Whats your cpu usage while watching live tv?

Based on the details you didn't give, all we can tell is that you have the same Asus motherboard and that you aren't using KnoppMyth. Note the system specs at the bottom of my post. Give is details like that.
By the way, KnoppMyth R5B7 uses kernel 2.6.15.chw-2.

The various version of the nvidia drivers give different CPU loads so that makes a difference. Version 8756 only puts a 25% load on my CPU if I turn on XvMC during playback of HDTV! With version 8178, which can't use XvMC, my CPU load never drops below 50% when watching HDTV.

Eric

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KnoppMyth R5.5, Asus A8N-VM CSM (nvidia 6150 onboard video), AMD Athlon 64 dual-core 4200+, two 1GB sticks DDR 400, HD-3000 HDTV card, PVR-150 card, Iguanaworks RS-232 IR receiver/transmitter, Pioneer DVR-110 DVD burner

mad_paddler: CPU usage without XvMC is around 50-60%. I can't get an accurate reading with XvMC because it freezes up so often.

neutron68: My systems specs are as follows:

Case: Ahanix MCE601
PSU: Ahanix custom-size 350W (comes with case)
MB: A8N VM CSM
BIOS: 1001
RAM: 512MB DDR PC400
Tuner: pcHDTV-3000
HDD: Samsung Spinpoint 250GB
Optical: NEC 3550A DVD+-RW
SW: FC4 w/2.6.16-1.2107_FC4 kernel
SW: nVidia GFX driver version 8756

My local cable provider is Comcast, SF Bay Area

I'm getting more and more suspicious of my power, I found the following notes in the ASUS manual (p. 1-29):

- We recommend that you use an ATX 12V Specification 2.0-compliant power supply unit (PSU) with a minimum of 300W power rating. This PSU type has 24-pin and 4-pin power plugs.

- If you intend to use a PSU with 20-pin and 4-pin power plugs, make sure that the 20 pin power plug can provide at least 15 A on +12V and that the PSU has a minimum power rating of 300W. The system may become unstable or may not boot up if the power is inadequate.

[...]

- We recommend that you use a PSU with higer output when configuring a system with more power-consuming devices. The system may become unstable or may not boot up if the power is inadequate.

- You must install a PSU with a higher power rating if you intend to install additional devices.


It sounds like I'm right at the edge of the specs. My PSU says 350W, but also 15A on +12, so it's already maxed out there. Plus I've got "other devices" connected -- the HD seems to be around 10 watts, I can't find anything about either the optical drive or the pcHDTV card itself. Then there are the fans and VFD on the parallel port.

Anyway, let me know what sort of power supplies you guys are using, or if you see any other gotchas with my setup. Thanks again. I'm still thinking it's a power issue, not a software issue, but I'll probably throw a different HD in there and try installing KnoppMyth.

-Joel

I'm using a 270W PSU in my units. It has a 24 pin plus 4 pin plug, and so far no power issues. Usually running an optical drive, IDE HD, and a dual tuner PVR500.

Standard case + PSU fans, and an LCD unit.

Doesn't sound like a power issue with the PSU you are using.

Any chance the unit is getting too hot.

Also how good is your HD signal. If your signal is garbage then you will have playback problems. Check your logs in /home/mythtv/.xsession-errors and /var/log/mythtv/mythbackend.log.

I've found the best video setting for some stuff is libmpeg2 with OpenGL sync set to off.

Steve

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OpenMedia Limited
New Zealands first open source PVR based on Knoppmyth
http://www.openmedia.co.nz for details

Have you got a spare beefy power supply in another PC? you could hook it up and leave it hanging out the case just for testing purposes.

I would definitely recomend installing knoppmyth on a different hard disk, at least then we're all on the same level.

Unfortunately I am in the UK so can't really say how well mine copes with HDTV, but watching DVB uses very little CPU (Athlon 64 3200+, 512mb ddr)

I will be taking all of your suggestions. I don't have a spare beefy power supply, but I did poke around the equiment graveyard at my office. An old PC that I'd recently dropped off there was a dual-CPU machine that had a ton of disk drives in it, on-board graphics, assorted other stuff, and it only had a 330W supply. So yeah, I'm sort of thinking at the moment that it isn't the quantity of power, but rather perhaps the quality, or the electrical noise in the enclosure. That said, I may stop at the local geek shop on the way home and pick one up just to try it out (assuming I can return it with little or no cost).

I also thought it might be a grounding issue, since I live in an older house (at least by US standards -- 60 years old) and grounding is spotty at best. I tried running an extension cord from my TV room to the bathroom, which I know is grounded because I rewired it myself. Didn't makeany noticeable difference.

As for quality of the input signal, MythTV reports 95-100% signal strength, 4.8db S/N ratio. 95-100% strength sounds like it's pretty good, but I don't know what range the S/N ratio should be in, 4.8db actually sounds kinda low, what are you guys seeing? I also sent an email to support@pchdtv.com to see if their newest card, the 5500, is as susceptible to noise and power issues as the 3000 is alleged to be, but I haven't heard back yet.

I also tried an experiment, using "azap" -- I tuned to a channel, watched the output for a while, the strength was "ffff", which I assume means 100%, and then I just started dragging windows around in the X display, to tax the graphics card and CPU a little. Signal quality dropped to f8xx or sometimes e8xx. So, activity in other areas of the system does seem to have a big effect on this card. Maybe I should try underclocking, too.

And, I've now got a Knoppmyth CD ready, and I know I've got a spare disk lying around somewhere. I wish I could feel more confident about just installing it on a separate partition on my FC4 machine, but it looks like KnoppMyth uses lilo, whereas FC4 uses Grub, and I've already been down the twisty maze of making my FC4 be a dual boot system, it all just seems like trouble. So, I'll just try a different HD altogether. I'll make it IDE, too (existing one is SATA), which might let me run the auto-installer, too.

Thanks again for all your suggestions, I hope I can get this sorted out soon, I'm ready for my beer and my armchair. This business of a computer with its guts spilling out on my floor is getting old

-Joel

Very interesting that the signal drops when you move windows around, not much more i can suggest atm

Sigh. Beefy power supply made no difference, though it might not have been beefy enough -- it says 500W, but then comparing to what's in the MCE601 case, I discovered that it really wasn't that different - it's just got an extra 12V rail, but I've got nothing to connect it to. Still I was able to put the power supply outside the case, possibly reducing EMI interference, but that didn't help.

I also started down the road of installing KnoppMyth, but ran into trouble immediately with not having any network connectivity. I started re-reading this thread, and it looks like there's a non-trivial amount of tweaking and rebuilding I have to do even with KnoppMyth. So, I've temporarily suspended that effort.

I also read that it's possible to have too strong a signal, so I tried sticking a couple of splitters in the way, beyond the one three-way that's already there, so that means the signal goes through a 3-way, and then two 2-ways. Didn't really see any difference, nor any difference in the signal strength numbers MythTV is reporting.

One other thing I thought of, on the grounding issue -- the MCE601 case is designed for a full ATX motherboard, and the A8N-VM CSM is a microATX motherboard. Because Ahanix didn't put posts in place for both types, and because the bolt patterns for the Micro ATX aren't a proper subset of those for the full size ATX, I actually have a couple of bolt holes that aren't bolted to anything, and both of them are near the pcHDTV card. I wonder if that's causing additional trouble. I can try just bolting them to a grounding wire that's bolted to a nearby grounded bolt, but I think I'm really going out on a limb here.

I still haven't heard a peep from the pcHDTV people, I think I'll try again tomorrow. Thanks for listening.

-Joel

What bios version do you have? I had network issues until i updated it to 1001

mad_paddler: I'm using BIOS 1001, but it's possible that as I was putting in the second disk drive to try out KnoppMyth on, I jostled a cable somewhere (my cable modem and wifi router are all in the same cabinet as my stereo and mythbox) and interrupted my network that way. I didn't think to try network access from elsewhere on my network.

Anyway, last night I *finally* got to see some live TV without appreciable signal degradation. But, it came at quite a cost. I figured that since people had been talking about interference from other devices on the motherboard, power supply noise, etc., I'd try moving my mythbox away from all the other electronic clutter. I just pulled it out of the cabinet, stretched the cables as far as they would let me go, and voila! I could watch TV. However, my machine was still running in a crippled mode, because I'd tweaked a bunch of BIOS settings to try to cut down on the noise. So, feeling brave, I turned all the BIOS settings back to their nominal values and restarted and to my dismay, I was back to watching crap.

But, at least I'd seen the light, so I went through each BIOS setting, one at a time, writing them down as I went, hoping that there'd be just one I needed to achieve success. I marched down the list, and finally got back to where I was, but as I watched, I noticed that I appeared to be losing frames quite regularly. That is, my TV was drawing beautiful, smoothly moving images, whereas MythTV was drawing them noticeably less frequently. The sound was fine, and it wasn't intolerable, but something was definitely not right. So, I opened up another window on the machine, and ran "top". To my horror, my machine was pretty much tapped out, running between 80-90% on HDTV content. All those BIOS settings I'd tweaked were basically all down-revving the processor speed, and now I was paying the price.

So, my adventure for tonight is to start turning the performance back up, hoping that there's maybe some combination of BIOS settings that works. Otherwise I'll be building a Stuart Little sized Faraday cage for that *!&^#@$! pcHDTV card.

Oh, here's the list of BIOS settings I tweaked, in order:

Step 1: HyperTransport NForce config from 800->200MHz
Step 2: AI Overclocking from Auto to 200
Step 3: LDT to Geforce(NB) Frequency: 200
Step 4: DRAM ECC Enable: false
Step 5: Down spread spectrum (was center spread)
Step 6: Northbridge memclk mode limit 100MHz - THIS ONE DID THE TRICK!

I couldn't tell if any of these individually made any improvements as I watched, it was the last one that really changed everything, so I'll be starting over tonight from Step 1 turning stuff back on.

-Joel

Don't hold your breath waiting for the HD-3000 card people to respond. I've never received any response to any communications - after I sent them my order and money.

I put my Asus A8N-VM CSM board into an Aspire mini-ATX case - with metal sides rather than the trendy plexi-glass sides. (Plexi-glass sides look cool, but they are window for RF. So if you need RF shielding, use a pc case with a metal panels and no-plexiglass.)

The Aspire case has a 24-pin 450W ATX supply in it. I'm not having problems. I'm using an outside antenna for my tv reception - and quad shielded RG-6 coax. So, the incoming signals are sheilded by the antenna distance AND the shielded coax.

I'm also running XvMC with tv playback. It helps reduce the processor load and smooth out your images too. The nvidia 1.0-8756 driver is necessary for XvMC to function with the Asus A8N-VM CSM board.

I wonder how close your receiving antenna is to your equipment cluster?

Are you using coax cable from antenna to the card?

I wonder if your HD-3000 card has a shielding problem - thus letting in EMI into the tuner enclosure? Got a friend with an HD-3000 card you could do a swap test with?

Last thought:
Do you have any kind of power line filtering you could put into your system?
Many of the better UPS units (like the APC brand) have some power line filtering inside them for keeping RF from getting put onto the power line by your pc and for keeping RF already on the power line from getting into your pc.
I'm running my Mythtv box on an APC XS-1000 ups, which has some power filtering in it.

Good luck,
Eric

_________________
KnoppMyth R5.5, Asus A8N-VM CSM (nvidia 6150 onboard video), AMD Athlon 64 dual-core 4200+, two 1GB sticks DDR 400, HD-3000 HDTV card, PVR-150 card, Iguanaworks RS-232 IR receiver/transmitter, Pioneer DVR-110 DVD burner