CUDA acceleration in preview window but no when render to the file (Windows)

[Ola Haldor voll]

I can’t imagine your computer isn’t utilizing the GPU. The manual clearly states

DaVinci Resolve uses GPUs for image processing, so the GPU status indicates the percentage of use that the current color correction demands of the GPU. A full green indication shows there is plenty of GPU headroom. As the GPU processing resources are used by additional color correction the green bars will reduce. A flashing red indication means that the GPU is unable to consistently process the correction in real time.

The fact that you can play the video means things are working as they should. During rendering, its perfectly normal that performance goes down. This is due to the writing speed of your hard drives and how powerful the CPU is, which, if I’m not mistaken, is responsible for moving data and writing it to the HDD.

But then again, this is a BETA. Things will break. So report it to davincihelp@blackmagic-design.com anyway.

And not least, this is on a totally new platform for DaVinci Resolve. It will take a little time until things are perfectly normal. The problem is that there are thousands of different configuration possibilities. BMD can only support so much, and that’s the reason they have put a few high-end systems in their conig guide – because they know they can do the job properly.

It would be helpful to know what read/write speeds you’re getting. Use BMDs own speed check and tell us the numbers you get on the different drives you use for media/rendering.

[Vladimir Kucherov]

Also remember, during playback, your computer is reading video, processing the image, and that’s it.

During render, it also has to compress, and write frames to disk, so, depending on drives and CPU bottlenecking, framerate WILL drop compared to playback.

[Tomasz Swierczynski]

Thank you for quick response. So if I understand correctly, if there is no green or red bar after “GPU”, that’s mean that GPU resources are utilised in 100%? I thought it was the other way around – that longer green bar shows bigger GPU utilisation. Once again thank you very much.
Tom

[Ola Haldor voll]

As I interpret this – yes.

[Peter Chamberlain]

Resolve uses CUDA for image processing and the CPUs for decompression and compression, disk I/O, memory buffer etc… my guess is the system config you have does not match the config guide so you are interpreting the GPU meter and slow speed of renders as a CUDA issue but its not. If you can play in real time and render a fraction of that the issue is likely disk I/O. One disk is too few for a compressed HD image. Try playing back from one and rendering to a second. That way the drives don’t need to change from read to write for each frame. The 1GB of ram in the GPU will also reach its limits if you have a few nodes, and you don’t mention the UI GPU, which should be separate.

Sounds like the application is working as it should given the hardware config.
Peter

[Lauri Laidna]

I understand that you are only using 1 GPU for both UI and GPU? From my experience when I only had one 1GB GTX285 installed, it did get slower and slower and slower. I think the memory (1GB) ran out. After restarting Resolve it was fast again for a while. With additional GPU for UI the same GTX285 does not show such problem.

I think this is your case also. So please use 2 GPU cards like suggeste by DaVinci.

Also try different output types (containers/codecs). Just did a test. Quicktime H264 got me 15fps, while Avid DNxHD 1080p 36 got 50-60fps rendering speed! Find your (or program) bottlenecks and try to avoid them. I hadn’t rendered out to H264 before from Resolve – this looks to be very slow and not optimized yet, CPUs were very little utilezed.

Have Task Manager runnig at all times and GPU-Z for GPU monitoring. This way you will see what is maxing out on your system.

[Tomasz Swierczynski]

Yes – I had a pop up message when Resolve started that this software working better with two graphic cards – one for GUI and another for CUDA acceleration. If this GUI card is for display only – that, in my opinion, could be any card supporting full HD resolution – not necessarily another CUDA compatible NVidia . Why not i.e. my on-board chip ATI 4250? So I turned on my ATI and plugged my monitor to it. The pop up message is now gone, but slow rendering problem remains. That possibly means, sadly for me, that GTX 560 Ti with 1GB ram is not efficient enough to work with DaVinci Resolve.

[Lauri Laidna]

Yes, any card is fine for monitors. In my case it is still nVidia because of Adobe and Avid.

GTX 560 Ti by the specs looks more powerful than GTX285 that I’ve used most. 560Ti has 384 cores while 285 has only 240. So 560Ti should be more than enough for even quite complex grading! You should get more than 50 fps rendering most of the time!

What codec are you rendering out to? Try Avid DNxHD 1080p. Are you running striped RAID? Rendering from one drive to another?

Sidenote: Looks like Resolve’s Quicktime h264 and MPEG4 encoding is done by a 32-bit process and it is VERY SLOW. Not utilizing CPU power available.

[Tomasz Swierczynski]

As I mentioned, I have just one, SATA 3, but still slow hard drive. This could be the possible bottleneck in my system. I’ve just ordered two additional Sagate Barracudas 7200. I hope they will solve my problem.

[Ola Haldor voll]

Did you read what we suggested? It doesn’t look like the bottleneck is the GPU. It’s most probably the CPU and/or hard drives you read/write to.