OpenGL video performance

Andy Furniss andyqos at
Mon Apr 30 13:09:26 PDT 2012

Greg G. wrote:
> Andy,
> On 25.04.2012 19:51, Andy Furniss wrote:
>> Some random thoughts/tests/questions in no particular order non of which
>> may help (maybe if you are using cpufreq try that first with myth).
> thanks for your feedback.
>> If your desktop is using compositing try to disable it if you can.
> Had already tought of that.
>> Can you reproduce with mplayer, with this -
> Never thought about trying that. Funny enough, with mplayer, both xv and
> gl juddered. Perhaps it's due to mplayer running with normal prio, I may
> try again with "nice".
>> If you are running a 60Hz screen of course it's never going to be smooth
> Yes, of course. Fortunately myth will choose a suitable screen mode, and
> I verified it works. Again - with Xv it's just fine.
>> On my box the gl won't be smooth unless I set my cpus to perf (and the
> I was not able to see any difference between ondemand and performance,
> except that the system got hotter quicker. But your hint reminded me
> that I'm using cpupowerd to undervolt my CPU and that it therefore uses
> the userspace governor. I had somehow completely forgotten about that
> :-) But anyway that didn't change a thing either.
>> What is your cpu and what res is the screen, are you using more than one
>> screen?
> Athlon X2 5000, 1080p, single screen on HDMI.
>> Does myth use vdpau if so does it allow software decode but still use
>> vdpau as you would gl or xv - I mean just csc and scaling rather than
>> full accelerated decode?
> Still need to check this.

list CC added, so others can see.

Ok, I am not sure what's going on then.

Maybe, as Michel suggested vblank is involved.

Can you repeat the mplayer test like this -

vblank_mode=0 mplayer ...

This should over-ride the dri vsync.

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