Ocula

A small Rust screen recorder designed to fail safely. The GUI binary is ocula; the CLI binary is oculo.

It records through the desktop screencast portal on Wayland and can use direct X11 capture on X11. Output is written to a temporary file in the same directory, finalized with EOS on stop, synced, then atomically renamed to the final .mp4, .mkv, or .gif file.

Why This Is Harder To Break

• Uses xdg-desktop-portal and PipeWire instead of brittle screenshot loops.
• Defaults to MP4/H.264 for compatibility, while keeping MKV/MJPEG available as the safest high-throughput option.
• Handles Ctrl-C and SIGTERM by sending EOS before stopping, so muxers can finalize.
• Writes to *.part first, then renames into place only after GStreamer has stopped.
• Creates the output directory automatically and avoids overwriting existing recordings unless asked.
• Probes existing output directories or their nearest existing parents for writability before capture setup.
• Can fall back to X11 capture when running under X11.
• Supports selected-region recording with --area or --select.
• Downscales large full-screen recordings to 1080p by default so 4K screens do not overload software encoders, without upscaling smaller captures.
• Keeps raw video buffering small and drops stale raw frames under encoder pressure so recording stays real-time instead of building huge lag.
• Caps capture framerate without manufacturing duplicate frames and feeds software H.264/VP8 explicit I420 input to reduce negotiation/conversion overhead.
• Skips unnecessary color conversion for direct X11/MJPEG capture.
• Chooses default H.264/VP8 bitrates from effective output size and FPS, while preserving explicit --bitrate exactly.

No recorder can save a file after SIGKILL, power loss, kernel crash, or disk failure, but this is built to preserve recordings for normal crashes, errors, and interrupts as much as GStreamer allows.

Requirements

• Rust 1.92+
• GStreamer 1.22+
• GStreamer plugins: matroskamux, jpegenc, videoscale, videocrop, pipewiresrc for Wayland, ximagesrc for X11, opusenc for MKV audio
• Default MP4 plugins: mp4mux, openh264enc or a supported hardware H.264 encoder, h264parse, and an AAC encoder such as fdkaacenc for MP4 audio
• Optional GIF plugin: gifenc
• For Wayland: pipewire, xdg-desktop-portal, and a portal backend such as GTK, KDE, GNOME, or wlr
• For X11 fallback: ximagesrc
• X11/XWayland for interactive --select, or use --area with explicit coordinates
• PulseAudio-compatible default input/output devices when --audio mic, --audio system, or --audio both is used

On Wayland, --backend auto uses the desktop portal only. Use --backend x11 explicitly if you intentionally want X11/XWayland capture.

Build

cargo build --release

Install from crates.io after release:

cargo install ocula --locked

Use

Launch the native desktop app:

cargo run --release --bin ocula

After install, launch it with:

ocula

The desktop app provides compact capture controls, audio, pointer, MP4/MKV/GIF format controls, optional GLSL effects, an output picker, a large record/stop button, and a live recorder log. In Area mode, Ocula shows an effect-aware crop preview panel before selection; click Pick Crop, drag an area, refine it with the glass-style selector handles, then click Use This Crop or press Enter before recording. Ocula keeps a real selected-area crop preview visible when X11 snapshots are available, falls back to a clean crop map otherwise, and shows a click-through crop outline outside the selected area after selection and while recording. It launches the same fail-safe recorder engine as the CLI and stops recordings with a graceful interrupt so GStreamer can finalize the output file.

Run the CLI directly after install:

oculo --mode area

Start from an interactive chooser in the current directory:

cargo run --release --bin oculo --

The chooser supports screen or monitor, window, area, audio, pointer visibility, and output-path choices. Use explicit flags below when scripting or when you do not want a prompt.

Record to a directory:

cargo run --release --bin oculo -- --dir ~/Videos

Record with microphone audio:

cargo run --release --bin oculo -- --audio mic

Record a selected region by coordinates:

cargo run --release --bin oculo -- --area 100,100,1280,720

Record a screen through the normal backend chooser:

cargo run --release --bin oculo -- --mode screen

Record a specific X11 monitor:

cargo run --release --bin oculo -- --list-monitors
cargo run --release --bin oculo -- --backend x11 --monitor 1

Record a window through the desktop portal:

cargo run --release --bin oculo -- --mode window --backend portal

Select multiple monitor streams through the desktop portal:

cargo run --release --bin oculo -- --multiple

Record a selected region interactively with Ocula's built-in selector:

cargo run --release --bin oculo -- --mode area

Selector controls:

• Drag to create or move a region.
• Resize from edge or corner handles.
• Arrow keys move; Shift+arrows resize; Ctrl changes keyboard steps to 10 px.
• Delete or Backspace clears the region.
• Click Use This Crop or press Enter/Space to confirm; click Cancel, press Escape, or right-click to cancel.

Record MKV instead of the default MP4:

cargo run --release --bin oculo -- --format mkv --output capture.mkv

MP4 uses H.264 video for compatibility. MKV remains available because it is faster to start, supports the MJPEG path, and is safer for interrupted recordings. GIF is video-only, defaults to 15 FPS unless --fps is provided, and requires gifenc.

Add an optional GLSL effect when GStreamer OpenGL elements are installed:

cargo run --release --bin oculo -- --effect neon
cargo run --release --bin oculo -- --effect heatmap
cargo run --release --bin oculo -- --effect glitch
cargo run --release --bin oculo -- --effect ripple
cargo run --release --bin oculo -- --effect glass
cargo run --release --bin oculo -- --effect crt
cargo run --release --bin oculo -- --effect holo
cargo run --release --bin oculo -- --effect vapor
cargo run --release --bin oculo -- --effect fracture
cargo run --release --bin oculo -- --effect prism
cargo run --release --bin oculo -- --effect aurora
cargo run --release --bin oculo -- --effect kaleido

Effects use glupload, glshader, and gldownload; Ocula preflights those plugins before capture starts. Available effects are neon, heatmap, glitch, ripple, glass, crt, holo, vapor, fracture, prism, aurora, and kaleido.

Record GIF when the GStreamer gifenc plugin is installed:

cargo run --release --bin oculo -- --format gif --audio none --output capture.gif

Record full resolution instead of the default 1080p safety downscale for large screens:

cargo run --release --bin oculo -- --no-scale

Stop with Ctrl-C. Press Ctrl-C a second time to abort immediately.

Audio capture is preflighted before area selection, portal consent, and output reservation. If the default microphone or system-audio monitor is unavailable, Ocula fails before creating an output file.

Useful flags:

--backend auto|portal|x11
--mode screen|window|area
--fps 30
--codec auto|mjpeg|h264|vp8
--h264-encoder auto|hardware|software
--effect none|neon|heatmap|glitch|ripple|glass|crt|holo|vapor|fracture|prism|aurora|kaleido
--format mp4|mkv|gif
--audio none|mic|system|both
--area 100,100,1280,720
--monitor 1
--multiple
--list-monitors
--select
--no-prompt
--scale 1920x1080
--no-scale
--output /path/to/file.mp4
--overwrite
--hide-pointer
--max-duration 60
--eos-timeout 15