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MOD to PSG Converter


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#1 Tursi OFFLINE  

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Posted Sun Nov 28, 2010 11:56 PM

About a year ago, I ported (to the TI) a playback library for the Master System called PSGMOD - it was a beautiful tracker system with ADSR-like instrument support and all kinds of effects. The playback library, unfortunately, was a little heavy-weight and saddled with non-commercial licenses. Also, the skill required to make good use of it was apparently a bit much for most people.

One thing this tracker did that I liked, but it didn't do very well, was convert 4-channel Noisetracker MODs. It has perpetually frustrated me that the very little tweaks I'd like to make to his converter were not available to me. So finally I went ahead and did my own.

I don't output PSGMOD format, but VGM, which has two main impacts. First, the files are larger than they would otherwise be, because they are a raw recording of soundchip data. Second, pretty much no CPU is needed to play them as a result. In fact the TI's console playlist routine can play these sounds, even though they sound pretty complex!

A nice side-effect of VGM format is that you can play the files on your PC to quickly listen to the results. A downside is that every soundchip byte needs a VGM command byte, so the file is twice the actual data size plus a 64 byte header. Of course you can easily strip this once you have a file you like. If you are clever, you might even find simple ways to compress the audio data (especially by compressing the wait bytes like the TI playlist routine does - the simple converter I did outputs one byte for every end of frame, even if the frame was empty).

So how's it sound? Well, not bad! Most MODs are recognizable. You lose all bass, because it's just converting frequencies. Complex samples are gone, which means that everything from distorted guitar to church organ becomes a single-tone square wave. And you have to tell it which samples are drums, which means a little manual pre-processing (my included sample has this done for you already). And sometimes you need to tweak the volume of channels or instruments. But in the end, you get a tune which is definately related to the original MOD, and sometimes pretty darn decent!

There's detail in the readme.txt about how it does its work, and what options you have for improving the conversion. There's also a sample - Arkanoid.mod, and converted to Arkanoid.VGM (with default settings). I also include links to Windows tools you can use to play both, if you don't have any.

http://harmlesslion....e/modconvertpsg

Edited by Tursi, Sun Nov 28, 2010 11:58 PM.


#2 Tursi OFFLINE  

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Posted Sat Dec 11, 2010 4:07 AM

For everyone who didn't get a chance to hear how this sounds (that'd be everyone by my download records? ;) ), I've finally put together a little YouTube video that covers some of the tech while playing a selection of musics. Enjoy!

#3 Pixelboy OFFLINE  

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Posted Sat Dec 11, 2010 7:51 AM

For everyone who didn't get a chance to hear how this sounds (that'd be everyone by my download records? ;) ), I've finally put together a little YouTube video that covers some of the tech while playing a selection of musics. Enjoy!

Great stuff, Tursi! The samples sound really nice. :D

I know next to nothing about sound output, I'm ashamed to say, but I'll have to learn at some point if I want to do my own CV games, and even more to the point, when I get around to programming a sound editor with BasicVision some time next year... :)

#4 Tursi OFFLINE  

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Posted Sat Dec 11, 2010 4:48 PM

You'll find it's pretty straightforward for the most part, PixelBoy! And from what I've seen in other YouTube vids we have one of the few masters of that chip on this very board, so you should be in good company if you need help. :)




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