there are two issues that fight to such an extent they are exclusive afaics, you can have good absolute time encoding so that you can drop anywhere into the timecode and quickly know the position within something like an hour of audio, or you can can have good relative encoding such that you can scratch the actual audio back and forth.
Old frame based timecode such as used on tape, I can say from experience is no use to scratch, it takes too long for the decoder to lock to the absolute position and the divisions between time markers is too big. You can get the decoder to interpolate (or freewheel) between marks but without enough marks per second of code it won't work for scratching.
Sounds like Pinkys system is using FSK, which uses two sine tones like a modem, the trellis encoding is an ECC layer that makes this more reliable and a little more efficient, but basically this is how you encode a binary number into vinyl to tape (if the groove actually had 1s and 0s it would break the stylus very quickly)
If we started at 0 and had one second of codes at 44.1Kz then
at 33 rpm (0.55555 revolutions per second) at 12 inches (30cm) diameter
gives us 1.885m/s (at the best case outside of the disc), which is
0.0000427m for each timecode chunk. In that chunk we would have to
encode at least 24 bits to have an integer time index over about
an hour, making the distance between timecode chunks 1.7e-6m.
Too small!
That's why we have CD technology not not vinyl, if there were a
way to squeeze that much digital info into a vinyl groove Phillips
or Sony would have looked at it
If we use an entirely relative approach, where instead of symbols we encode a constantly
variable analogue signal (what vinyl is best for) and use that to increment or decrement a
counter in the decoder much better results are possible.
Some timecode is reversible, that's kind of the point when you work with tape, you have a buffer and a way to detect frame boundaries and read the frames in reverse.
> Any other Ideas?
Personally I believe the best way is not to encode on the vinyl at all, but to make a turntable
that very accurately measures the angular velocity of the wheel and the angular position
of the tone arm pickup. You can probably do this using bits hacked from a disk drive. It would need
occasional calibrating, but is the best all round solution for high resolution with absolute time. (think of the tone arm and the table rotation like the mantissa and exponent of a floating point number, they're both part of the same number with the tone arm counting the big divisions and the turntable wheel counting the smaller ones.)