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How the Gates Stole Christmas... :)

Started by Cybernoid, Dec 14 2004 11:00 AM

9 replies to this topic

#1 Cybernoid  

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Posted Tue Dec 14, 2004 11:00 AM

Just a little 6-bit 4kHz sampling PCM demo. :wink:

Run this in the emulator with 128k memory...wait... then listen...

Happy Holidays!

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#2 Cybernoid  

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Posted Tue Dec 14, 2004 1:34 PM

Here is another experiment with some higher fidelity audio. This time the audio is sampled at 16kHz, but I am doing some tricks to vibrate the speaker faster than the ear can hear it to cause some half volume samples. This creates a pseudo-7bit PCM playback and works great on the emulator.

I need to try this on the real hardware. I would guess that it might cause some frequency aliasing, and you might hear some unwanted high frequencies...

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#3 Cybernoid  

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Posted Tue Dec 14, 2004 5:40 PM

Oops. Had a bug in the code. This fixes a few hisses and pops... :)

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#4 Goochman  

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Posted Tue Dec 14, 2004 7:47 PM

Im not actually sure what I am supposed to be hearing - though I tried it on Atariwin 3.1 emu

#5 Cybernoid  

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Posted Wed Dec 15, 2004 7:42 PM

Well, you are just supposed to hear some audio.

Just as I expected, the 6bit+ doesn't work on the real hardware, showing that frequency aliasing is not really emulated properly. Well, it works but with a horrible hiss.

6bit PCM at 13.3KHz sampling rate it not that bad though...

#6 Sheddy  

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Posted Sat Dec 18, 2004 9:08 AM

Nice one Cybernoid - Pretty good sound quality :) :thumbsup:

Just curious regarding your first one - 6 Bit, 4Khz.
(I'm too lazy to dissable your code I guess) If your're not wiggling the volumes faster than the sample rate like the other example, how're you doing it then?

thanks!

#7 miker  

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Posted Sat Dec 18, 2004 5:18 PM

maybe use some more mem-banks :)

#8 Cybernoid  

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Posted Sat Dec 18, 2004 5:59 PM

Sheddy said:

Nice one Cybernoid - Pretty good sound quality :)  :thumbsup:  

Just curious regarding your first one - 6 Bit, 4Khz.
(I'm too lazy to dissable your code I guess) If your're not wiggling the volumes faster than the sample rate like the other example, how're you doing it then?

thanks!

Thanks! Yeah, that one was pure 6bit. Here are a few more 6bit 13.3kHz samples, and the source code. These sound great on the real hardware.
The code uses all 4 pokey voices in volume only mode for an effective 6bit range. There are some more experiments I am working on, so it may still be possible to do better than 6bit.


I am ultimately working on a player for the MaxFlash Cart and for MyIDE.
The Flash Cart code is written, but I still have a few more questions for Steve... I have talked to Mr. Atari as well.

~C~

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#9 Cybernoid  

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Posted Sat Dec 18, 2004 6:01 PM

Oops, forgot the Samples...

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#10 Sheddy  

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Posted Mon Dec 20, 2004 8:36 AM

Thanks for sharing the code Cybernoid - I'll be looking at it with a fine tooth comb - My experiments with combining channel volumes on samples
were awful! In fact I was even thinking that when using volume only the full excursion of the speaker was effected by just one channel. Nice to know it can be done :)
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