With Windows as the choice of OS, it was decided that the core application would be developed using Visual Basic 6. The simplicity of working with the language meant I could code a finished mp3car application quickly and makes changes to the functionality of the application easier at a later date if required. The application is divided into three main components - playlist selector/mp3 playback, mp3 playlist builder and the IR remote config utility.

The playlist selector/mp3 playback component is the main program, executed on bootup of the Windows 98 OS. It firstly sets up the IRman receiver and resets the LCD display ready for use. Information for the IRman is then loaded from a data file which defines what IR signals will perform what tasks. Playlists are loaded into memory, ones starting with an exclamation mark (!) are treated as albums/cd's and will be played in their defined order, with all other lists playing in random order. Finally Winamp is loaded in the background and the welcoming screen is presented on the LCD.

From there a user can browse the playlists, select a starting track from within that playlist and begin playback. When playback commences Winamp is called to load the playlist at the selected track. The display shows the current track playing, time information and handles tasks from the IR remote such as volume controls, next/prev track and stop of playback. When playback is stopped the user is then taken back to the select playlist/track menu and the process is repeated. The image to the right shows the component in action, of course this is never seen whilst in the car, but proved useful to have a working on-screen interface when developing the application.

Since starting to use the mp3car system on a very regular basis with adding/moving/deletion of mp3s from the systems hard drive happening on a regular basis the mp3 playlist builder component has proved to be almost essential. Essentially, it scans all the subdirectories within the mp3 folder of the hard disc and builds a playlist for each subfolder. Folders containing a Winamp .m3u playlist file will use that file for track ordering, with all other subfolders having their files ordered alphabetically. This solves the problems of having playlists of assorted music tracks and albums, the later are played in their defined order. The compiled playlists are then saved to a playlists directory to be read by the mp3car application on startup. Previous to this application being written, playlists were re-compiled manually using Winamp - very tedious.

The final component is the IRman setup utility program. It reads incoming remote control signals from the IRman device and assigns the keypresses to functions within the mp3car application. The IR codes are then written to a data file to be loaded upon startup of the mp3car system. The utility is not used very often, but it is nice to be able to re-configure the system to use a different remote control unit if needed.

For playback of the mp3's the decision was made early to use Winamp. For me it was not a hard decision to make at all -

• It is still very actively developed and supported by a dedicated programming team (Nullsoft) with dollar support from AOL now making that task a bit easier.
• Interfacing to Winamp's functionality is made really simple thanks to a very complete and well documented API, which is available along with quite a few source code samples at the Nullsoft/Winamp developer network website (well worth the visit). This helped make the task of working with winamp a no-brainer.
• In my opinion winamp is still the best sounding, configurable and reliable mp3 player for the PC.

I addition I have Winamp running the excellent SqrSoft Advanced Crossfading (ver 1.72) output plugin. As the name suggests, this plug-in crossfades the end of a track with the start of the next. With plenty of sliders and switches to play with in the settings and with pre-defined crossfading presets I can have my mp3 playlists sounding like a club with no-stop, zero gap playback. With a huge amount of dance/house music at my disposal, this sounds great and hands down beats any CD car system. I would highly recommend this plugin for anyone using Winamp.