> For the complete documentation index, see [llms.txt](https://docs.viesus.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.viesus.com/get-started/key-concepts.md).

# Key Concepts

The essential concepts behind VIESUS — one shared engine and configuration, how features are controlled, and GPU vs CPU.

A few concepts make the rest of the documentation straightforward. Expand any that's new to you.

<details>

<summary>One engine behind every product</summary>

Every VIESUS product is a wrapper around the same C++ enhancement library — image analysis, correction algorithms, AI models, and output logic all live there. The wrappers just change how you invoke it.

This matters in practice: prototype a configuration in the Viewer, then run it in production through the CLI or Node.js module, and you get identical results. Configure once, run anywhere.

For a side-by-side comparison of every interface, see [Choose Your Interface](/discover/choose-your-interface.md). For direct library access, see the [C/C++ SDK](/reference/overview.md).

</details>

<details>

<summary>One configuration, every interface</summary>

All on-premise interfaces (CLI, PDF Enhancer, Node.js module, C/C++ SDK) read the same `viesusini.json` configuration file, with identical parameters. Tune a configuration in the VIESUS Viewer, export it, and use that exact file in production.

Each feature is controlled the same way: a **mode** that turns it on or off (and sometimes selects a variant), plus a **strength** from `0.0` to `1.0` that sets how strongly it's applied. Once you know that pattern, the whole [Parameter Reference](/configuration/parameter-reference.md) reads consistently.

```powershell
┌─────────────────────────────────────┐
│  viesusini.json                      │
│  (your enhancement configuration)   │
└──────────────┬──────────────────────┘
               │ same file works with
       ┌───────┼───────────┐
       ▼       ▼           ▼
    CLI    PDF CLI     Node.js Module
```

</details>

<details>

<summary>GPU vs CPU, and optional AI features</summary>

VIESUS ships in two installer variants: **GPU** and **CPU**.

| Variant       | When to use                                                                                                                                                                                      |
| ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| GPU installer | Systems with an NVIDIA GPU (Ampere architecture or newer, ≥ 8 GB VRAM). Enables full-speed AI features: AI upscaling, Artifact Removal, Background Handling.                                     |
| CPU installer | Systems without a compatible NVIDIA GPU. All standard enhancement (color, sharpening, noise, faces) works normally. AI-heavy features (AI upscaling, Artifact Removal) run significantly slower. |

The AI features — AI upscaling, Artifact Removal, and Background — are **optional**. On Windows each is a separate add-on installer and is unlocked only if your license includes it (on Linux the models are bundled in the main package). Standard enhancement is always included and runs on either variant.

See [AI Add-ons](/installation/add-ons.md) for installing the AI models and [Benchmarks](/operations/benchmarks.md) for processing-time reference data.

</details>


---

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