A fast, friendly non-linear video editor for Linux, Windows and macOS, built with C++20, Qt 6 and FFmpeg. Velo follows the familiar Premiere-style layout — project bin, media-preview/sequence monitors, effect controls and a multi-track timeline — while staying small, hackable and quick.

The bundled showcase project: nested sequences, picture-in-picture with keyframed rotation + Gaussian Blur + Vignette, titles with outlines, cross dissolves and fades, audio waveforms with volume keyframes — generate it yourself with dist/demo/make_demo.sh.

Features

• Media — import video, audio, images and SVG (drag files into the Project panel or Ctrl+I); thumbnails in the bin; double-click or drop onto the monitor to open it in the Media Preview; offline media is flagged and can be re-pointed via right-click → Locate / Replace File….
• Media Preview monitor — keeps a dropdown of loaded media (✕ unloads), mini-timeline with draggable in/out brackets (I / O at the playhead); drag the picture into the timeline to insert just the in→out range. Stills show without a transport.
• Sequences — create manually with delivery presets (YouTube 1080p/4K, Cinema 4K DCI, TikTok/Reels, Instagram Square, …) or right-click a clip → New Sequence from Clip. Multiple sequences open as timeline tabs.
• Timeline — unlimited video/audio tracks; magnetic snapping (toggleable, Alt bypasses); drag clips between tracks; edge trimming with bracket cursors; razor tool; split selected (S) or all tracks (Shift+S); ripple delete (Alt+Del); copy/paste; per-track mute/hide, lock and rename; rubber-band selection; sequence tabs.
• Linked A/V — video and its audio move, trim, split and delete together; Unlink from the context menu when needed.
• Nesting ("Chain") — select clips → Alt+C collapses them into one nested-sequence clip; double-click it to open the nested sequence in a tab.
• Monitor interaction — move the selected clip directly in the Sequence monitor, scale with corner handles (uniform by default, Shift distorts), rotation/opacity in Effect Controls; drag any numeric label in Effect Controls left/right to scrub its value (Shift = 10×). Preview quality: Full, 1/2, 1/4, 1/8.
• Keyframes everywhere — position, scale, rotation, opacity, volume, track volume and every effect parameter animate via the stopwatch/diamond controls; smooth-step interpolation.
• Audio — waveforms on clips, a draggable volume line (Ctrl+click adds keyframes, drag dots to shape, double-click removes), per-track volume with sequence-time keyframes, clip speed with resampled audio or pitch-preserving time-stretch ("Preserve pitch" in Effect Controls ▸ Time); audible scrubbing while dragging the playhead (Playback ▸ Audio Scrubbing).
• Effects (modular) — Gaussian Blur, Color Correction (brightness / contrast / saturation / temperature), Color Grade (exposure, contrast, highlights/shadows, whites/blacks, white balance, hue, saturation, vibrance, lift/gamma/gain), Sharpen, Black & White, Vignette, Flip, audio Gain; drag onto clips or double-click to apply; reorder-safe parameter UI is generated from the effect description.
• Transitions — Cross Dissolve, Fade, Dip to Black; drag onto a clip edge or use the context menu; adjust the length by dragging the wedge in the timeline or in Effect Controls.
• Titles — T adds a text clip (font, size, bold/italic, fill colour, outline); text clips are normal clips: move, trim, animate, effect.
• Export — H.264/H.265 (x264/x265), NVENC hardware encoding when available, VP9, AV1 (SVT), ProRes, or audio-only; CRF or bitrate; any resolution/fps; renders through a piped ffmpeg process with progress and cancel.
• Projects — portable JSON .velo files; full snapshot undo/redo (Ctrl+Z / Ctrl+Shift+Z); unsaved-changes guard.
• Custom keybindings — every action is rebindable in Edit ▸ Keyboard Shortcuts; stored per-user.

Download (no installation required)

Prebuilt, fully self-contained bundles for Linux, Windows and macOS are on the releases page — Qt, the FFmpeg libraries and the ffmpeg export binary are bundled at the exact versions Velo is developed against, so nothing else needs to be installed:

• Linux — Velo-<ver>-linux-x86_64.AppImage: chmod +x and run (on systems without FUSE add --appimage-extract-and-run); or the -portable.tar.xz: extract anywhere and run ./AppRun. Needs glibc ≥ 2.39 (Ubuntu 24.04+, any 2024+ rolling distro).
• Windows — Velo-<ver>-windows-x86_64.zip: extract, run velo.exe.
• macOS (Apple Silicon) — Velo-<ver>-macos-arm64.dmg: drag Velo to Applications. The build is unsigned, so on first launch right-click the app → Open (or xattr -d com.apple.quarantine /Applications/Velo.app).

Every bundle is smoke-tested in CI (decode → composite → mix → export) on its target platform before a release is published. Versions are pinned in .github/workflows/build.yml; the app version comes from CMakeLists.txt and releases are cut by pushing the matching v<version> tag.

Building

Dependencies (Arch/CachyOS package names):

pacman -S qt6-base qt6-multimedia qt6-svg ffmpeg cmake ninja gcc pkgconf

cmake -B build -G Ninja
ninja -C build
./build/velo            # optionally: ./build/velo project.velo

Install system-wide (binary, .desktop entry, icon):

sudo cmake --install build --prefix /usr

A headless engine smoke test (decode → composite → mix → save/load → export) is built in:

QT_QPA_PLATFORM=offscreen ./build/velo --selftest

Default shortcuts

(Ctrl+wheel zooms the timeline at the cursor; plain wheel scrolls.)

Adding a new effect

Effects are self-contained descriptions in src/effects/Effects.cpp. Register one and the effects browser, drag-and-drop, Effect Controls UI, keyframing, serialization and rendering all pick it up automatically:

registerEffect({
    "posterize", "Posterize", "Stylize",
    {{"levels", "Levels", 2, 32, 6, 1, 0}},
    [](QImage &img, const QMap<QString, double> &p, double scale) {
        // mutate img in place; p has the keyframe-interpolated values
    }});

Architecture

src/core      Project / Sequence / Track / Clip model, keyframes,
              JSON (de)serialization, Document (selection, undo, edit ops)
src/media     FFmpeg probe/decode (video + audio), waveform peaks,
              thumbnails, per-thread decoder caches
src/effects   modular effect registry + built-ins
src/engine    Compositor (frame rendering), AudioMixer/AudioEngine
              (sample-accurate mixing + playback), RenderWorker
              (coalescing preview thread), Exporter (ffmpeg pipe)
src/ui        main window, project bin, effects browser, monitors,
              timeline, effect controls, dialogs, dark theme

The model is shared between the GUI, the preview render thread, the audio callback and the exporter behind a single recursive mutex; preview requests coalesce so scrubbing never queues stale frames, and decoders only seek when playback jumps. When one file is needed at two distant positions every frame (cross dissolves, footage reused across nests) the cache opens an extra decoder "lane" per position so both streams decode sequentially.