# Core Concepts

> The vocabulary of the Decodx engine — spec, sources, scenes, stages, determinism.

# Core Concepts

Understanding the fundamental concepts of Decodx.

## Spec

The source of truth for your video. A committed YAML specification that includes:

- Project metadata
- Source definitions
- Scene compositions
- Timing and effects

## Sources

Input files used in your video:

- Video files
- Audio files
- Images
- Fonts
- Subtitles

## Scenes

Building blocks of your video. Each scene:

- Has a duration
- Contains layers
- References sources
- Applies effects and transformations

## Stages

The pipeline stages that process your specification:

1. **Parse** — Read and validate the spec
2. **Compile** — Prepare sources and assets
3. **Render** — Generate the video
4. **Post-process** — Add captions, chapters, metadata

## Determinism

Decodx ensures the same spec always produces the same output video, pixel-for-pixel.