Polarity-sensitive tape-loading routines

[SkoolKid]

In short, are there any? And were any of them used commercially?

(By polarity-sensitive, I mean sensitive to whether an edge on the tape was created by a MIC on/off transition or a MIC off/on transition.)

I've never run into any such loaders myself, but if there are any out there, I'd like to make sure that SkoolKit's tap2sna.py can handle them.

[jpnz]

From the Spectaculator 6.2 release notes:

Added support for TZX files that are polarity sensitive.
This includes Basil the Great Mouse Detective, The Mask and La abadia del crimen.

[SkoolKid]

Added support for TZX files that are polarity sensitive.
This includes Basil the Great Mouse Detective, The Mask and La abadia del crimen.

Thanks! Now the question is: How do you tell what the starting polarity of each tape block is?

That info doesn't appear to be in the TZX file itself, and I'm not sure how to infer it (if that's what you're supposed to do). My go-to emulator (Fuse) also seems confused by these TZX files and doesn't load them correctly, so I'm stuck!

[zx81]

From my POV, the worst polarity-sensitive routine is in Forbidden Planet.

[SkoolKid]

From my POV, the worst polarity-sensitive routine is in Forbidden Planet.

I just ran a Forbidden Planet TZX through both Fuse and tap2sna.py, and they both loaded it just fine. Maybe they got lucky? (There is only one data block after the BASIC loader on the tape, after all.)