[mythtv-users] Slight picture jerk every 10secs

Yan-Fa Li yanfali at best.com
Thu Oct 14 14:44:16 UTC 2004

Since it's happening under load, take a look at PCI latency on both 
cards.  Maybe it's set too low.

	lspci -v

will print that info.  Then you can set it using setpci.


02:08.0 Ethernet controller: Intel Corp. 82801CAM (ICH3) PRO/100 VE 
(LOM) Ethernet Controller (rev 42)
         Subsystem: IBM ThinkPad A/T/X Series
         Flags: bus master, medium devsel, latency 66, IRQ 11
         Memory at d0200000 (32-bit, non-prefetchable) [size=4K]
         I/O ports at 8000 [size=64]
         Capabilities: [dc] Power Management version 2

setpci -s02:08.0 latency_timer=0x40

for example would set my ethernet latency to 64 instead of 66.  You can 
try experimenting with higher values and see if that helps, or if it is 
using higher values try lower values and see if that helps.  Is your 
kernel running with IO-APIC turned on ?  This will require you to 
recompile the kernel.  Sometimes this helps if both cards are sharing 
IRQs, as it allows the system to use Level triggered IRQs which are more 
efficient to process in the kernel driver system and allow the kernel to 
assign higher value IRQ numbers rather than the basic 15 for XT edge 
driven ones.


Dan Robinson wrote:
> Guys,
> I'm running the latest setup from Jarod's guide along with 2 Nova-T
> cards.  Since moving to FC2 and the latest DVB modules then stability
> has really improved.  However, I'm noticing that when recording on
> both cards and watching a previous recording, then I get a slight
> picture jerk every 10 to 15 secs.  There isn't a jump in sound, it
> just looks like some frames get skipped.  I don't think my system is
> really being over worked, but I could be wrong.
> I have an Athlon 1900 and 512GB memory.  I'm recording to a Samsung
> 120GB disk, with OS and swap etc on a Western 80GB.
> Could someone give me some pointers as to how I can determine where
> the problem might be?  Would 'top' give me enough info?
> Danny

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