Digital Audio Revolution IIGS (MP3 how-to for IIGS)

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Playing MP3 music on the Apple IIGS

The Apple IIGS is a computer that's famous for doing
what's commonly considered impossible.  Years ago,
they said there would never be workable fax software
for the IIGS.  The IIGS proved them wrong.  Then
they said there would never be multitasking on the
IIGS.  GNO/ME and The Manager proved they were wrong.
They said the IIGS could never run TCP/IP.  They
were wrong.  They said the IIGS could never run a
web browser.  They were wrong.

The latest "impossibility" seems to be the playing
of MP3 songs on the IIGS.  This too is wrong.  Yes,
decompressing the MP3 songs on the IIGS would take
unreasonably long, but playing the resulting digital
audio is a piece of cake for the IIGS' Ensoniq 5503
sound chip.  So put on your mission impossible caps,
folks, and get ready to take your IIGS into the
21st century.

The software that's needed on the PC side is Winamp
and Goldwave.  On the Apple IIGS side, you'll need
Oversampler and a program to set file types and
aux types (such as ProTERM or UtilityWorks).

Fire up Winamp on the PC.  The trick is to redirect
the audio of Winamp from the speakers to a .wav
file on your hard drive.  Click on the menu icon in
the upper left hand corner of the Winamp window and
from the drop down menu select Options then
Preferences.  Under Plug-ins select Output and
select and configure the Nullsoft Disk Writer plug-
in to an output folder of your choice.  This is
where Winamp will drop your converted .wav files.
Close the window.  Now click on the Playlist (PL)
button and load up the MP3s you want to convert.
Then hit the play button.  Winamp will convert
each of your songs in real time (since the output
is redirected to disk, you will not hear your
songs through the speakers).  After the last song
has played, click the stop button so Winamp does
not try to reconvert the first song on the play
list.  Close Winamp.

There should be some HUGE .wav files in the output
folder you selected.  These will be reduced in
size and processed for the IIGS using the Goldwave
program.  Although you can take the .wav files as
is to the IIGS, the quality will not be optimum
and you'll go crazy trying to move such huge files.

Launch Goldwave and load one of the .wav files.
Goldwave will load the file into memory.  The
first thing to keep in mind for outputing audio
on the IIGS is the playback rate.  The IIGS'
audio system is on the motherboard and picks
up noise from the switching power supply.  This
power supply operates at a frequency of 26360Hz.
An audio file playing back at this rate, double
this rate, or half this rate will be clean
because the power supply will not interfere with
the sound chip.  It will be less clean at other
playback rates.

Go Effects menu and select Resample.  Type
26360 in the Rate box and click Ok.  Goldwave
will resample the .wav at this sampling rate.

The second thing to be aware of is that the
IIGS sound chip has a different frequency
response than most PC sound cards.  It favors
bass to treble.  So, go to the Effects menu
and select Filter, then Parametric EQ.  What
looks like a graphic equalizer appears.  That's
exactly what this is.  Like the graphic
equalizer of a stereo system, it is meant to
adjust for the frequency response of different
playback devices.  For PC to IIGS transfers,
you'll want to boost the treble (incidentally,
if you sample something on the IIGS and
convert it into a .wav for the PC with Goldwave,
you'll want to dampen the treble with the
Goldwave Parametric EQ otherwise the audio
will come out rather sharp...so IIGS to PC
transfers are OPPOSITELY equalized with
respect to PC to IIGS transfers).  Select
band 5 and boost the Gain by five.  Repeat with
bands 6 through 10.  When you are finished,
click Ok.

The file is now ready to be saved.  Under the
file menu, select Save As.  Type in a file
name or use the default if you do not want to
keep the original Winamp generated file.  For
Type, select Wave.  For File Attributes, select
8-bit, mono, unsigned.

Repeat this process for each of the music files.

You now have .wav files which are the MP3 songs
converted for IIGS playback and they are only a
little larger than the MP3 originals.  The next
step is to get them to the IIGS.

Getting such large files over to the IIGS
(several megabytes each) is best done with a
Zip disk and Peter Watson's MUG! desk
accessory.  However, null modem or AppleTalk
would also work.  They take a lot longer,
though.

Once on a IIGS hard drive, the files are ready
to be played with the Oversampler program.
However, constantly setting the playback rate
manually is a drag.  Instead, let's set the
file type and aux type so that Oversampler
knows it is an audio file.  Using ProTERM,
UtilityWorks, or another program with file
type/aux type setting ability, set file type
as $D8 and aux type as $0200.  This will turn
your mystery file into a file instantly
recognizable to GS/OS as an audio file and
more importantly, Oversampler would be able
to simply load and play the file.

Before proceeding to the next step, now is a
good time to borrow the amplified speakers
from your PC and plug them into the IIGS'
audio output jack.  Just like on the PC, you
would not want to listen to your MP3s through
your PC speaker, would you?  ;-)

Fire up Oversampler and open one of your
converted MP3 files.  All the controls are
preset, so just hit the Play button. Surprise,
an MP3 song is playing on your IIGS!

Oversampler spools the file as it is playing
from disk so you do not need lots of memory
to completely preload the song.  If you can
run GS/OS, you can usually get Oversampler to
play just about any song. The only catch is
the speed of the playback device.  Since
Oversampler is playing the song in real time,
the drive needs to have a fast response time.
A Zip disk is fast enough for for regular
play as is any hard drive.  AppleTalk volumes
or floptical disks are not fast enough,
however.

One feature of Oversampler is, you guessed
it, oversampling.  You might have seen this
feature in the advertising for your CD
player.  This feature works by INTERPOLATING
the waveform of the digital audio.  The file
is doubled in size in memory and the plot
points between two adjacent data points are
generated as the average of the two.  This
smooths out playback.  The resulting audio
is played back at the oversampled rate.
Oversampler supports two times and four
times oversampling.  As saved by Goldwave,
the converted MP3s are 26360Hz.  If
Oversampler is set to two times
Oversampling, it'll interpolate one set of
data points, double the size of the audio
file internally, and play it back at
52720Hz.  Zip disks are fast enough for
two times oversampling as is any hard
drive.  For four times oversampling (best
playback quality 105440Hz) usually
requires a fast hard disk drive and an
Apple High Speed SCSI or a RamFAST card.
Hard disk drives of this speed are usually
500MB or greater in size.

Surprise a PC or Mac user by playing your
converted MP3s on your IIGS to them.  With
only large hard disk drives available
these days (1GB minimum) what ELSE are you
going to do with all that space?  Build a
collection.  Put the "S" back into the
Apple IIGS!