[MEncoder-users] Fwd: Questions on Mencoder performace

[Raphael]

larrystotler at netscape.net wrote:
> -----Original Message-----
> From: Corey Hickey <bugfood-ml at fatooh.org>
>
>> I don't know specifically about your systems, but I wouldn't expect 
> much performance out of a P4. I did some rough tests with lavc and 
> x264 a while back and found >that a 1.2 GHz Athlon Thunderbird was 
> outperforming a 1.7 GHz P4 by 10-20%. As far as I know early Athlon 
> processors were roughly equivalent to late P3s, >clock-for-clock, so 
> the numbers you posted don't seem out of line.
>
> Hmmm, I was under the impression that the P4 was actually optimized 
> for stuff like this and that it should outperform the Athlon in this 
> regard.  I've never been a fan of the P4 series, but I ended up with 
> with some chips and was hoping that they would be well suited for this 
> type of stuff.  Oh well.  Thanx for the insight.
>
> I appreciate all the advice that has been given to me by the list 
> members.  Thanx.
> ___________________________________________________


Whenever anybody starts being rude on this list it's because they don't 
know the answer. So don't worry about that :) 

Your best bet is to experiment.  There are too many unknowns and in 
particular of course the behaviour of the compiler will make a 
considerable difference.  One version of gcc with one set of 
optimisation flags may accidently squeeze some crucial piece of data 
into the L2 cache on a particular processor etc.   gcc has never given 
any guarantees and I remember compiling code with higher optimisation 
levels that ran more slowly and finding that after using -Os it didn't 
fit in cache etc.

You may be able to find tools that give you useful stats (e.g. 
cachegrind http://valgrind.org/info/tools.html). If you can run 
systematic tests using such tools with as many different gccs and 
options and cpus as possible then I am sure we would all be very 
interested to see the results.

Raphael