HDMI over cat5 sync problems - AVS Forum
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post #1 of 8 Old 10-26-2011, 02:10 PM - Thread Starter
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Hi, i have been having a strange issue with a tv signal problem sent over cat5. I think it may be useful for some of to read some of my findings & problems.

I am currently using a HDMI signal running over an old HDMI over2 cat5e cables. As far as i remember, this converter could output a max 1080i signal. I have tried an DVD player (i have lowered the resolution to 720p, and even lower to test), a SKY satellite receiver, as well as a Denon 3312 Amp(newest model which supports HDMI 1.4). Normally, all my devices plug into the amp which upconverts the signal to a resolution of my liking into the HDMI-CAT5 adaptor, where cables run about 10-15 metres to the roof deck, where a Plasma tv sits.

The problem starts after around 10 minutes.......the Plasma (which uses DVI, so i have a DVI-HDMI adaptor), loses the signal, therefore it shows "No signal" until i turn off the source (eg DVD, SKy box etc). I tested with a small lcd TV and around 10 mins when i first play my source, i see a flash on the screen where the signal changes (the screen goes dark for a second) but the image comes back after a second. Therefore, it seems the lcd recovers from the signal change but the plasma doesnt.

2 reasons that i can think of:

1) the HDMI-cat5 adaptor is near the back of the AV rack which has all my equipment may be getting ElectroMagnetic Interference (EMI), although the same adaptor has been used for 2 years (although the Denon amp is new, replacing an older Denon 2008 model amp). The roofdeck Plasma is new. The old one never had this problem (although may not have noticed, so may have had similar result to the lcd i tested).

or 2) The HDMI-Cat5 adaptor is old and needs changing. I have seen a new model that sends 1080p over 1 Cat5 cable (mine runs over 2).
Could this solve my problems? Doesnt explain why this happens at around 10 mins.........

Someone please help!
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post #2 of 8 Old 10-26-2011, 02:21 PM
 
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Quote:
Originally Posted by aseman View Post

Hi, i have been having a strange issue with a tv signal problem sent over cat5. I think it may be useful for some of to read some of my findings & problems.

I am currently using a HDMI signal running over an old HDMI over2 cat5e cables. As far as i remember, this converter could output a max 1080i signal. I have tried an DVD player (i have lowered the resolution to 720p, and even lower to test), a SKY satellite receiver, as well as a Denon 3312 Amp(newest model which supports HDMI 1.4). Normally, all my devices plug into the amp which upconverts the signal to a resolution of my liking into the HDMI-CAT5 adaptor, where cables run about 10-15 metres to the roof deck, where a Plasma tv sits.

The problem starts after around 10 minutes.......the Plasma (which uses DVI, so i have a DVI-HDMI adaptor), loses the signal, therefore it shows "No signal" until i turn off the source (eg DVD, SKy box etc). I tested with a small lcd TV and around 10 mins when i first play my source, i see a flash on the screen where the signal changes (the screen goes dark for a second) but the image comes back after a second. Therefore, it seems the lcd recovers from the signal change but the plasma doesnt.

2 reasons that i can think of:

1) the HDMI-cat5 adaptor is near the back of the AV rack which has all my equipment may be getting ElectroMagnetic Interference (EMI), although the same adaptor has been used for 2 years (although the Denon amp is new, replacing an older Denon 2008 model amp). The roofdeck Plasma is new. The old one never had this problem (although may not have noticed, so may have had similar result to the lcd i tested).

or 2) The HDMI-Cat5 adaptor is old and needs changing. I have seen a new model that sends 1080p over 1 Cat5 cable (mine runs over 2).
Could this solve my problems? Doesnt explain why this happens at around 10 mins.........

Someone please help!

Without being there, it's tough to diagnose. But the first thing I thought of when you said the problem doesn't occur until 10 minutes into a run was that this is heat related. Of course the thought that this is just random noise also occurred to me and that was adapter related. But I find it strange that it is a constant 10 minutes.
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post #3 of 8 Old 10-26-2011, 02:25 PM - Thread Starter
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I have another possible problem......the cat5 cables may be slightly different lengths, maybe one cable is longer than the other by several centimetres.

Could this be causing the video sync issues? If so, then the single cabled HDMI-CAT5 adaptor may be the solution.

Id still like to hear your views if anyone may have seen this problem.

thanks
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post #4 of 8 Old 10-26-2011, 03:47 PM
 
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Quote:
Originally Posted by aseman View Post

I have another possible problem......the cat5 cables may be slightly different lengths, maybe one cable is longer than the other by several centimetres.

Could this be causing the video sync issues? If so, then the single cabled HDMI-CAT5 adaptor may be the solution.

Id still like to hear your views if anyone may have seen this problem.

thanks

An electric field propogates at almost the speed of light in copper. Each electron actually moves very slowly but the field propogates much faster. For this exercise, let's say the field propogates at c/3 or 100,000,000 m/sec.

Speed of an HDMI signal was originally 742.5 mbps (now is 3.4gbps for deep color).

If you had two cables and one was 5 cm or 0.05 m shorter than the other. The electric field would propagate on that cable 0.0000000005 seconds faster than the other. During that time, 0.37125 bits would transfer at 742.5 mbps, if that were possible. At 3.4gbps, the number of bits would be around 1.7 - so not even a full byte yet.

None of this actually matters because any device trying to do this higher speed conversion would contain buffers and other sync'ing mechanisms.

Again, the above calculations probably short-changed the electric field propogation speed and used a lower speed for HDMI transfers than is normally used now. So, the actual numbers may be even less delta time than the calculations above.
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post #5 of 8 Old 10-27-2011, 02:49 AM
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Power Everything Off at the wall.

Now connect the SKY+ HD box direct to the Extender Transmitter (Tx) box then repower SKY, Tx, Rx and Display - do you still loose the signal?

I suspect your New AVR may be the problem item in the HDCP chain.

Joe

PS Odd that your 'New' Display is DVI only!

If I've helped 'Like' me on Facebook - www.facebook.com/Octavainc

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post #6 of 8 Old 10-27-2011, 05:30 AM - Thread Starter
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Thanks for your suggestions guys. I am buying an adaptor and will hope for the best which supports HDMI 1.4 and 3d.

hxxp://www.amazon.co.uk/Cablesson-HDelity-Extender-Single-Bi-Directional/dp/B004URQ0IK/ref=sr_1_11?ie=UTF8&qid=1319666089&sr=8-11

For the interference in the cables, can i reduce this by using something like foil around the cat5 cables (at least to the point it runs into the walls).

For the new TV, yes, unfortunately it only supports DVI (not HDMI). It is made by Sharp and it is a waterproof.

Will let you know on the results.
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post #7 of 8 Old 10-27-2011, 07:41 AM
 
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Quote:
Originally Posted by aseman View Post

Thanks for your suggestions guys. I am buying an adaptor and will hope for the best which supports HDMI 1.4 and 3d.

hxxp://www.amazon.co.uk/Cablesson-HDelity-Extender-Single-Bi-Directional/dp/B004URQ0IK/ref=sr_1_11?ie=UTF8&qid=1319666089&sr=8-11

For the interference in the cables, can i reduce this by using something like foil around the cat5 cables (at least to the point it runs into the walls).

For the new TV, yes, unfortunately it only supports DVI (not HDMI). It is made by Sharp and it is a waterproof.

Will let you know on the results.

Foil around the cable will not provide anything except the foil manufacturers will sell more product. Checking the ground will help you more. Don't forget the possibility that the cable has been somehow damaged.
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post #8 of 8 Old 11-15-2011, 11:08 AM - Thread Starter
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I eventually bought another adaptor which has single hdmi (works with 1.4 and supports 3d).

Didn't see a picture at all (I tried all the resolution settings).......I was scratching my head for a week!

I tried again yesterday before making any new changes and strange enough, the new device works perfectly. Can't explain why it didn't work last week..........I shall put it down to one of life's mysteries.

Thanks for all your help guys
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