English Amiga Board - View Single Post - Generating an accurate Paula period table

8bitbubsy · 19 June 2013, 08:12

Ok, so I assume it's an error in the BASIC interpreter's floating point that Lars (?) used... Or maybe PERIODTA.BAS actually generates a more correct table, like the C code, but that he edited the "errors" by hand to match the older tables found in Ultimate Soundtracker.
Ultimate Soundtracker's table is also wrong (and identic to the ProTracker one, but without finetune shifting), which dates back from 1987 (!):

Code:

	dc.w	856,808,762,720,678,640
	dc.w	604,570,538,508,480,453
	dc.w	428,404,381,360,339,320
	dc.w	302,285,269,254,240,226  
	dc.w	214,202,190,180,170,160
	dc.w	151,143,135,127,120,113
	dc.w	000

Maybe I can get in touch with Karsten Obarski and ask him some questions. He has by big chance forgotten all of this though, but it's worth a shot.
Anyways, the table *must* be like the one used in ProTracker, because I am looking up and comparing values, to get an index (which is the note

). These hard-coded period values are inside the MOD pattern data as well. With the "correct" table, I get wrong notes (not by a cent, but by a lot!).

19 June 2013, 08:12	#10
8bitbubsy Registered User Join Date: Sep 2009 Location: Norway Posts: 1,712	Ok, so I assume it's an error in the BASIC interpreter's floating point that Lars (?) used... Or maybe PERIODTA.BAS actually generates a more correct table, like the C code, but that he edited the "errors" by hand to match the older tables found in Ultimate Soundtracker. Ultimate Soundtracker's table is also wrong (and identic to the ProTracker one, but without finetune shifting), which dates back from 1987 (!): Code: dc.w 856,808,762,720,678,640 dc.w 604,570,538,508,480,453 dc.w 428,404,381,360,339,320 dc.w 302,285,269,254,240,226 dc.w 214,202,190,180,170,160 dc.w 151,143,135,127,120,113 dc.w 000 Maybe I can get in touch with Karsten Obarski and ask him some questions. He has by big chance forgotten all of this though, but it's worth a shot. Anyways, the table must be like the one used in ProTracker, because I am looking up and comparing values, to get an index (which is the note ). These hard-coded period values are inside the MOD pattern data as well. With the "correct" table, I get wrong notes (not by a cent, but by a lot!). Last edited by 8bitbubsy; 19 June 2013 at 08:20.