Re: CiderPress v2.1.0 released

[Andy McFadden <fadden@fadden.com>]

Terry Olsen <tolsen64@hotmail.com> wrote:
> I'm curious...how did you figure out how to decode audio into bytes???

Read the F8 ROM listing in the back of the 1981 Apple II Reference Manual.

Read online references for the structure of a WAV file.

Spend a *lot* of time staring at sound files, trying to figure out ways
to recover the signal from 25-year-old cassette tapes.

So far I've pulled the data off of 44 sides of tape.  7 weren't
recoverable with the algorithms I'm using.  (A couple were pretty obviously
not recoverable with anything.)  Six of the seven bad ones were published
by Softape, one was from Apple.  The Apple tapes are usually pretty good,
but I've got two (Starwars/Startrek and BlackJack/SlotMachine) where the
tape broke and I need to do some reconstructive surgery.

One from Programma (Scramble) appears to have spent an unfortunate amount
of time near a strong oscillating magnetic field.  That's the trouble
with eBay -- you don't always know what you're going to get.

Some of the stuff on the tapes is fascinating.  A lot of old Programma
games loaded at $0200, auto-starting with data filling the command
buffer.  The data loading onto the text page served as a "please wait"
splash screen.

One, called "module 6", loads at address $30.  I thought that was a typo.
Nope: it fills up most of zero page, overwrites the stack, and keeps on
trucking.  Sort of tricky to run that one without loading from cassette,
because the JSRs in the F8 ROM routines RTS to the wrong place after the
stack gets trampled.

-- 
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