[mythtv-users] pauses during hd playback

[James C. Dastrup]

>I have been running mythtv for almost two years now and until 
>recently everything has been fine. It seems that in the last few 
>months, when I playback HD content on the frontend it will seem to 
>skip a few seconds and show mpeg noise on the screen. When the 
>backend starts recording, it gets worse. It starts to pause every few 
>seconds. I am only showing about 20% cpu usage on X on the frontend 
>while it is happening.
>
>The frontend is a P4 3ghz with 1gig memory, NVIDIA card.
>The backend is an Athlon XP 2000 with 512 megs memory.
>
>The backend has been able to record 2 HD streams and 1 250 at the 
>same time while I playback one on the frontend (until recently). I 
>have updated to the latest cvs yesterday. I am usually a few weeks 
>behind. It has not made any difference. The backend seems to be 
>having problems. I am no expert, but here is the TOP results:
>
>Is it an interrupt problem? I noticed that ivtv1 is on an interrupt 
>by itself, but ivtv0, eth0, and skystar2 are on one interrupt with 
>the highest number and the ERR number keeps rising:
>
>           CPU0
>   0: 1095715619          XT-PIC  timer
>   2:          0          XT-PIC  cascade
>   3:       6114          XT-PIC  ohci_hcd
>   5:          1          XT-PIC  ohci_hcd
>   8:          1          XT-PIC  rtc
>   9:          0          XT-PIC  acpi
>10:     398925          XT-PIC  Skystar2, SiS SI7012
>11:    4301199          XT-PIC  ivtv1
>12:  180839091          XT-PIC  ehci_hcd, eth0, ivtv0, Skystar2
>14:   38733591          XT-PIC  ide0
>15:     554797          XT-PIC  ide1
>NMI:          0
>ERR:      13806
>
>
>My next question would be how to change / move what interrupts the 
>cards use and how I should group them.
>The frontend reports 'video behind (or audio ahead), playing video at 
>double speed'.

Even the fastest machines out there can be affected by IRQ sharing. I've
especially seen problem with NIC's and USB controllers sharing IRQ's with
anything else.  To solve this, first attempt to spread out the IRQ's using
your computer's BIOS.  Also, trying moving some cards from one slot to
another, as it's common for particular slots to share with on-board devices.
Also, disable unused devices in the BIOS and don't load drivers for devices
you don't use. For example, do you really need three USB host controllers
loaded on your backend?
 
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