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Old 16 January 2017, 02:02   #97
Pat the Cat

Join Date: Dec 2016
Location: Nottingham, UK
Posts: 482
Originally Posted by meynaf View Post
You're right, it's NTSC that can go the highest.
IIRC frequency limit is 28604 for PAL, 28867 for NTSC (period 124 in both cases).
First edition HRM lists minimum period values as 123 PAL, 124 NTSC. Measured in clock ticks. That gives a total maximum playback rate of 28.867 KHz on BOTH kinds of Amiga.

CBM didn't ever write that part of the HRM of course, Hi-Toro/Amiga Inc did. I have not checked the later HRM edition, so it could be a typo, or perhaps CBM just didn't like the idea of their American customers having a slightly suspect sample rate. It might explain Akira's claim that the released version is different in pitch to the original. Not sure about that, have no idea what tools they used or their source of the audio, but in terms of playback on a PAL system it is a match, for frequency response.

As Sonique is French, with a SECAM background, the writer probably took account of the different playback rates and adjusted accordingly. That's my guess, perhaps it only works with PAL sourced mods after all.

I think I muddied the waters when I said that Paula was limited. Other posters are more accurate here, it is the DMA via chip RAM that causes the limits, and while you could use the CPU to write a custom copper list for the next vertical blank so that the copper writes the values into the audio DACs on time, it would probably be very glitchy unless you got it absolutely perfect every time. That's on the Amiga, of course.

Amiga 8 bit Sampling software capable of capturing audio at that rate shut down all activity while sampling, and started up again when the user had clicked a mouse button or similar to indicate the sample recording be stopped and the system returned to "normal" again.

Last edited by Pat the Cat; 16 January 2017 at 02:32.
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