Posted By
IstvanV
on 2009-05-16
16:52:46
|  Re: TED Music Collection?
That is not exactly how I implemented it, since both the TED and SID sound emulations are cycle based and run at 221681 and 886724 Hz in PAL mode, respectively. So, generating bandlimited signals is not really needed there.
The audio output is then downsampled to 48000 Hz (or whatever sample rate the user chooses), with a windowed sinc interpolation if the "high quality" mode is enabled, which is the default. There is one trick, though, that slightly reduces SID quality for speed: rather than having an (expensive) 886724 to 48000 Hz resampler, blocks of four SID samples are averaged and mixed to the TED output.
You can test how this sounds in practice in plus4emu: try generating some high frequency TED square waves, and check if the aliasing is audible. For comparison, test other emulators as well.
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