DirectFB

This page was obtained from DirectFB Analysis by IGEL Co.,Ltd.

What is DirectFB?
DirectFB (Direct Frame Buffer) is a set of graphics APIs implemented on top of the Linux Frame Buffer (fbdev) abstraction layer.
 * Input Device and Window System are also available
 * Linux version of `DirectDraw`, in a manner of speaking
 * www.directfb.org
 * DirectFB wikipedia entry

DirectFB is primarily developed by the German Company, Convergence GmbH
 * Specialty in Linux based DTV benchmark and middleware development Hosts LinuxTV, `FusionSound` and DirectFB projects
 * Member of Multimedia Home Platform (http://www.mhp.org/)
 * www.convergence.de

Goals of DirectFB

 * Small memory Footprint
 * Maximize utilities of hardware acceleration
 * Support of advanced graphics operations such as multiple alpha blending modes
 * No kernel modifications
 * No library dependencies, except for libc
 * Meet the requirements of MHP specifications

Features of DirectFB
Graphics
 * Rectangle Filling/Drawing
 * Triangle Filling/Drawing
 * Line Drawing
 * Blit
 * Alpha Blending (texture alpha, alpha modulation)
 * Porter/Duff
 * Colorizing
 * Source Color Keying
 * Destination Color Keying
 * Integrated Window System
 * A subset of OpenGL API (Mesa)

Devices supported by DirectFB
As of DirectFB 0.9.21 Graphics Drivers Input Drivers
 * Matrox Mystique/Millennium, G100, G200, G400/450, G550
 * Via CLE266
 * ATI Mach64/Rage Pro series
 * ATI Rage 128
 * ATI Radeon
 * 3dfx Voodoo3/4/5/Banshee
 * igs `CyberPro` 5xxx
 * S3 Savage 3/4 series
 * `NeoMagic` 220/2230/2360/2380
 * nVidia `TNT/GeForce` seiries
 * SiS 315
 * Intel i810
 * NSC Geode
 * Standard Keyboards
 * Serial and PS/2 mice
 * joysticks
 * Linux Input Layer Devices
 * Infrared Remote Controller (lirc)
 * iPAQ Touch Screen
 * ucb 1x00 Touch Screen
 * Microtech Touch Screen
 * Sony PI Jogdial

Supported Media Format
Still Images Motion Picture Fonts
 * JPEG (libjpeg)
 * PNG (libpng2)
 * GIF
 * Image format supported by Imlib2
 * mpeg1/2 (libmpeg3)
 * AVI (avifile)
 * MOV (`OpenQuicktime`)
 * Macromedia Flash (libflash)
 * video4linux
 * DirectFB bitmap font
 * `TrueType` (`FreeType2`)

DirectFB Architecture


DirectFB runs on top of the Frame Buffer Device (/dev/fb), and utilize hardware acceleration with their chipset drivers DirectFB performs only the following tasks thru /dev/fb? DirectFB uses their own chipset driver to utilize hardware acceleration through the memory mapped I/O ports
 * Also runs on VESA frame buffer
 * Setting up the video mode (resolution, color depth and timings)
 * Memory mapping of the frame buffer and I/O ports
 * Changing the viewport (e.g. for double-buffer)
 * Turns off the frame buffer drivers acceleration features

DirectFB API
DirectFB APIs are simple APIs whose design concept seems to be referring the DirectX APIs Might be enough for STB, but further analysis is required
 * Does it covers enough features?
 * Performance and quality, such as flickers, when used in conjunction with `Video4Linux`
 * Based on their presentation at FOSDEM, the DirectFB has capability to synchronously overlay MPEG-2 video on DirectFB window, i.e. no flickers

Upper Layer APIs supporting DirectFB

 * XDirectFB
 * X Server for DirectFB
 * DirectFBGL
 * OpenGL extension for DirectFB
 * Uses Mesa/DRI
 * GTK+
 * GTK+ for DirectFB
 * DFB++
 * C++ Interface for DirectFB
 * DFBTerm
 * Terminal runs on DirectFB
 * DFBSee
 * Movie player runs on DirectFB
 * DFBPoint
 * Presentation application runs on DirectFB
 * MythTV
 * PVR runs on DirectFB
 * Qt on DirectFB
 * Qt for DirectFB
 * SDL (Simple Directmedia Layer)
 * Game Development API that also supports DirectFB
 * Enlightenment Foundation Libraries (Evas and Ecore)
 * Object-oriented and stateful canvas (Evas) and main loop integration (Ecore) that have DirectFB engines/backends.

Fusion Sound
Audio subsystem that runs in conjunction with DirectFB Uses Fusion IPC, kernel function for synchronization, to synchronize with DirectFB
 * By using Fusion IPC, DirectFB and Fusion Sound can achieve fine granularity synchronization
 * Not enough documentation is available for Fusion IPC, requires source code level analysis

Consideration
Need further investigation and tests on the following points:
 * How well and smoothly works with video4linux
 * Internal architecture of Fusion Sound and Fusion IPC
 * Coverage of features

Architecture, at a glance, seems to be well designed, however, to increase supportability of new video and audio devices, we may need to re-design the architectures, e.g. both DirectFB layer and the Linux Frame Buffer Device To accomplish inter-media synchronization, i.e. synchronization of device access and temporal synchronization, concrete synchronization subsystem needs to be designed Based on the synchronization subsystem, API similar to `DirectDraw`, `DirectSound` and `DirectShow` has to be designed (See next slide)

Porting Guides
See Porting DirectFB - which describes the process of porting DirectFB to an SSH platform.

Performance benchmarking
See Benchmark DirectFB