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Old 14 October 2016, 19:51   #36
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Join Date: Jul 2008
Location: Netherlands
Posts: 360
Originally Posted by mark_k View Post
I wonder how useful those figures are. Which clock source in your PC are they calculated with reference to? Unless you have some kind of atomic clock and batool64 uses that, surely the tolerance/error in the PC clock reference would be higher than the tiny difference between 48000.00 and 48000.02 (say).

That's a difference of less than 0.000042%; to put that in perspective, if the timing reference is a 2GHz CPU clock, that would be a difference of 833Hz.

While (I think) figures of 48000.02 & 48000.70 might not exactly match the real-world actual sample rates as you could measure with some calibrated instrument, the relative difference between them probably is accurate. And (if tiny deviations in the sample rate matter at all) the figures probably are relevant, in that WinUAE's timing will be based off the same source. In other words, WinUAE "sees" 48000.70Hz, even if the real-world actual rate is 48000.01Hz or whatever.
What would that mean to WinUAE, could we possibly benefit from some calibration adjustment?

Your point is well taken on the accuracy of the clock timer measuring these differences though, it could well just be smoke and mirrors.

On the other hand, the research from the GroovyMAME forums showed larger deviations even than the 0.7Hz for some users. The sound stability with GroovyMAME ASIO also got more stable after correcting for these "measured" differences for various users (we're talking very low latencies for GMASIO). So I guess there may be some truth to it.

Did you have a chance to do a check with the batool for your systems?

Possibly a "quick and dirty" inbetween road could be for Toni to allow for a temporary commandline manual "adjustment factor" that gets applied to the internal resampling frequency calculation. Purely for testing purposes to see whether + or - "0.XHz/48000Hz" adjustments have any noticable effect on the sound stability.
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