[Sam-users] So what's up in SAM Wolrd?

[Stefan Drissen]

Hi Edwin (moving back on list) :-)

Regarding Anton's 4 bit SAA1099 sample player:

You stated: "Snap niet helemaal waarom 192 scanlines gewacht wordt want dit
is ongeveer 12,3 ms (192/312*20ms/frame) (een halve periode @ 61Hz is
ongeveer 8,2 ms. Maar er zal vast een reden voor zijn en de sample in Rick
Dangerous klinkt geweldig!" (you all know how google translate works)

Just jotting some numbers down to see if I can reason why this works:

Tone 0, octave 0 is 31 Hz.
To counter phase this, you need to jump in at 62 Hz.
Frame is 50 Hz

All channels are triggered on line 0 (detected by lightpen port)
Counter phase channels are triggered on line 192 (detected by lightpen
port).

Total screen lines (1 frame) = 312.
192 / 312 = 61%

So I must be missing something - since you are also suggesting something
else,
Unless the lightpen port would return 0 on the first border line, which it
does not.

Anton did open an issue on SimCoupe about some very minute differences, see
https://github.com/simonowen/simcoupe/issues/36 - but that was about
gradual phase shift that became increasingly noticeable.

I do not think that I'm hearing a ticking distortion in SimCoupe (I'm using
v1.2.3 dated 2021-08-15) - but well, a SAM playing samples and no
distortion? ;-)

Cheers!


Stefan
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