audio processing (shameless plug)

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Nils_Pipenbrinck 101 Jan 12, 2009 at 02:25

I’m currently toying around with some audio processing. It’s not a real project (yet), but lots of fun.

I’ve written a little proof of concept micro-pitchshift based chorus effect that I’d like to show to you. It still needs waaaay to much CPU-time (almost 40% load on my 2Ghz Core), but I’m amazed how much better it sounds compared to the sound I get out of my expensive multi-effect boxes.

Here’s the original sample:

http://madamp.biz/audio/a15_Clean1.mp3

And here is my processed version:

http://torus.untergrund.net/misc/out.ogg

Yes - I know. It’s not subtle, but doesn’t it sound nice?

If I some day get audio on my BeagleBoard (www.beagleboard.org) working I’ll make a small effect unit out of this code.. :-)

Cheers,
Nils

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TheNut 179 Jan 12, 2009 at 05:02

It does add a nice touch. Makes me think of that game Diablo. The town music or something, heh. Cool though.

Are you feeding the signal in live or just post processing it? I find that as long as you don’t get crazy with the number of effects, software DSP is an awesome pastime and you can produce some amazing results on par with the hardware synths. I just recently got into using Fourier transforms to work on sounds in the frequency domain and it’s amazing at what can be done in real time.

BTW, that beagleboard is crazy! Still prefer my netbook, but that’s some snazzy tech.

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Nils_Pipenbrinck 101 Jan 12, 2009 at 10:12

@TheNut

Are you feeding the signal in live or just post processing it? I find that as long as you don’t get crazy with the number of effects, software DSP is an awesome pastime and you can produce some amazing results on par with the hardware synths. I just recently got into using Fourier transforms to work on sounds in the frequency domain and it’s amazing at what can be done in real time.

I’m just post processing, but there is no reason why it can’t be done in realtime as well. I’m just to lazy to write a streaming audio in/out framework with low latency.

The effect is btw fft-based. It’s just a pitch-shift, +7 cents on the left channel, -11 cents on the right mixed with 50% of the original signal. FFT-blocksize is 512 samples, overlap-factor is four. I started with much higher numbers (2048 blocksize and overlap of 32) but it turned out that I wasn’t able to hear all the extra quality.

@TheNut

BTW, that beagleboard is crazy! Still prefer my netbook, but that’s some snazzy tech.

The beagleboard is a fun toy, and a lot faster than you might think. The Cortex-A8 CPU does a good job and has the best designed SIMD-unit I’ve ever seen. The real fun starts if you get the DSP going.

I do all my coding on a notebook though. It’s much more comfortable. When I’m done I’ll port the stuff over to the beagle. :-)

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SamuraiCrow 101 Jan 14, 2009 at 17:26

The Beagleboard is close enough to the Pandora that you may be able to run your stuff in a next-generation handheld without much effort. Good idea to support the Beagleboard.