Following
is a list of some common questions that many HDMI retailers and installers
get asked regularly. Click on each question to go straight to the answer;
General
Questions
~
Why
should I use HDMI over other formats?
~ How
does HDMI differ from DVI?
~ Are
DVI and HDMI cross-compatible?
Cable
Questions
~ What's
the difference between approved and non-approved cables?
~ What's
the difference between "Standard HDMI" and "High Speed HDMI" cables?
~ What's
the difference between the various conductor materials, such as tinned
copper vs silver plated?
~ What
does AWG or gauge mean, and is there any particular number that I should
be using?
~ Are
there any length restrictions with HDMI cables?
~ What's
with the huge price differences between cables, and does a higher price
mean a better cable?
~ My
cable is too short - how do I extend it?
~ Can
I solder my own HDMI plugs on to the end of a raw or cut cable?
~ Can
I use my existing HDMI cables with the new HDMI 1.3 specification?
Connector
Questions
~ What's
the difference between approved and non-approved connectors?
~ Does
gold plating on the connectors and receptacles make a difference to
performance?
~ Why
are there so many pins, and what are they all for?
~ Why
are there two different main sizes of HDMI connectors, and what are
they?
Application
Questions
~ How
do I connect more than one HDMI (or DVI-D) source to my display?
~ How do I connect my HDMI
source/s to multiple displays?
~ How do I connect multiple
HDMI sources to multiple displays?
~ What's the difference
between a splitter and a distribution amplifier?
~ Can HDMI adapters,
joiners and wall plates be used safely without compromising performance?
~ Can I convert analogue
video (eg Component Video) to HDMI? If so, will it be as good as direct
HDMI?
~ Why doesn't my DVI source
(eg: PC, Mac Mini) work on my display when I connect it via an AV reciever,
HDMI switcher or HDMI distribution amplifier?
ANSWERS
Why
should I use HDMI over other formats?
HDMI
is an all-digital audio visual interface which offers quite simply the
best quality the industry has ever seen. As many of the source devices
in a modern home theatre are entirely digital (eg Digital TV, DVD, Blu-ray
etc), and the displays are also (eg plasma, LCD, projectors etc), HDMI
enables this high quality material to be accessed without any analogue
conversion. In other words, it stays in its pure digital form from source
through to display, giving the best possible picture and sound.
Secondly,
HDMI is easy to connect, being just one cable for both video and audio.
It's like a modern all-digital version of SCART, but in a much smaller
package.
Back
to top
How
does HDMI differ from DVI?
HDMI
was developed using the same "TMDS" bitstream as is used in
DVI-D, but was enhanced to include multiple formats of digital audio.
It also includes a few other useful additional features like the "CEC"
remote control channel. HDMI is smaller than DVI, so it doesn't take
up too much real estate on the ever shrinking devices on the market.
HDMI is far wider supported in the AV sector, meaning more brands and
devices use it, making it the first choice for digital home theatre
connectivity. Lastly, with the advent of HDMI 1.3, HDMI is now capable
of even greater quality than DVI-D. The result? DVI is now essentially
redundant, and will be superceded by HDMI in the coming months or years.
Back
to top
Are
DVI and HDMI cross-compatible?
Yes,
HDMI and DVI are cross-compatible, but with the following stipulations;
-
that
the HDMI format in question is version 1.1-1.2a, and NOT the higher
bandwidth 1.3
-
that
the DVI carrier in question is DVI-D, with the "D"
being for digital. DVI-A (analogue) and the analogue component of
DVI-I (combined Analogue/ Digital) are NOT at all
compatible with HDMI
-
The
audio component of HDMI is not compatible for use with DVI-D
-
The
"CEC" component of HDMI is not compatible for
use with DVI-D
-
Dual
link DVI-D is not compatible with HDMI (the common type A connector,
that is), only single link
Back
to top
What's
the difference between approved and non-approved cables?
The
term "Approved", in relation to HDMI products, is generally
used when a product is made by a HDMI Adopter member.
In the case of a cable, it means that the cable has been made to pass
the required information and bandwidth as set out by HDMI Licensing,
LLC. In other words, an "Approved" cable will work properly!
To
see if a manufacturer is a HDMI Adopter member, please refer to the
worldwide listing of ADopter members on the global HDMI website here.
Back
to top
What's
the difference between the various conductor materials, such as tinned
copper vs silver plated?
There
are four main conductor material types, as listed below;
-
OFC
- Oxygen Free
Copper, the higher
the purity the better, expressed as a percentage of pure copper
vs other materials. eg 99.9999% OFC contains contamination of only
0.0001% other metals, in other words very pure. Contrary to popular
belief, the difference between 99.99% and 99.9999% is like picking
the difference between 300kW and 301kW power output in a car (all
other things being equal).
-
TC
- Tinned Copper,
which is OFC coated in a fine layer of tin plating. This is the
most common in HDMI cables, as the tin plating, although technically
inferior to straight OFC, increases the durability and longevity
of the cable and is hence more stable in the critical tests of HDMI
Licensing.
-
SPC
- Silver Plated
Copper, the higher
quality and preferable option over the common TC in HDMI cables.
As silver is the greatest of conductors, the use of this expensive
material in coating the copper improves the flow of the bitstream,
reducing digital "jitter". The result is a more vibrant
and noise-free picture with more dynamic sound. The actual silver
content (eg 2.5%, 5% etc) plays less of a role than the quality
of the silver used, and the method of plating. Brand reputation
is often a better guide over quoted specs.
-
Pure
Silver - The use of pure silver in HDMI cables is
prohibitively expensive, and agruably unnecessary. The "skin
effect" which is present in HDMI cables negates the need for
silver at the core of each conductor, hence the considerable extra
cost of getting pure silver could not be justified in the end result.
The
bottom line - SPC is best, whilst TC
is the more common and economical alternative.
Back
to top
What
does AWG or gauge mean, and is there any particular number that I should
be using?
AWG
stands for American Wire Guage. It is an internationally accepted standard
(but not the only one) for determining the relative sizes of electrical
conductors. The thicker the conductor, the lower the number. HDMI cables
are most commonly available in 28AWG (thin) and 24AWG (thick). The 24AWG
has conductors more than twice the size of those in the 28AWG, and hence
cangenerally carry a wider bandwidth digital signal, usually required
for longer lengths
Many
manufacturers use 28AWH up to 7 or 8m, and upgrade to 24AWG for lengths
of 10m or more. Some of the very high end cables aim for extreme bandwidth
capability by using 24AWG even on short lengths. It's important to note
that the size of a conductor is not specified by HDMI Licensing, only
the required performance for test approval.
Back
to top
Are
there any length restrictions with HDMI cables?
No,
there are no length restrictions quoted in the HDMI specification. There
are however bandwidth restrictions of which are determined by the manufacturer's
own R&D, and these do dictate maximum lengths. HDMI Licensing suggest
that all manfacturers should be able to produce cables to full
performance up to 5m in length (but this doesn't mean that all do!).
Some better manufacturers have pushed the envelope to produce cables
up to as much 25m, or even longer with active boosting. Do your research
before you buy...
Back
to top
What's
with the huge price differences between cables, and does a higher price
mean a better cable?
This
is the one question which is truly difficult to answer diplomatically.
We are very much of the belief that cable quality DOES make a difference
to overall performance, so please take care in buying
a good quality cable. It would be a shame to utilize a technology so
advanced as HDMI and use a poor quality cable. Like many things, you
unfortunately can't judge what's best by how much it costs. To borrow
a quote from elsewhere in this site, it's easy to make an expensive
cable, but it's not so easy to make a good one. Comparing the price
of two different level cables in the same brand will help to determine
how they compare, but you unfortunately can't compare apples with apples
between two brands. Just because one fruiterer sells apples for a higher
price than another fruiterer, it does not mean that they have better
apples! Reputation is king.
By
the way, country of origin is NOT a factor in determining quality. In
fact, most HDMI products generally come out of China, as they still
appear to have the most advanced cable technologies.
Back
to top
My
cable is too short - how do I extend it?
Some
brands now have available products to join HDMI cables together to make
one overall longer length. There are two main types to look out for;
-
HDMI
Joiner - this is a simple passive adapter to join two cables.
It does nothing to the signal but pass it right on through. Be careful
when using this type to ensure that the total joined cable length
does not exceed the limit as suggested by the manufacturer of the
cable for the gauge (AWG) being used. eg: if a manufacturer suggests
8m is the maximum for 28AWG, then do not join a 5m and an 8m together
with a passive joiner as it will then lack the bandwidth to be able
to work properly, if at all
-
HDMI
Extender - Sometimes called a repeater. This is an active
(ie powered) device which processes the HDMI signal, and boosts
it to drive through a longer length. Some extenders use external
power supplies (plug pack), but other more clever designs draw their
power requirements through the 5V DC power line contained within
the HDMI cable. Please refer to the manufacturer's guideliines as
to the use and limitations of such a device.
Back
to top
Can
I use my existing HDMI cables with the new HDMI 1.3 specification?
Maybe.
It depends on the bandwidth capabilities of your existing cables. Some
manufacturers have been making cables all along which have had bandwidth
capabilities in excess of the new HDMI 1.3 requirements, so they will
be fine. The connector and pin configuration etc has not changed, so
the only thing to check is the bandwidth. Some brands may be
fine up to 3m or so, but it's highly unlikely that longer lengths of
1.2a spec cables can be used for 1.3. Again, ask the store from which
you purchased the cable.
Back
to top
What's
the difference between approved and non-approved connectors?
You'll
start to see a pattern forming by now regarding "HDMI Approved"...
in the case of connectors, like everything else HDMI, Approved means
that it is made by a HDMI Adopter to the exacting standards as dictated
by HDMI Licensing LLC. The Adopter system is a pre-emptive quality tick,
saying "yes, we'll make only HDMI products that comply to the required
standards and specifications".
HDMI
connectors which are not approved may be lacking in terms of reliability
of pin termination and alignment, the most common symptom of non-approved
connectors. Bottom line is that they may not work.
Back
to top
Does
gold plating on the connectors and receptacles make a difference to
performance?
Not
specifically, but it does definitely improve the longevity. Gold is
not a particularly good conductor, so gold plating does not improve
performance over raw brass (the most common connector raw material).
What gold is amazing for is its incredible resistance to corrosion -
high purity gold does not tarnish. Therefore the use of gold
plating will ensure that the connector remains in the same operational
state, free of tarnish, indefinitely. This is a very good thing.
If
a gold plated connector does tarnish, then this is a sign of the gold
plating either being too thin, or of insufficient quality.
Back
to top
Why
are there so many pins, and what are they all for?
There
are 19 pins on a standard single link HDMI connector (ie: normal 1.2a
or 1.3 spec). 12 of the pins are for the four main
TMDS channels, which carry the digital video and audio information.
There are another 4 pins for the CEC (Consumer Electronics
Channel) and DDC (Display Data Channel), 1 for "Hot
Plug Detect" (to tell if a HDMI source is on or not), and 1
is used as a +5V DC power supply line.
That's
18 pins... not 19!? That's right, there's one pin that is not used -
pin 14. This is simply referred to as "Reserved".
For
more information, please go to our technology
- connectors page
Back
to top
Can
I solder my own HDMI plugs on to the end of a raw or cut cable?
Short
answer - NO. HDMI is a very exacting specification,
and the hand termination of a cable outside of an approved factory WILL
result in a non-approved cable. If you can get a site terminated HDMI
cable to work at all, it will most likely not pass any of the higher
bandwidth formats such as 720p, much less 1080i or 1080p.
Where
a cable needs to be pre-wired into a premises whcih will provide little
or no access after completion, there's a few things you can do to safeguard
yourself against the huge costs associated with having to pull out a
fualty or damaged cable;
- Test the cable
prior to pre-wire installation to ensure operation out of the box
-
Always
k eep the connectors covered and protected during installation
-
Attach
the cable to a draw cord or yellow tongue by taping around both
the connector and a few inches of cable. This ensures that
the connector itself does not take all of the load when pulling
through. We've seen examples where the joints of a cable onto the
PCB inside the connector (yes, there's a PCB inside...)
are fractured due to excessive pulling on the connector during installation.
-
Install
the cable in such a way that it can be removed again, or used as
a draw wire to pull a replacement cable through. Not always practical,
but could potentially save a lot of headaches later on.
IMPORTANT
NOTE: a HDMI cable is an advanced piece of electronics
technology, comprising a very complex cable structure, PCB assembly
and fine multi-pin connectors. Treat with appropriate care and respect,
remebering that it is not robust like an old coax cable. Excessive tugging
on the cable and connectors, rough handling of the cable on insertion
and removal with AV devices, and allowing grit and plaster dust in amongst
the connector pins (common if you don't properly cover the connectors
during internal installation) is asking for trouble!
Back
to top
Why
are there two different main sizes of HDMI connectors, and what are
they?
Actually
there are three different sizes of connectors, if you want to get technical.
There are only two that are actually in use though... well one currently,
but another on its way. Confused yet? Here's the brief;
-
HDMI
Type A - the most common type of HDMI connector.
Standard sizes 19 pin version, as can be seen on the overwhelming
majority of HDMI supporting devices
-
HDMI
Type B - as originally specified as the HDMI equivalent
to DVI-D dual link, this larger 29 pin connector was never introduced
to production. It's the Titanic - it's big, and it just didn't
make it...
-
HDMI
Type C - this is the new tiny version of type A.
It's HDMI in miniature, designed and announced in 2006 as the alternative
for portable devices, where space is at a premium. It's totally
cross-compatible with type A, and will support all single link HDMI
formats (there aren't any dual link) right up to HDMI 1.3a
Back
to top
How
do I connect more than one HDMI (or DVI-D) source to my display?
A
HDMI switcher is required
to connect multiple HDMI and/or DVI-D sources to one HDMI supporting
display. A switcher may be a stand-alone device, or integrated into
a modern AV receiver (many of which now offer multiple HDMI inputs).
As you may expect, switchers vary in quality and performance. The best
models to buy are those which buffer and equalize the HDMI signal, ensuring
that the output is equivalent to the output level and quality of your
original source device. The electronics in some switchers may restrict
cable length options and high definition applications. Check with the
manufacturer for long length cable and at least 1080i support. If you
can get one with full 1080p support, then you'll be able to use it properly
with Blu-ray, HD-DVD, PS3 etc.
Back
to top
How
do I connect my HDMI source/s to multiple displays?
For
this you need a HDMI distribution amplifier.
This device will take a single HDMI input, and duplicate it to mulitple
outputs (eg 2, 4 or even 8). A high quality unit should reliably support
up to 1080p, offer full bitstream buffering, and identical output on
every port.
A
common practice with HDMI distribution amplifiers is to have the source
device sync with the display connected to output port number 1 on the
DA. This means that the resolution output from your source will be determined
by the supporting resolution of this first display, and the other displays
will all share the same input settings. With this type of splitter,
it is usually important to ensure that you do in fact use port #1 for
this reason.
Back
to top
How
do I connect multiple HDMI sources to multiple displays?
To
connect mulitple sources to multiple displays, you can use one of two
options, depending on your required combinations (egh number of displays
vs number of sources);
-
Use
your choice of HDMI switcher/AV receiver together with your choice
of HDMI distribution amplifier. Plug your sources into the switcher,
the output of the switcher into the input of the DA, then each DA
output to each display. This is a rather expensive way to do it,
but can offer the best results and flexibility
-
Choose
a model of switcher with multiple outputs. This is far less common,
but is ideal if your required combination is more conservative.
For example, there are a few models on the market with 2-4 inputs
switching through to 2 HDMI outputs. This is great if you have a
plasma screen and projector set up in the same room, and want either
to work without plugging in/unplugging HDMI cables. There's even
the option for "matrix" switchers which give you the ability
to have a different source to each display simultaneously.
Back
to top
What's
the difference between a splitter and a distribution amplifier?
Often
a HDMI splitter and distribution amplifier (DA for short) refer to the
same thing. The term "distribtuion amplifier" however confirms
inherently that it is a powered device which amplifies the signal. A
good HDMI DA will buffer the incoming signal, perhaps even making allownance
for input level and calbe length, ensuring that each output is identical
and equivalent in level and performance to the original source device.
Please check with the maunfacturer of a HDMI DA to verify these features.
If
a splitter is quoted a being a powered device, either via an external
power supply, or via the +5V power line through the HDMI cable itself,
then it will be a distribution amplifier. A passive splitter on the
other hand will be a Y-adapter with one input and two outputs, but with
no buffering, equalizing or amplifying. In fact it will take the incoming
bandwidth of the HDMI bitstream, and split it evenly amongst the tow
outputs. That is, it halves the HDMI bandwidth - bad news! In brief,
stay well away from non-powered HDMI splitters.
Back
to top
Can HDMI adapters, joiners and wall
plates be used safely without compromising performance?
Yes,
providing that the accessories being used are all demonstrably HDMI
approved. The quality of such adapters is just as important as the quality
of source and display devices, and the cables used. As there is always
a slight unavoidable loss of bandwidth over such connections, its best
to minimize the number of joins in the system, but a few is fine.
Back
to top
Can
I convert analogue video (eg Component Video) to HDMI? If so, will it
be as good as direct HDMI?
Yes,
converters from composite/s-video and component video are now commercially
available. Some basic models enable a straight conversion, with input
resolution equalling the output (eg 576i input results in 576i output
only), and some even have the ability to input digital audio to make
up a complete HDMI bitstream. These are great for use with source devices
which don't have a HDMI option, such as Foxtel. The end result would
be expected to be about as good as the original connection, but with
the added benefit of convenience. For example, if all of your source
devices are HDMI enabled except Foxtel, then you could convert Foxtel
to HDMI and connect them all through a HDMI swithcer. Such converters
generally sell for $250-$400. Some better models on the market will
do a very good job of scaling images, providing a genuinely improved
picture over the original. Such models would ordinarily sell for $2000+.
Back
to top
Why
doesn't my DVI source (eg: PC, Mac Mini) work on my display when I connect
it via an AV reciever, HDMI switcher or HDMI distribution amplifier?
Many
DVI-D sources which have variable output resolutions (eg computers and
scaling DVD players) require a constant communication code called EDID
to be present in order to output the correct resolution to the display.
This code is sent from the display back to the source, and contains
information regarding optimum display resolution and format. The absence
of this data can result in the source (eg Video card on the PC) to not
output the picture at all, as it does not know what resolution to set.
Where a direct connection to a display is present, there's usually no
problem, but when the source is connected via a HDMI switcher or splitter,
the EDID code may be effectively blocked or interrpted by this intermediary
device. If the computer is booted up whilst the switcher is on the appopriate
input, then the code should pass through without problem, but the EDID
stream is lost when another input is selected on the swithcer, then
returned to the original position.
If
you are suffereing from this problem, then the solution is an EDID interface.
Such a product is first used to store the EDID data from your display,
and it is then connected between your DVI source and the switcher or
splitter. The EDID data is continually output to the source, enabling
a constant image output, and is not interrupted by changing inputs on
the switcher. It works as there is a direct connection between source
and display, even if the display is turned off! The leading example
of such a product is DVI
Detective from Gefen.
Back
to top
