HD QAM Smooth as butter, SD QAM "Jittery"

Greetings all. I am having an unexpected road-block in my trip to all HTPC based home entertainment. I have an HDHomeRun pumping Clear QAM video out on my home network. I also have a FusionHDTV 5 RT Lite in my office machine that allows me to watch the same Clear QAM channels on that machine. On all machines that I have configured, HD QAM channels come through smooth as butter. But the video on all of the SD QAM channels vertically "shakes"..."bounces"..."jitters"...I'm not sure what to call it.

My problem is not that the video "stutters". The SD QAM video timing is perfect. I'm not losing any frames. The audio is perfectly synched. The issue is the video itself seems to jump up and down a few lines of resolution. It seems to happen more during scenes with a lot of movement. If I switch to an HD QAM channel, the video is perfect.

I have to assume that someone else has experienced this, but professor google knows nothing of it. It happens to me in Vista Media Center, VLC Media Player in Vista, and the FusionHDTV player in XP. I can't imagine that I'm having any bandwidth or processing power issues, since HD QAM works just fine. Please help...

I re-installed my old Hauppage WinTV card and analog cable SD signals do not have this issue. DVDs, Divx, and Xvid also work fine, so I do not believe I have a decoder issue.

I must be doing something wrong because I'm sure plenty of people are viewing clear QAM signals on their HTPCs; I can't be the only one that's picky enough to notice these "jitters". It makes SD QAM channels almost unwatchable to me, especially on the projector in my main media area.

I'm so close to having everything done. I've been preparing my wife for the day we give back the 2 Comcast DVRs that we pay way too much per month for. I now have HD QAM in Vista Media Center, all the displays are calibrated right, I've finished running Cat6 throughout my house so I can ditch the wireless for gigabit ethernet on everything but the laptop. The list of my finished projects goes on and on. To have come so far and to hit this little glitch with STANDARD DEFINITION is killing me!

I've also posted this in the HDHomeRum forum on SiliconDust's web site. I'll post any further information here if I find a resolution...

The admin on the HDHomeRun site suggested that the issue is caused by de-interlacing, and that I should try adjusting the de-interlacing settings in VLC to troubleshoot. Low and behold, after I turned off the de-interlacing in VLC, the video on SD QAM channels became rock solid (in VLC).

Since I didn't see any obvious settings to adjust the de-interlacing for the default VMC MPEG-2 decoder, I dug out the old Nvidia PureVideo install, downloaded the VMCD app, and switched the decoder that Vista Media Center uses to Nvidia PureVideo. Now...SD QAM channels are even more beautiful than I was hoping for, however...HD QAM channels are all out of whack - dropped frames, high CPU usage, and way over-driven colors and brightness.

So...is there any way to adjust and/or turn off the de-interlacing for the VMC built-in MPEG-2 decoder? I think that would make the most sense.

Yeah, it doesn't look like PureVideo can cut the mustard in VMC.

I get some SD QAM channels but not enough to make the PureVideo decoder the answer. My goal has always been HD QAM in VMC. I wish I could just turn off de-interlacing in VMC so the few SD QAM channels I do want to watch are tolerable.

Well, I'm still having issues. I tried different decoders, without much luck. I don't know what the deal is with HDHomeRun, Vista Media Center, and QAM SD content. IT appears to be related to the decoder as different decoders show different problems. The Cyberlink decoder actually does a similar thing but horizontally. I also tried the ATI AVIVO mpeg2 decoder, which was almost tolerable for SD QAM, worked fine for HD QAM, but won't work for DVDs. I'm feeling a little discouraged. I guess other people with HDHomeRun/VMC setups are just living with poor de-interlacing? I've tried Nvidia and ATI hardware. Not sure where to go from here. The Comcast DVR box doesn't have any problems de-interlacing SD QAM content. Can the technology in the cable box really be better than my HTPCs?

Yes, I have both SD QAM and HD QAM for local channels. The HD QAM for a local channel will be crystal clear, the SD QAM from the same channel will suffer from what I am now calling "standard def de-interlacing jitter" The SD QAM channels like Food Network aren't broadcast in clear HD QAM, so I use the SD QAM for the few cable channels that I care about.


Yeah, I noticed that. The funny thing is that so far the only way I've been able to view the MPEG2 stream from the HDHomeRun without "standard def de-interlacing jitter" is through VLC. I've been playing with VLC and I can get what I consider to be perfect SD QAM picture quality by switching VLC's de-interlacing to "Blend". Turning off de-interlacing also stabilizes the picture, but leaves horrible jaggies.

I just don't understand why this isn't a bigger issue. Am I just that picky?

If I can view the same MPEG2 stream on the exact same PC through another piece of software and it looks good, then I believe I can eliminate the source material as the cause. It must be the decoder. Still, I've used my old Hauppage analog tuner for years in XP MCE without these decoder issues.

I don't think I ever tried viewing SD QAM in XP MCE. At the time you needed an analog tuner in the machine to get Media Center to recognize the HDHomeRun, so I only used the HDHomeRun for HD QAM. I may take the time to re-install XP MCE and try SD QAM channels, just out of curiousity.

Last night I tried DScaler5, but I can't tell if VMC was actually using DScaler5. I think it was, because I've mastered the art of copying the CLSID from RadLight Filter Manager into the PreferredMPEG2VideoDecoderCLSID2. I almost kind of hope that VMC wasn't using DScaler5 as it had the same issues as the Microsoft decoder.

Also, my "standard def de-interlacing jitters" existed in VMC out of the box and after installing VMC's TV Pack 2008.

Yes, I guess technically I'm lucky in comparison to some stories I've heard of people not even receiving local channels in QAM as the cable company is required to provide unencrypted. However, since I pay for the Food Channel (111.6), me thinks that the day my local Comcast encrypts the Food Channel and makes me use a STB to watch Good Eats will probably also be the day that I connect my HDHomeRun to the big antenna in the attic and switch to OTA broadcasts!

Perhaps Comcast is way ahead of all of us and knows that SD QAM won't look right on an HTPC? Maybe they've got something in their STB that knows how to display the stream properly, because I'm pretty sure my Comcast DVRs are entirely QAM based now, based on the PQ from the STB vs. the analog signal on the old cable-ready TV in my guest bedroom.

Surely there has to be a third-party decoder out there that is VMC compatible and allows better control over de-interlacing. Whose decoder does VLC use? Why can't I buy that?


Hmmm...I'll save my comments about CableCARD for another thread. Let's just say that if the cable companies actually wanted us to use CableCARD, they wouldn't have colluded with Microsoft and OEMs to make the CableCARD tuners only available in garishly overpriced HTPCs that I could build myself for $500. OK, I'll save the rest of my comments for another thread!


I was hoping to avoid proprietary STBs or MythTV. They're not as "wife-compatible" as VMC. But the mere fact that you see the same issue in VMC (the channel logos are always the most obvious) and don't have that problem on your 'tank makes me even more determined.

OK...I was able to watch Live TV in VMC with good picture quality in both SD QAM and HD QAM, but the steps I had to take to make it happen are extremely brutal and not really feasible. I installed Media Control which allows you to actually run Live TV in VMC through ffdshow. I verified that Live TV was actually going through ffdshow by turning on the OSD in ffdshow, and the OSD showed up in Live TV.

The problem is that you can't permanently set ffdshow as the decoder. Media Control adds a new menu to VMC that you can access during playback which allows you to switch to ffdshow. VMC defaults to the regular decoder at startup. This will definitely not work in a wife and family friendly HTPC. Has anyone been able to setup ffdshow as the actual MPEG2 decoder for Live TV?

If Tru2Way cards actually become available for purchase without having to buy a ridiculously priced HTPC I will be very impressed. I would guess that the majority of the HDHomeRuns that have been sold are because of the hole that was left wide open by not allowing CableCARDs to be purchased so HD QAM could be viewed in Windows Media Center.

I'm not holding my breath though...