On Mon, 2012-01-16 at 11:55 -0600, David Engel wrote: > Hi, > > I have a MythTV backend with a Hauppauge HVR-2250 (dual tuner, > ATSC?QAM, PCIe) and a Ceton InfiniTV4 (quad tuner, QAM/cable card, > PCIe). Over the weekend, I started intermittently seeing corrupt > recordings that were painful to watch. > > I eventually narrowed the problem down to when both tuners on the 2250 > are active at the same time. In this case, both recordings have > corruption (CRC errors, etc.). The InfiniTV4 does not appear to be > affected by anything going on on the 2250. Likewise, the 2250 does > not appear to be affected by anything going on on the InfiniTV4. > > I noticed something strange while diagnosinig the problem. When the > 2250 is busy recording, top reports the CPU as being in wait for an > abnormally high amount of time (~30% for one tuner busy and ~50% for > both tuners busy). I don't recall seeing that before. I quickly > tried a KWorld ATSC 110 on a different system and it showed no, or > negligible wait time. > > Thinking that the 2250 was going bad, I replaced it with two KWorld > ATSC 110s (single tuner, ATSC/QAM, PCI). The two 110s had the same > problem as the 2250 -- corruption when both tuners are busy and > unusually high wait time when either is busy. > > At this point, I'm suspecting a motherboard, memory or grounding > issue, but would like some feedback in case there's anything I'm > missing. The high wait time seems extremely odd to me. Perhaps it > means something to those of you who are much more familiar with the > cards and drivers. A long time in IO Wait and (presumably) dropped video data buffers for a TV card driver usually means: a. The devices are not producing interrupts b. Your system is dropping interrupts from the devices c. Something in your system keeps interrupt processing disabled for a long time. Of the above c. is unlikely. The root causes of a. and b. are many and varied. However most of those root causes are under control of kernel software: core IRQ handling, core PCI/e bus setup, or tv card driver modules and their supporting modules. Hardware related root causes would be buggy PCI chipsets, poor RF signal, a motherboard problem, or a power problem. I tend to blame the software before the hardware. Sometimes, dust in the shared, conventional PCI bus can cause problems. If you have conventional PCI slots in the system - whether you use them or not - unplug the conventional PCI cards, blow the dust out of all the slots, and reseat the cards. You should not need to do this for any PCIe card slots, but it doesn't hurt. Regards, Andy > Oh, the problem appear shortly after switching to the 3.1.9 kernel. I > also tried the 3.1.8 and 3.0.14 kernels to rule out software and there > was no effect on the problem. > David -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
