I've come into some troubles lately with my MythTV recordings. They are horribly littered with flipping graphics and garbage. It all started after I had bought a PVR500 and it wasn't working properly (snow, unable to tune channels). It took a few returns to the store to finally get one that seemed to work reasonably.

Then when MythTV started in with my recording schedule, the recordings look horrible with this random flipping video garbage (a short two meg clip to illustrate). It is sporadic within a typical 30 minute show, sometimes just a few seconds of this flipping than things go just beautifully. Other shows it's 90% garbage and only brief moments of clarity. What confuses me even more, is when I watch live tv through myth, or just mplayer directly to /dev/videoX, it is crystal clear. Just as these tests start looking like it's working, the next recording comes and it's back to the same old thing.

This is a heavily modified install of R5B7 that went from working just fine to crapping out with just merely replacing the first PVR500 I had a while ago (which recorded great, but had lots of snow on the higher US cable channels). It had the Samsung tuners and at the time that was undergoing some tweaking on the ivtv mail list, so I chalked it up to that. Since then I also bought a new PVR150, and it does the exact same things.

Then I read about issues with Hauppage cards and VIA chipsets. Well, all my computers at home just happen to be VIA based. This myth box was rather under-powered, so I took the opportunity to upgrade it's mothatboard/cpu/video card from an old Athlon 1700+ to Athlon64 3000+, nvidia chipset, etc. The computer compiles ivtv drivers remarkably fast, but it still does the same artifacts in recordings.

I have tried ivtv drivers from 0.4.3 that came with R5B7 to the latest 0.4.6. The PVR500 has the Samsung TCPN 2221P30A tuners, and the PVR150 is LG TAPE H001F MK3. I had seen a few posts of people trying other tuner options upon loading the ivtv modules, but as things view very well while watching live tv and directly reading from /dev/videoX, I'm starting to think my problem might something outside of just an ivtv-driver issue.

Any ideas where else to target my investigation? I've been holding off a complete reinstall to R5C7 or another distro (a rt2500 wireless card that needed lots of hand-holding to get started ) unless it was absolutely necessary. At this point, I'm not sure even that would work.

Thanks.

Can you check the signal with another player (STB, etc..) to see if it's a crappy signal? I didn't watch your movie, but from the description it sounds like digital artifacts. Could be poor reception. Caused by leaves on the trees, weather, bad cable, wet cable, transmission problems, too many splitters, bad amp, no amp, too much amp, etc.. Can happen with cable as well as OTA, but with cable TV it'll usually affect some stations and not others.

As best I can tell, it is a good signal when plugging directly into the tv, tivo, etc. The signal comes from the street, split 3 ways into my house. I then split it 3 ways to the two cards and the tv. I have tried it without this internal splitter, but had the same results.

After plenty more messing around today, I had gotten a couple times for it to do this behavior while playing directly into "mplayer /dev/videoX". During this time, mplayer complains that my system is too slow to play the stream and offers a few suggestions. Unfortunately, it doesn't appear to be anything I can force it to do myself, other than have Myth start a recording. Going through my last couple days of recordings, every show has some of these artifacts. But then I can watch live tv in Myth, even two tuners with picture-in-picture, and they look just perfect when I try and put the system under more of a load.

The behavior isn't like simple blocky artifacts I've seen before, but bits of the picture are appearing shifted vertically from where they're supposed to be every few frams to give it a blinking sort of effect. Sometimes the audio will skip a syllable during this. It usually corrects within 10 seconds, but a few times it kept on flipping like this and eventually the audio gets completely out of sync with the rest of the show. For instance, on the news channels with the crawler along the bottom, it will flash like this along the top of the screen. Might it be a tuning issue, a few hertz off? I may play with that later. I haven't gone out and gotten an amplifier yet, as it has been restricted to these Hauppage MPEG tuner cards. I can still use my antique WinTV bttv card, but buying all this equipment was to get away from it...

Are you recording digital or analog?
In my case, plugging the cable into the (analog) Tivo has no bearing on whether I'll see a decent (digital) picture when I plug it into my PCHD5000.

If you are seeing digital artifiacts on an analog recording, then it's something internal, and not as I suspected, a weak digital signal.

It is just analog recording of standard cable, nothing fancy here.

Hi,

Since you have another computer, have you tried to use vlc and play a recording from the pretty folder? It may be a way of checking to see if the recording is ok and only a play back issue.

Mike

It is recording with these problems. The file linked in the first post is a brief sample from the mpeg on the myth box.

You're effectively splitting the signal 6 times. I think maybe you're expecting too much for that
Hauppauge card to pick up a decent signal after it's been split 6 times.

Can someone remind me again the dB loss amount each time a coax cable is split? Shouldn't splitting
the signal 6 times basically just destroy any decent signal?


EDIT: Changed from 9 times to 6 times in first parag.

Shplad

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Well the ones I've got handy all say at least 3.5dB per tap, and 6 splits is really out there around the point where you need a signal amp. Especially if it's already split before it comes into the house, or if the runs past any of the splits are long, or if the splits are cascading. Searching for "n-way splitter" should find the last detailed discussion of this. A couple back before that we had EE with RF experience in the discussion.

Hi,
A typical 3db loss is a cut by 1/2 of the signal, for each 10 db (pwr) you take off a zero.. ~100 mw in, 3db split = 2 x 50 mw signals.

It doesn't take much to loose signal, each connection, piece of cable, splitter and you could reduce the level significantly.

The video doesn't look like weak signal, I have been able to record a blizzard and it stayed locked. Appears more to be interferance or the vertical hold (that was a knob to adjust in a previous life)

Mike

The outside splitter has it's connections labelled 7db, 7db, and 3.5db. I am using one of the 7s into the cards. And I have tried it without the internal 3-way splitter also, 7db directly to the card, with the same effects on my recordings. So I doubted it was merely a weak signal issue.

Well, I may have found a part of the problem here. First, I read the wiki page about firmware and started looking around my install CD. Comparing md5 sums, ivtv was using the file HcwMakoB.ROM for the encoder firmware. There was another file named HcwMakoC.ROM that was just a couple kb bigger. I dropped it in place as the encoder firmware, and that helped significantly. Recordings went from 80-90% jumbled down to a minor flipping here and there.

Thinking more about how I saw a fine picture on LiveTV and crappy picture on recordings, I browsed the recording profiles. Many months ago I read people's stories on saving drive space and lowered their bitrates. So I had set the "Default" profile like they mentioned, 2200 bitrate and smaller resolution (352x480 or so I think). But LiveTV was still at the old high bitrate, 6000 and 720x480. I cranked default back up to the same values and it looks great now. I will have to mess around a bit more to see how low I can go and maintain some reasonable quality.

What's puzzled me the most with this issue was how things were just fine back in the beginning, before I upgraded my equipment. I had a bttv card (still works like a champ) and a PVR 150. But then the coax connector popped off during a move, so I decided to move up to the PVR 500 and another 150 to replace the bttv card. So while the low bitrates worked just fine for that first 150, they had been misbehaving badly with newer manufactured cards.

To get the latest recommended firmware follow steps 5-7 from the (recently updated) ivtv driver upgrade instructions here - http://www.knoppmythwiki.org/index.php?page=CompileIvtv