WDM Drivers and FM Synthesis \ VOGONS

WDM Drivers and FM Synthesis

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First post, by onethirdxcubed

Posted on 2026-02-05, 16:33

onethirdxcubed Offline

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Is there any known WDM audio driver that passes through or emulates FM Synthesis for a DOS window?

I'm trying to figure out the feasibility of creating a filter driver that traps the Adlib/OPL ports in the 9x DOS box and using Nuked OPL or similar creates an audio stream. From what I can tell this would require the port trapping driver to be a VxD but some inspection of SBEMUL.SYS shows that it's using int 20h like a VxD even though it is a SYS driver (WDM). Sbemul traps the Adlib port 388h but only to emulate the presence detection and the timers, it doesn't do any FM synth.

I understand that FM was out of style by 1998 and Microsoft's own WDM sample drivers don't support FM in any way. Just curious if someone ever figured out how to do it BITD so I can inspect that driver.

Reply 1 of 5, by Jo22

Posted on 2026-02-05, 17:23

Jo22 Offline

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VDMSound? It's at home here at Vogons, next to DOSBox..
https://en.wikipedia.org/wiki/VDMSound

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Reply 2 of 5, by onethirdxcubed

Posted on 2026-02-05, 19:16

onethirdxcubed Offline

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Yes I know about VDMSound but for 9x a complete version with source code was never released, just the alpha 02 with source and the alpha 03 without. What I'm trying to do is extend the OS stock SBEMUL driver to add Adlib instead of replacing it completely which means it needs to be a Kernel Streaming filter driver and thus WDM.

Reply 3 of 5, by Tiido

Posted on 2026-02-05, 19:22

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YMF71x driver monopolizes Adlib IO ports to itself, but I think it just traps the IO writes using CPU's IO trapping feature and then passes the data to the physical chip.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 4 of 5, by onethirdxcubed

Posted on 2026-02-05, 21:19

onethirdxcubed Offline

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Which driver was that with? My experience with the OPL3-SAx chip on a Libretto 110CT was that with the windows 98 default WDM drivers the OPL was only available as a General MIDI synth (using the Windows default FM patches which sound strange for DOS games) and with the Windows 95/98 VxD drivers the OPL was directly available from a DOS box (and could not be used to play MIDI from a Windows application if a DOS box was running).

Reply 5 of 5, by Tiido

Posted on 2026-02-05, 21:31

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I always got proper FM with the WDM drivers in Win98SE in games like Supaplex and 4th Commander Keen game, and if I chose MIDI in a game such as Duke3D, while having set the MIDI device in Control Panel to FM rather than the MSGS softsynth, I would indeed get the poor windows FM MIDI playback. But I never lost Adlib compatibility, and got MIDI via whatever Windows is able to offer in DOS stuff.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

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