Linux development

NOTE! This article documents an current event. Information may change rapidly as the event progresses.

Currently, a few developers on Team-XBMC have begun porting XBMC to Linux (and OpenGL using the SDL toolkit). The goal is for this to become a full port of XBMC with all the same features and functions that are available on the Xbox version of XBMC. This is a huge task which is why we are now making this public request, seeking C/C++ programmers who may or may not yet have already contributed to The XBMC Project in the past to volunteer in assisting us with this Linux porting development project. Those unfamiliar to XBMC can get a good overview of what XBMC is capable of by reading the XBMC article on wikipedia.org

Note to XBMC end-users! Please understand that this XBMC Linux port project is not yet mature enough for you to play with. No media can even be played back yet and we can not give you an ETA when it will be useful for end-users. Respect that we can not yet accept any bug reports or feature/function requests for this Linux port. If you as an end-users have any questions or need to get something of your chest about this then please direct that towards the existing XBMC Linux port end-user discussion topic-thread in our community-forum

What is XBMC and why port it to Linux?

For those who does not know; XBMC (short for XBox Media Center, not to confused with Microsoft's Windows Media Center Extender for the Xbox) is an award-winning free and open source media player, originally designed to run on the Xbox game-console. The GPL/LGPL licensed source code basically consist of a GUI framework that has been written from scratch by Team-XBMC, this GUI acts as a front-end control interface for several audio/video players designed for specific purposes (and those are loaded when needed as DLLs), the GUI is also the interface to all of XBMC multimedia handling functions such as databases and sorting, etc.. The XBMC Project, (who's members maintain XBMC source code), is a non-profit open source hobby project that is developed by volunteers in their spare-time without any monetary gain. The team of developers working on XBMC have always encouraged anyone to submit your own source code patches for new features or functions, improve on existing ones, or fix bugs.

The difference this time is that we are not asking for new features/functions, what we are asking is for the existing code to be ported so it will compile and run under a Linux operating-system (with the same features/functions that are already available on the Xbox version of XBMC). The main reasons for porting XBMC to Linux are non-technical, (so it is not that the Xbox hardware is too slow or to old for the XBMC GUI or its existing features/functions), the real reasons are that we want XBMC to get a larger end-user and developer-base, because the more people who use XBMC and help maintain the code (and skins) the longer the project will grow and stay alive. The main reason from an end-user point of view is that the Xbox can not playback native high-definition video (at 720p and 1080i/1080p), especially not if the video is encoded with a H.264 or VC-1 codec. Nevertheless, note that we will still keep the old Xbox as the reference platform for standard-definition resolution video for a few more years, meaning that the same GUI (and skins) that runs smooth under Linux on a relativly new computer must also run just as smooth on the old Xbox hardware (or a old computer that matches the Xbox hardware).

Skill requirements and where to start

Proficient in C/C++ programming language, and though not required knowledge of DirectX, OpenGL and/or multimedia is a plus, as well as prior cross-platform or porting development experience. You do not need to have access to an Xbox game-console or any special tools/softwares in order to take part - XBMC development is well underway on Linux (Ubuntu 7.04).

Where do I start (Linux)?

The recommended Linux development platform is currently Ubuntu 7.04 (Feisty Fawn). There is a Kdevelop project file available in SVN. After you done a SVN checkout, follow the install guide in the SVN to setup the required packages and so on. The best thing to do is just take a look through the source code and try to understand how it all fits together. Test things out, find what works and what does not, then try and track down why.

Non-Linux developers can also help

XBMC can also be compiled for Win32 (Microsoft Windows) operating-systems with Microsoft Visual Studio .NET 2003 (7.1) or higher, so even though Team-XBMC will be concentrating on the Linux port of XBMC, it will not hurt if some people who prefer Microsoft Visual Studio as a developement platform volunteer to help with getting the Win32 port of XBMC up to par as well, as a preperation for possible future cross-platform versions of XBMC.

• HOW-TO compile XBMC for Win32 from source code (to come soon!)

Other tools and resources

Though any other tools or resources are not required they can possible help make in development.

• Valgrind - free Linux programming tool for memory debugging, memory leak detection, and profiling.
• Sysprof - free System-wide Linux Profiler for tracking CPU usage

Technical summery of XBMC

The basics

The XBMC code structure uses a fairly modular design (with libraries and DLLs), and we think that there are enough modules/libraries to keep a wide skill-level range of developers busy for a while in the porting of them all. So please, take a look at the source code, then with the help of our To-Do list (futher down in this article) assess where the porting stage is today and think about where and how you can try to help out. Note that we are not planning on completly abandoning the Xbox hardware any time soon - XBMC will be a cross-platform software application, using the same code on multiple hardware platforms, (the old Xbox do have a good amount of years left to live).

Detailed technical information

For more details please visit the Development Notes section on this manual.

The XBMC source code

The XBMC source code is in our SVN repository on sourceforge.net. Full instructions for compiling/builing XBMC under Linux is available here:

• HOW-TO compile XBMC for Linux from source code

Linux porting

The Linux port plan

To come.

What has already been done

• Kdevelop] project file available in SVN
  • Linux development and debug enviroment
• Initial implementation of SDL
  • OpenGL for SDL
  • ?
  • ?
• X11
• More stuff to come.

To-Do

This is a To-Do list of thing that still need to be done, you are more than welcome to help out with any of these tasks:

• [MAJOR - HIGH PRORITY] Audio output modules (ALSA and OSS via SDL).
• [MAJOR - HIGH PRORITY] PAPlayer porting to Linux (so that same DLL runs on both Linux and Xbox?).
• [MAJOR - HIGH PRORITY] MPlayer porting to Linux (so that same DLL runs on both Linux and Xbox?).
• [MAJOR - HIGH PRORITY] DVDplayer porting to Linux (so that same DLL runs on both Linux and Xbox?).
• [MAJOR - HIGH PRORITY] Pixel Shader video renderer(s) (hardware overlay via Xv is an outdated and limited technology?)
• [MAJOR - HIGH PRIORITY] Development of a platform-independent wrapper interface to DirectX / OpenGL / SDL graphics interfaces, particularly with respect to how this interface should be exported to visualisations (.vis) and screensavers (.xscr), etc.
• [MAJOR - HIGH PRIORITY] Development of a platform-independent wrapper interface to DirectX / ALSA /OSS / SDL audio interfaces.
• [MAJOR - LOW PRORITY] XvMC and/or Pixel Shader (Shader Model 3.0) or Cg video hardware acceleration.
  • NVIDIA PureVideo technology support via XvMC will be great using NVIDIA's closed-source device driver as NVIDIA GPUs have a dedicated programable video acceleration core, however those closed-source device driver only support MPEG-2 video acceleration even though NVIDIA GeForce 7 GPU hardware and later support hardware acceleration of H.264 and VC-1 (WMV9) as well. So unless you have the skill/knowledge to add full XvMC support to the open source NVIDIA deveice drivers then we either have to wait for NVIDIA to support XvMC for MPEG-4 under Linux, or we can add hardware acceleration support by writting pixel shaders using GLSL or Cg (or Lib Sh) code for the decoding processes we can to offload some of the decoding onto the GPU, (which even though not as effective as using the NVIDIA PureVideo will be better than nothing).
• [MINOR - HIGH PRORITY] Port all PAPlayer codecs DLLs so they will also run under Linux.
• [MINOR - HIGH PRORITY] Fix hacks which might not work on some platforms
• [MINOR - LOW PRORITY] Lirc or alternative implementation for IR/IrDA (infrared) remote support under Linux
  • Also add Wlirc for IR/IrDA (infrared) remote support under Win32 for consistency.
  • Though probably not possible, it would be great if could be added via SDL for platform-independence.
• [CLEANUP - ALWAYS AN ONGOING PROCESS] Document all of the current/existing code (DocBook, rst, or doxygen, preferably the latter)
• [CLEANUP - ALWAYS AN ONGOING PROCESS] Valgrid debugging under Linux (and back-port any fixes to the Xbox and Win32 code)

XBMC programming and code formatting convention guidelines

More to come based on this ongoing discussion => Proposed code formatting conventions for XBMC

• Code documentation (DocBook, rst, or doxygen for the code documentation steps, preferably the latter, doxygen)
• Modular design (independent modules made upp by localized/isolated code libraries without dependcies)
• XBMC should still compile and run if a module is disabled/removed
• Cross-platform/multi-platform support; aim to compile and run on at least, Xbox, Linux, and Win32 (Microsoft Windows)
• Aim for the GUI/interface to run smoothly on a low spec computer (less than 1Ghz)
• Avoid harddisk trashing (excess read/write/erase cycles), utilize RAM memory, no harddrive paging. Aim to run on Solid-State (CompactFlash)
• Fast load and boot times for end-user perception (other thing can still run/start in the background without the user knowledge)
  • 15-seconds or less from when the end user press the power-button on the computer til he/she can browse the GUI

Mentors

Mentors are developers from Team-XBMC and members of The XBMC Project that have volunteered to assist and mentor non-official XBMC developers in any non-trivial way they can, helping you by checking, commenting and commiting your code patches to our SVN source code tree. These mentors have chosen an area they prefer to specialize in, usually this is an area in which they feel they have most interest, knowledge, and expertise in. Initial patches are welcome, and can and will be merged by the team. If you wish to join the team in an official capacity, please let us know.

Linux post mentors:

• Yuvalt: Everything Linux
• Elupus: DllLoader, Mplayer and DVDPlayer
• Spiff: Anything other than DllLoader/MPlayer/DVDPlayer internals.
• JMarshall: Anything GUI related, Music Library, Video Library, PAPlayer, etc.

Note! If you are a C/C++ porting guru/expert and like volunteer as a 'third-party developer mentor' then please let us know.

Contact methods

• IRC: #xbmc on freenode
• Development XBMC Development Forum
  • Developers forum for XBMC development. Programmers/Coders only!
  • Not for posting Feature Requests or end-user support requests!
• HOW-TO submit a patch