[x264-devel] Re: o and g flags

[David Wolstencroft]

Guys,


On Mar 27, 2006, at 12:56 PM, Tim Greatrex wrote:

>
> i'm trying to optimise for the mac a bit, and am having problems  
> changing the -o flags to -g to use with my analysis tool (shark). i  
> gather this is the right thing to do, but for some reason changing  
> all the ones i can find in the makefile does not change all the  
> ones at compile, and it returns an error.
>
> any ideas?
>
>
>


Make sure when you ./configure you also --enable-debug. This will  
turn debugging symbols on and is all you have to do



On Mar 28, 2006, at 3:35 AM, Tim Greatrex wrote:
> also have been looking into finding an altivec discrete cosine  
> transform algorithms, as there seems to be this bit missing in the  
> code for altivec. all i can find is suggestions to modify an  
> existing fft algorithm. what have you found?
>
> finally, to all; are there any other osx programmers out there  
> reading this list?


The IDCT is defined within the H.264/AVC spec (unlike ASP's) which is  
slightly modified and this largely results in the ability to do the  
transform/quant steps using only adds/subs and shifts... and one  
multiply per element (using AltiVec, however you may encounter the  
need to use permute operations such as vec_mergeh()  on a matrix  
transpose). Looking at modifying an AltiVec FFT won't help much -  
though you may be able to learn more about coding in AltiVec. The DCT  
is defined in H.264/AVC for a reason - I'd highly suggest not to try  
and modify it.


Just for giggles, the fastest compile flags you'll find for OS X  
is.... -fast :) (it's Apple specific, last I checked)

- David


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