Hi,
I'm using a HDHomeRun to watch HD content.
Sometimes I have a problem with the recordings. (I don't use LiveTV at all, I can't say if it occurs with LiveTV or not).
When the problem occurs, the image pixelates and frames are dropped.
The picture can be a little bit pixelated (with no dropped frames) up to very pixelated (with lots of dropped frames) which makes the recording unwatchable!

The first thing I thought was a bad signal. I plugged my HDHomeRun on my Mac with EyeTV Software to monitor the signal. I watch TV on it for one hour and the signal strength, quality never went lower than 85%.

Then I thought it could be the hard drive in my MythBox. It's a WD 320 GB with 8 MB cache ATA133 with default filesystem (not jfs or xfs). Sometimes I can hear it working a lot. I have a SATA hard drive 500GB I could only use for HD Recording.


The last thing which could make this problem would be a network bottleneck. For example, when I tried to look at HD content via WiFi g even I'm closed to the router, I have lots for dropped frames.

I don't use my network a lot, but I'm searching for a solution everywhere.
This is my network config.



The router and the first desktop are in a room. Dlink Dss5 and the 2nd desktop are in another room (45 ft from the router), then 3Com,MythBox and HdHomeRun are in another room as well. Maybe the 3Com Hub can be the problem, doesn't it?


This is my mythbox specs:
Athlon64 X2 4600+
Corsair 2 GB RAM dual channel.
M2N-PV
I'm using the onboard GPU 6150 (DVI->HDMI) @ 1920x1080. (My TV says it's 1080p)
Knoppmyth R5F27.

Any advice?

zetoune
Signal quality meters are a good term to use because they do not measure signal strength. They are suppose to measure the amount of packets received that have arrived undamaged. These signal meters are not calibrated to anything so they are just relative to the type of card you are measuring. My experience with the HDHomeRun has been that if you drop below 90% you could be in a low signal condition. About 6 months ago I installed a 20 dB variable antinuator to a 4way splitter that had attached one HDHR and two pcHD3000 attached.

Antinuator ..................................... HDHR...............pcHD3000......Picture
No antinuation ................................100%.................92%.............Good
Some antinuation.............................100%................. 78%.............Good
To the point of picture problems......90%..................65%..............Problems

All four tuners seem to take a nose dive at the same levels of antinuation. Both HDHR channels and both pcHD3000's produced identical results.

With the pcHD3000's nomater how high I crank up the dB's with a good quality signal I have never seen a reading higher that 95%.

Where are you getting your signal from/ OTA or cable.

TVBox

_________________
TVBox
LinHES R8.6.1

Hi TVBox,

How can I monitor the signal quality on my mythbox? I looked for a such software to help me to fix this issue. I would like to monitor it for one week with a graph.. It will be helpful.

I'm getting the signal from OTA with an indoor antenna. (Terk HDTVa).
I'm located at less than 2km from the source.

BTW: I can see a difference in the power of my HDTV tuner signal. It's stronger than the HDHomeRun.

zetoune
I need more information. 2KM from source and a amplified antenna my first guess is that you are overdriving your tuner. It only takes one overdriving channel to send turmoil threw the entire system. Can you describe your antenna layout using this format below. Adapt information to reflect your setup.

Terk HDTVa .............Amplifier Gain:...... 12 dB
Cable length antenna to Terk power injector? ...............Cable type RG-59 or RG-6
Terk power injector
Cable length Terk power to Splitter ? ...............Cable type RG-59 or RG-6
Splitter Type ...............2 way, 3 way, 4 way
Cable length splitter to HDHR tuner?...............Cable type RG-59 or RG-6
Cable length splitter to Other tuners?...............Cable type RG-59 or RG-6

What kind of ends are you using on your cables?
Do all of your stations come from one tower 2KM away?
list what channel are you receiving and distance from tower?
What kind of siding do you have on your house?
Where are you located? kilometers and ATSC I am guessing you live North of my domicile.

TVBox

_________________
TVBox
LinHES R8.6.1

I'm gonna try to answer as best as I can.

My antenna is plugged into the HDHomeRun without any splitter. I'm using Tuner1 of the HDHR.

Terk HDTVa .............Amplifier Gain:...... 12 dB
Cable length antenna to Terk power injector? Cable type RG-59 - between 3 and 4 feet.

Terk power injector
Cable length Terk power to HDHR tuner? Cable type RG-59, around 3 inches.

What kind of ends are you using on your cables? The ends are the standard ones which came with the antenna (look at the picture at the end).
Do all of your stations come from one tower 2KM away? No, two different towers but there are closed.

list what channel are you receiving and distance from tower?
CBFT-DT , 4 km
CBMT-DT , 4 km
CFJP-DT, 4 Km







What kind of siding do you have on your house? Wood, Gypse
Where are you located? kilometers and ATSC I am guessing you live North of my domicile. You right... Montreal, Canada

My antenna is next to a window, but it lays on a little table and an air-heater which are both made of iron. Can this iron make some interferences?

Picture of my antenna

zetoune
Thanks for the good information.
With transmitters that close I think your are severely overdriving (signal to strong) your preamp in your Terk antenna and the first stage amplifiers in you tuner.

As a test could you make a low gain antenna? Strip the center core out of a piece of coax. What I want is the single copper wire in the center with the insulation on it (remove all shielding). Cut this wire 15 centimeters long and strip the insulation off of one end 1 centimeter. Make a 90 degree bend so it looks like a antenna on a wifi router and plug it into one of your coax inputs on your HDHR.

Can you post back your signal quality results like this.
CBFT-DT Ch 19 ???%
CBMT-DT Ch 20 ???%
CFJP-DT Ch 42 ???%

On my HDHR using this antenna (in good weather) I could receive two UHF digital station 48 kilometer (30 miles) away with a 75% signal quality. The receiver locked in but i did experience pixeling every once in a while but it did not lose the lock.

To monitor TV signal while watching TV use F7 for R27 and Alt-F7 for R5.5 . Change channels like normal.

To switch tuners while Watching TV use the menu and select Switch Input

TVBox

_________________
TVBox
LinHES R8.6.1

TV Signal with Power Injector On and Terk antenna:
CBFT-DT Ch 19 100%
CFJP-DT Ch 42 100%

TV Signal with Power Injector Off and Terk antenna:
CBFT-DT Ch 19 80%
CFJP-DT Ch 42 95%

TV Signal with your low gain antenna:
CBFT-DT Ch 19 67% (no picture)
CFJP-DT Ch 42 92%

TV Signal with Terk Antenna without Power Injector:
CBFT-DT Ch 19 40% (no picture)
CFJP-DT Ch 42 53% (no picture)

Is it possible to create a script which would be launched before each recording to monitor the signal during it's recording?

CBMT-DT is temporary offline.

Good using the low gain antenna schedule a half dozen recordings on CFJP-DT Ch 42 92% over a 24 hour period and see if you problems go away.

TVBox

_________________
TVBox
LinHES R8.6.1

Actually, all the recordings I scheduled in the past was on the other channel.
I never recorded on this channel, but I can test it with my antenna and the power injector to see if the problem occurs on this channel as well, then test it with the low gain antenna.

Do you think I should activate the second tuner and record on both tuners with the both antennas.

Disconnect all antennas except one low gain antenna and move it to whatever tuner you are currently using to record from. We are trying to run a test to see whether your signal input is to high. In my experience for every 100 OTA antenna systems that have problems 90 of them are from to high of signal. Signal problems that you (and your TV) can tolerate while you are watching a channel will cause problems when it is turned into a recording. Strong pixeling even once during a recording can create a file that is unreadable. In multiple tuners I have seen overload bleed into the other tuner and cause problems. It dos not make any difference whether you are tuned to the overload channel or not. Your problems could be a higher power analog broadcast from one of those two towers or any other form of transmitter like a cellphone tower.

One of the things that raise a red flag for me is that you have a 12 dB pre-amp in your Terk antenna system. Removing the power injector dos not take the pre-amp out of your system. Pre-amps in a antenna system can not make a bad signal good they are only usefully to make up for coax cable and splitter losses. 12 db would equal about 100 feet of RG-6 coax and a 4 way splitter, nether of which you have at this time.

Antenna pre-amp do not selectively amplify your signal only in the areas that you need it, they amplify everything across the board whether you need it or not. If at any time at any frequency the signal strength exceeds the maximum output of the amplifiers that pre-amp will produce distortion across the entire frequency output. Your close proximity to two transmitter towers is what raises the second red flag.

It is possible to create a script but I am not aware of one that functions at this time.

I can give you another antenna to make. How much coax do you have laying around? is it copper braid, aluminum braid or aluminum foil?

TVBox

_________________
TVBox
LinHES R8.6.1

I did one by my own with no pre-amp. You can take a look. I did have strong pixeling with it that's why I changed it for the Terk Antenna.

I have one 2 feet-long cable left but I can sacrifice another one (3 feet long)! I'm ready to create another antenna.

It seems to be aluminium foil

I think I found the problem. I have to investigate a little bit more. I will update soon.

I see their is a is at least one more antenna experimenter. Is there any Canadian websites like www.antennaweb.org , www.tvfool.com, or www.antennapoint.com . Just FYI if you are close to the border www.antennapoint.com will accept Canadian addresses to locate US TV stations.

When the digital stations started up in my area most where not broadcasting from there main analog tower location. I am guessing that is the case with your DTV stations. I would give the stations a call and ask to speak to one of the engineers and ask them where their DTV tower is located.

TVBox

_________________
TVBox
LinHES R8.6.1

thank you for the links.

But it seems the problem didn't come from a bad reception or a signal which was too much strong.

First I moved all my recordings (with Storage Group) to a new SATA drive formatted with xfs. it didn't change anything.

According to rrd, the network bandwidth is around 2.5 MB/s when I record an HD program. The total bandwidth on my local network is around 6 MB/s. Once again, the lan bandwidth doesn't seem to be the problem.

So I started to make some tests with the low gain antenna to find a position where I could get the better signal. After finding it, I started to record several short programs. It worked flawlessly. I switched back the antenna to my Terk antenna. I started new recordings and it also worked very well.
Then, I started two HD recordings in the same time + one CD ripping + streaming MP3 with firefly server. Ten minutes after, my mythbox shut down.
I went to Bios to see what temperature my CPU was! 96°C ... VERY hot..
There was a problem in the wire of the fan. Sometimes the fan worked, sometime it didn't.

Since I've changed it, the CPU stays at 45°C and I haven't noticed any pixels in recordings yet.

I'm gonna make more recordings and update this thread whether it works or not!

Ah, sounds like thermal throttling, either by the CPU core itself, or by the Northbridge or BIOS. At 96C I'm surprised that the CPU wasn't damaged. If you're not already using RRD or the like to monitor your system health it might be a good thing to enable.