ahi_v2 device driver (uae2.audio)?

[FrodeSolheim]

Hi, I copied od-win32/ahidsound_new.cpp (AHI/OpenAL) into FS-UAE and made necessary changes to make it compile and enable it.

But the problem I face now is that I cannot find the Amiga-side device driver (uae2.audio) anywhere. Is this perhaps a work in progress without any released driver?

[Toni Wilen]

Unfortunately it was not finished, I found some AHI feature that OpenAL couldn't do or something. I don't remember, it was years ago..

[FrodeSolheim]

OK, I suspected as much since a google search returned next to nothing, and the copyright notice said 2008

I guess AHI in FS-UAE will have to be implemented using ahidsound_dsonly.cpp as reference implementation instead (code from scratch, or perhaps some applicable code borrowed from the OpenAL implementation).

Thanks!

[Toni Wilen]

Unfortunately (also), current ahi driver is quite stupid, 2 channel only, requires mixing, most of the heavy stuff is done on m68k side and so on..

[FrodeSolheim]

Yes I noticed the ahi_winuae interface was much simpler than the ahi_v2 interface (I guess the upside of that is that re-implementing the host interface in FS-UAE will be quite simple).

[Der Wanderer]

AFAIK, the uaeaudio AHI driver is on the Amiga side a rip-off from the demo Paula driver from the AHIDev package. (Wasn't it Bernd Roesch?). The Paula register calls are replaced with the all mighty UAE call

             GetReg d2,AHI_unit\samplerate    ;samplerate
              GetReg d3,\buffer_outsize
              MOVEQ #0,d0
              MOVEQ #0,d1              ;Mode= open sounddevice
              JSR $f0ffc0              ;call the uaelib    (d0 contain samplerate)

I wrote a direct WinUAE driver for HD-Rec, to avoid the double latency from AHI und Host side. This is clumsy, and I would highly prefere a proper AHI driver.
A proper driver could make it more direct, having the AHI buffers directly the host buffers allowing optimal latency through AHI. Low latency it important for games to have the sound events react instantly, and for a music synthesizer (what I do) to be real-time playable.
Ideally the driver would map the host devices and bit resolutions to the AHI driver as well. The WinUAE one only allows the "default" device and 16bit, which is better than nothing of course.
Let me know if I could help with a concept or implementation for a proper driver. What I dont want is more splitting between "platforms", so a solution that would work for both, WinUAE and FS UAE (Mac & Linux etc. too) would be preferred.

Remember to put the difficult part on the cross platform code, so it is easy to have Mac, Linux, Android <future platform X> etc. drivers.

[Toni Wilen]

Which is exactly what "uae2.audio" was supposed to solve. Direct mapping to host audio channels (up to 7.1), light wrapper to native sound system, all mixing and other heavy stuff is left for native drivers and so on.

Unfortunately AHI requires behavior that no native sound libraries (at least portable ones) don't directly support which would require moving resampling/mixing back to UAE side. Which would suck again.

I think it was on the fly pitch change or something like that. (I don't remember).

Check AHI driver API spec, find matching PC side API. Done

[Der Wanderer]

Maybe it was playing samples at different frequencies at the same time (that was probably inspired by Paula, but is not really something nowadays sound cards do). I would be happy to provide code to do that. Let me check this in more detail.

[Toni Wilen]

Originally Posted by Der Wanderer

Maybe it was playing samples at different frequencies at the same time (that was probably inspired by Paula, but is not really something nowadays sound cards do). I would be happy to provide code to do that. Let me check this in more detail.

No, that was not it. Any modern sound API can play 10+ samples at the same time using different sample rates and volumes.

I think it was some on the fly operation that had to be synced to exact sample position that is not supported. (Which Paula can easily do too)

[Der Wanderer]

Then it was maybe the "playfunc". This is required in HD-Rec to sync MIDI output to audio output.
The playfunc need to be called in sample exact intervalls.