Horizontal scrolling

SDL Development
1

Hi

Um…This is a real long shot, but…

I’m scrolling an image horizontally across the screen using an alpha channel.
I can easily get over 50fps which works well with TV-out ( 50Hz refresh ).
The one little problem I have is with interuptions from the operating system
( linux ). Every .5 to 1 second a get a small delay that causes the
scrolling to jerk slightly. I’m using DGA so for the rest of the time it is
as smooth as silk…perfect even :wink:

Anyway, I have tried using “nice(-20)” as root to get a little more priority
to my programme but it doesn’t seem to help at all. Another thing I tried
was to put a usleep call in to give some time voluntarily give some time back
to linux…no go. I’ve stripped all background tasks to the bare minimum to
help but it still jerks :frowning: I also have checked for any disk accessing and
there is none.

Has anyone seen this before or perhaps could give me some pointers to some
things the kernel might do that could cause this?

I know it’s a long shot :wink:

Thanks, Paul.

2

Has anyone seen this before or perhaps could give me some pointers to some
things the kernel might do that could cause this?

You may want to go to the linux kernel traffic archive and search for the
linux real time/low latency patches. There should be some good discussion
on the matters.

MadsOn Wed, 28 Nov 2001, Paul wrote:

–
Mads Bondo Dydensborg. @Mads_Bondo_Dydensbor
He who sacrifices freedom for a little comfort, deserves neither freedom nor
comfort.

3

You could try Robert Love’s Preemptible Kernel patch that was created
for problems like this. Check out: http://www.tech9.net/rml/linux/

Bryan–
http://www.bokeoa.com/ | @Bryan_Stillwell
GPG fingerprint: 33F7 44F2 8612 E02F 8DE8 97FB 621E 8A36 6DC1 32AF

On Wed, Nov 28, 2001 at 08:22:46PM +1000, Paul wrote:

Hi

Um…This is a real long shot, but…

I’m scrolling an image horizontally across the screen using an alpha channel.
I can easily get over 50fps which works well with TV-out ( 50Hz refresh ).
The one little problem I have is with interuptions from the operating system
( linux ). Every .5 to 1 second a get a small delay that causes the
scrolling to jerk slightly. I’m using DGA so for the rest of the time it is
as smooth as silk…perfect even :wink:

Anyway, I have tried using “nice(-20)” as root to get a little more priority
to my programme but it doesn’t seem to help at all. Another thing I tried
was to put a usleep call in to give some time voluntarily give some time back
to linux…no go. I’ve stripped all background tasks to the bare minimum to
help but it still jerks :frowning: I also have checked for any disk accessing and
there is none.

Has anyone seen this before or perhaps could give me some pointers to some
things the kernel might do that could cause this?

I know it’s a long shot :wink:

Thanks, Paul.