First post, by zbiggy
Hi!
This patch is not finished yet. It is just the same as 'DAC on LPT1, covox emulation added' previous patch but with little fixes and first attempt to stereo implementation.
I finally understood how LPT stereo DACs autodetection works and since this patch dosbox tells DOS applications about Stereo-on-1 LPT DAC presence.
After running mp.com from mp219b.zip the stereo-on-1 output device is autoselected instead of SoundBlaster. Without this patch in dosbox the SoundBlaster is autoselected and Stereo-on-1 is greyed out/unavailable.
There is another kind of stereo on LPT which is also implemeted in this patch. However could not find any application with autodetection of this format the emulation should work.
Sound output is still in mono because could not find in documentation how to feed dosbox mixer with 8bit stereo data.
If anyone knows how AddSamples_s8 function works tell me.
Reading sources can lead to misinterpretation.
Google shows me only 1 link to 1 header file. Not too much...
I learned that all commercial games and commercial LPT DAC designes were pure mono.
LPT stereo design by hardware limitation just simply toggle signal to left or right dac from single mono 8bit output from LPT port using strobe signal lines.
Such design cuts sample rate by half to feed both DACs which reduces quality of signal.
Stereo DAC support was available only in module players and some demo productions. Such appliactions usually supports better sound outputs like GUS or SB so developing stereo LPT DAC support in dosbox has no sense. There are many better module players for current operating systems with much better sound rendering and hardware support so using oldies has no reason.
My patch at present adds raw LPT DAC support (known as covox or intersound MDO species) and autodetection support (described inside patch as 'stereo') which can improve current emulation in dosbox. I think that in this way the goal of dosbox to support DOS games is met without adding redundand mess. Autodetection will help in DOS games where there is no user config but everything is done internally before falling down to PC Speaker or No sound at all.
have a nice day,
Zbigniew 'zbiggy' Luszpinski