This is implemented by calling NVENC SDK API, and asks driver for default value. Therefore it may vary depending on GPU gen and driver version and codec, preset and tune options. Of course, options can be overwrided by settings options manually.

Below are examples.

Default

Y:\Encoders>x64\NVEncC64.exe -i sample_movie_1080p.mpg -o test.mp4 -c hevc
--------------------------------------------------------------------------------
test.mp4
--------------------------------------------------------------------------------
NVEncC (x64) 9.04 (r3455) by rigaya, Oct 19 2025 16:07:01 (VC 1944/Win)
OS Version     Windows 11 x64 (26200) [UTF-8]
CPU            AMD Ryzen 9 7950X 16-Core Processor [5.51GHz] (16C/32T)
GPU            #1: NVIDIA GeForce RTX 4080 (9728 cores, 2505 MHz)[PCIe4x16][581.42]
NVENC / CUDA   NVENC API 13.0, CUDA 13.0, schedule mode: auto
Input Buffers  CUDA, 20 frames
Input Info     avcuvid: MPEG2, 1920x1080, 30000/1001 fps
Vpp Filters    copyDtoD
Output Info    H.265/HEVC main @ Level auto
               1920x1080p 1:1 29.970fps (30000/1001fps)
               avwriter: hevc => mp4
Encoder Preset default
Rate Control   VBR
Multipass      none
Bitrate        0 kbps (Max: 11520 kbps)
Target Quality 25.00
QP range       I:0-51  P:0-51  B:0-51
QP Offset      cb:0  cr:0
VBV buf size   auto
Split Enc Mode auto
Tuning Info    hq
Lookahead      off
GOP length     300 frames
B frames       3 frames [ref mode: middle]
Ref frames     5 frames, MultiRef L0:auto L1:auto
AQ             off
CU max / min   32 / auto
Others         mv:auto

encoded 5203 frames, 477.78 fps, 9431.16 kbps, 195.18 MB
encode time 0:00:10, CPU: 0.6%, GPU: 6.8%, VE: 44.1%, VD: 46.5%, GPUClock: 2736MHz, VEClock: 2145MHz
frame type IDR   18
frame type I     18,  avgQP  23.56,  total size    3.57 MB
frame type P   1301,  avgQP  24.38,  total size  110.92 MB
frame type B   3884,  avgQP  27.92,  total size   80.70 MB

--preset quality --tune uhq
Seems to be lookahead enabled, b frame increased with tf4?

Y:\Encoders>x64\NVEncC64.exe -i sample_movie_1080p.mpg -o test.mp4 -c hevc --preset quality --tune uhq
--------------------------------------------------------------------------------
test.mp4
--------------------------------------------------------------------------------
NVEncC (x64) 9.04 (r3455) by rigaya, Oct 19 2025 16:07:01 (VC 1944/Win)
OS Version     Windows 11 x64 (26200) [UTF-8]
CPU            AMD Ryzen 9 7950X 16-Core Processor [5.51GHz] (16C/32T)
GPU            #1: NVIDIA GeForce RTX 4080 (9728 cores, 2505 MHz)[PCIe4x16][581.42]
NVENC / CUDA   NVENC API 13.0, CUDA 13.0, schedule mode: auto
Input Buffers  CUDA, 39 frames
Input Info     avcuvid: MPEG2, 1920x1080, 30000/1001 fps
Vpp Filters    copyDtoD
Output Info    H.265/HEVC main @ Level auto
               1920x1080p 1:1 29.970fps (30000/1001fps)
               avwriter: hevc => mp4
Encoder Preset quality
Rate Control   VBR
Multipass      none
Bitrate        0 kbps (Max: 11520 kbps)
Target Quality 25.00
QP range       I:0-51  P:0-51  B:0-51
QP Offset      cb:0  cr:0
VBV buf size   auto
Split Enc Mode auto
Tuning Info    uhq
Lookahead      on, 25 frames, Level 3, Adaptive I, B Insert
GOP length     300 frames
B frames       5 frames [ref mode: middle]
Ref frames     5 frames, MultiRef L0:auto L1:auto
AQ             off
CU max / min   32 / auto
Others         mv:auto tf4

encoded 5203 frames, 144.02 fps, 9973.60 kbps, 206.41 MB
encode time 0:00:36, CPU: 0.5%, VE: 83.5%, VD: 14.3%, GPUClock: 2769MHz, VEClock: 2158MHz
frame type IDR   18
frame type I     18,  avgQP  21.00,  total size    4.16 MB
frame type P    867,  avgQP  21.27,  total size  113.55 MB
frame type B   4318,  avgQP  27.99,  total size   88.70 MB

Now defaults for options below should differ by --preset and --tune. #735

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