CE Pro May 2022 - 24

Networking+Home Control
HDMI CORNER by DPL Labs
Revision Confusion Persists
as Potentially Problematic
WHEN HDMI WAS introduced,
it was as a High
Definition Television Interface
Standard that could
offer better resolution, an
assortment of aspect ratios,
and even better color with
improved audio (PCM). It
was referred to as HDTV
- short, sweet and understandable.
As with any standard,
improvements are made
providing more features while
likely fixing bugs. The way
new versions are introduced
has become a common practice.
When was the last time
you updated your phone?
How was it identified?
I have a Mac PC and I get
updates all the time; currently
I'm using Version 10.14.6.
These are important to follow
because some apps may need
to operate under different
version numbers; everyone
knows and gets this. Mac (Android
OS, too) names every
new OS, which I appreciate
- Mojave, El Capitan, High
Sierra, et al. I find it easier to
follow and identifiable.
Similarly, each time a new
HDMI specification is introduced
it comes as a Revision
with a number, starting at
Rev 1.0 to today's new Rev
2.1a. Each has its differences
comprising fixes, additional
features, and always technical
content. However, HDMI
relies on manufacturers'
products to use feature sets
along with Revision numbers
24 | CE Pro May 2022
to identify each change. This
isn't a bad idea, but such
additional features over time
have increased substantially.
From an integrator and
consumer standpoint, it can
raise havoc trying to purchase
equipment that will
operate seamlessly with little
to no issues. Some folks claim
2.1 will eliminate this. At DPL
Labs, we're not as optimistic.
(HDMI even addressed this
on a recent CE Pro Podcast.)
One major change with
Rev 2.1 was in its transmission
format from TMDS (Transition-Minimized
Differential
Signaling) to FRL (Fixed Rate
Link), which in turned moved
the interface from a 3-channel
to 4-channel video system
providing a 25% increase
in channel allotment. Great
Speed, with higher frame
rates and even color that Rev
2.0 does not support. If you
had a system that offered
Rev 2.1's data rates and all its
new features and you were
operating with Rev 2.0 transmission
lines there could very
likely be an electrical hiccup
due to channel limits, EQ
differences and lack of extra
fourth channel!
From an integrator and
consumer standpoint,
[revision introductions]
can raise havoc trying to purchase
equipment that will operate
seamlessly with little to no issues.
It means feature specs would
have to be well understood
by the buyer or user, and
thoroughly spelled out by
the maker. Some may opt for
speed names such as Ultra
High Speed, High Speed and
Premium as cables go, while
others may want to stick
with Rev numbers.
If you compare Rev 1.2
having basically three or four
meaningful feature sets to
today's Rev 2.1a having better
than 40, the dynamics are
huge. How does that get
shared and understood? Plus,
HDMI announced this year
that it will eliminate Rev 2.0
and fold it into its adjacent 2.1
spec. This can become a real
marketing nightmare not only
for brands but for integrators
idea except for one slight
issue. Under Rev 2.0 the total
data rate is 18Gbps, calculated
by having three channels
with 6Gbps per channel ...
but in FRL mode this changes
to four channels and internal
correction equalization is
completely different.
Plus, since Rev 2.0 only
needs three 6Gbps channels,
many cables only provide
1Gbps clock channels because
the clock was only 150MHz
under 2.0. Let's assume the
cable did provide four 6Gbps
channels, doing the math
brings the system aggregate
to 24Gbps. Well, if you look
deep into the feature sets
of Rev 2.1 there is a 24Gbps
function that provides 4K
under the name of Ultra High
Fortunately, there is substantial
guidance designed
to keep some order, but we
are talking about a massive
amount of configurations and
not necessarily a canned software
package used for each
product - they are usually
customized by vendor, which
can create some surprises.
Every scenario would have to
be picked apart and processed,
and even then confusion
could understandably
remain. There are many more
examples, too. By throwing
Rev 2.0 into 2.1, it will complicate
things further.
JEFF BOCCACCIO,
president of DPL Labs, can be
reached at info@dpllabs.com,
or visit dpllabs.com.
cepro.com
http://www.dpllabs.com http://www.cepro.com
CE Pro May 2022

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