Converting Audio to 8-bit depth without noise?

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Xeeko

New member
Hi

I have to make sounds for a game with the hardware limitations of a Game Boy Advance. This means 8-bith depth and no more than 26000 in samplerate. The samplerate is no problem, but how do you convert, or filter away, the noise when reducing the sound to 8-bit?

Thanks in advance
 
every bit give you an additional dynamic range of 6dB. The dynamic range equals the signal to noise ratio (snr). which simply means 8 bit always contains noise you can percieve:

8bit * 6dB = 48dB

16bit * 6dB = 96dB (<- here's where it becomes inaudible on most systems)

8 bit is always full of noise, a samplerate of 26kHz also has big limitations: the bandwidth is limited to 14kHz, and any kind of pitching will create a lot aliases in the signal.
 
Yes, I'm aware of the limitations, and of the course noise can't be completely removed, but there must be some way to make it less audible? I've tried various noise-reductions and the such, and I've tried phasing out the noise, but it's quite persistent.
The alias problem should be avoided by merely removing all information above 14kHz, shouldn't it?
 
no, noise is a random signal, a signal contain every frequency at the same time. for white noise for example, every frequency has the same level.

but what you're hearing is quantisation noise (http://en.wikipedia.org/wiki/Quantisation_noise) this kind of noise is periodic, "pattern-like". but you cannot remove them, it's a part of the 8 bit restrictions - it's not "in" the signal.
 
I assume that you have tried dithering stuff. I think this may be for covering the noise made by truncation rather than the "natural" noise of 8 bit though.

I'm sure there will be stuff on the web to help though. Freescale seem to have a whole site devoted to 8 bit with some noise removal stuff too. I'm sure there must be some noise masking techniques too somewhere.

The crude way is to choose sounds in the recording that will make the noise less obvious.

EP
 
What program are you using?

Xeeko said:
how do you convert, or filter away, the noise when reducing the sound to 8-bit?
Thanks in advance
Click to expand...

Logic Pro has all kinds of things for this. It has a "Bitcrusher" that lets you control Resolution, Drive, Downsampling, the Mode and Clip Level.

Then you can insert a "Denoiser" and there's already presets for filtering out pink and white noise.

Other DAWs might have these plugins too. But if you're asking about 3rd party plugins I would ask at gearslutz.com as well.

I don't know if this helps you but here's a downsampled drum kit you can buy



http://popmusic.dk/hitkit-uk.html
 
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