NVIDIA Encoder (NVENC)

Updated 1 December 2025

NVENC is NVIDIA’s dedicated hardware video encoder integrated into GPUs, providing real-time throughput with deterministic, low-latency output for UHD streaming.
The encoder employs a fixed-function ASIC for efficient motion estimation, split-frame encoding, and rate-control, ensuring near-software quality at much lower power consumption.
NVENC supports H.264, HEVC, and AV1 codecs, and its advanced tuning modes and control mechanisms enable seamless adaptation for live production, gaming, and cloud streaming.

NVIDIA Encoder (NVENC) is a fixed-function, fully on-die hardware video encoder block integrated into modern NVIDIA GPUs, beginning with the Kepler microarchitecture. NVENC provides high-performance, real-time hardware offload for video encoding in advanced codecs, notably H.264/AVC, H.265/HEVC, and AV1. Its usage spans data center UHD transcoding, live media production, interactive cloud gaming, and quality-controlled digital production workflows. NVENC achieves rate-distortion efficiency comparable to state-of-the-art software encoders with an order of magnitude lower power draw and substantially lower end-to-end latency, making it a central component of high-throughput, low-latency media computing (Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025, Vibhoothi et al., 14 Oct 2025, Arunruangsirilert et al., 24 Nov 2025).

1. Microarchitecture and Codec Support

NVENC is implemented as a fixed-function ASIC block within NVIDIA GPUs. Each NVENC instance consists of the following principal hardware blocks:

Motion estimation and compensation engine (ME/MC)
Intra-prediction and transform block (IP/TX)
Quantization and entropy coding engines (CABAC/CAVLC)
Rate-control and lookup tables (supporting CBR/VBR logic)
Bitstream assembler and output formatter

High-end GPUs (e.g., RTX 40-series, A100/H100, RTX 5070 Ti) can contain up to two independent NVENC chips per die, each presented as a separate encoder device through the NVIDIA Video Codec SDK.

NVENC supports the following codecs:

H.264/AVC (all modern generations)
H.265/HEVC (Turing+; B-frame support from Turing onward)
AV1 (Ada Lovelace+; 10-bit pipeline supported)

Architecturally, NVENC contrasts with software encoders (e.g., x264, x265, SVT-AV1), which run on general-purpose CPU or GPU cores and perform full RDO, deep lookahead, complex reference structures, and flexible adaptive quantization. NVENC purposely simplifies search (max two B-frames, single reference, reduced RDO) and disables complex adaptive quantization, in order to guarantee deterministic and low-latency real-time throughput, especially for UHD (4K/8K) content (Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025).

2. Split-Frame Encoding (SFE)

Split-Frame Encoding (SFE) is a technique introduced to maximize encoding throughput for UHD content. SFE divides a single high-resolution frame into multiple horizontal slices, each processed in parallel on separate NVENC chips. Following parallel encoding, the slice bitstreams are stitched together at the bitstream level, merging headers and concatenating payloads without re-encoding motion vectors across boundaries.

For a frame of width $W$ and height $H$ , using $N$ -way SFE results in $N$ slices:

$R_k = \{(x,y)\mid k\cdot(W/N)\leq x < (k+1)\cdot(W/N),\ 0\leq y < H\}$

Encoding proceeds as:

encode_sfe(frame F):
    for k in {0,1} in parallel do
        input_k = crop(F, R_k)
        bitstream_k = NVENC[k].encode(input_k)
    end parallel
    return stitch(bitstream_0, bitstream_1)

Stitching combines the slice metadata and payloads, forming a single output bitstream. SFE is enabled and controlled via driver flags (e.g., split_encode_mode=2) and is exposed in ffmpeg via corresponding NVENC API controls (Arunruangsirilert et al., 24 Nov 2025).

3. Rate-Distortion Performance and Quality Metrics

Objective RD performance of NVENC is evaluated using metrics such as PSNR, SSIM, and VMAF. At UHD resolutions and typical live-streaming bitrates (4K: 10–50 Mbps, 8K: 20–100 Mbps), NVENC matches or nearly matches the RD efficiency of leading software encoders at real-time presets (e.g., NVENC P7 vs. x264/x265/SVT-AV1 P7/P8):

4K (2160p), NVENC Ada Lovelace:
- Low bitrate (10–20 Mbps): VMAF: AVC 71.1, HEVC 73.7, AV1 74.95
- High bitrate (40–50 Mbps): VMAF: AVC 84.13, HEVC 83.68, AV1 84.74
8K (4320p), NVENC Ada Lovelace:
- High bitrate (80–100 Mbps): VMAF: HEVC 90.02, AV1 90.81

SFE incurs a negligible quality penalty:

4K, HEVC: $\Delta\mathrm{PSNR} \approx -0.042$ dB, $\Delta\mathrm{VMAF} \approx -0.053$
4K, AV1: $\Delta\mathrm{PSNR} \approx -0.040$ dB, $\Delta\mathrm{VMAF} \approx -0.095$
8K: penalties are essentially zero or slightly positive (Arunruangsirilert et al., 24 Nov 2025).

Average BD-rate penalty from enabling SFE is $<0.1\%$ , well within imperceptibility thresholds. "Negligible RD penalty" is defined as $\Delta\mathrm{PSNR}<0.05$ dB or $\Delta\mathrm{VMAF}<0.1$ , below typical subjective sensitivity (Arunruangsirilert et al., 24 Nov 2025).

4. Encoding Throughput, Power Consumption, and Latency

NVENC achieves high real-time throughput at low energy cost. Throughput scales near-linearly with the number of NVENC chips when SFE is enabled:

Resolution	Preset	FPS (1 chip)	FPS (SFE, 2 chips)	Throughput Gain
4K, HEVC P1	P1	285	520	+82.6%
8K, HEVC P1	P1	72	135	+86.4%
4K, HEVC P7	P7	---	---	up to 96.2%

Power draw for typical encoding:

1-chip HEVC: 38.5 W; AV1: 42.0 W
2-chip HEVC: 43.0 W; AV1: 48.0 W

Energy per encoded bit (4K @25 Mbps, HEVC): $E_b^{\text{HEVC,1-chip}} \approx 1.54\ \mu\text{J/bit}$ , about one-tenth the energy of CPU-based software encoders (~150 W total) (Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025).

End-to-end latency:

SFE adds no extra frames at 4K, may reduce latency by 1 frame at 8K.
Ultra Low-Latency (ULL) tuning yields 6–7 frames at 60 fps ( $\approx$ 100–117 ms), invariant to quality preset or codec.
NVENC's latency performance is superior to software encoders, which incur 40–100 frames delay or cannot maintain real-time throughput for UHD (Arunruangsirilert et al., 24 Nov 2025).

5. Latency-Tuning Modes and Practical Real-Time Performance

NVENC exposes multiple latency-tuning configurations via preset and tuning parameters:

Normal Latency (“-tune hq”): Default, allows limited B-frames, disables multipass/lookahead.
Low-Latency (“-tune ll”): Disables B-frames, eliminates frame reordering/lookahead.
Ultra Low-Latency (“-tune ull”): Strict in-order pipeline, minimal frame queuing.

RD penalty for moving from high-quality to ULL is $<0.2$ dB PSNR—even for demanding content. Under all modes, AV1 and HEVC on Ada Lovelace meet or exceed 60 fps at 4K/8K; SFE enables all quality presets to achieve this threshold.

Latency invariance to preset allows high-quality (e.g., P7) encoding at low latency, a property not shared by CPU and most competing hardware encoders (Arunruangsirilert et al., 24 Nov 2025).

6. Control, Adaptation, and Perceptual Targeting

Advanced control methods such as LiteVPNet leverage NVENC to enable accurate, perceptually-motivated quantization parameter (QP) selection for content-specific VMAF targeting. LiteVPNet combines low-complexity bitstream features, video complexity analysis, and CLIP-based semantic embeddings to predict QPs corresponding to target VMAF scores, invoking NVENC AV1 encoder (via ffmpeg or SDK) in single-pass constant-QP mode.

On a test corpus, LiteVPNet achieved:

Mean QP MAE = 4.5; mean VMAF MAE = 1.0; $87.3\%$ coverage for $\Delta\mathrm{VMAF} \leq 2$ .
End-to-end feature extraction + QP prediction: 3.0 s/shot (9.5 s AV, 1080p); inference alone: 0.28 s/shot (Vibhoothi et al., 14 Oct 2025).

This enables high-confidence real-time or near-real-time adaptation and quality control for workflows such as on-set virtual production and high-value remote post-production.

7. Limitations, Deployment, and Future Directions

NVENC's architectural constraints include:

Limited reference frames (typically one), maximum two B-frames, simplified RDO strategies, restricted scene-adaptive quantization, and incompatibility with ultra high-quality multi-pass (2-pass) strategies in SFE mode.
Generation-over-generation RD gains are marginal; major improvements are codec-driven (e.g., AV1 in Ada Lovelace, B-frames in Turing).

NVENC is recommended for real-time UHD streaming/transcoding at 25–40 Mbps (4K/AV1 or HEVC), with Spatial/Temporal AQ disabled to maximize objective quality metrics. SFE and ultra low-latency tuning render it highly suitable for AI-centric data centers, edge servers, and high-throughput live production pipelines. Ultra-high-quality, offline two-pass transcoding remains outside the operational envelope of SFE and, by extension, current NVENC approaches (Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025).

Ongoing research targets formal subjective quality-of-experience evaluation for slice-boundary artifacts, BD-rate–driven code improvement, integration with adaptive quantization, and deployment in edge/cloud AI-RAN architectures.

References:

(Arunruangsirilert et al., 24 Nov 2025, Arunruangsirilert et al., 24 Nov 2025, Vibhoothi et al., 14 Oct 2025, Arunruangsirilert et al., 24 Nov 2025)