On Tue, Apr 7, 2009 at 2:17 PM, Marko Mäkelä <email@example.com> wrote: > On Tue, Apr 07, 2009 at 09:47:06AM -0400, Ethan Dicks wrote: >> ... I probably have a small stack of tapes that had read >> errors, at least one of which is commercial (and occasionally had read >> problems back in the day). > > Can you archive the problematic tapes in the *.tap format? That should be > enough for decoding. I'll give that a try first. I last tried this long ago with a PC parallel-port interface to a real C2N drive and some, IIRC, DOS software on a 486. > If the *.tap files are too corrupted, then you could > try playing with the azimuth settings or sample it in PCM format (*.wav) > and use an appropriate digital filter. That should be easy enough to do on modern machines. > A few years ago, I made some > experiments with TAPir <http://tapir.sourceforge.net/>, but I can't remember > if it was of any use to me. I didn't try to mess around with the stereo > head of the analog tape deck that I used. OK. I might consider that, too. >> ... I do >> have a number of "PET Rabbit"-format tapes. > There are four decoder functions implemented so far: decode and decode264 > in decode.c, decode_kim in kim_d.c and decode_oric in oric_d.c. You could > start by studying the decoders in decode.c. Thanks for the pointer. > Hmm, I seem to remember that I once encountered VIC Rabbit. Sure enough, > I even documented the format: > > http://www.zimmers.net/anonftp/pub/cbm/vic20/roms/tools/4k/Rabbit.txt Nice. > I probably wrote some throw-away Perl one-liners to decode the samples > that I produced with the cartridge image. I must have run the "save" > command on the VIC-20 and sampled the pulses with the C2N232 directly > from the tape port, without going through analog tape. OK. > If the PET Rabbit is anything like Vic Rabbit, I wish you luck. That sounds like you put some time into it and gave up. Maybe I should go the route of digitizing these tapes and cleaning the audio up with filters. > Basically, the decoding can be divided to four steps: > > (1) sample the tape > (2) detect edges or pulses from the samples > (3) quantize the pulse widths to symbols B, C, D (using the c2n232 notation) > (4) decode the string of symbols to binary Got it. > The decoder functions in the "c2n" program implement step (4). > > I hope that this helps. It does. Very much so. Thanks! -ethan Message was sent through the cbm-hackers mailing listReceived on 2009-04-08 20:09:34
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