[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.
 > [deleted]
 > > 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?
 > Yes.
 > 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?
 > http://www.mythtv.org/wiki/index.php/PCI_Latency
 > 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!!!!!!!

More information about the mythtv-users mailing list