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OTA plays great but records pixelated


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11 replies to this topic

#1 OFFLINE   rjnorman2

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Posted 07 March 2011 - 02:07 PM

Hi,
We have a VIP722K DVR. The tech just installed a converter so we could get the local channels with our new outside antenna for over the air local channels.
The local channels have good strength and look great while watching them. When we record them they are pixelated and choppy. I have watched a program live while recording it and it plays great yet the recording is terrible.
Any ideas?
Thanks

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#2 OFFLINE   AlbuquerqueJohn

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Posted 16 March 2011 - 11:56 AM

Multipath? Just a thought.

http://www.cisco.com...08019f646.shtml

In order to understand diversity, you must understand multipath distortion.

When a radio frequency (RF) signal is transmitted towards the receiver, the general behavior of the RF signal is to grow wider as it is transmitted further. On its way, the RF signal encounters objects that reflect, refract, diffract or interfere with the signal. When an RF signal is reflected off an object, multiple wavefronts are created. As a result of these new duplicate wavefronts, there are multiple wavefronts that reach the receiver.

Multipath propagation occurs when RF signals take different paths from a source to a destination. A part of the signal goes to the destination while another part bounces off an obstruction, then goes on to the destination. As a result, part of the signal encounters delay and travels a longer path to the destination.

Multipath can be defined as the combination of the original signal plus the duplicate wave fronts that result from reflection of the waves off obstacles between the transmitter and the receiver.

Multipath distortion is a form of RF interference that occurs when a radio signal has more than one path between the receiver and the transmitter. This occurs in cells with metallic or other RF-reflective surfaces, such as furniture, walls, or coated glass.

More via above link.

#3 OFFLINE   TulsaOK

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Posted 16 March 2011 - 12:03 PM

Have you watched the program delayed? IOW, not recording but watching from the buffer?
I believe multipath would also affect the live broadcast, not just the recording.
<span style='font-size: 10px;'>“Life is hard; it's harder if you're stupid.”<br /> - John Wayne</span><br /><br />Avatar: Tanner 1992 - 2009

#4 OFFLINE   rjnorman2

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Posted 16 March 2011 - 02:34 PM

I can watch the program live with ho problems. Picture and sound is excellent. I can't use the buffer (which I assume is the pause button) as anything that plays back is pixelated and choppy.
I am not a technical guy in this field and would appreciate any help anyone can offer.

#5 OFFLINE   Stewart Vernon

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Posted 16 March 2011 - 02:48 PM

Are you having problems on SAT channels too?

This is starting to sound like a hard drive problem.

-- Respect the S.H.I.E.L.D.


#6 OFFLINE   rjnorman2

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Posted 17 March 2011 - 11:56 AM

No problems at all with the SAT channels, just when we try to record an OTA broadcast. Signal strength is about 73% on the OTA. Plays perfect when you watch it live. Can't pause and playback on the OTA but no problems with the SAT
Thanks

#7 OFFLINE   Stewart Vernon

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Posted 18 March 2011 - 12:01 AM

Ok...

Theory #2...

I have a 922, which is very much like a 722K with extra stuff... and they share the same OTA tuner module.

I have told Dish repeatedly about a problem with OTA channels... where if I tune from a SAT channel OR especially from a lower-signal level OTA, I find my OTA tuner is either not locking OR locking at a lower than available strength.

Example...

Channel 5-01 comes in nearly 100 all the time.
Channel 11-01 comes in nearly 80 all the time.

Both are typically solid at those levels when they lock...

BUT...

If I change directly from 11-01 to 5-01... I find that 5-01 will breakup and lock at 80 instead of 100... and I have to actually tune to another channel and then back again to lock at the best available signal.

Obviously this isn't something you can do with a timer... because it will change once and lock to whatever it gets.

It looks to me like the OTA tuner is somehow not completely releasing frequencies when it tunes to another OR the firmware is doing something very funky on channel changes... Either way, I find some glitches from time to time in recordings that wouldn't have been there if I had been able to do the workaround watching live.

In your case... if you have a lot of marginal channels... it could very well be that they too are locking at lower than possible signal levels when the timer fires, and then the recording is even more glitchy than mine.

I think there are also issues when using both OTA tuners at the same time where a glitch on one can cause a glitch on the other... but I haven't been able to verify that.

Take a look at all of your OTA channels and their signal levels when you tune to them... then try changing back and forth between some of the higher-signal ones and see if you ever get better signal locks doing that.

IF so... then you could be experiencing something similar to what I've seen on my 922.

-- Respect the S.H.I.E.L.D.


#8 OFFLINE   TulsaOK

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Posted 18 March 2011 - 10:39 AM

I still don't understand the "live" vs. "buffered/recorded" issue. I've noticed the slow lock on my local Fox OTA (5.01) on my 722k. It locks in the low 70's then after a while goes into the mid to upper 90's signal strength. But, live or buffered it exhibits the same behavior.
OP's problem is very puzzling.
<span style='font-size: 10px;'>“Life is hard; it's harder if you're stupid.”<br /> - John Wayne</span><br /><br />Avatar: Tanner 1992 - 2009

#9 OFFLINE   rjnorman2

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Posted 19 March 2011 - 10:27 AM

The installer (really good private guy not from Dish) came out and tried a few things but still having the same problems. He talked with the wizards from Dish on the phone and they had no idea. They finally said that we were probably too far from the transmitter where the local channels are broadcast from. We have a signal strength of about 73%. No one seems to know what might be causing this. I am going to go to the local electronics store to see if they have an antenna booster that is a little stronger than the one on the OTA line now.
Hope it helps.
Thanks for all the help from people on the forum.

#10 OFFLINE   TulsaOK

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Posted 19 March 2011 - 10:32 AM

If you're getting a signal strength greater than 65 that should be enough to get a good lock. I have one station that's in the lower sixties and it's fine. If it drops below 60, it will lose (not loose) the signal.
How far are you from the broadcast towers" Not that it has anything to do with your problem.
<span style='font-size: 10px;'>“Life is hard; it's harder if you're stupid.”<br /> - John Wayne</span><br /><br />Avatar: Tanner 1992 - 2009

#11 OFFLINE   rjnorman2

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Posted 20 March 2011 - 12:03 PM

We are about 20 miles from the broadcast towers.

#12 OFFLINE   Rolf Donahower

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Posted 27 March 2011 - 03:54 PM

Same problem here. Only occurs on one OTA channel, KTVZHD NBC. Dish says signal corrupted by broadcaster. KGW going HD with TP late summer or fall. This could cure NBCHD record problem.




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