xcamera 0.1.0

A lightweight Flutter camera plugin for Linux supporting high-performance V4L2 streaming and synchronized H.264/AAC video recording.

XCamera

A high-performance, lightweight Flutter camera plugin built exclusively for Linux platforms.

It uses a Clean Architecture design with Flutter Method Channels, Event Channels, and Flutter Textures to provide efficient real-time camera streaming with low CPU and memory overhead.

Features

Core Video & Audio Operations

• Device Discovery & Hotplug Events: Enumerate camera devices and listen to udev connection events in real-time.
• High-Performance Live Preview: Render real-time camera streams using optimized Flutter Textures (FlPixelBufferTexture).
• H.264 Video Recording: Capture and encode video in H.264 format with optional AAC audio support into MP4 files.
• Multi-Backend Streaming: Support for both direct kernel Video4Linux2 (v4l2) and modern PipeWire multimedia framework.

Network & Streaming

• RTSP & HTTP MJPEG Stream Server: Stream H.264 video over RTSP/TCP or MJPEG over HTTP directly from the local camera.
• IP Camera Stream Client: Connect to and preview remote RTSP and HTTP network IP cameras using a single client interface.
• Virtual Camera Output: Stream processed frames to a local v4l2loopback virtual webcam node (e.g. for OBS/Zoom/Teams).

Advanced Hardware & PTZ Controls

• Hardware V4L2 Controls: Discover and adjust hardware parameters (brightness, contrast, focus, exposure, gain, white balance).
• Digital Zoom & PTZ Crop: Apply digital zoom (1.0x to 8.0x) with horizontal and vertical panning.
• Retroactive Pre-Roll Buffering: Maintain an in-memory ring buffer to retroactively save video recorded before pressing record.

Image Processing & Analytics

• Real-Time Motion Detection: Frame-difference luminance motion analysis with configurable threshold events and snapshots.
• OSD Watermark & Timestamp: Overlay custom text watermarks and microsecond-accurate timestamps directly onto frames.
• Image Filters: Low-light CLAHE Night Vision enhancement, Green Screen Chroma Key background removal, and Barrel Fisheye Distortion lens correction.
• Camera Assist Overlays: Focus Peaking edge highlights, and Zebra exposure lines.

Hardware Acceleration & Telemetry

• Hardware Acceleration: Native hardware video encoding via VA-API (Intel/AMD) and V4L2 M2M (ARM/SoC), with OpenH264 software fallback.
• DMA-BUF Export: Export V4L2 video buffers as DMA-BUF file descriptors for zero-copy memory sharing with GPU/Vulkan.
• Performance Telemetry: Real-time metrics monitoring (FPS, frame drop count, latency, bitrates).

System Prerequisites & Dependencies

Ensure the following tools and development headers are installed on your Linux host:

Ubuntu / Debian

sudo apt install -y libgtk-3-dev libudev-dev libyuv-dev libopenh264-dev libpipewire-0.3-dev libva-dev

Fedora / RHEL

sudo dnf install -y gtk3-devel systemd-devel libyuv-devel openh264-devel pipewire-devel libva-devel

Arch Linux

sudo pacman -S --needed gtk3 systemd libyuv openh264 pipewire libva

Virtual Camera Support (Optional)

To use Virtual Camera loopback streaming, install v4l2loopback:

# Ubuntu / Debian
sudo apt install -y v4l2loopback-dkms

# Fedora / RHEL
sudo dnf install -y v4l2loopback

# Arch Linux
sudo pacman -S --needed v4l2loopback-dkms

Load the kernel module:

sudo modprobe v4l2loopback video_nr=10 card_label="Virtual Camera" exclusive_caps=1

Native Implementation Details

The native Linux C++ plugin is built directly into the application bundle using CMake. It leverages:

• Video4Linux2 (V4L2): Kernel level video capture and hardware control management.
• PipeWire: Modern Linux desktop multimedia capture backend.
• udev: Linux kernel device hotplug tracking.
• Hardware Acceleration (VA-API / V4L2 M2M): GPU hardware video encoding on Intel, AMD, and ARM SoCs.
• OpenH264 & libyuv: System-level software video encoding and SIMD pixel color space conversions.
• Bundled C Libraries (in linux/third_party/):
  • vo-aacenc: Embedded VisualOn AAC encoder for offline audio encoding.
  • miniaudio: Header-only C audio capture engine.
  • minimp4: Header-only C MP4 container multiplexer.