Song properties

[garvalf]

bonjour,

dans le manuel, je n’ai pas trouvé de référence à l’option “Song properties”.
Quand on modifie les PSG settings, on peut modifier le master clock, pour passer d’un Amstrad à un ZX ou Atari ST.

Par contre je ne comprends pas trop l’incidence du “replay rate”. Est-ce que cela correspond à la fréquence d’interruption que l’on retrouve dans Vortex Tracker ? (50 hz pour ZX, 60 ou 200 hz pour Atari).

Si on cible un Amstrad CPC, est-ce qu’il faut rester sur un replay rate de 50 hz ? Ou si on compose en 100 hz, et qu’on rejoue sur un amstrad, ça va réduire la vitesse ?

[Admin]

Hi,

Yeah, this part is lacking in the manual, but I think it’s simple enough. I may find time to improve it, but not right now :).

The replay rate is important, because it defines how often must the player is called. 95% of the time, you will play it at 50hz (so yes, this is the option you talked about in Vortex Tracker). 50hz is convenient, because on CPC for example, you simply have to wait for the frame flyback (the famous VSync). On MSX/Spectrum, simply wait for the next HALT.

Some games use a 25hz player, so call the player every two VSyncs.

If you decide to use another replay frequency, then you have to make sure you CAN, as a coder, call the player more or less often. If you use a 100 Hz song, you must call the player twice a frame, if possible at equal duration for a smoother result. On CPC, reaching 300hz is easy as the interruption system manages this automatically. However, it consumes a lot of CPU.

If you choose exotic values like 78hz, then welcome to hell, as you have to play the song accurately, but you’re on your own, timing-wise, as no hardware facilities will help you.

All the replay frequencies shown in AT2 are easy to produce on a CPC, thanks to the interruption system.

[garvalf]

Merci beaucoup !

I’ll stay with 50 hz interrupt then!

[Author]

Posts