I'm using Kdenlive 21.12.3 on updated Arch. When performing the config wizard, it successfully detects my NVIDIA card (RTX 2070) and indicates it is enabling the appropriate codecs. I have the NVIDIA proprietary driver v510.60.02-15 and nvidia-utils v510.60.02-1.

1. The NVENC H265 ABR profile is available as are VAAPI Intel H264 and VAAPI AMD H264 but both NVENC H264 VBR and NVENC H264 ABR are both greyed out with a red X. When clicked on, the message "Unsupported video codec: nvenc_h264" is displayed. Any ideas why the NVENC H264 options are unavailable?

2. When using the NVENC H265 ABR profile, Kdenlive successfully renders videos. However monitoring my RTX 2070, I notice almost no GPU utilization (especially as compared to Shotcut encoding with NVENC). Additionally, it seems to render at the same speed as CPU encoding. In addition to that, my CPU utilization seems similar for both CPU and NVENC renders (~30% or so on a Threadripper). It seems as though even when using NVENC H265, my CPU is being used to render.

Is it possible that these two issues are related and, if so, what do I need to look into in order to address this?

I'm seeing the same situation. I'm using Fedora 36 and have installed Kdenlive Version 22.04.0. I see in the Project Rendering, in the 4k section NVENC H265 is available, but in the Hardware Accelerated (experimental) section the H264 ABR and H264 VBR options are (red) X out and when clicked report the "Unsupported video codec: nvenc_h264". H265 VBR is available and looks usable. The VAAPI AMD/Intel H264 options are also available. This system has a GTX 1650 NViDIA video card.

However, I have had a different OS disk in this system running Ubuntu 20.04.x and both of these NVENC H264 options were available and worked good in the Hardware Acceleration section.

Does anyone know what the missing piece is or what the difference is between the Ubuntu system and Fedora/(or Arch above)?

Thanks, Rob