tpowell.ca wrote on 2023-01-12, 16:23:

Keep in mind that the ONLY cards that I am aware of that support the user-defeatable output filter are the genuine Sound Blaster Pro and the Yamaha YMF71x cards.

Nice work! Thanks for making this utility.

BTW, did you ever try turning off the filter on an OPTi or an ESS card? Or is it hardcoded to always stay on there?

Joseph_Joestar wrote on 2023-01-14, 06:26:

Nice work! Thanks for making this utility.

BTW, did you ever try turning off the filter on an OPTi or an ESS card? Or is it hardcoded to always stay on there?

Thanks Joseph
So I ran some more tests and unfortunately the TSR had limited success with different cards.
Many do not respect the CT1345 mixer registers in read or write.

The Yamaha YMF71x cards and genuine Creative Sound Blaster Pro cards support the TSR 100%.
The ESS688 and OPTi 82C929A cards do NOT work at all. These cards implement the output filter like a Sound Blaster 16, and it is not defeatble.
The CMI8330/HT1869V+ chips only support changing the MONO/STEREO mode.
The Crystal CS4237B chip (such as Orpheus) only support changing the MONO/STEREO mode when NOT playing audio (pause playback first or switch modes between sound effects).

I'll continue testing on other cards.

Thanks for this handy tool! 😀

Two downsides though: Although it is a very unlikely scenario, there isn't a way to check if the TSR is installed after running the application, meaning that it can be loaded many times until it runs out of conventional memory. The other one is that it can't be uninstalled.

Gmlb256 wrote on 2023-01-15, 19:46:

Thanks for this handy tool! 😀

Two downsides though: Although it is a very unlikely scenario, there isn't a way to check if the TSR is installed after running the application, meaning that it can be loaded many times until it runs out of conventional memory. The other one is that it can't be uninstalled.

You are absolutely correct.
I am however having a very hard time finding useful information these days on writing TSRs in C, but I'll keep looking.
If anyone has an example program or references I can use.

Thank you

Out of curiosity, would it be possible to implement a "Reverse Stereo" hotkey? For games which don't have that option in setup.

Or is that functionality something that's dependent on the game's own sound driver?

Joseph_Joestar wrote on 2023-01-17, 19:40:

Out of curiosity, would it be possible to implement a "Reverse Stereo" hotkey? For games which don't have that option in setup.

Or is that functionality something that's dependent on the game's own sound driver?

Interestingly enough, just toggling the mono/stereo modes repeatedly can reverse the stereo on some cards (Yamaha, Creative and CMI8330/MK83330).
For the other cards, it's really trial and error; mostly error.

Just hit F11 and F12 back and forth a few times to test with your card.
The result is not predictable and so cannot be programmed in. Its all a question of timing the command.

tpowell.ca wrote on 2023-01-16, 00:51:

You are absolutely correct. I am however having a very hard time finding useful information these days on writing TSRs in C, but […]
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Gmlb256 wrote on 2023-01-15, 19:46:

Thanks for this handy tool! 😀

Two downsides though: Although it is a very unlikely scenario, there isn't a way to check if the TSR is installed after running the application, meaning that it can be loaded many times until it runs out of conventional memory. The other one is that it can't be uninstalled.

You are absolutely correct.
I am however having a very hard time finding useful information these days on writing TSRs in C, but I'll keep looking.
If anyone has an example program or references I can use.

Thank you

I guess install an interrupt handler on TSR load, then you can query it to determine TSR presence and to also signal to the loaded TSR to unload itself.