Athlon 64X2 and h.264 encoding - performance pb

[sean_malice]

It was my belief that Videolan supported multithreading.
I recently upgraded from an Athlon XP 2800+ to an Athlon 64 X2 3800+
Knowing that the latter had a similar processor speed per core compared to my old cpu, i only expexted an improvment in encoding performance through the use of the second core. I use it to stream live TV in H.264 / AAC

However, my results are barely better. Here's what troubles me :

When encoding at high resolutions >384x288, video becomes choppy as if the CPU couldn't cope with the frame rate or size.
However, my CPU is barely above 50%, with both cores in use. So there should be plenty of room for additional computing power.

This reminded me of something similar about a performance test on the games F.E.A.R and FAR Cry that was reported some time ago.
Although supposed to be able to use the two cores, they only seemed to use 50% of each, resulting in the equivalent of a 100% usage of a single core.

Could there be something similar in VLC ?
Could the actual code not be optimised to take full adcantage of dual core processors ?
100% usage of one core balanced between the two ?
(i use version 0.8.4a)
Is there a particular build that might adress this problem ?

Thanks a lot for any input

[sean_malice]

to answear my own question :

I was able to "force" my CPU usage to 83% and above by going to the parameters > preferences > Sout stream > transcode > (advanced options ticked) > number of threads : 2

However, wathever bitrate i used, video was still more or less jerky.

Any ideas ?

[Marius]

I've got the same problem. I know it doesn't help you much, but it's good to know you are not alone, no ?

[sean_malice]

Seriously Marius, the setting i mentioned above seems to have solved the problem. You actually HAVE to tell VLC to use two threads.

I now have a cpu usage close to 100% and am able to stream live 640x480 H.264 at 25fps through my home LAN.
I'm doing this with vlc beta 0.8.5. The 64X2 3800+ is currently ovecklocked to 2550Mhz (instead of 2000Mhz per core originaly)
As for choppiness, i guess VLC still have its limits with higher resolutions.

I keep thinking that vlc is a great software that is not well enough documented.

[Rizal]

I have been playing with this some to on a Pentium D 3.4 GHz on a Debian sarge install.

Sarge comes default with 2.4.x kernel which was not able to do fps 25, atleast to my eye it didnt, so I upgraded to 2.6.15-686-smp which basically made it worse. When I downgraded to 2.6.15-686 with no smp support it got better. This is without using the threads option, as soon as I set it, it becomes bad again.

My theory is that the SMP kernel adds "overhead" that slows it it down, while the none SMP kernel, lets the CPU actually figure out how to "load balance" the jobs, and the cpu does it better than the kernel.
Then again what do I know

Would you mind sharing the parameters you set to achive 25 fps in your setup?

[Rizal]

Upgrading to 2.6.16-1-686-smp I get it to work better with threading command.

Now my cpu's are at 80% each, but still have to use scale 0.5 to achive anything close to 25 fps.

[Guest]

It was my belief that Videolan supported multithreading.
I recently upgraded from an Athlon XP 2800+ to an Athlon 64 X2 3800+
Knowing that the latter had a similar processor speed per core compared to my old cpu, i only expexted an improvment in encoding performance through the use of the second core. I use it to stream live TV in H.264 / AAC

However, my results are barely better. Here's what troubles me :

When encoding at high resolutions >384x288, video becomes choppy as if the CPU couldn't cope with the frame rate or size.
However, my CPU is barely above 50%, with both cores in use. So there should be plenty of room for additional computing power.

This reminded me of something similar about a performance test on the games F.E.A.R and FAR Cry that was reported some time ago.
Although supposed to be able to use the two cores, they only seemed to use 50% of each, resulting in the equivalent of a 100% usage of a single core.

Could there be something similar in VLC ?
Could the actual code not be optimised to take full adcantage of dual core processors ?
100% usage of one core balanced between the two ?
(i use version 0.8.4a)
Is there a particular build that might adress this problem ?

Thanks a lot for any input