[Ffmpeg-devel] Re: Using Intel's fDCT

g. the_ether
Sun Nov 20 01:42:50 CET 2005

M?ns Rullg?rd <mru <at> inprovide.com> writes:
> IIRC, the output from the MMX/SSE DCT functions is permuted because of
> some design quirk of the CPU.  There's a flag somewhere indicating
> this.  Make sure it is set correctly.

Thanks for the suggestion but having looked at the code, the permuation is 
only relevant to iDCT, not fDCT which is where my problem lies. I tried all 
the different permutation settings anyway, just in case, but it made no 

Perhaps I have to add a new permutation step to the fDCT function before 
quantisation when using Intel's fDCT?

Can anyone explain what is going on?


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