OPL2LPT and MOD Tracker

Discussion about old sound cards, MIDI devices and sound related accessories.

OPL2LPT and MOD Tracker

Postby Rolandradio » 2018-2-08 @ 21:29

The OPL2LPT is an FM (Adlib) sound device for the LPT port.
Why can Adlib also play MOD file such as Visual Player 2 and Inertia Player ?
Normal a Soundblaster has FM (OPL) chip and Sound FX output for MOD S3M IT WAV file ....

Why can Visual Player play MOD files over an Adlib ?
OPL2LPT works with Visual Player (select Adlib) when jadlipt.dll is loaded but with some noise and Pop signals.

OPL2LPT test with OPL2TEST.EXE = Perfect
Playing MIDI is perfect

Tested on P200MMX
FreedDos
HIMEM and JEMM386 loaded
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Re: OPL2LPT and MOD Tracker

Postby Scali » 2018-2-08 @ 21:39

Rolandradio wrote:Why can Adlib also play MOD file such as Visual Player 2 and Inertia Player ?


It's a trick, that can be used on various sound chips in similar ways.
You have to trick the chip to play a frequency of '0 Hz'. This effectively means that the wave is stuck at a given output.
By then manipulating the volume register, you can adjust its amplitude, effectively giving you a DAC.
So for every sample you want to play, you have to send a new volume command, which has to be timed exactly with the CPU (very CPU-intensive, unlike the DMA-driven DAC on a Sound Blaster).

Because the OPL2LPT requires virtualization of the AdLib ports to redirect them to the LPT and manually signal the chip lines, there's quite a bit of extra overhead, which means you will also get less accurate timing, which reduces the quality of this sample replay method.
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Re: OPL2LPT and MOD Tracker

Postby Rolandradio » 2018-2-08 @ 22:44

Ah, so that its works.
DMA driven DAC is the most CPU efficient to play music, I understand. It's stil nice how they done it with so many tricks.

For a MOD tracker is a Co-CPU important ? has FPU benefits for playing MOD, S3M,WAV files or is it only benefits for MP3 ?
Im testing a 386DX with and without a 387DX.
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Re: OPL2LPT and MOD Tracker

Postby derSammler » 2018-2-09 @ 09:32

Depends on the MOD player. The FPU can be used for interpolation or oversampling, for example. But it's not automatically used only because it's there. If the MOD player has no FPU support, it's simply not used. I'm pretty sure Inertia Player uses the FPU if present and also supports Adlib.
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Re: OPL2LPT and MOD Tracker

Postby Scali » 2018-2-09 @ 11:03

Early MOD trackers/players don't have FPU support, as it's not really required for simple mixing and interpolation.
They mainly started using FPUs in the Pentium-era, firstly because on a Pentium, the FPU is faster with multiply than the main CPU, unlike 486 and earlier machines. Secondly, because as you support more channels, you require more advanced mixing algorithms, to get logarithmic volume curves. If you just use linear mixing, then if you were to play on only a single channel of say 32 channels, the volume would be 1/32nd of the total, resulting in very soft sound.
But for the original Amiga MODs that only had 4 channels, this is not an issue... For the later 8 channels it's not much of an issue yet either.
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Re: OPL2LPT and MOD Tracker

Postby Rolandradio » 2018-2-10 @ 11:09

On early music players they are not even written to use FPU most people believe, only for heavy graphics use in the early 90s.
Open Cubic Player make use of FPU if present, right ?

I have one audio player "DSS" ( Freedos Digital sound system) a FPU is required it won't start without FPU in other words it cannot emulate FPU.
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Re: OPL2LPT and MOD Tracker

Postby Scali » 2018-2-10 @ 11:33

Rolandradio wrote:On early music players they are not even written to use FPU most people believe, only for heavy graphics use in the early 90s.


Yes, back in the days of the 386 and 486, FPU was basically rarely used at all. A lot of people didn't even have an FPU, and the FPUs weren't very fast anyway.

Rolandradio wrote:Open Cubic Player make use of FPU if present, right ?


Yes, especially if you use the advanced mixers with spline interpolation.
CP is mainly aimed at Pentium and newer systems, although it works quite well on 486.
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Re: OPL2LPT and MOD Tracker

Postby Rolandradio » 2018-2-12 @ 21:48

Digital Sound System (DSS Sergey Sapelin) cannot run without FPU ist that true ?

Can OPL2LPT also work as a 8-Bit FM sound device or is it only designed for MIDI ?


Btw,
Scali's OpenBlog is very interesting
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Re: OPL2LPT and MOD Tracker

Postby Scali » 2018-2-13 @ 08:48

Rolandradio wrote:Digital Sound System (DSS Sergey Sapelin) cannot run without FPU ist that true ?


I don't know that software.

Rolandradio wrote:Can OPL2LPT also work as a 8-Bit FM sound device or is it only designed for MIDI ?


It doesn't do MIDI at all. It's basically an AdLib sound card, connected to a printer port. So it's an OPL2 FM synthesizer, nothing more.

Rolandradio wrote:Scali's OpenBlog is very interesting


Thanks!
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