[vlc-devel] [PATCH] Added a performance check to marquee filter

basos g noxelia at gmail.com
Fri Jan 9 22:36:42 CET 2009

2009/1/9 Rémi Denis-Courmont <rdenis at simphalempin.com>:
> On Fri, 9 Jan 2009 15:35:31 +0100, Antoine Cellerier <dionoea at videolan.org>
> wrote:
>> Well it prevents computing the marq string more than once (everytime the
>> filter function is called). So basically you save 1 strftime call and 1
>> str_fmt_meta call per run (except on the first one).
> Which consumes what? 100µs everytime? I haven't measured, but if it _is_
> slow, then there must be something wrong with the way invoke strftime().
I haven't measured either but i know that i'm avoiding things that are
not needed in a command sequence that is too be executed 25 times per
second or each 40 ms :
And assuming that i'm updating the marq-marquee (with var_Set) each
100 ms from another module that wants to print stats on the video, i
could get way with only 10 times per second.
what am i calling :
 a) system call (time)
 b) strftime
 c) str_format_meta

I just made this optimization keeping in mind that system calls should
be avoided.

But i admit that it's not much of a gain of speed . Sent it to paradise.

> If you're into optimizing marquee, I'd bet hunting memory copies in the
> video filtering/scaling/output stuff would be way way more meaningful.

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