Chip-8 emu

[Shendo]

Probably everyone has done one so I figured I might try as well.
After reading a few documents and a thread at EmuTalk I was able to do a really buggy Chip-8 emulator which properly runs about 1% of the games

Since this was just to get a basic idea how emulators work I didn't bother to polish the emu or fix the bugs.

Now it might be a while until I start anything similar or fix the issues on this emulator but I was wondering about one thing:
How to actually emulate (make) a sound?
Can anyone post links to some docs about that?
For Chip-8 I simply used system beep which was enough but for any more advanced system (eg. Game Boy) that simply won't cut it.

Thanks in advance for any help on that subject.

Btw: If you decide to download this alpha (should be pre-alpha really) emulator i hope that you will have fun laughing at glitches like I did.

[TheCloudOfSmoke]

Best of luck with your emulation projects. It's good to see more aspiring emu authors out there. It gives me hope for the scene. I hope to see a really awesome emu from you one day Shendo. Good luck. Sorry if my post didn't help you whatsoever.

[blueshogun96]

Okay, there's not much out there related to emulating sound and you'll soon find out the google is not your friend on this subject. I'll do my best to answer your question.

1. Before learning about sound emulation, it's highly recommended that you learn about how sound works (if you don't know already). First learn a low-level sound API such as DirectSound, OpenAL or XAudio (which is still in beta stages) and create some sound programs that can output sound by sending some raw data to a sound buffer. DirectSound is so far the most prominent while sound emulation with OpenAL is rather hard and XAudio... I don't know because I haven't seen it used for anything yet. Finding tutorials on low level sound APIs are very hard to find (except OpenAL which is more for 3D games) and once again Google might not be your friend on this subject. If you want you can either read the docs on the sound API such as the microsoft SDK documentation or MSDN. If you need tutorials on DirectSound, ask me and I will write them for you personally.

2. As far as tutorials on how to emulate sound, this is the best I can find to date: Blargg's Video Game Sound Emulation
Here's another: How to write an emulator It's an overall tutorial on emulation, but the sound emulation section is the largest and it shows some actual DirectSound code being used.

3. Be sure to have the documentation on the sound hardware you're trying to emulate!

4. I'm not sure how far indepth you want to get with sound emulation, but let me tell you this, emulating sound [usually] gets harder and harder as the console gets more advanced VERY quickly (sometimes more then the CPU itself). While GameBoy, SpaceInvaders, and NES usually aren't so bad, other old consoles such as Atari2600 and SNES have certain issues to be dealt with (for Atari usually has to deal with Pitfall II, for SNES the DSP) in order to get accurate emulation. The newer consoles and arcade hardware such as SegaSaturn/Titan Video, GC, PS2 have very advanced audio systems with either more than one core or advanced and undocumented DSPs. Instead of using basic PSG or FM based audio chips that generate simple waveforms (i.e. sin and cos for wave generation), these are APUs that create more complex audio effects and uses more complex methods (i.e. envelopes, KON/KOF, attack - sustain - decay rates, etc.). So far the most complex audio system I've seen [actual] specs on to date is Xbox1 with(at least 3 DSPs, an AC'97 Audio codec, and an NVIDIA SoundStorm APU. I know that PS3's audio system is the most advanced (where every object can have it's own sound channel!), but I don't think you'll be trying to emulate anytime soon (or even in your lifetime) Anyone can feel free to correct me if I'm wrong about any of this.

So if you need anything else, feel free to ask me anytime. Know this, I don't know everything

And about your emulator, what APIs are you using? btw, nice debugger! Looking great!

[Phil]

well direct sound is not supported in Vista...only XP downwords..stick with OpenAL

[blueshogun96]

Originally Posted by Phil

well direct sound is not supported in Vista...only XP downwords..stick with OpenAL

Yes it is. DirectSound only can be used in software mode, but it still works just fine. EAX support has been resurrected but only for the Creative Audigy users. I wouldn't recommend using OpenAL for sound emulation for beginners because it's harder for beginners to grasp it.

[Phil]

that's what i meant. A card using directsound will have to run on software mode...which sucks as i was going to get the Auzentech Prelude specifically for it's hardware mode...I still might get it....just waiting till Auzentech sorts out Creative's drivers

[blueshogun96]

But for emulation it's not too critical, unless the hardware you're trying to emulate uses features that can only be emulated in hardware (which so far no situation like that has come up yet afaik). Besides, using low-level DirectSound is still great for beginners to learn because the APIs and interfaces are usually self explanatory.

[Phil]

you have a point...

[@ruantec]

Looks like you progressed well since last time we talked about it

Directsound should be fine to reproduce the sounds and it works with Vista. i don´t know if you worked with directsound before.... but i think it shouldn´t be a problem for you

[refraction]

when i first made a chip8 emu with sound, i basically sent a load of rubbish in to the SDL buffer, but it made random buzzes, as the original system only had a buzzer, so it was no need to be impressive

altho my current (newest) one isnt quite as advanced as yours, it works pretty well, you can see it here with games and source ;p
RefChip8 - Chip8 Emulator

[Phil]

Ref i love the deflicker system.
Nice (if basic) emu though

[Shendo]

@TheCloudOfSmoke: Thanks. Though it will take a lot of time before/if I even make something that can be measured with other emulators.

@blueshogun96: Thank you for the links, I'll check them out.
As for API it's GDI+. That probably is not suited for emulation but in this case I think it's ok.

@@ruantec-Man: Yeah I got rid of the most graphic glitches.

@refraction: Nice emu.

[refraction]

Originally Posted by Phil

Ref i love the deflicker system.
Nice (if basic) emu though

cheap as hell but i worked Chip8 is very simplistic, so it uses 1 frame to draw the sprites, then the next to clear them, then the next to draw them in the new location, etc.

Originally Posted by Shendo

@refraction: Nice emu.

thanks, i know its nothing special, but i literally threw it together for an australian magazine thingy, so budding authors have something to go off. But if it helps with your emu thats all that matters

[@ruantec]

Originally Posted by refraction

cheap as hell but i worked Chip8 is very simplistic, so it uses 1 frame to draw the sprites, then the next to clear them, then the next to draw them in the new location, etc.




thanks, i know its nothing special, but i literally threw it together for an australian magazine thingy, so budding authors have something to go off. But if it helps with your emu thats all that matters

i think we shouldn´t understimate a Chip8 emulator........ indeed is nothing special(in comparation to emulators for consoles etc) but if you think what we learn from it then you will realize is actually very special because most of us started with a chip8 emulator that help us get the idea how emulation works.

[refraction]

Originally Posted by @ruantec-Man

i think we shouldn´t understimate a Chip8 emulator........ indeed is nothing special(in comparation to emulators for consoles etc) but if you think what we learn from it then you will realize is actually very special because most of us started with a chip8 emulator that help us get the idea how emulation works.

that was the whole concept i worked on

i did intend on commenting it more but i couldnt be arsed lol. But the idea was keep it reasonably simple so people can work out for themselves how the emulator actually works.

can you see the copy and pasta from sdl tutorials? *hides*

[@ruantec]

"Copy and pasta" that was a good one anyways i think every chip8 emula8r is another step to a better emulation world

btw nice chip8 emu

[refraction]

thx ;p but really, i think it sucks it just does the job lol

ill appreciate it more if people learnt from it

[cottonvibes]

cool emulators, i might try to make one for the learning experience as well. (well, thats after i become more familiar with c++ :/)


Shendo do you mind posting links to the documentation you used?

[Shendo]

Chip 8 instruction set
CHIP8 documentation by David Winter.

There is also a great thread at EmuTalk which contains a lot of information.