How to determine if NVENC Codec is being used.

I have just upgraded from the non-Studio version of Resolve 15 to a dongle licence. Most of the functions seem to be present and accessible, however, I am unable to find any indication that rendering is using the NVENC GPU hardware codec in the Format/Codec selection of the delivery screen. Furthermore, the render times to MP4 or MOV H264 don't seem to be any faster than was the case with the non-Studio version which only used the CPU.
I would be grateful if anybody could point me to any settings that might be inappropriate for the hardware configuration or if the hardware itself is preventing a faster render. Details of the system are listed below. The equipment is mainly for personal use with most of the current footage originated on a GH5.

System Specification:
Hardware:
Processor: Intel Core i7-6700K @ 4.00GHz
RAM: 16GB (2 x 8GB) Corsair DDR4, PC4-25600 (3200) Non-ECC
GPU: Asus Strix GTX970 (Nvidia GM204 4GB)
GUI Monitor: Dell 2407WFP
Capture/monitor card: BM Intensity Pro 4K
Video Monitir: Home made with 15.6inch 8-bit FHD IPS panel
Storage: System drive (SSD) Samsung SSD 840 (240GB)
Project cache drive (SSD) Crucial CT1000 MX500 (960GB)
Media storage (HDD) Samsung HD103SI (2x1TB in SW raid 0)
Online storage (NAS) 2TB

Software:
OS: Windows 10 Home, version 1803 build 17134.523
GPU driver: 23.21.13.8813 version 388.13
Davinci Resolve: 15.2.0033
BM Desktop Video: 10.9.10.0

Unless you select the Nvidia decoder explicitly, it's not going to use it. If you don't have that options the driver doesn't advertise that functionality. Check if your card does support it and your drivers are up to date. Your GPU driver seem very old.

You may be limited by something else than encoding itself. Disk speed, gpu rendering speed etc. See what your GPU, CPU and disk metrics are while rendering. You can also test if very lightweight sequence with something easy to decode and small enough file size (prores clip for example) as input and no processing renders any faster.

From my experience it only works with NVIDIA driver 399.24 at the moment.
You will then have e.g. H265 output Option under MP4 and Quick Time in the delivery page.

Unless you select the Nvidia decoder explicitly, it's not going to use it. If you don't have that options the driver doesn't advertise that functionality. Check if your card does support it and your drivers are up to date. Your GPU driver seem very old.

Thanks for the steer Peter, - I wasn't getting the third drop menu for Encoder 'type' on the Deliver page so I updated the driver to version 418 (I think). The menu is now there and I can select 'native', which I think is a software encoder running in the CPU and 'Nvidia' which is the GPU. Running some test renders, a 41 second UHD clip with video and audio fade ins and outs plus a lift and gain correction to force a full encode gives a 2m:02s render time in software and a 0m:29s second render time using the NVENC hardware. That to me is the sort of improveent that I upgraded for.

You may be limited by something else than encoding itself. Disk speed, gpu rendering speed etc. See what your GPU, CPU and disk metrics are while rendering. You can also test if very lightweight sequence with something easy to decode and small enough file size (prores clip for example) as input and no processing renders any faster.

Thanks for the tip Hendrik, - When running the tests I used the performance tab in task manager. Interestingly, I could also see that the clip (which was an H264) straight from the GH5 used the NVENC hardware to decode to apply the timeline changes before encoding the render. Previously it was necessary to use optimisation for all timeline activities whereas all but the most exacting scrubbing needs could be managed without any intermediate encoding, saving workflow time and (temporary) storage space.

From my experience it only works with NVIDIA driver 399.24 at the moment.
You will then have e.g. H265 output Option under MP4 and Quick Time in the delivery page.

Thanks Juergen for the info about version 399.24. I previously had version 388.13 installed as it was recommended a year or two ago on this forum in response to reports of Resolve crashing with a later version. I wasn't aware that a later version would now be OK. As far as HEVC goes, I note from the 'DaVinci Resolve Supported Codecs' document, that for the Windows version, HEVC decoding is available but encoding isnt. It may be that an older GPU like the GTX970 that I have, doesn't support either in hardware, but I was expecting there to be a 'native' version that uses the CPU. If I can't find it then it is back to Handbrake where necessary.

As of v15.2 the Studio version of Resolve can use Intel Quick Sync or NVENC on Windows and Linux for encoding HEVC as long as the GPU supports it. But like you've discovered, there's no software encoder.

As of v15.2 the Studio version of Resolve can use Intel Quick Sync or NVENC on Windows and Linux for encoding HEVC as long as the GPU supports it. But like you've discovered, there's no software encoder.

That's useful to know as I could change the gui back to Intel as Skylake processors can encode 8-bit HEVC (but not 10-bit), which would be fine for non-HDR distribution. I haven't had any issues with RAM shortages but the GTX970 does seem have this 3.5GB limitation despite being sold as a 4GB GPU so moving the gui role to the CPU could release VRAM for CUDA and delay the need to upgrade the graphics card.

Why is AMD being left out of the video decoding/encoding game in Resolve? Their GPUs have h265/HEVC decoding and encoding onboard.

Likely because of development resources and priorities of other features.