Re: [TCLUG:22703] Dedicated MP3 distro project?

[Callum Lerwick <lerwick@tcfreenet.org>]

Suppose I'll reveal my plans for my DEC Multia based car MP3 Player..

> kind of an "instant MP3 player, just add your own kernel" approach. I'm
> initially discounting the UMSDOS approach, as it is generally considered an
> inferior filesystem - but might there be some speed advantages to using a
> DOS or FAT32 filesystem for a dedicated MP3 system? What about
> defragmenting DOS / FAT32 filesystems under linux?

UMSDOS is slower than snot. e2fs is far faster. And ReiserFS is even
faster and does journaling, thus will be more resilient to being
abruptly shut off... Too bad Reiserfs doesn't seem to be Alpha friendly
yet.

There is no reason to use FAT unless you're using DOS. ;)

> I would expect the player to be controlled from a simple telnet (or SSH?
> you tell me the advantages / disadvantages of either approach) and possibly
> a dumb terminal running on a serial port. In this way, the player could be
> commanded from any machine on my LAN (read: in my house), or from the
> terminal. I suppose an IRDA port on the machine, and a generic
> remote-control might also be a very nice feature to implement...

Multia's have built in serial, ethernet and whatnot. I can plug it in to
the LAN or serial console to a laptop as wanted.

I'll be investing in Wavelan and CDPD soon as I'm rich and famous. And
maybe a GPS reciever... Hmm, how to keep it powered when the car is
off...

> So my first questions are, does such a distro already exist? It seems like
> everything needed would fit on several floppies... What sort of Linux
> software exists for 'jukebox' type MP3 playing, from the command line? For
> managing all of the MP3 files? Has someone else already done this, such
> that I can just focus on my hardware issues and not ask any more questions
> about software or OS?

I'm using debian potato at the moment, debating an upgrade to Woody. I
plan to make use of runlevels, a default one that boots the yet to be
written jukebox system as fast as possible, and a when-not-in-the-car
one that will startup networking, sshd and all that good stuff.

I still want to have a full Linux setup, for future expantion. ;)
(Imagine a road trip, a Multia loaded with a CDPD modem in one PCMCIA
slot, Wavelan in the other, a hub hooked up to the ethernet, and all
passengers with laptops...)

> On the subject of hardware, have there been any A/B listening tests of
> various soundcard's audio quality? Are there any true "high end" soundcards
> - meaning cards that use film caps instead of electrolytics, low noise /
> low inductance resistors, low-noise op-amps, extra EMF / RF shielding,
> decent design & metallurgy in the audio connectors etc ?

Multia's outputs are kinda noisy, turning down the damn line input
certainly helps things.

Cars are noisy anyway, and so's my wonderful stock audio system. The
audio will tie in via a tape adapter...

> Finally, does anyone have a mini-case upon which I can start the hardware
> portions of this project? It will need space for a CD-ROM and at least 2
> ISA slots - to take the soundcard and NIC. Onboard video would be fine. 1
> Serial port is also a requirement. From what I gather, I should not need

Multia's are small. Everything you could want built in, SCSI, IDE,
Serial, parallel, audio, ethernet, a PCI slot, two PCMCIA. Only thing
missing is a CDROM. I aquired a 12x SCSI cdrom at the computer sale,
which will be its primary storage medium initally, and will still be
useful for loading new songs on via CDRW if I ever decide to tack a nice
big HD onto it. Right now its booting off the stock 300mb laptop SCSI
HD...

Primary user interface will be via a laptop keypad attachment, and audio
cues, (Speech synthesis?) similar to the Knight Rider mp3 player.
http://knightrider.linuxave.net/ Initally visual display will be forgone
due to cost, unless maybe running a small 9in POS (As in Point of Sale.
;) display via an inverter proves viable. Or maybe LCD...

I plan to develop the UI myself in C, making use of SDL, SDL_mixer and
SMPEG. SMPEG plays mp3's using about 30% CPU time on the Multia. (166mhz
21064) Having all the hard stuff already written for you is nice. ;) I
can't get mpg123 to compile right for Alpha so screw it. ;P

Electrical engineering peoples, how would I measure how many watts my
Multia draws? I have a mulimeter and no idea how to use it for such a
task. Suppose I can just dig up a spec sheet somewhere. Using an
inverter would be the easiest thing, but maybe I'll build a DC-DC
converter later on...

> more than a 486DX-2/66 with about 8-12MB of RAM to do the job. I have

Way too slow. A 486-100 can just barely play mp3, using 100% CPU time,
and thats using integer math, which degrades quality quite a bit. You
want something P-100ish or better.