[MEncoder-users] Fwd: Questions on Mencoder performace

[Raphael]

Phil Ehrens wrote:
> Raphael wrote:
>   
>> 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.
>>     
>
> As warm and fuzzy as that may sound, since mencoder does not have
> a uniquely defined data path there is nothing to test. Would you
> have him benchmark '... -oac copy -ovc copy ...' or '... -oac mp3lame
> -ovc lavc -vf ??? ...'?
>   
I would have thought that he should test something that he is interested 
in actually doing. If he only ever wants to make x264 vids from dvds 
then that would be a good area to explore.   He can of course then try 
some different options and note  how much difference it makes if he 
wants to.

Raphael