Web Client Video frequently pauses

[jcain 7]

Can I alter the webm call: -threads [num] to 12 (in my case) or is there another issue as to why webm isn't utilizing multi-threading multi-core?

[Tikuf 663]

It is actually ffmpeg and the lib that google has written it is beyond our control upping the threads will result in slower conversions

[Guest virtualtinker]

Something else you might want to consider trying is to disable hyperthreading, which I am assuming your CPUs at the very least support since they sound like Xeon E5645s.  I'm not quite sure how hyperthreading works on a straight physical, but I at least know in a VMware environment, I've seen a single VM double dip on the same core even when there was plenty of additional physical cores that needing hyperthreading wasn't necessary.  In the case of transcoding, considering this is a CPU intensive process, I could see a double dipped core could max out the available clockspeed on that core, causing your studdering.

[jcain 7]

I'm using amd Opteron 2431's. No HT here.

[jcain 7]

What is it about Google that doesn't like multithread/core? I know it isn't ffmpeg because I just made ffmpeg use all 12cores at 98% to re-encode a file.

[Tikuf 663]

H264 is multithreaded libvpx is not if the lib that ffmpeg uses has multithread ability then ffmpeg can do it but libvpx is not multi threaded properly

[Tikuf 663]

Here are some results of tests

Webm

11 threads to the cpu and 68% cpu converting @116 fps

 2 threads  25% cpu converting @ 124 fps

I did do other tests but just didn't bother recording the results as they were much the same

 

libx264

threads 0 - 45% fps=121

threads 1 - 12% fps= 41

threads 2 - 26% fps= 94

threads 3 - 34% fps=108

threads 4 - 37% fps=113

threads 5 - 40% fps=118

threads 6 - 42% fps=120

threads 7 - 43% fps=121

threads 8 - 41% fps=120

threads 9 - 44% fps=121

threads 10 - 44% fps=123

threads 11 - 43% fps=123

threads 12 - 43% fps=122

 

 

Obviously these result will depend on cpu grunt.

[jcain 7]

so are you goin tweak this via the CRF value or VBR?

[Luke 42077]

so are you goin tweak this via the CRF value or VBR?

 

I don't think there's anything to tweak. We're not miracle workers. We do our best with the tools we use but sometimes they have limitations that we have to try and work around. Luckily we have Tikuf who knows everything there is to know about this stuff. We are going to cap the framerate though which should help with this particular video.