Quality Controls

By default, the CLI preserves source quality (match-source) for both video and audio.

Video quality presets

--video-quality supports:

• match-source
• 360p
• 480p
• 720p
• 1080p
• 1440p
• 2160p

These presets apply resolution caps and target bitrate ranges suitable for common direct-play scenarios.

Audio quality presets

--audio-quality supports:

• match-source
• 320k
• 256k
• 224k
• 192k
• 160k
• 128k
• 96k

Custom bitrate overrides

Use these for explicit control:

• --max-video-bitrate <RATE> (for example 4800k, 6M, 12.5mbps)
• --max-audio-bitrate <RATE>

When overrides are provided, they constrain the selected quality profile.

Resizing

When a source exceeds a selected device or quality cap, the video is resized down while preserving aspect ratio and keeping encoder-friendly dimensions. The tool does not enlarge source dimensions as part of this deterministic FFmpeg resizing path.

--resize-quality supports:

• fast-bilinear (fastest)
• bilinear
• bicubic
• lanczos (default, highest-quality deterministic default)
• spline

Higher-quality resize kernels generally cost more CPU time. They remain deterministic FFmpeg scalers and do not add AI model dependencies.

--resize-backend controls where resizing runs:

• auto (default): use CUDA scale_cuda when CUDA decode, NVENC encode, filter support, and selected quality make a zero-copy GPU resize path possible; otherwise use software.
• software: always use libswscale on CPU.
• cuda: require CUDA scale_cuda and fail if the GPU resize path cannot be used.

The CUDA backend currently supports bilinear, bicubic, and lanczos interpolation. fast-bilinear and spline fall back to software in auto mode because scale_cuda does not expose matching kernels.

The resize benchmark harness compares downscale speed and full-reference quality against a deterministic 360p reference:

scripts/resize-tools/run_resize_benchmark.sh

The benchmark writes a CSV report with elapsed time, FPS, realtime factor, output size, and full-reference quality metrics. It reports VMAF when FFmpeg has libvmaf, PSNR component/average/min/max scores in dB, and SSIM component/aggregate scores including the SSIM dB transform. Set DPN_RESIZE_REF_VIDEO=/path/to/reference.mkv to use a real source clip. If DPN_RESIZE_REF_VIDEO is unset, the harness also honors the benchmark-runner BENCHMARK_SOURCE_PATH environment variable. Set DPN_RESIZE_BENCH_SS=00:01:30 to start from a representative section. Set DPN_RESIZE_CUDA=1 to add a lanczos,cuda,nvenc candidate alongside the software scaler candidates.