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Long HDMI cable

4K views 40 replies 12 participants last post by  Nyal Mellor 
#1 ·
#27 ·
Thanks for the link to the article.


In my case I'm only using 1080i no 1080p.

Secondly it's coming from a TivoHD that sends everything as 1080i not as native resolution. So a follow up question is given that fact does that mean that the bandwidth used is the same no matter what channel (meaning source) is being viewed. Meaning does an analog source upscaled by Tivo to 1080i generate the same data as if it came from a 1080i channel? If that's the case any differences between channels must be from my source (cable provider) rather than "interference". Does that make sense?


Thanks.


Finally I have seen "pixelation" on digital or HD channels sometimes, how does that differ in appearance from "interference sparks" or HDMI signal quality issues?


Thanks again.
 
#28 ·

Quote:
Originally Posted by britdiver /forum/post/14326769


...if I get really close to the screen (50 inch plasma) it looks a little "snowy" but of course it may always look like that and I never look that closely. I guess I'm now paranoid that the quality has dropped whereas it probably hasn't.

It depends somewhat on what you mean by "snowy." Many images will look mottled at fine detail in solid color areas, simply because the source material is like that. For example, motion picture film often has a sort of dye-cloud effect in dark areas which is part of the nature of the film; if you're viewing this in close detail it might seem "snowy" in a way.


Pixel-dropout sparkle with a failing HDMI cable is pretty obvious. Usually the dropout pixels will either render as white or as a solid primary color (for some reason I see them in green fairly often), and usually they'll all be the same color. Accordingly, if you see lots of green or white one-pixel sized dots all over your screen, that's probably HDMI pixel dropouts. If, instead, you feel that you're seeing a bit of crawly, cloudy, random color in solid color areas that's probably simply what the source material looks like. Sometimes you'll see the latter for the first time when you view material at higher resolution than before, simply because lower-resolution gear tends to smear out these dye-cloud kinds of effects. At the extreme, standard VHS tape, for example, will pretty well obliterate that effect because it simply can't provide enough color definition or resolution to distinguish small areas from horizontally-adjacent areas sharply.

Quote:
Originally Posted by britdiver /forum/post/14326769


...does an analog source upscaled by Tivo to 1080i generate the same data as if it came from a 1080i channel? If that's the case any differences between channels must be from my source (cable provider) rather than "interference". Does that make sense?

I'm not quite sure what you're asking here but will give it a whirl.


An analog source upscaled by your HD Tivo is NTSC standard-def. The source itself being analog, and being by the nature of NTSC rather low-quality, it will differ from a native 1080i digital broadcast or cable (ATSC or QAM) signal considerably. If you are seeing a lot of noise in it, it is fairly likely that that's because the signal coming into your home has a lot of noise in it; this is quite common as most cable companies do an absolutely wretched job of keeping signal quality clean. I have Comcast here in Seattle and the analog channels have always looked atrocious.


I am not sure how the TiVo handles these internally but my guess would be that it encodes the NTSC broadcast in MPEG-2 and sticks that on the drive; then, at playback, it upscales it, and delivers that upscaled image through the HDMI port. The datastream it sends through the HDMI port will have the same basic characteristics as it would if the original source had been an ATSC or QAM channel, but of course the quality of the picture that datastream represents may be considerably different.

Quote:
Originally Posted by britdiver /forum/post/14326769


Finally I have seen "pixelation" on digital or HD channels sometimes, how does that differ in appearance from "interference sparks" or HDMI signal quality issues?

If by pixellation you mean that areas of the screen become consolidated into multi-pixel rectangular blocks of the same color (which is also called "macro-blocking") then this will look completely different from HDMI signal quality issues. HDMI is run uncompressed and cannot cause macroblocking; if you see macroblocking, that's in the source.


If I've misunderstood any of what you've asked or you need some further explanation, let me know...


Kurt
Blue Jeans Cable
 
#29 ·
Hi Kurt,


Wow. Great info and from BJC. Perfect.


I think you have pretty much confirmed the conclusions I'm already coming too. From your description of what I called "pixelation" and you called "macroblocking", that is exactly what I was seeing. The square blocks is definitely what I was seeing. It wasn't on all channels, or even all digital or all HD channels, and I would have thought if it was a signal issue down your cable it would affect ALL channels. Or at least all channels using the same bandwidth - meaning all digital or all HD. And it wasn't.


I have also now realized that I had to add a new coax (100ft) cable to the Tivo's new location. Of course this might have added the source of a weaker signal. In fact I also remembered about an hour ago that I have a signal booster that I have now added into that coax line. I plan on doing some testing using Tivo's signal meter to see if I can see any difference with and without it.


Finally of course the most likely problem is my cable provider. Let's face it they normally are! And it might have just been my bad luck that poor signal happened at the same time I was doing all these changes. I will give it a few days and see what happens and do testing with and without the signal booster.


Thanks so much for the detailed reply. I think I'm now pretty sure it's not a problem with our long HDMI cable as it only the squares (sorry - macroblocking) and not all the same color either.


Thanks again.
 
#30 ·
By the way, I might not have been completely clear there; when I say "the same color" referring to the squares, all I meant was that within a square, the contents will be all one color. When a picture goes to macroblocking, of course, the various squares will each have a different color from one another, but the point is that all of the detail within them has been obliterated.


Kurt
Blue Jeans Cable
 
#31 ·
OK. Yes may squares are different colors but they are "large" squares rather than pixel size which it sounds like is what I would see if it was HDMI signal quality issues. In fact the squares I'm talking about, I have seen occasionally before I even had this long HDMI cable and they look like the same "squares" you see on bad satellite reception.


In fact I thought your same "all the same color" comment was referring the pixel-dropout sparkles rather than macroblocking.
 
#32 ·
Ah...okay, now I see. And yes, typically (though not necessarily) when one sees pixel dropouts, they will all be the same color as one another. My suspicion would be that this is because in any marginal failure there's a good chance that two of the three data channels are getting through just fine and the third is failing. How that renders will then depend on issues like what the colorspace is, and how the display behaves in the face of corrupted data.


Kurt
Blue Jeans Cable
 
#33 ·
I just realized that I never really thanked you Kurt. That's great customer support and I appreciate that. By the way everything is looking great. A few days after we started this posting, I had a problem across the border with my cable. So it was all a signal issue. Looks great now.


Thanks again.
 
#34 ·

Quote:
Originally Posted by britdiver /forum/post/13734681


I need a long (about 100 feet probably) HDMI cable. I found this cable http://sewelldirect.com/Accell-Ultra...I-Cable-35.asp

They even have a longer version. Has anyone tried these cables?

Thanks.

I think the limit is usually around 50 feet for really good cables. Monoprice.com has a converter that extends it like 50 meter (150 ft) over 2 cat5 cables, it will be cheaper that way also. I don't think that you can go that far with 1080p (shorter range) but if you are doing 1080i or 720p it should be fine. I think they are like 100 bucks and a 100ft cat5 cable should be like 10 or 15 each.
 
#36 ·
Guys,


Equipment:

Samsung 6000

Denon 2313ci


Need a 50' hdmi cable to run from my av closet to the tv. Cable will be run through the floor to the crawl space under the house, back up through he floor to the tv. 50' will give me a couple of feet of slack on each end.


Please recommend a high quality hdmi cable. Is BJC recommended? Does temperature affect anything?
 
#37 ·
Have you considered using a HDMI extender? It runs a HDMI signal over cat5e ethernet cable. You can run it over 100m of ethernet cable. This way you will only need one short length of HDMI cable to plug into the receiver, one short length of HDMI cable to run into the extender, and an ethernet cable to join the two units. A lot of HDMI devices such as bluray players, PS3 etc recommend that you only use up to a 15m length of HDMI cable. The signal quality can be weak on the longer lengths unless its a really good quality HDMI cable.
 
#38 ·

Quote:
Originally Posted by techguy1975  /t/1023337/long-hdmi-cable/30#post_23106321


Have you considered using a HDMI extender? It runs a HDMI signal over cat5e ethernet cable. You can run it over 100m of ethernet cable. This way you will only need one short length of HDMI cable to plug into the receiver, one short length of HDMI cable to run into the extender, and an ethernet cable to join the two units. A lot of HDMI devices such as bluray players, PS3 etc recommend that you only use up to a 15m length of HDMI cable. The signal quality can be weak on the longer lengths unless its a really good quality HDMI cable.

I've got some hands-on experience with HDMI extenders. For doing 2048x1080 video the circa-$120 boxes I used would not work with 150 feet of CAT5E. They would work at lower resolutions. They were fine with 50 feet and would probably go a little further than that.


As I understand the technology, it is very important to get the lengths of the two pieces of Ethernet cable exactly the same length.
 
#39 ·
Personally I use Fiber Optic HDMI cables for this kind of thing. I've found them to be more reliable than the lower priced CAT5/6/7 based extenders. The new ones from Celerity also have detachable ends for an easy wire pull.
 
#40 ·

Quote:
Originally Posted by Nyal Mellor  /t/1023337/long-hdmi-cable/30#post_23107285


Personally I use Fiber Optic HDMI cables for this kind of thing. I've found them to be more reliable than the lower priced CAT5/6/7 based extenders. The new ones from Celerity also have detachable ends for an easy wire pull.

Neat package, but at a price!
 
#41 ·

Quote:
Originally Posted by arnyk  /t/1023337/long-hdmi-cable/30#post_23107310


Neat package, but at a price!

Sure but also avoids any ground loop issues if the TV / projector is plugged into one outlet and the equipment is on another since the fiber optic connection is not a direct electrical connection like the type you get with a normal HDMI cable.
 
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