Forum

Hdmi / dvi

Hey all

Thanks for the great input on the https://discourse.vvvv.org/ thread.

Now it’s time to talk HDMI :)
HDMI’s lovely since it’s a nice compact rugged connector (always hated d-sub), and shifts lossless signal, but is prone to digital interference, causing signal drop outs or lost pixels.

We note that “HDMI is electrically compatible with the CEA-861 signals used by Digital Visual Interface (DVI)”
But cannot presume that we can interchangeably consider HDMI as a single link DVI signal.

Later editions of HDMI (e.g. 1.4 which introduces support for 120Hz/3D) use higher frequency of bandwidth in the cable than a standard DVI connector, but it is noted that HDMI equipment will still provide backwards compatibility with DVI.

HDMI connector B is electronically compatible with DVI dual-link, but as yet is not available in any products (and my guess is that we’re not likely to ever see this connector).

1. Mini DP -> HDMI

Any specific suggestions for active Mini-DP ->HDMI?
Tested at what resolutions?

2. HDMI cables

Length of cable

The specification for DVI notes maximum signal length as 5meters (despite evidence of up to 30meters or more working on occasion).
However, HDMI doesnt specify a maximum signal length.

Wikipedia notes:

A cable of about 5 meters (16 ft.) can be manufactured to Category 1 specifications easily and inexpensively by using 28 AWG (0.081 mm²) conductors.
With better quality construction and materials, including 24 AWG (0.205 mm²) conductors, a HDMI cable can reach lengths of up to 15 meters (49 ft.)

This seems to suggest that improments in cable quality could result in even longer lengths (e.g. 30meters), and due to the unidirectional video signal (i.e. unlike USB’s Tx/Rx), we can presume that any waveform effects / delay caused by the cable length is unimportant.

Affordable repeaters such as this one for £20 on Amazon:
http://ecx.images-amazon.com/images/I/41PHv3SLhRL.SL500_AA300.jpg
http://www.amazon.co.uk/Neet®-Extender-Amplified-Repeater-Supports/dp/B002C77FTI/ref=pd_sxp_grid_i_0_2
promise to extend 1080p over 50meters

Furthermore, cables are popping up with inline extenders (£33 on Amazon for 20meters)
http://ecx.images-amazon.com/images/I/41M3nyzwx2L.SL500_AA300.jpg
http://www.amazon.co.uk/Cable-Tex-Cable-Active-Extender-Repeater/dp/B003WUMM5Q/ref=pd_cp_ce_2
in 20 and 30meter lengths

Speed of cable

According to the HDMI spec, there are:

  • Standard cables : 1080i/720p
  • High speed cables : 1080p/4K/3D/Deep Color

Personally I don´t like HDMI because the connectors cannot be secured
at least not as easily as with DVI.

Some notes on long HDMI cable lengths:
http://www.hdcable.co.uk/long-hdmi-cable-information/
Not seminal, but educating.

@bjoern : you’re right about the lack of strain relief
some cables are sold as ‘locking’ (referring to a kind of ‘squeeze to release’ mechanism)
but these are more rare

I’m thinking it’s time that I finally ‘moved on’ from VGA onto something else
DVI seems too impractical / expensive / unknown / untested for long distances
HDMI’s interoparability (and case studies) somewhat vouches for DVI’s workability…
(and if we’re using a Mini-DP->HDMI, are we already presuming a DVI standard signal, as opposed to the higher frequency possibilities of a HDMI signal? Is it the same thing entirely as a DVI signal but with a different connector?)

still. HDMI’s looking like a worthwhile world to live in now (especially with many projectors opting for it over a DVI connector)
any other opinions on this?
You prefer VGA / DVI / HDMI / DisplayLink / Composite / Component / SCART / UHF?

I’d prefer DVI over HDMI any day.
how do you come to the conclusion that hdmi connectors are more rugged than dvi (or d-sub)?!? dvi can even be screwed in!
I would not trust hdmi for installs of any big cable lengths, honestly, especially in noisy environments. I disagree with the notion that unidirectionality eliminates cable length deterioration.
Also, HDCP is an issue sometimes.

I prefer VGA. If you got the budget, fiberop or hd-sdi (if the resolution fits). Maybe baluns+Cat5e cables. So many options better than hdmi. OTOH, I still (too) often find myself laying bnc-composite (where’s the cheap vj-compatible hd mixer?).

Just take a read on vjforums, there’s lots of threads about this. :-)

edit: sorry for the harsh tone, I haven’t had my coffee yet. :-/

from what i saw the last 5 months the importance of HDMI in the professional Video world is close to zero.
we have a few adaptors “HDMI to something” but recently we bought the complete stock of DVI cables of Kramer Germany…

@bilderbuchi:
morning :)

HDMI more rugged than DVI:

If you step on both, which one bends? try and snap pins from both… :)
A HDMI head needs a lot more pressure on it before it gets damaged, and the pins don’t break, unlike DVI
I’d say it’s definitely physically more rugged

But lack of strain relief is the downside. and that’s what you seem to be referring to
obviously strain relief is a stability issue.

Unidirectionality

unidirectionality doesn’t remove the issue with cable length
I was saying that unidirectionality makes it technically possible to indefinitely increase the cable length (either electrically or electronically)

Why move to something new

VGA i’m finding to be too unreliable for pixel perfect works (such as the tree). It’s a bit of a special case for me i guess

With HDMI/DVI, everything’s consistent/repeatable, no artefacts (once it works :) )

e.g. I did one job with dotdotdot last year, which involved 6 Projection Design projectors, each on ~20-30meter straight HDMI lengths, fed from the DVI outputs of 3 TripleHead2Go’s.
And the signal was beautiful, never had to think about it, even with lots of swapping everything would be pixel perfect when reconnected. This kind of repeatability i find to be unnatural for VGA.
Obviously having Projection Design at one end of the system helped things along…
And in this case, the signal was strictly DVI

HDCP

We know HDCP isn’t an issue if you’re not sending HDCP content (e.g. media player) / haven’t got something super crazy in the middle / are generally in control of the sending side
The projectors will be HDCP, the computers won’t be.
My experiences of HDCP issues is that they’ve always been trivial, unless you’re trying to capture the signal

120Hz

Another thing that I’m particularly interested in is 120Hz for a bunch of different installations we’ve got, and this generally doesn’t fly so well on the DVI connectors (low cost 120Hz projectors require VGA or HDMI signal, whereas if using DVI, you’d need dual link DVI, or 2 separate DVI links)

@kalle - very interesting
I presume that works loosely defined as >5,000lumens/projector will tend towards your advice here.
Can you confirm what resolutions / lengths you’re using
Also examples of what you’re using to send / receive the signal over that length?

I’ve got a HDMI screw socket lock on some m-ITX motherboards I use. see here

Also, I’ve had problems getting a span in windows using DVI to HDMI cables more than once. DVI outputs on nvidia GPUs to HDMI sockets on projectors and can’t get span. Swap to go via VGA and span no problem. Swap to DVI to DVI span no problem. Never really got to the bottom of it. Anyone else seen this?

Also, yeah VGA a pain when mapping cos of jumping around X and Y shift when new sync. Depends on projectors though I’m guessing.

I always DVI where possible and use DVI fibre over distances of more than 5m to avoid potential problems. Fibre not cheap and hire it where budget allows.

longest cables we have are around 8m, for everything else we usually convert/reconvert on fiberoptics or Twisted Pair Extenders.
(although we have a few 10m cables, but those are really exceptional.)

I use a 25m dvi regularly with no repeater and no issues.

Think they’re made by Lindy

DVI-D Duallink? What resoultions do you run?

DVI-D Singlelink

Only tested at 1024*768

It’s called Lindy E193793 ‘super long distance cable’

wohoo
super pricey as well! £130 for 20meters

http://www.lindy.co.uk/lindyshop/pictures/41267xxl.jpg
http://www.lindy.co.uk/20m-premium-super-long-distance-dvi-d-extension-cable/41267.html

but still much cheaper than fibre / oCat5

Yep well pricey but they work and they last.

At least mine do :)

@mrboni -
can you let us know what resolutions / equipment you’ve tested with?

Hi sugo

Only tested at 1024*768 into an Optoma Ep776 projector, as they are used together as part of a regular installation. Nvidia cards through TH2gos on the other end.

I can do some tests though if you like. What’s most useful? max res?

useful ballpark resolutions would be 480p, 720p, 1080p at 60Hz

We can see that these cables are single link DVI from the image so anything higher (except 1920x1200) shouldn’t work at 60Hz

Easiest test would be just trying it on a 1080p monitor:

  • from the TH2G (2x1920*1080)
  • direct from the graphics card

Other tests could be:

  • Try it with different hardware on the receiving end
  • Run it parallel to a power cable
  • Run it along a metal beam with a power cable

if it fails then try it with a shorter cable in the same configuration.

I’m not expecting you’d do all this :),
personally I’m quietly already buying HDMI for a couple of installations (don’t tell bilderbuchi…)
but I’m sure the results would be invaluable to others / myself in the future / perhaps yourself in the future :)

cheers!

Ha. Give me a minute :)

elliot, you can buy what you want, but when you ask for an opinion, i give it. ;-)

@all
we’re getting somewhere real fast in these threads.
am really grateful for all the input.
i hope my contribution to organising / reflecting on content is useful to others
and that i’m not being too subjective

Hey.

Still haven’t had time to do any tests on those cables but there is some info regarding tested resolutions here - http://www.lindy.co.uk/25m-premium-super-long-distance-single-link-dvi-d-cable/41263.html

Also, they do a 25m dual link - http://www.lindy.co.uk/25m-premium-gold-dvi-d-dual-link-super-long-distance-cable/37008.html A snip at only three nine nine, nineee nine