[linux-audio-user] Re: Sample Rates / Sample Sizes

[Greg Murphy]

> On Thu, Jun 24, 2004 at 07:51:04 -0700, Mark Knecht wrote:
> 
>>I'm sure you're right Rick. I was looking at some technical dither 
stuff 
>>yesterday. The noise floor different dithering plugins insert is not 
>>flat, or the same, over frequency, so that could certainly effect 
>>different types of music differently. 

Yes, POW-R algorithms seeem to be pretty popular and many engineers
will select a particular POW-R type to suit the source material. For me
(and my crap ears) the difference in dither types is hard to hear and
it was only when I had the chance to use decent monitoring systems
(Dunlavy /B&W/ Levinson) that I (think) I heard a difference.

> but it does 
> raise the question of how to best import a 24-bit track into a 16-bit

> session. I've have to do this once or twice. Possibly I should have 
> dithered the track. I'd guess the normal conversions just strip the 
> bottom 8-bits?

Yep, dither beats truncation. I'm not a Pro Tools user so I this
information is secondhand but I think that if there is a chain of
plugins, data is maintained as float and then converted to the final
form (16, 24 or whatever) at the end of the chain. I think that the
same goes for most of the Windows DAWs. Somebody correct me if I'm
wrong though. So, there should be no need for dither apart from the
final word length reduction from 24 to 16 bit. Also, remember that
dither is cumulative and so the noise floor can rise.

Now, question about LADSPA and DAWs. Is it standard practice to dither
from float (or fixed) to integer post-processing? Also, do any (or all)
of the Linux DAWs act as described above i.e. maintaining a float
datatype if there is >1 plugin in a chain? I suppose that this would
require a standard "internal" format of some sort.

Greg










I'm also new to Linux audio (although not to Linux) so perhaps 



	
	
		
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