[mythtv-users] [ATrpms-users] Confused: why did video performance DECREASE (up to 70%) after upgrading video? PARTIALLY SOLVED
Jeffrey J. Kosowsky
mythtv-users at kosowsky.org
Tue Dec 9 17:00:06 UTC 2008
George Mari wrote at about 09:01:08 -0600 on Tuesday, December 9, 2008:
> Jeffrey J. Kosowsky wrote:
> OK - main thing is, it's working reasonably well now. I think the myth
> player tries to keep audio and video in sync more than other players.
> If the audio is "slow", or cannot be decoded and played back in time
> because of driver or hardware issues, it will "pause" the video, which I
> think results in stuttering. This is just my understanding / theory.
That makes sense.
> > This is my typical CPU usage (from top):
> > Cpu(s): 61.6%us, 9.7%sy, 0.0%ni, 27.3%id, 0.5%wa, 0.5%hi, 0.5%si,
> > 0.0%st
> > 20 0 326m 103m 34m S 62.0 5.1 14:52.29 mythfrontend
> > 20 0 364m 82m 11m S 9.0 4.1 1:58.87 mythbackend
> > 20 0 56312 5432 3688 S 6.0 0.3 1:57.03 pulseaudio
> > 20 0 59240 23m 9088 S 4.6 1.1 1:42.21 X
> > I'm curious now how you seem to be getting better performance. Could
> > it be that your 2.2Ghz Athlon 64 is just that much faster than my
> > 2.8GHz P4? (and I am using XvMC).
> Probably not - CPUs are about the same. My understanding is P4s are
> generally slower per-clock than Athlon 64 chips, so your 2.8ghz P4 is in
> the same ballpark as my 2.2ghz Athlon 64. Motherboard / chipset might
> be a different story. They're probably in the same ballpark, I've just
> been tweaking mine for mythtv longer than you have.
> I have pulseaudio installed, but it's not running. Also, my system is a
> dedicated frontend only - no backend running.
Well on my machine that would have saved 5-10% which is something.
> > Two questions that remain:
> > - Any other suggestions about things I can do to tweak my mythtv/video
> > setup to grind out a few more marginal cpu or video points?
> 1. Are you running hyper-threading on the P4? There have been a few
> reports on the list of people getting better performance - better
> throughput - with hyperthreading turned off. Or, if you already have it
> off, try turning it on.
My chip is pre-HT so doesn't support it.
> 2. Have you tried adjusting the PCI latency on any of your PCI devices?
> This made a big difference for me on my dedicated backend - an old Dual
> 600mhz-P3. I have a PVR-350 in it for recordings, and it was very
> glitchy when I first set it up - there were frequently messages in the
> system log from the ivtv driver about buffer underruns or overruns (I
> forget which), until I maxed out the PCI latency on the device - and it
> has worked perfectly, glitch free ever since.
> You might want to experiment with increasing the latency on your audio
> device and/or video card.
Interesting... never knew about this.
My 6200 video card is already set at maximum latency (248) by default.
The AC'97 Audio Controller was originally latency 0 but setpci didn't
seem to be able to increase it (i.e. it stayed stuck at 0).
Note: the article talked about increasing the latency for the IDE/SATA
drives - mine originally was 96. I tried increasing this further but
it made no difference. I also tried decreasing it ;)
There are many other devices and bridges I could play with but since I
wasn't seeing any effect I stopped.
> There is a link to good article on PCI latency and how it works at IBM's
> website at the bottom of the wiki article.
> > - Would upgrading further to a 7600gs card be likely to help or is
> > this likely to be more of a CPU issue? (note: I clearly got some
> > benefit in moving from the 4600 to the 6200 card and turning on XvMC)
> Not sure if the video overlay on the 7 series offers any more offload
> than the 6 series. However, if you try to use any of the OpenGL
> rendering methods for Mythtv, the 7600 would likely give you more oomph
> for this than the 6200. OpenGl performance is more closely related to
> GPU clock speed, memmory bandwidth, etc. I believe a 7 series card is
> reported to be good enough for OpenGl rendering of up to 720P video.
> Again, this is just my understanding - no direct experience with this yet.
That probably wouldn't help me since my problem is 1080i.
Thanks so much for your help!!!!!!!
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