Category Archives: Chiptune
And to complete the trilogy here another bit of fractal fun (in case your PC is not equipped with a fast enough graphics accelerator you can find a video recording here: https://youtu.be/PzTwOfoZp0E):
I just did a little revival of my old WebGL fractal stuff. The two below screens use the latest version of my Commodore C64 emulator to play two fitting music creations by Markus Klein.
Just a little experiment for how to synchronize visualization of additional data streams with the the playback of WebAudio music: The music samples are generated on the fly using a ScriptProcessor emulating some legacy AtariST. In addition to the stereo output the respective ScriptProcessor also generates three streams containing “playback volume” for the AtariST’s internal soundchip voices:
just for fun a more psychedelic WebGL based rendering of the same data (the WebGL here combines an orbit trap fractal with an inverse distortion, and the “music volume” is used to parameterize the rendering):
are certainly not a good idea if a program is supposed to be portable. Unfortunately that is exactly what ZXTune is using to parse the different binary music files.
“One of the rules of packed structs is that you have to access them directly through the packed struct type. In other words, you can’t, in general, take the address of a packed field and then access the field through that pointer, because the pointer type won’t reflect the packed attribute.” (sunfishcode)
Unfortunately ZXTune used boost::array instances within the various packed structs.. Problem: when methods are invoked on boost::array (or std::array, etc). The ‘this’ argument to the boost::array functions may be misaligned, but the boost::array functions themselves don’t know this.
On CPUs which don’t mind unaligned memory access you may get away within without realizing that there is a problem.. and in this case it was my attempt to cross-compile the program using Emscripten that revealed the issue. Not wanting to rewrite too much of the foreign code I opted for a quickfix: replacing the boost::array with a built-in array fixed the immediate problem…
Naturally a clean implementation should better refrain from depending on unaligned memory access at all… not all the CPUs are as forgiving as Emscripten.
(click on the below image for a live demo).
It was back “in the old days” and I remember my relief when some day I found out that all PCs were not necessarily mute: Thanks to some “walking frame” called “AdLib” they could actually make sounds… and a bit later things became pretty neat with the rise of Sound Blaster…
AdPlug plays sound data, originally created for the AdLib (OPL2) and Sound Blaster (Dual OPL2/OPL3) audio boards, directly from its original format on top of an emulator.
My latest bit of Xmas tinkering is a HTML5/WebAudio version of AdPlug (Thanks to Simon Peter and the other authors of AdPlug.). For a live demo click on the below image..
To complete the set of chipmusic emulators, here my WebAudio version of SC68 – an AtariST music emulator (that plays files like *.sc68 or *.sndh).
Eventough I had done some programming on the MegaST 4 back in the 90ies, I have to admit that at the time I had not realized that the machine had anything resembling a sound chip. Those were the days of 68k assembler, DSP machine code and GFA-Basic.. and we were just doing a Paintbox software for the “CHILI” framegrabber and realtime video-effects extension card… 🙂
But it seems the ST not only did have a MIDI interface but also a built-in sound chip…
Thanks to Photon Storm for sponsoring this little project.
This experiment once again confirmed my ealier observations that the debugger support built into today’s web browsers is utterly useless (but for the most trivial scenarios). So this not only was a travel back in time with regard to home computer music but also with regard to the modern developement tools that I had gotten used to: bye bye IDE – welcome back debug/trace output.
For all those thinking ‘ahhh but Chrome is so much better’ – think again: While it is true that Chrome’s developer tools are real quick there is a catch. Or as a colleague once said: “if the result does not have to be correct my code can be real quick!”. Here is an example of a situation that you may encounter while debugging in Chrome (this is actual – non tampered with – debugger output):
The debugger here has just stepped over a line of code that sets some variable to 0. On the very next line the debugger tells you that this very variable is NOT 0.. Another fun Chrome surprise is when you find that Chrome’s garbage collector will actually trash ‘event handler’ functions that are still in use – unless you separately anchor them to some dedicated variable.
I am so glad that I never make any mistakes as a matter of principle 🙂 So my latest bit of music playback programming could not be stopped by foul developer tools:
And what was this experiment about? xmp is a module player that plays over 90 mainstream and obscure module formats from Amiga, Atari, Acorn, Apple IIgs and PC, including Protracker (MOD), Scream Tracker 3 (S3M), Fast Tracker II (XM) and Impulse Tracker (IT) files. This functionality is now available on my little web page (click on the image above) 🙂
(You’ll find the source code here: http://sourceforge.net/projects/webxmp/)
Did I mention that I love fractals? In fact I do and that’s why I created the below intro:
I am using orbit trap logic that I implemented in a WEBGL fragment shader. The add-on text scrollers/messages sport an exploding-pixels effect which is done using plain Canvas pixel operations. For good measure I added my WebAudio based SID chiptune playback (see my previous posts).
I guess that next time I’d better leave all the graphics to the GPU .. because my CPU is just getting too old. In case you are using a recent browser and if you have some sort of GPU in your computer, you might try to see the online version by clicking on the above image.
On my second trip to the world of THREE.js and WEBGL I tried out yet another bunch of “new” things:
- use of THREE.js EffectComposers and Shaders to create “glow” effects, etc
- creating lightweight 3D text rendering by rendering a 2D font into a texture and by creating a geometry that then represents each character as two simple textured triangles
- create THREE.ShaderMaterials (i.e. WEBGL vertex and fragement shaders) to then apply visual effects to the above 3D text (e.g. rolling the characters or exploding the text-page, etc)
Then I came across Felix Woitzel’s fascinating “Travelling Wavefronts” demo and I had to understand how its WEBGL shader logic is done 🙂 After some tinkering I ended up with a slightly cleaned up version of my own with some added visual effect features:
After throwing all of the above together and and adding a bit of WebAudio based SID chiptune playback (see my previous experiment), I ended up with a little Web intro 🙂 Those with a reasonably fast GPU may see it in action here (due to my old CPU I really like to use as much of the GPU’s power as I can..).