Does HDMI cable length degrade quality?

Forums › Home Theatre (including HTPC and EPG Collector) › Does HDMI cable length degrade quality?

TeaLeaf

6325 posts

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#210470 28-Mar-2017 17:21

I asked the Mrs to pick up a longer HDMI cable than my ARC one for my TV/Sound bar connection which is 1m.

She ended up getting a 5m model lol. Which is plenty as its just to connect the notebook to the TV. It doesnt mean I can place the notebook almost anywhere, but will it degrade the video and sound quality?

coffeebaron

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#1749616 28-Mar-2017 17:25

At 5m metres, unlikely. 10m+ maybe

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surfisup1000

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#1749618 28-Mar-2017 17:28

10m is generally fine so your 5m cable should be ok too.

The longer the cable, the more quality counts.

The signal will not degrade in the way that analog cables degrade anyway. If you get hdcp dropout outs you will likely just have a blank screen.

Maxcat

273 posts

Ultimate Geek

#1749643 28-Mar-2017 17:53

Yes.

Which is why these are made for long cable runs.

https://www.jaycar.co.nz/hdmi-over-1-x-cat5e-6-50m-with-ir-extender/p/AC1732

Dunnersfella

4086 posts

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#1749647 28-Mar-2017 17:59

Most decent Custom Install companies run HDBaseT or HDMI over IP for any length over 7 meters.

There's still quite a few people running 10m + cables, but experience tells me that 7 is a safe distance to move away from a 100% HDMI cable delivery. If it's not run through a wall, go with the longest you can get away with, if it's in the wall and it's not easy to run cables in-case of failure, go for a Cat cable solution.

Jaxson

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#1749651 28-Mar-2017 18:02

coffeebaron:
At 5m metres, unlikely. 10m+ maybe

This.

5m should be fine.

Try it and see. You'll soon know if you have any issues. Digital signals don't degrade slowly like analog does, they tend to work fine right up until they rather suddenly don't.

TeaLeaf

6325 posts

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#1749660 28-Mar-2017 18:23

Thanks all, much appreciated. 5m, might reach the couch avoiding the need for a wireless keyboard.

Are the HSMI male/female connections, like if Im putting it in and out every day (once a day woot, upgrade). Just worried if it wears pins out etc?

Dont have much choice as thats how the mrs likes to use her lappy on the TV, as stupid Sony TV is recognised by Win10 but for some reason wont connect in miracast, common problem evidently.

Dunnersfella

4086 posts

Uber Geek

#1749670 28-Mar-2017 18:57

Constant plugging in and un-plugging while the devices are still powered on isn't necessarily ideal...

Hot swapping causes issues for some people, others seem to get away with it.

Either way it's not a connection that is designed to be plugged in and out on a constant basis.

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antoniosk

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#1749682 28-Mar-2017 19:19

Generally anything with copper involves sending audio signals, and for digital comms this means a series of high/low pulses at very high frequency (everything in technology land is pretty much reduced to a series of on/off signals that get transformed into useful comms).

Audio signals inside a copper line can degrade over distance - the old adage of power in and how far it can punch without degrading etc - and the HDMI spec doesnt specify lots of power to transmit over long distance. As the quality of the signal deteriorates over distance, the opportunity for the connection at either end to 'mishear' goes up, and the more 'mishearing' the greater the errors till the connection is useless.

The standard seems to be about 7m (25 feet) for good quality, with a maximum of 50 feet (15m) being the top end point. After that you're using repeaters and regenerators, ie powered equipment.

I've got a 10M HDMI cable from the defunct Dick Smith - A $70 thing that I got eventually for $5 on their bizarre sales strategies - and it works well.

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richms

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#1749740 28-Mar-2017 20:30

Since the clock rate on HDMI depends on the pixel rate then dropping the resolution or colour depth down can lead to it working better on a long cable. I have one that cant do 4k at 4:4:4 60Hz, but is fine at 30Hz, or if I change to 4:2:0 - both of which are tradeoffs but better than constantly dropping out and having sparkles over the picture.

Just another area where a consumer interconnect designed for price fails to deliver on quality.

Richard rich.ms

fe31nz

1229 posts

Uber Geek

#1749817 28-Mar-2017 22:25

HDMI is a digital signal. If the signal at either end of the cable meets the HDMI specification, it will work. If the signal at either end of the cable does not meet the HDMI specification, then the cable is not an HDMI cable and you take it back to the retailer for a refund under the CGA as it does not work to its advertised specification. With older HDMI specifications, it is possible to have a passive cable up to 10 metres long if you use good quality components. Much longer than that normally requires an active cable that takes power and regenerates the signals. With the newer, faster HDMI specifications, I think it is likely that 10 metres will be too long for a passive cable, but I do not have any experience with HDMI > 1.4.

PhantomNVD

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#1750137 29-Mar-2017 13:52

In my experience it's the sending device that counts most.

My iSky box sent a perfect signal over the 10m HDMI cable I installed while the walls were bare in my new built house, unfortunately over the exact same cable the Samsung BluRay/DVD (even on the same cable) just couldn't get any signal through at all (swapped cables and same result)

Might have been a problem of cheaper (but same 1.4 spec?) cables and a weaker signal... but the sky box still worked perfectly while theDVD couldn't at all... \_0_/

Masterpiece

247 posts

Master Geek

#1750860 30-Mar-2017 19:38

Most HDMI 1.4 devices are limited to 9~10.2Gbps and in some cases lower.

1080p24 @8bit 4:4:4 = 2.23Gbps

If you struggle with this, lower settings 1080i, 720p or even 576i to get a signal then step up one level at a time until it fails then drop back one setting. That then is the device/cable transport limit. Note: some DVD/BD players amp up the signal more than others at the risk of swamping the HDMI cable.

If you struggle to do this over any connection you are in trouble for anything related to 4k or HDMI 2.0a~2.1

2160@24 8bit 4:4:4 = 8.91Gbps

A lot of people should be able to do basic 4k as above with short/medium cables and transitional 4k devices.

2160@24 10bit 4:4:4 = 11.14Gbps
2160@24 12bit 4:4:4 = 13.36Gbps

This is where people will start having issues when they raise bit depth to 10bit/12bit, this will be the default future for 4k +HDR as 8bit is just not good enough.

2160@50/60 8bit 4:4:4 = 17.82Gbps

So you want 60fps, you drop to 8bit but probably overwhelm your systems.
8 bit is not the way to go.

You are better off setting this

2160@24 10bit 4:4:4 = 11.14Gbps
or
2160@50/60 10bit 4:2:0 = 11.14Gbps

I'd argue that the 24hz would be better on a modern display that ups the Hz.
this does depend on the source material and what it is as default.

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Masterpiece

247 posts

Master Geek

#1750871 30-Mar-2017 20:03

Oh, back to the question, Does HDMI cable length effect signal quality?

It can do, older low gauge types and longer lengths can suffer signal loss.

I would argue that the contact surfaces degrade on plugs and sockets causing a loss of signal over time.

Here is a doc that backs up signal and cable lengths.

white paper cliff effect
Note: time has moved on and some equipment is getting cheaper to test things with, I have a bit level tester as noted in the above doc, still thousands of dollars, but luckily not tens of thousands

Me:"I'm not a robot!"

ET: "Maybe; you have some freewill, but you chose your path by arrangement"

Me "That sounds like a program with no freewill?"

ET: "We will catch up when you end this cycle"

Me: "Sounds like a 'KPI'!"

ET: "Did you read the terms and conditions?"

Me: .....