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Old 14 October 2016, 00:32   #32
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Join Date: Jul 2008
Location: Netherlands
Posts: 347
Now that the Wasapi modes are working so great, I wondered whether it would be useful to take account of the "calibrated" soundcard frequency.

Just as that " 60Hz" screenmodes are almost never exactly 60.0000hz, it appears a soundcard output is also not exactly the advertised rate. I.e. 48Khz may actually be someting like 48000.27Hz.

Attached is a little tool which I hope the author doesn't mind me including it here. It's from the ASIO implementation/patch of GroovyMAME.

You can run the "batool64.exe" and it will supply some information on the enabled sounddevices. For this test to work you need an ASIO enabled driver. In case your default doesn't have that, you could use/install ASIO4ALL.

Running batool64 for my setup gives for example:

dev 0: ASIO 2.0 - ESI Juli@
driver: C:\WINDOWS\system32\JulaASIO.dll
dev 1: ASIO4ALL v2
driver: C:\Program Files (x86)\ASIO4ALL v2\asio4all64.dll
    out 0: HD Audio-luidspreker 1 (group 0, format 18)
    out 1: HD Audio-luidspreker 2 (group 0, format 18)
    out 2: HD Audio-luidspreker 3 (group 0, format 18)
    out 3: HD Audio-luidspreker 4 (group 0, format 18)
    out 4: HD Audio-luidspreker 5 (group 0, format 18)
    out 5: HD Audio-luidspreker 6 (group 0, format 18)
    out 6: HD Audio-luidspreker 7 (group 0, format 18)
    out 7: HD Audio-luidspreker 8 (group 0, format 18)

usage: batool64 [device] [sample rate] [# decimals] | [--cp]
So if I run "batool64 1" it will run a calibration test via asio4all on my realtek chip. The output will be the "real" rate of the card.

Mostly the onboard audio chips (realtek) are quite accurate and close to 48000Hz. But for pci cards this may differ a bit more.

The rate for my realtek is 48000.02Hz, and for my PCI-E Juli@XTe 48000.70Hz.

Now these seem only small deviations, but somewhere along the line they will eat the audio buffer more quickly (or more slowly for <48.000 values) then the emulator assumes.

Could it as such possibly be useful to create a calibration test/tool for WinUAE's Wasapi mode, and take the result into account for the sound resampling rate (which currently is based of " VSync calibrated" only)?

I know the impact will be minor, but with the wasapi mode now being so low latency, it could be a " dotting the i" in terms of accuracy?
Attached Files
File Type: zip (24.9 KB, 44 views)
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