Distorted Cable TV Images?

[BradyB]

Hi All,

I built my first HTPC using Intel i3 with HD3000 graphics. TV is coming from SiliconDust HD Homerun Prime. PC is connected to a projector via HDMI cable, and to sound system with optical connector. HTPC and Homerun Prime are connected w/ gigabit Ethernet.

Everything (Blu-ray, Netflix, HD home video) runs perfect except for the Cable TV. I occasionally get distorted images. I am trying to share a screen shot here:

http://hdvideo.shutterfly.com/pictures/9

Any idea what causes this?

Thanks,
BradyB

[Scallica]

What firmware are you running on the HDHR?

[barnabas1969]

Looks like a signal strength/quality issue to me. Have you checked those on the HDHR Prime's web page?

You'll want to be watching a channel that has this problem, then look at the web page to see the signal strength and quality for the tuner that is in use. Ideally, you want your SNR (Signal to Noise Ratio, a measure of signal quality) to be 35 or higher, and signal strength should be as close to 0 as possible, but not less than -7 nor higher than +7.

The signal strength/quality varies by frequency, so you may want to try various channels. Make sure to refresh the page between channel changes.

[mcewinter]

I would check your cabling and perhpas your signal. If that's all tip top then I would check and most likely disable network throttling.

http://www.silicondust.com/hdhomerun/hd ... ooting.pdf

You can always ask for help on their forums and they can help you determine if you have a weak signal or network packet loss.

http://www.silicondust.com/forum/viewtopic.php?t=5877

[BradyB]

Hi All,

Thanks for the suggestions. I did a little testing tonight.

During the test, things were working great; the picture never distorted. AND THEN... I turned on the XBox extender, and tuned it to an HD channel. The picture on the primary HTPC started breaking up.

The firmware version is 20120405.

I could not find the Signal to Noise information, and the Signal Strength was stated in percentage. The only thing I know to use is the HDHR Config Utility.

Signal Strength hovered around 92%, Signal Quality stayed around 100%, and would occasionally dip to low 90's, but it did not stay there long at all. Symbol Quality stayed around 100%

Here is the network config:
Cable modem -> Linksys E3000 Wireless N router.
Linksys E3000 -> Linksys SE2500 gigabit switch. The primary HTPC and the HDHR are hardwired to the gigabit switch.
Linksys SE2500 -> Linksys WRT54G Wireless G router. The Xbox 360 is hardwired to the WRT54G router.

We also have a secondary HTPC that is hardwired to the Linksys E3000 router.


Thanks a bunch. Your input is greatly appreciated.

Brady

[barnabas1969]

It sounds like you may have some kind of network congestion that is causing the problem, but first, let's look at the signal levels.

While you are watching a channel that exhibits this problem, do the following:

First, open the HD HomeRun Config GUI program. Click on the "Device" tab, then click on one of the tuners listed in the left pane. It looks like this:

Next, click the link next to "Device webpage". Mine says 192.168.1.121. Yours will probably have a different IP address. When you click it, a web page will open in your browser.

You'll want to click on the link that says "Status Menu". That will take you to a page that lists all three tuners. You can click on each of the three tuners to display more information. The information displayed looks like the picture below. You can see the percentage, with a value in parenthesis. Post back here with the values shown when the problem occurs (you'll need to refresh the page by pressing F5 in order to see the values changing when/if the problem occurs).

2.jpg (47.65 KiB) Viewed 2789 times

[BradyB]

I was able to get some numbers tonight.

Ch 947
Signal Strength -2.6 dBmV
Signal Quality 35.8 dB

Ch 951
Signal Strength -4.5 dBmv
Signal Quality 35.2dB


After turning on the XBox extender, the numbers stayed pretty much the same.

The picture distortion lasts less than a second. It is difficult to hit the refresh button at the exact time.

Thanks again for your help.

Brady

[barnabas1969]

Those numbers look very good. The next thing to start looking at is your network.

First, try disabling Network Throttling. You need to change this in the registry editor. Make sure to make a backup of your registry (or even better, make a system image) before you start, just in case you make a mistake and mess up something.

You'll want to change the value in the registry key located in:

Code: Select all

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\NetworkThrottlingIndex

to FFFFFFFF

For more information, see this Microsoft Knowledge Base article:
http://support.microsoft.com/kb/948066

If turning off Network Throttling doesn't help, the next step I would recommend is to try to reduce the number of "hops" between your XBox and your Media Center PC. You have more than one switches and routers between the two. It's best to have only one device between them. The same is true for your HD Home Run Prime tuner.

There are other settings to play with, but let's start here.

[BradyB]

Thanks for the info.

I set the network throttling index this morning.

We'll see how this looks.

Thanks for your input,
Brady

[BradyB]

Adjusting the throttling did no seem to work.

I have an very old HTPC in the kitchen and a brand new HTPC in theater room (both running Win7).

I ended up associating the XBox to the old HTPC and it works like a champ.

The old HTPC has on board 100mbs nic vs 1 gigabit on the new machine.

[barnabas1969]

First, make sure flow control is turned on in your Network Interface (NIC) properties on the PC.

If that doesn't work, then your problem is in one of your network switches. Some switches cannot convert from gigabit to 100Mbps very well (the extender runs at 100Mbps). It has partly to do with the size of the buffer in the switch. A 1 megabit buffer in the switch seems to work fine.

If all else fails, you could try setting your NIC to 100Mpbs, full-duplex. That should fix your problem with the switch. However, 100Mbps will only work well for you if you NEVER use more than 3 network-tuners simultaneously, AND you NEVER use more than 3 extenders simultaneously.

The reason for this is at 100Mbps, running 3 tuners simultaneously will put you between 45-60% network utilization. When you get into 70-80% network utilization, things can get dicey. The same goes in the other direction... if you run more than 3 extenders over 100Mbps network, you will be in the same situation. You should be able to do both at the same time, and that's fine (that's what full-duplex means).

But... my recommendation is to reduce the number of network switches between the PC and the extender(s)... and to get a better switch with a larger buffer.

[BradyB]

I have a gigabit switch in the theater room, connecting the HTPC, HDHR Prime, and of course the Internet.

One wire from the gigabit switch runs upstairs to the living roop to a Linksys WRT54G Wireless G router.

An Xbox, blu-ray player, and a WDTV LIve device are hanging off the WTR-54G.

I bet the primary cause is the WTR-54G. I will get around to replacing it one of these days.

Thanks again for all your help.

[barnabas1969]

I would tend to agree. The WRT-54G isn't just a switch. The traffic going through the LAN ports, even when just switched between them, still gets processed by the software in the router. A normal network switch does this all at the hardware layer, and is faster.

I have several of the switches listed below, and they work great. You can pick one up at NewEgg for less than $35 including shipping. Here's a link:
http://www.newegg.com/Product/Product.a ... 6833320047