page@swan.ulowell.edu (Bob Page) (03/25/88)
I just saw the "Pal [sic] and Audio" article in AmigaMail (a support publication from CBM, contact CATS for info). The article states you should look at GfxBase->DisplayFlags to find out if you're running on a PAL or NTSC machine, for determining clock rates (to accuarately generate audio frequencies and periods). Why not use SysBase->VBlankFrequency instead? Wouldn't it be more accurate? PAL 3.546895 50Hz ---- = -------- = 0.990878 ---- = 0.833333 NTSC 3.579545 60Hz ..Bob -- Bob Page, U of Lowell CS Dept. page@swan.ulowell.edu ulowell!page "Nicaragua" is Spanish for "Vietnam."
stever@videovax.Tek.COM (Steven E. Rice) (03/28/88)
In article <5679@swan.ulowell.edu>, Bob Page (page@swan.ulowell.edu) writes: > PAL 3.546895 > ---- = -------- = 0.990878 > NTSC 3.579545 Perhaps I have missed a whole lot of context, but the European PAL standards use a subcarrier frequency of 4.43361875 MHz. Thus, this equation would be: PAL 4.43361875 ---- = ---------- = 1.238598 NTSC 3.579545 Steve Rice ----------------------------------------------------------------------------- * Every knee shall bow, and every tongue confess that Jesus Christ is Lord! * new: stever@videovax.tv.Tek.com old: {decvax | hplabs | ihnp4 | uw-beaver}!tektronix!videovax!stever
grr@cbmvax.UUCP (George Robbins) (03/30/88)
In article <4925@videovax.Tek.COM> stever@videovax.Tek.COM (Steven E. Rice, P.E.) writes: > In article <5679@swan.ulowell.edu>, Bob Page (page@swan.ulowell.edu) writes: > > > PAL 3.546895 > > ---- = -------- = 0.990878 > > NTSC 3.579545 > PAL 4.43361875 > ---- = ---------- = 1.238598 > NTSC 3.579545 Well, you're both sort of right. The PAL burst frequency is 4.433 MHz, however a "PAL" amiga uses a multiple of the 3.546 MHz frequency for its internal time base, and the 4.433 MHz is generated by frequency multiplication/division in the composite video or genlock circuitry... -- George Robbins - now working for, uucp: {uunet|ihnp4|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@uunet.uu.net Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)