[FFmpeg-devel] [RFC] H.264/SQV3 separation: h264data.h

Baptiste Coudurier baptiste.coudurier
Tue Dec 16 19:55:45 CET 2008


Uoti Urpala wrote:
> On Tue, 2008-12-16 at 13:31 +0100, Michael Niedermayer wrote:
>> On Tue, Dec 16, 2008 at 11:01:34AM +0100, Panagiotis Issaris wrote:
>>> Besides that, in my opinion you can't benchmark code on one particular
>>> machine and expect a 0.5% performance loss to say anything about the
>>> codes performance on other machines (other then that the code hasn't
>>> introduced a substantial performance change on similar machines).
>> What evidence is there to support this claim?
> Many known cases where changes that are known not to affect the real
> quality of the code alter performance by more than 0.5%. I just tried
> adding an unused global function to h264.c. The first attempt didn't
> show any quickly measurable difference. Then I made the function a bit
> larger, and now the benchmark ran consistently 0.8% faster. Removing the
> unused function made things correspondingly 0.8% slower again.

Could we please see the code ?

>> if i remove some unneeded code and that results in a 0.5% gain on one machine
>> chances are it also does on most others, its not as if the removial of
>> code will likely make it slower.
> You can expect that removal of useless code won't make things slower _on
> average_. However if the CPU use of the removed code was significantly
> less than 0.5% 

??? Code was _useless_ so CPU did never _use_ it.


Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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