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Topic: 8x8 bit patterns
Replies: 3   Last Post: Mar 13, 2013 12:09 PM

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bert

Posts: 280
Registered: 1/4/06
Re: 8x8 bit patterns
Posted: Mar 1, 2013 8:57 AM
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On Thursday, February 28, 2013 10:51:02 AM UTC+1, Martin Brown wrote:
> I have a little puzzle where I think the answer is that it is not
> possible but having tried all the tricks I can think of cannot prove it.
>
> The problem arises from considering the possible bit patterns in an 8x8
> JPEG encoding square and searching for one that includes all possible
> states for subsampling up to 2x2 - that is 2x1, 4x1, 2x2
>
> It is obvious that the 4x1 subsampling requirement means that the final
> solution if it exists must be a permutation of the nibbles 0,1,...,15


No, I think that's quite unlikely to be true, on the basis that there are
one or two 16-bit strings which, cyclically, contain all sixteen nibbles
(I remember using them as read/write patterns in disk tests). One 8-bit
row of your square can contain five different nibbles, not just two.
--



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