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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
Bit rate reduction
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dorremifasol



Joined: Sep 28, 2006
Posts: 768
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PostPosted: Tue Jan 05, 2010 3:26 am    Post subject: Bit rate reduction
Subject description: How to simulate lower bit rate without affecting frequency rate
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Cheers,


I'm trying to achieve lower bit rate, without affecting sample frequency. The Digitizer module seems to affect sample frequency somewhat, so it's out of tue question.

The idea is to reduce the bit rate of the signals to achieve a 8bit sound chip character.

I've tried the note quantizer module, but it doesn't show the effect I'm searching for. I've also tried to send the sound trough an ADC module and then trough a DAC module, and it seems to bring better results, but still I don't find it convincing enough.

Any ideas? thanks!

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Antimon



Joined: Jan 18, 2005
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PostPosted: Tue Jan 05, 2010 4:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Have you tried the control sequencer?

It's weird that the digitizer lowers carrier frequency...

/Stefan

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Moody33



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PostPosted: Tue Jan 05, 2010 5:30 am    Post subject: Reply with quote  Mark this post and the followings unread

And why not use the digitizer with sample rate set to 50khz? 50 khz is not enough?
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dorremifasol



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PostPosted: Tue Jan 05, 2010 7:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Have you tried the control sequencer?


Ho can I lower the bit rate of a signal using the control sequencer?

Quote:
And why not use the digitizer with sample rate set to 50khz? 50 khz is not enough?


The G2 works at 96khz, and I only want to lower the bit rate, not the frequency. Otherwise I would have not asked Razz[/code]

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jksuperstar



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PostPosted: Tue Jan 05, 2010 8:25 am    Post subject: Reply with quote  Mark this post and the followings unread

The ADC/DAC trick is what you want, but most Generators for chip music also have very low sample rates, so you might find something much more convincing once it's resampled to a lower rate.
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dorremifasol



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PostPosted: Tue Jan 05, 2010 8:50 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't agree... most of the sound chips I have worked with can produce frequencies well far above audition range. The Game Boy for example can produce frequencies up to 4mhz / 4 (main clock divided by 4).

However, the DAC was only 4 bits, so it only had 15 volume levels for the envelopes.

What I hear (and I really hate) is that most emulators of sound chips have lots of aliasing. Real sound chips don't have aliasing as they do not have "sample rate"-

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Antimon



Joined: Jan 18, 2005
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PostPosted: Tue Jan 05, 2010 2:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

dorremifasol wrote:
Quote:
Have you tried the control sequencer?


Ho can I lower the bit rate of a signal using the control sequencer?

Quote:
And why not use the digitizer with sample rate set to 50khz? 50 khz is not enough?


The G2 works at 96khz, and I only want to lower the bit rate, not the frequency. Otherwise I would have not asked Razz[/code]


Like this! It's just an idea, I haven't tried and it obviously needs some ironing out but you get the idea:


ctrlseq.jpg
 Description:
 Filesize:  32.82 KB
 Viewed:  3040 Time(s)

ctrlseq.jpg



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Tim Kleinert



Joined: Mar 12, 2004
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PostPosted: Tue Jan 05, 2010 2:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Since reducing the bit rate directly influences the dynamic range, perhaps might be a good idea to preprocess the dynamics of the ingoing audio with a compressor in order to get the desired sonic result.

Dunno, just something I would try out if it were me.

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dorremifasol



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PostPosted: Wed Jan 06, 2010 5:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've done some experiments following Antimon's suggestion. I find the results pretty interesting! It's a bit similar to my old "Alias" experiments based on the bit reduction module (already posted long time ago), but this technique has a nice new flavour, it's noisier but also richer.

Here is a patch with 8 variations.


audio quantize experiments.pch2
 Description:
audio quantization using a SeqCtr module

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 Filename:  audio quantize experiments.pch2
 Filesize:  2.83 KB
 Downloaded:  568 Time(s)


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