LMC1992

A forum for anything about the Steem Engine STE emulator, comments, problems, bug reports etc. Steven Seagal regularly provides updated versions of the original STEem code. The current version is v3.9.4.

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RA_pdx
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LMC1992

Post by RA_pdx »

Does Steem emulate the LMC1992?

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Post by Steem Authors »

Yes, well the volume features, not the bass and treble.

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Post by unseenmenace »

Are there any plans to add the Bass & Treble contol? I am using STeem as a development environment and intend to add all the LMC1992 controls to my music player I'm working on and it would be nice to see all the features in STeem.
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Post by Steem Authors »

Hi,

There are a few things putting us off doing microwire bass and treble controls:

1) As far as I understand these things, we'd have to do fast Fourier transforms on the samples, which would complicate and slow down the sound processing;

2) Even if we did that, we probably wouldn't be able to get it working just like it did on the STE;

3) I don't know of any ST programs that used it.

Please put me straight if any of these points are wrong. As things stand, we're not planning to implement it.

Ant (Steem)

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Post by clam »

Those controls were used in Protracker STE and I also used them in one of my demos. But the only advantage of using the bass/treble controls was to get a better sound out of the STE so as the sound of the emulator is good enough I don't think it worth the pain. And if I remember well, when you exit my demo before the end, the bass/treble were no reset to the default values so after that, all soundchip musics sounded like crap in the other screens of the disk. So please don't mind about implementing it in Steem :wink:

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Post by simonsunnyboy »

Modern demos aand programs are most often compatible for Falcon and STE as well. However Falcons do lack this chip afaik so most programmers will not miss it in STEEM.

Might be a feature for completeness of the emulator however. What about implementing it and making it optional so ppl with slower machines can disable it?
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Post by Nyh »

Steem Authors wrote:1) As far as I understand these things, we'd have to do fast Fourier transforms on the samples, which would complicate and slow down the sound processing;

Please put me straight if any of these points are wrong. As things stand, we're not planning to implement it.
Reading the specs of the LMC 1992 there is no need for any fourier trandforms to emulate the chip. The chip implements a highpass and lowpass filterr. Nothing that can't be solved by implementing some simple exponential filters:
new_output=(1-a)*old_output + a*input with a the 'filter value'
To give exact numbers and formula's I would have to look at the exact implementation of the LMC in the STE. I expect some very simple formula's will completely describe the filtering capabilities and volume and fading functions of the chip. The other part is the statemachine for the serial communication functions of the chip but that is not hard either (compared with the rest of the STe).

Hans Wessels

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Post by earx »

i agree with ni. you don't need to do filtering in the fourier domain at all, certainly not for such lo-fi and linear stuff as the LMC. just design a decent linear filter. the one that ni provides may already do fine. it won't take more than a few multiply + adds per sample. that's really less than nothing for modern hardware.

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Post by Showaddywaddy »

Steem Authors wrote:Hi,

3) I don't know of any ST programs that used it.

Ant (Steem)
I think the LX and Amberstar digi tunes used microwire.

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Microwire thing

Post by Steem Authors »

Thanks to everyone for the info. It sounds like it might not be as hard as I thought to do this processing. We might put it in when we have time.

Ant

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Re: LMC1992

Post by Hippy Dave »

RalfZenker wrote:Does Steem emulate the LMC1992?
Steem Authors wrote:Yes, well the volume features, not the bass and treble.



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