Posted By
IstvanV
on 2010-01-13
08:31:44
|  Re: First Release Of 2010!
The sound of the noise generator with a frequency value of 1020 should not be very complex, since it has a period of 221681 / 3 / 255 ~= 290 Hz, so it is not really "noise" at that setting. I have made a comparison of the emulators and a real Plus/4 using this program:
http://www.sharemation.com/IstvanV/plus4/p4noise.jpg
The recorded sound is in this archive:
http://www.sharemation.com/IstvanV/plus4/p4noise.7z
The contents are:
- plus4_48.ogg - the real machine, captured from the A/V output at 48000 Hz
- plus4_96.ogg - the real machine, captured from the A/V output at 96000 Hz
- p4emu_48.ogg - plus4emu-1.2.9.2 with the default settings
- p4emu_96.ogg - plus4emu-1.2.9.2 with 96000 Hz sample rate
- yape_48.ogg - YAPE 0.84, using the default settings (oversample = 1, sample rate = 48000)
- yape_48o.ogg - YAPE 0.84, with the oversample set to the maximum (8)
- yape_96.ogg - YAPE 0.84, 96000 Hz sample rate and 8x oversampling
Note that in the first YAPE file, the frequency seems to be clamped by the emulator, and not changing at all. The second has pretty bad aliasing, so that may be why you thought that it is "noisier"; however, it is not "noisy" on the real machine, so it is plus4emu which is correct. The 96 kHz YAPE file is somewhat better, but still not quite as good as plus4emu is already on 48000 Hz, and obviously different from the real machine.
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