So the following combination seems to be bugged with Blackwell specifically. I tested RTX 3080 and RTX 5070 ti.
Encoding a H264 Video using the UHQ Tune in combination with "-highbitdepth 1” using FFMPEG.
Used a simple batch like this
"@echo off
ffmpeg ^
-i “test.mkv” ^
-c:v hevc_nvenc ^
-preset medium -tune uhq ^
-profile:v main10 -highbitdepth 1 ^
-bf 4 -b_ref_mode middle -rc-lookahead 32 ^
-b:v 2000k -maxrate 2000k -bufsize 4000k ^
-c:a copy ^
“test_ffmpeg_10bit_look32_uhq.mkv”
pause"
Only UHQ → no problem
Only highbitdepth 1 → no problem
Combining both with the 5070ti leads to heavy(!!) artifacts. Doing it in the same system with the RTX 3080 leads to no problem combining both. OS: Windows 11 Pro
I tried multiple ffmpeg versions: 7.1.1. and 8.0.1 and a snapshot version from Dec 8 2025. Always the same. Tried multiple drivers and the latest one. No change.
The 5070ti cannot combine both with FFMPEG where as the 3080 can. I contacted Timo Rothenpieler (dev at ffmpeg) and he says with that observation this is not an ffmpeg issue but an Nvidia issue. Here the link to the reported bug on the code.ffmpeg site: Making sure you're not a bot!
And this is how the artefacts look like (as I said only with the 5070ti combining uhq and highbitdepth regardless of driver and ffmpeg version - the 3080 is always fine regardless of combination; and also it is reproducable with any H264 Video I have!):
