[HELP] AV1 NVENC B-Frames

[Selur]

As far as I can tell Hybrid is telling NVEncC to use '--bframes 3' by default. (assuming 'NVEncC --check-features' reported that you gpu supports using b-frames)
Looking at the output of the encoder in my quick test:

NVEncC (x64) 8.09 (r3369) by rigaya, Jul 16 2025 12:08:21 (VC 1944/Win)
OS Version     Windows 11 x64 (26100) [UTF-8]
CPU            AMD Ryzen 9 7950X 16-Core Processor [5.52GHz] (16C/32T)
GPU            #0: NVIDIA GeForce RTX 4080 (9728 cores, 2505 MHz)[PCIe4x16][577.00]
NVENC / CUDA   NVENC API 13.0, CUDA 12.9, schedule mode: sync
Input Buffers  CUDA, 44 frames
Input Info     y4m(yv12(10bit))->p010 [AVX2], 640x352, 25/1 fps
Vpp Filters    copyDtoD
Output Info    AV1 main 10bit @ Level auto
               640x352p 1:1 25.000fps (25/1fps)
Encoder Preset quality
Rate Control   VBR
Multipass      none
Bitrate        1500 kbps (Max: 240000 kbps)
Target Quality auto
QP range       I:0-255  P:0-255  B:0-255
QP Offset      cb:0  cr:0
VBV buf size   auto
Split Enc Mode auto
Lookahead      on, 32 frames, Adaptive I Insert
GOP length     250 frames
B frames       3 frames [ref mode: middle]
Ref frames     6 frames, MultiRef L0:auto L1:auto
AQ             on (spatial, temporal, strength 5)
Part size      max auto / min auto
Tile num       columns auto / rows auto
TemporalLayers max 0
Refs           forward auto, backward auto
VUI            matrix:smpte170m,rangedav1d :limited
Others         mv:Q-pel

the encoder git get the information.

From what I remember AV1 does not have b-frames to begin with and the 'b-frame' option in some encoders just referes to a specific combination of interframes referencing each other.

AV1 does have bi-directional predicted frames, but it is not like the way as H.264/HEVC. Instead it has so-called "mini-GOP", which includes series of inter frames that reference each other.

Because of this difference, it is not counted as B frames in the log.

=> https://github.com/rigaya/NVEnc/issues/438

Cu Selur

Cu Selur