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2024-08-19 12:21

Flavioweb

Registered: Nov 2011
Posts: 463

Vice 3.8 r45312 tape emulation problem?

I was experimenting with writing tapes on rh and Vice when I realized that the exact same program (a small basic code of two lines) produced two different signals.
The signal produced on rh was slightly longer than the signal produced by writing the TAP generated by Vice using a U2+.
I then tried to sample the signal on the C64 using a U2+ through the "capture save" function, therefore working directly on the signal produced by the C64 and not by the Datassette.
I immediately noticed a difference.
The "pilot CBM" generated by the C64 is:

$2F, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30 , $2F, $30, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F, $30, $2F, $30, $2F, $30, $2F, $2F , $30, $2F, $30, $30, $2F, $2F

while the one produced by Vice is a simple sequence of $2F. I don't know if there are other differences in the signals afterwards.
On Vice I have "Tape Speed Tuning", "Wobble Frequency" and "Wobble amplitude" all at zero.
Since in all the dumps I've seen the pilot is similar to the one found on my rh, I think Vice has a problem with TAP management.

Is it just my problem/am I doing something wrong, or should I fire a bug report?

... 20 posts hidden. Click here to view all posts....

2024-08-20 07:35

Flavioweb

Registered: Nov 2011
Posts: 463

I'm not making any speculations.
I reported a simple fact: a program for c64 analyzing a standard save provides different values between rh and Vice for the same operations performed.
This is a fact, not speculation.

So I provided three data demonstrating this difference: the waveform extracted directly from Datasette, the frequency value reported by the tool and the TAPs extracted on RH compared with the one created by Vice.

I checked the test file you posted and I saw that the situation is more similar to the one I check on rh and I reported the frequency I get by analyzing its pilot, which is close to the one I get on rh and I specified that probably this variation is caused by the "rounding problems" you mention.

As soon as I can I will try your latest fix and report the results.

2024-08-20 15:34

chatGPZ

Registered: Dec 2001
Posts: 11386

And you can't post the file you produced in #3 because Zibri still has to give it to you? I don't get it.

2024-08-20 17:00

Flavioweb

Registered: Nov 2011
Posts: 463

You really were traumatized by Zibri, huh? =)
No, don't worry, it has nothing to do with these files.
I didn't put them because I thought they were easy to reproduce: they are simple SAVEs made on Vice and RH.
Anyway, here they are (I also add the file for Audacity with the audio extracted from the datasette using the 1530USB cable):

File saved on real hardware:
https://www.flavioweb.it/DaCondividere/C64SaveTape.tap
File saved on Vice:
https://www.flavioweb.it/DaCondividere/ViceSaveTape.tap
Audio dump from my Datasette:
https://www.flavioweb.it/DaCondividere/PhasesAudioProject.zip

2024-08-20 17:11

chatGPZ

Registered: Dec 2001
Posts: 11386

Quote:

I didn't put them because I thought they were easy to reproduce: they are simple SAVEs made on Vice and RH.

Its about the exact test cases - the file you linked doesn't even match the first post for that matter, it looks like its captured on a slightly slower setup, there are even $31 pulses in the pilot.

2024-08-20 17:17

Flavioweb

Registered: Nov 2011
Posts: 463

I just tried your fix.
I can confirm that now the TAP is much more similar to what I get on RH.
I don't know if it's perfect: however it works better than before!
Here is the file I get now:
https://www.flavioweb.it/DaCondividere/ViceSaveTape-Fix.tap

I'll try to write it on tape with the U2 and compare it with the save on RH but I think it's already better than before.
If I find "strange things" I'll write everything here.

2024-08-20 17:22

chatGPZ

Registered: Dec 2001
Posts: 11386

Quote:

I'll try to write it on tape with the U2 and compare it with the save on RH

That doesn't make a lot of sense (you are only factoring in U2 writing, and whatever tape-speed related effects, making it worse). To compare, you should directly capture from C64 the same file.

2024-08-20 18:09

Flavioweb

Registered: Nov 2011
Posts: 463

I have now recreated the TAP from my C64.
Now I can confidently say that your latest fix works 100% because, now, my machine and vice are 100% aligned!

When I started doing these tests, my 64 was slow and Vice was fast.
WTF!?!?
Now I see the frequency of the pilot as it should be, i.e. 2596hz exactly like in Vice!

This is the file saved directly from my 64:

https://www.flavioweb.it/DaCondividere/C64SaveTape2.tap

2024-08-20 18:18

chatGPZ

Registered: Dec 2001
Posts: 11386

Fine, case closed :)

2024-08-21 15:07

Danzig

Registered: Jun 2002
Posts: 440

@C0 Mach schnell zu!

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