[sdiy] converting white noise to pink noise

Dave Manley dlmanley at sonic.net
Wed Mar 5 18:21:33 CET 2008


Tom Wiltshire wrote:
> 
> On 5 Mar 2008, at 14:41, Scott Gravenhorst wrote:
>>
>> I will add that sometimes the bit labeling is a bit weird.  I'm very 
>> much used to a
>> zero based numbering system for anything with "N bits" where N > 0, 
>> but some LFSR bit
>> taps I've seen, including the Xilinx link I posted, use a 1 based 
>> system.  From this
>> confusion an error can easily arise.
> 
> 
> Yes, I've been caught out like this too. Finished up writing a LFSR that 
> wasn't anywhere near as good as it was supposed to be. It was only when 
> I really went back over it and checked everything that I spotted the 
> numbering difference and the error.
> Being a longtime computer programmer, I obviously count "0, 1, 2, 3" 
> rather than "1, 2, 3" but for some reason LFSR taps seem to mostly start 
> with bit 1. Weird. Maybe they were designed by normal people or something.
> 

Pretty sure the blame for this lies with the mathematicians.  If you 
ever do any crypto stuff you'll find similar numbering, and an annoying 
habit of numbering the MSB "one".

-Dave




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