uvc2gl

A Linux application that captures video and audio from USB capture cards (UVC/V4L2 + ALSA) and renders to OpenGL with real-time format switching via GUI.

Features

• Multi-Device Support: Switch between multiple video and audio capture devices at runtime
• Dual Format Support: MJPEG and YUYV video format support with runtime switching
• V4L2 Video Capture: Direct capture from USB capture devices with V4L2
• ALSA Audio Capture: Real-time audio capture with SDL2 playback
• Optimized Decoding:
  • FFmpeg-based MJPEG hardware decoding
  • Custom YUYV decoder with ITU-R BT.601 color space conversion
  • Achieves 60fps at 1080p on modern CPUs with compiler auto-vectorization
• OpenGL Rendering: Modern OpenGL 4.6 with custom shaders
• Live Format Switching: Right-click context menu to change resolution/framerate/format/devices
• Audio Volume Control: Adjustable volume with real-time slider
• Configuration Persistence: Saves device preferences, resolution, framerate, format, and volume settings
• Fullscreen Support: Press F11 or F to toggle fullscreen mode
• Auto-detected Formats: Queries available formats from each capture device
• Dynamic Aspect Ratio: Automatically maintains correct aspect ratio for any resolution
• Multithreaded: Separate capture/decode threads for smooth performance
• Dear ImGui UI: Lightweight immediate-mode collapsible menu overlay
• Semantic Versioning: Auto-generated version info from VERSION file

Building

Prerequisites

# Fedora/RHEL
sudo dnf install SDL2-devel glew-devel cmake ninja-build clang ffmpeg-devel alsa-lib-devel libc++ libc++-devel libc++abi libc++abi-devel

# Ubuntu/Debian
sudo apt install libsdl2-dev libglew-dev cmake ninja-build clang libavcodec-dev libavformat-dev libswscale-dev libavutil-dev libasound2-dev libc++-dev libc++abi-dev

Compile

mkdir -p build && cd build
cmake -G Ninja -DCMAKE_BUILD_TYPE=Release ..
ninja

Note: Release mode is recommended for optimal performance (includes -O3 -march=native flags for 60fps YUYV decoding).

Run

cd build
./uvc2gl

Right-click anywhere in the window to open the device/format selection menu.
Press F11 to toggle fullscreen. Press ESC to exit fullscreen or close the menu.

Project Structure

GameCapture/
├── main.cpp            # Entry point
├── CMakeLists.txt      # Build configuration
├── build/              # Build artifacts (Ninja)
│   ├── uvc2gl          # Main executable
│   ├── uvc2gl.conf     # Configuration file (auto-generated)
│   ├── Probe           # V4L2 device info utility
│   ├── StreamMjpg      # MJPEG stream capture test
│   ├── MjpgDecodeTest  # FFmpeg decoder test
│   ├── YuyvDecodeTest  # YUYV decoder test
│   └── shaders/        # Copied shader files
├── external/
│   └── imgui/          # Dear ImGui library
└── src/
    ├── core/           # Application lifecycle & config
    │   ├── Application.h/cpp
    │   └── Config.h
    ├── graphics/       # Window & rendering
    │   ├── Window.h/cpp
    │   ├── Renderer.h/cpp
    │   ├── Shader.h/cpp
    │   └── Quad.h/cpp
    ├── audio/          # Audio capture & playback
    │   ├── AudioCapture.h/cpp
    │   ├── AudioPlayback.h/cpp
    │   └── ALSACapabilities.h/cpp
    ├── video/          # Video capture & decode
    │   ├── VideoCapture.h/cpp
    │   ├── MjpgDecoder.h/cpp
    │   ├── YuyvDecoder.h/cpp
    │   ├── Frame.h
    │   ├── RingBuffer.h
    │   ├── V4L2Capabilities.h/cpp
    │   ├── v4l2Probe.cpp
    │   ├── v4l2StreamMjpg.cpp
    │   ├── MjpgDecodeTest.cpp
    │   └── YuyvDecodeTest.cpp
    └── assets/
        └── shaders/
            ├── Quad.vert
            └── Quad.frag

Configuration

The application automatically saves your preferences to uvc2gl.conf:

• Last used video device
• Last used audio device
• Resolution and framerate
• Video format (MJPEG or YUYV)
• Audio volume level

Settings are restored on next startup. If devices are unavailable, defaults to first available device.

Performance

• MJPEG: Hardware-accelerated decoding via FFmpeg (low CPU usage)
• YUYV: Optimized CPU-based conversion with ITU-R BT.601 color space
  • 60fps at 1920x1080 on modern CPUs with AVX2 support
  • Compiled with -O3 -march=native for auto-vectorization
  • Higher CPU usage than MJPEG but no hardware encoding required

Utilities

• Probe: Query V4L2 device capabilities
• StreamMjpg: Capture raw MJPEG frames to disk
• MjpgDecodeTest: Test FFmpeg MJPEG decoding
• YuyvDecodeTest: Test YUYV decoder with known patterns

Releases

• Stable releases (e.g., v1.1.0): Tested and ready for production use
• Experimental releases (e.g., v1.2.0-yuyv.1): Pre-release builds for testing new features
• Dev builds: Automatic builds from dev branch available as GitHub Actions artifacts

Download the latest release from the Releases page.