Discuss the various methods you use in music production, from compressor settings to equipment type.
By m56p87 Sun Aug 05, 2012 3:56 pm
peterpiper wrote:
m56p87 wrote:if you simply just drop bit rates (not sampling rates) all your doing is adding noise - nothing else.



I dont think so. search for a-law and µ-law and you know what I mean.

peace


I'm not talking about a/d conversion, I'm talking purely about dropping bits in a digital domain.
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By peterpiper Sun Aug 05, 2012 5:34 pm
MoreBuck$ wrote:
jonestown massacre wrote:
MoreBuck$ wrote:resample on the mpc4000 allows you to change bits data rate and other parameters as it's resampled



:oops: The 60 and the 4000 are not 16 bit....



My 4K is set up to sample at 16bit and then i can resample with a lower data rate and bit rate to achieve Lo-Fi sounds.



Isn't it 24bit ?


m56p87 wrote:
I'm not talking about a/d conversion, I'm talking purely about dropping bits in a digital domain.


And this is the difference between sampling at 12bit and simply dropping 4bits in the box. But for example the plugin jb timemachine allow to reduce the bitdepth with µ-law on or off and also dithering on or off.
Another method to drop bits (well, kind of) is to not use all available bits when sampling. every bit represents 6dB. Sampling with a 16bit converter but at a very low level (-24dB) and you won't use 4 of the 16bit.
To get a usable result your sampler should be able to normalize the sample otherwise the sample is too quiet.

peace
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By Funkydrops Mon Aug 06, 2012 3:49 am
peterpiper wrote:
Another method to drop bits (well, kind of) is to not use all available bits when sampling. every bit represents 6dB. Sampling with a 16bit converter but at a very low level (-24dB) and you won't use 4 of the 16bit.


peace


That's clever! Worth experimenting;-)

PEACE
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By MoreBuck$ Mon Aug 06, 2012 10:35 am
peterpiper wrote:Isn't it 24bit ?


You can set the bit rate to whatever you want, 24bit is just the max it can go to
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By AntonPD Mon Aug 06, 2012 12:11 pm
Funkydrops wrote:
peterpiper wrote:
Another method to drop bits (well, kind of) is to not use all available bits when sampling. every bit represents 6dB. Sampling with a 16bit converter but at a very low level (-24dB) and you won't use 4 of the 16bit.


peace


That's clever! Worth experimenting;-)

PEACE


wouldnt you need to compress it with 24 db gain reduction? (so that the loudest part is 24db lower, but the most quiet part is still the same level) or am i wrong thinking that the one bit, 6db rule changes with the bit depth of the sampler? i was always assuming that those 12bits represent the same range as what a 16 bit sampler does, only less fine
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By peterpiper Mon Aug 06, 2012 1:04 pm
As far as I understand it is cutting on the other side of the scale. If the sampling source signal goes lower than -72dB in a 12bit A/D it can't be heard cause there is nothing but a noisefloor down there.
To get this effect with a 16bit A/D you'll have to lower the signal -24dB cause the noisefloor of a 16bit A/D is 24dB lower.

But like I said before. There are two laws (curves) of bit representation in A/D converters and they are compression

http://en.wikipedia.org/wiki/%CE%9C-law_algorithm


To be honest. Thats just how I understand the theory but it can be totally wrong. I'm not really an expert on this topic :)

peace
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By AntonPD Mon Aug 06, 2012 4:55 pm
peterpiper wrote:As far as I understand it is cutting on the other side of the scale. If the sampling source signal goes lower than -72dB in a 12bit A/D it can't be heard cause there is nothing but a noisefloor down there.
To get this effect with a 16bit A/D you'll have to lower the signal -24dB cause the noisefloor of a 16bit A/D is 24dB lower.

But like I said before. There are two laws (curves) of bit representation in A/D converters and they are compression

http://en.wikipedia.org/wiki/%CE%9C-law_algorithm


To be honest. Thats just how I understand the theory but it can be totally wrong. I'm not really an expert on this topic :)

peace



hmm yeah, what im making of that chart: the closer to 0 db, the finer the encoding gets (more per db); there is some room for user error (the recorded signals +1 db (or so) is encoded as 0db, the recorded 0db is about 1db in encoded terms); i THINK the companding is there to make optimal use of the available bits (this chart is a convention i think, so they just could have 'spaced the bits more', but there probably is a reason (ease of calculation?) why the bits are closer together near the 0db)

what i'm wondering about: this chart goes to -42 db (in encoded terms, otherwise about 64 or 76 depending on the used law), is 128 values (if i read the code underneath the chart correctly), so 7-bit.
would an 8-bit encoder add more values inbetween these, or add more values so the range would be 48 db?

im guessing the second, that would mean that dropping the 4LSB indeed does not give the same result as sampling in 12 bit (if these laws would be followed in the AD encoding, which im not sure, the mpc 60 emphasises the high end before sampling, no idea whether it's compensated in the DA)
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By dabmeister Mon Aug 06, 2012 5:04 pm
MoreBuck$ wrote:
peterpiper wrote:Isn't it 24bit ?


You can set the bit rate to either 16 bit or 24 bit, 24bit is just the max it can go to


Yep, those are the two selected bit rate options. The 4k houses 24/96 AD-DA converters.

edit: I just rephrased your comment a lil' bit there MB. :lol: