Nandemo PiGa the binary <-> wav converter for tapes

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By Manuel

Ascended (15960)

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11-12-2019, 09:26

mcolom wrote:
Manuel wrote:

there are still examples that do not work.

Do you mean samples that can be read in a real machine and not in openMSX? That's interesting, because the circuits to read the tape are really simple (DC filter + saturation + 1-bit counter). Perhaps some models had better circuits with synchronization, I don't know.
If the real machine neither can read it, that's a different story, of course.

indeed, stuff that loads in real machines, but not in openMSX. We tried to emulate the analog circuitry, but we couldn't get it working reliably.

By pgimeno

Resident (48)

pgimeno's picture

11-12-2019, 12:37

I've commented it on #openmsx in freenode, but let me repeat it here.

After my previous post, I looked at the source of wav2cas and realized a few things about it.

It's asymmetric, it treats raising and falling edges differently, which is probably why changing the phase helps sometimes. Also, the "threshold" value is used in the code with two purposes, one about the volume above which the data are considered data and not silence, and the other related to the interpretation of the data signal.

"Phase shift" is a horrible name IMO, it's phase inversion, or phase shift by 180°, but "shift" makes it sound like a shift by an arbitrary angle.

By Manuel

Ascended (15960)

Manuel's picture

11-12-2019, 12:52

This is the releveant openMSX code:
https://github.com/openMSX/openMSX/blob/master/src/cassette/... (has the comparator)
https://github.com/openMSX/openMSX/blob/master/src/cassette/... (has the DC filter)

Any improvement suggestions are most welcome. Please try them first yourself, if you can :)

By Manuel

Ascended (15960)

Manuel's picture

11-12-2019, 13:12

See also here for some examples: https://github.com/openMSX/openMSX/issues/766

By mcolom

Resident (57)

mcolom's picture

11-12-2019, 13:34

Are there any WAV samples that I can download and play with?
The ones that don't work with openMSX, but do in real machines.

By mcolom

Resident (57)

mcolom's picture

11-12-2019, 13:35

mcolom wrote:

Are there any WAV samples that I can download and play with?
The ones that don't work with openMSX, but do in real machines.

Ups, I didn't see Manuel's previous post in time Smile

By Manuel

Ascended (15960)

Manuel's picture

11-12-2019, 13:51

mcolom: we're discussing about this on IRC at the moment. Feel free to join! Then I can also give you some more examples (files are large).

By Takamichi

Champion (269)

Takamichi's picture

11-12-2019, 16:16

"Reverse the phase", "phase reversal", "flipping the phase", "位相反転" (isou hanten) are used with Nandemo Piga and most other applications and data recorders (incl mine), also with many audio/music equipment. I referred to same thing as "phase shift" just because Castools says so.
According to the tweet by Tiny Yarou the NPG developer, the wav files that used to work with Windows 7 no longer worked with Win 10 unless phase-reversed so he added this function. He has our account.

By Manuel

Ascended (15960)

Manuel's picture

11-12-2019, 16:40

OK.

Another question: can anyone with a WAV file that works on a real MSX (verified with the actual WAV file, so not the original tape!) but not on openMSX, contact me so we can investigate?
It's always good to have more examples.

By mcolom

Resident (57)

mcolom's picture

11-12-2019, 20:34

Manuel wrote:

mcolom: we're discussing about this on IRC at the moment. Feel free to join! Then I can also give you some more examples (files are large).

I couldn't, I had to be in some work meetings with non-MSX people Sad
But I'll start looking at the WAVs in the GitHub issue. I find this problem exciting, since it seems pretty simple to solve, but of course I'm sure it isn't if there's no solution so far.
I'll have a look, I'm curious to figure out why is not working.
BTW: I'd be useful to know which MSX model could load the WAVs, to look at their input circuit and reveal their hidden magic! Big smile

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