Features

libavg includes a hardware-accelerated display mixer and screen layout engine and integrates high-performance video playback. It supports paragraph-level text layout and rendering as well as cameras. Nearly all parameters can be changed at runtime using python scripts. Input is supported using mouse and keyboard as well as standard touchscreens and multitouch surfaces. Among others, libavg projects have used motors, coin rejectors and relays attached to parallel and serial ports, worked with usb bluetooth dongles and integrated printing.

Screen Layout Engine

The screen layout engine is at the heart of avg. It is responsible for dealing with graphical elements (images, videos, text, camera output) in a generic way and for putting these on the screen. Among others, it supports:

Hierarchial layouts
Cropping
Scaling
Rotation
Element-level transparency
Image alpha channels
Separate mask bitmaps
Additive and subtractive as well as averaging blend modes
Subpixel precision for smooth animations
Hardware-accelerated OpenGL rendering
Warping and mirroring of elements

Video Support

libavg video support means:

Playback pause and restart, playback at user-determined framerates
Complete display engine integration, including cropping, scaling, rotation and transparency.
Videos with an alpha channel are supported.
Very high performance: A Core 2 Duo system can play back two full HD videos at once with the right setup. That's 2x1920x1080 pixels at 25 frames a second. Video decoding is accelerated using shaders if available or sse2 assembly if not.
Seeks at interactive rates: Essentially, libavg allows random access to the frames of full HD videos without delays using mjpg files.

Text Support

Text rendering is supported with:

Paragraph-level layout using html <div>-like syntax
Bold/italic etc.
Colored text
Left-/Right-justified as well as centered paragraphs
Kerning and antialiasing
Full internationalization using utf8: Arabic, Chinese and Hebrew are all rendered correctly and can be mixed
Custom letter and line spacing
Layout - including font face and size - changes in mid-paragraph

Vector Support

libavg supports vector nodes rendered on the GPU. Available vector node types are Line, PolyLine, Curve, Circle, Polygon and Rectangle. Vector nodes can be textured, with the closed vectors taking two textures: one for the outline, one for the fill.

Sound Support

libavg supports mixing of an unlimited amount of stereo sounds with a high-quality limiter to avoid artifacts on volume spikes. It supports alsa on linux and core audio on Mac OS X for low-latency sound output.

Camera Support

libavg supports a wide variety of firewire and USB cameras. Setting camera parameters such as brightness, exposure, saturation and gamma is also possible.

Plugin Support

Plugins written in C++ have access to all libavg internals and can define complete new node types, including xml and python interface.

Animation

libavg has built-in support for smooth time-based animations. Any numeric attribute of a node - x, y, angle, etc. - can be animated with a single line of code to create linear and spline-based movements.

Tracking

libavg was used as the basis for the c-base MultiTouch Console MTC and thus supports camera tracking and multitouch surfaces built using firewire and Video4Linux cameras.

Authoring

All of python is available for scripting. libavg directly provides:

Properties of display elements as python variables
Full-featured event handling system
Timers (setTimeout, setInterval)
Support for logging
High-level profiling to find performance bottlenecks
High-precision frame timing and synchronization to vertical blanking for smooth animations