On Feb 3, 2021, at 12:36 PM, Mattis Lind via cctalk
<cctalk at classiccmp.org> wrote:
...
So you store a full track worth of data and then write it to the SD-card.
Then move the flux-length data over to a PC and do post processing there,
right?
Isn't there performance in the CPU to do the actual decoding as well? FM,
MFM, GCR or whatever into data. Find marks, check CRC and all that stuff?
A nice benefit of capturing the raw waveforms and post-processing them is that you can do
all sorts of very complex processing. If the media are nice and clean then simple
processing is sufficient. If they are badly damaged, you may need more. If you do the
processing in real time you may not know what all is needed. But if you do
post-processing, you can add to the algorithms after data capture has been done, if what
you have so far isn't yet good enough.
I can imagine techniques like digital filtering, adaptive filters, maximum likelihood
decoders, etc.
In recovering data from tapes, with multiple tracks, people have often done this same sort
of thing, full high bandwidth analog signal capture. You don't even need to know at
the time what the data format is. If you think you know but you don't have it quite
right, no matter, you just change the software and run another pass through the captured
waveforms. No need to run the (possibly fragile) media through the machine again.
paul