HD 7xxx card that works every time? Please let me know. Other card recommendations? $200-$250 budget.