Apple Logic Pro /LogicExpress Discussion

Thank you for spending so much time giving such a detailed answer  
Ifron,  that was very easy to follow and I understand what you are  
saying now. I just have two follow up questions, if I may: can you  
switch bit rates in the middle of a project, and can you import audio  
recorded in one bit rate into a project in a different bit rate. I  
think the answer to the second is going to be yes you can, but not  
sure about the first!


thanks again

Andy Brook

On 17 Sep 2010, at 05:50, Irfon-Kim Ahmad wrote:

> Okay, so here is the deal with bits. A bit can be a 0 or a 1. If you  
> had a 1 bit audio interface, it could either be on or off at any  
> given moment. Now, you could still do something with that. I mean,  
> we all know such an interface as the square wave oscillator, right?  
> It's off or on. The other factor, the sampling rate, gives you the  
> ability to turn it on or off really fast, thus creating various  
> frequencies and so on. But you can't make a lot of sounds with a  
> square wave.
>
> So if you add a second bit, you get a 0 or a 1 followed by another 0  
> or 1. You can make the numbers 00, 01, 10 and 11. That's four  
> settings. With that you can capture a little more complex of a  
> sound, you have a few more subtleties. Your interface can be either  
> full on, pretty high, pretty low, or off, and it can vary those at  
> the sampling rate. So instead of just being able to make square and  
> pulse waves you can now make a whole bunch of different waves,  
> including extremely crude sines, triangles, etc., as well as sampled  
> or recorded sounds with some more veracity. But try to imagine  
> drawing a sine wave with only four levels -- it still won't be that  
> accurate a reproduction.
>
> The number of possible values for each bit depth is easy to figure  
> out -- it doubles each time:
>
> 1 bit: 2 values
> 2 bit: 4 values
> 3 bit: 8 values
> 4 bit: 16 values
> 5 bit: 32 values
> 6 bit: 64 values
> 7 bit: 128 values
> 8 bit: 256 values
> 9 bit: 512 values
> 10 bit: 1024 values
> 11 bit: 2048 values
> 12 bit: 4096 values
> 13 bit: 8192 values
> 12 bit: 16384 values
> 13 bit: 32768 values
> 14 bit: 65536 values
> 15 bit: 131072 values
> 16 bit: 262144 values
>
> So once you get to 16 bits, you are effectively drawing your sound  
> wave with 262,144 possible values for its height at any given point.  
> You can draw curves with extreme subtleties to them with that kind  
> of accuracy, and at that point we can more or less not hear the  
> difference anymore between the real thing and our stair-stepped  
> approximation, for most people.
>
> So why ever use more than 16 bits, especially if you master to CD,  
> which is a 16 bit medium? The answer is that you sometimes process  
> sounds in ways that make the teeny tiny bumps more apparent.
>
> Suppose you've recorded a wave in 3 bits, so it has 8 possible  
> values. And let's suppose that wave is a straight diagonal line.  
> Your values look something like this:
>
> 1,2,3,4,5,6,7,8
>
> That makes an okay line, right? Right. (Well, assume it is for the  
> purposes of our discussion.) I mean, you have a "stair height" of at  
> most 1 unit, and we'll suppose that looks pretty good.
>
> However, suppose the line you were recording were half as loud. Your  
> values would look like this:
>
> 1,1,2,2,3,3,4,4
>
> Still the stair stepping is about the same, one unit at a time.
>
> Now you normalize it. Do you wind up with our original line above?  
> No. The computer says that the maximum value was half as loud as the  
> maximum possible loudness, so it will double every value. Now your  
> line looks like this:
>
> 2,2,4,4,6,6,8,8
>
> The stair steps are twice as apparent now. The volume jumps by 2  
> each time it changes. Also, we're only using 4 of our 8 possible  
> values. It's as if our recording was made with 2 bits instead of 3.
>
> Now think how many times you cleanse, fold and manipulate your audio  
> in a given project. If you're like me, you run it through the  
> wringer and back. Every manipulation stretches and mutates the  
> resolution of your recording. The more possible values, the more  
> resolution your data had, at the outset of the process, the more  
> data you're likely to be left with at the end.
>
> This is exactly why many good instruments will have 16 bit outputs  
> but perform their internal processing at 24 or 48 bits. And that's  
> why, if you do a lot of processing, you can benefit from recording  
> or processing at a higher rate and then dithering down to the target  
> format at the final mastering stage.
>
> -- 
> Irfon-Kim Ahmad
> http://www.ramp-music.net
>
> On 2010-09-16, at 11:48 PM, brianmc7@... wrote:
>
> > From what I've been told more bits equals more dynamic  
> range???????????
> >
> >
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