Mark 3 : Mpeg 1 layer 3 compression based portable jukebox
Started at the begining of July 1999, the idea was to build a box for use at parties which was more portable than the full size jukebox. It's built into a 2U 19" rack mount case.
Features :-
Hardware :-
A Pentium motherboard with on-board audio and video (no plug in cards means it's less than 70mm high).
An IDT 200MHz processor (although a Pentium P120 just about works).
A pair of 4.3G drives, on rubber mounts (to protect them a bit more during transit).
Just 16Mb of RAM.
A standard PC power supply, removed from it's original case, with heatsinks modified to fit.
A mono VGA LCD display with an ISA bus controller card (Which disables the on-board video).
Some push buttons wired to the parallel port.
Reuses the mpeg 1 layer 3 decoder from the Mark 2, (you can get the Source code).
Enough disc space for over 2000 tracks.
Best next track search from the Mark 2 (Including the categories).
Menu driven interface, from either PC keyboard or the parallel port connected buttons.
A set of password protected menus (well actually it's a special key sequence) allowing :-
Adjusting the output level (volume)
The deletion or priority boost of tracks in the playlist.
Varying the maximum number of outstanding (unplayed) tracks.
I've had to add a processor usage limit for the menuing system.
If the menuing system does something which takes a reasonable amount of time to complete then a timeout
is set which ignores futher inputs for a short while.
This allows enough time for the MPEG decoder to buffer up the audio stream again.
Before I coded this you could cause audio dropouts by quickly switching between some of the menus.
Parts
Several people have asked me where I some of the parts; Well the usual PC parts came mainly from my junk box or were got 2nd hand, the power supply was a standard one which I took out of it's case and modified to fit. Don't do this at home without adult supervision (-: Maplin electronics supplied the case (order code XM68Y), and the rubber mounts for the hard drive (order code FB98G). Computer Chopper supplied the LCD display at great price.
The display
The menu display is split into three sections
The top section lists the currently queued tracks
The main section shows the "Current artist" or "Track list" (depending on mode)
The bottom section shows the online help, the status, and, if in debug mode, the debug info.
Mark 4: Laptop based
Mark 4 : Mpeg 1 layer 3 compression based portable jukebox
Started during 2003, the idea was to build a smaller, more portable version of the Mark 3.
Rather than build a PC into a small case, I bought an old laptop (with a knackered battery).
Features :-
Hardware (An old laptop) :-
Pentium MMX 200MHz
Just 8Mb of RAM.
An 8Gb 2.5" laptop drive
A CD-ROM - To get the music onto it, in the first place
A floppy drive (easier to use for small updates, than cutting a CD)
Put the normally closed contact of a relay across the power button, so it's effectively held down until the power turns on. (So just plugging it in, turns it on)
Some push buttons wired to the parallel port.
Initially this ran the old software, but the new soundcard (WSS instead of Soundblaster) used more CPU, and would drop samples.
