
Explaining 4K 60Hz Video Through USB-C Hub - tambourine_man
https://www.bigmessowires.com/2019/05/19/explaining-4k-60hz-video-through-usb-c-hub/
======
Nextgrid
The USB-C spec is an insane mess.

The fact that every port used to be different is actually a feature, as it
helps you identify which device supports what based on the ports it had. If
you see an HDMI port on a laptop you can be sure it's going to output some
kind of video signal over that. If you see Thunderbolt then you're sure the
machine supports Thunderbolt.

USB-C just jams all these incompatible standards into a pin-count-constrained
port (so they can't even all fit in, and trade-offs need to be made) without
any way for the user to tell nor select which features should be enabled on
which port.

My 12-inch MacBook for example has a USB-C port just like the MacBook Air and
Pro, and yet if I plug in a Thunderbolt Display it won't work on the 12-inch
one but will on the Air and Pro. As a user there is no easy way for me to tell
the 12-inch Macbook's USB-C port is different than the Air/Pro unless you
explicitly search for it in the tech specs (which is counter-intuitive as the
whole point of USB-C is to be universal so in an ideal world you
wouldn't/shouldn't even think about searching that).

~~~
dheera
Not only that, but the USB-C plug itself is the worst-designed plug I have
seen in a decade. It's flimsy sheet metal on the plug side with a nice big
cantilever, and flimsy sheet metal soldered to a PCB on the other. Perfect
recipe for broken ports and cables.

I break about a cable a week and break a device every now and then. Mostly
doing very normal things like charging a phone in my pocket while hiking.

USB-C seems like a perfect example of a product designed by people who sit in
an office chair all day and never go hiking, skiing, ice skating, rock
climbing, or otherwise seek to understand what their users normally do with
plugged-in devices in the field.

I miss the old DC barrel connectors -- they never broke, and they were usually
designed such that housing of the electronics took the brunt of everything,
not the PCB.

~~~
coldtea
> _I break about a cable a week and break a device every now and then_

You're doing it wrong then. I have about 5 USB-C cables and have never broke
one in 3 years...

Kinds of cables I have broken over my IT life:

\- A few Apple charger cables (on the Mac connecting end)

\- A few headphone cables

~~~
dheera
I disagree with the notion that just because they break that I'm "doing it
wrong". Please listen to the customer. Rather, I'd say that they're just not
rugged enough for my (consumer) standard of use, which needs to be more rugged
than office use. I have legitimate needs to engage in sports while devices are
plugged in and accessible. Other consumers get stuff bitten by children and
pets, stepped on, tangled, and caught in things. That's consumer life. It
should be accepted as a valid design problem to make a product rugged enough
to tolerate that. Often a simple change in housings and shrouds would deal
with this problem inexpensively -- in the case of USB, all it would take is
for the shroud to be a part of the standard itself, and the housing it mates
with to hold and relieve strain on the shroud.

What about IEC cables? They're super rugged and virtually impossible to break.
Proportionally downsizing that connector to be small enough would likely
maintain the same level of ruggedness while being small.

I'd appreciate if people don't downvote me just because you disagree with me.
That discourages useful discussion on HN. I downvote trolls and people who
abuse the system with spam, not people I disagree with.

~~~
coldtea
> _What about IEC cables? They 're super rugged and virtually impossible to
> break. Proportionally downsizing that connector to be small enough would
> likely maintain the same level of ruggedness while being small._

Those are only designed to carry power though... not a complex list of
protocols...

------
nrclark
USB-C is a train-wreck for those of us who work in electronics design.

USB-C's chipset support isn't all that good, it seems like. With USB 3 type A,
you pretty-much just run your USB lines to the ports on your CPU. Simple,
straightforward. Manufacturers are happy to do it, because it's dirt cheap and
requires nothing except the connectors and maybe some ESD protection.

USB-C is a different beast entirely. Just to use the USB 3 lanes, you need to
put down a high-speed mux just to deal with both connector orientations.

Want to support USB Power delivery (transmitting or receiving)? That'll be
another set of chips to put onto the board. Plus software to deal with the PD
negotiation.

Want to support Displayport? That'll be _another_ mux chip. Plus more software
to advertise the functionality.

The cables are also much harder to manufacture, and this is reflected in their
average price after you chop off one or two outliers.

Is your item a USB host? A device? Does it accept or provide power over USB?
Does it support Displayport? Thunderbolt? Analog audio? Something else
entirely? There's no way to know from looking at the connector. And no
standardized markings that I've ever seen.

~~~
BiteCode_dev
I'm completely ok with it being complicated to design and cost 10 euros more
if it delivers.

And despite all its flaws, USBC does. It's small. It's reversible. I can
charge all my devices on it: my samsung tablet, my oneplus phone, my logitech
mouse, my jabra headphones, my switch and my XPS 13 laptop, which I can also
dock to my screen/ethernet. It's amazing.

So yes, I had to take the time to find the proper cable, and I bought a few
before finding brands I can trust to work with all my machines... and not fry
them.

It sucks, but it will improve with time, like it did with early USB and HDMI
(too many people forgot how terrible THAT was). It already has, in fact,
improved a lot, and it will keep it up.

Meanwhile, I have only one cable and one dongle in my bag that do everything.
I don't even have to get them out most of the time.

This is imperfect. This needs fixing.

But this is better than what we had before. Way better.

~~~
janlaureys
I'm soon switching a lot of things to USB-C. What brands of cables would you
recommend ?

~~~
lmm
Anker. They're consistently reliable, and accessories are their whole
business, so a problem would hurt their reputation a lot more than one of the
big hardware companies.

~~~
floatboth
Well, if you look at the spreadsheet linked below
[https://docs.google.com/spreadsheets/d/1vnpEXfo2HCGADdd9G2x9...](https://docs.google.com/spreadsheets/d/1vnpEXfo2HCGADdd9G2x9dMDWqENiY2kgBJUu29f_TX8/pubhtml)
Anker did have one model of cable that was recalled because it was dangerous
:)

------
bgorman
Great article. I was recently wading through this problem for my work setup. I
was going crazy wondering what the actual technical limitations were with
USB-C vs Displayport over USB-C versus Thunderbolt. I ended getting this
WAVLINK dock for $150 with Thunderbolt 3. If you want Dual 4k montiors and USB
3 output + power for your laptop I recommend this.

[https://www.amazon.com/WAVLINK-DisplayPort-Thunderbolt-
Charg...](https://www.amazon.com/WAVLINK-DisplayPort-Thunderbolt-Charging-
Ethernet/dp/B07T2RW54X)

~~~
bloopernova
I got one of these for just the 2 DisplayPort outputs:

[https://smile.amazon.com/Cable-Matters-Thunderbolt-
DisplayPo...](https://smile.amazon.com/Cable-Matters-Thunderbolt-DisplayPort-
Supporting/dp/B01DYFI1OE/)

Then bought one of these from a coworker for $40 to drive all the other ports.
I've been pretty lucky. (all being driven by a 2018 macbook pro)

[https://smile.amazon.com/Docking-Station-Laptop-Power-
Delive...](https://smile.amazon.com/Docking-Station-Laptop-Power-
Delivery/dp/B07MCVY29J/)

The first dongle is driving 2 Dell 23" 1080 screens, my 27" 4K screen is
driven directly by a thunderbolt to displayport cable, and all my USB stuff
goes through the second dongle. It works really well so far, and I have an
upgrade path for 2 more 4K screens with the Cable Matters dongle.

Yours is an all-in-one that really looks nice though. How warm does it get?

~~~
bgorman
It is a little bit warm, but nothing concerning. I can leave my hand on it no
problem.

~~~
bloopernova
Thank you, that's my experience with the USB-C hub that I'm using. I kind of
wish it wasn't tucked out of the way behind monitors, then I could use it as a
hand warmer :)

------
oflannabhra
As much as people complain about USB-C, I absolutely love it. I have a 2018
MacBook Pro, and I use the Caldigit TS3 hub (referenced in the article) as my
docking station at work. I plug a single cable in, and I immediately have 2 x
27" 4k monitors, power, USB peripherals, headphones, Ethernet, and much more
if I need it.

I travel with a single dongle that cost $15: SD card, HDMI, 2xUSB 2.

I have not had to buy any extra cables, besides what came with the computer.

~~~
bradstewart
When you find a computer/dock/cable combination that works, it's fantastic.
But, in my experience, it's extremely hit or miss whether a different monitor,
or laptop, or cable will work with other components. Particularly with
4k@60Hz.

------
treyfitty
Last night, I was ready to pull my hair out trying to figure out what dock +
cable I need, so this article is quite the blessing. However, I’m still left
confused on whether I need a USB3.1 usb-c cable or Thunderbolt 3 cable.

In light of the MBP16 announcement, I wanted to plan my purchase, including
the peripherals. I currently have 2 4K monitors on a PC. I’d still like to use
that PC from time to time, but it’d be convenient to do so through a dock.
Enter the Targus dock that I happen to have received through work
([https://www.amazon.com/dp/B07BPQKP8V/ref=cm_sw_r_cp_api_i_0b...](https://www.amazon.com/dp/B07BPQKP8V/ref=cm_sw_r_cp_api_i_0buZDbZSW5P8M))
which claims to be Thunderbolt 3 “compatible.” However, none of their ports
are specced to be such. Furthermore, the included host attachment USB-C up
cable is only capable of transferring 5GB/s instead of the 40GB/s a la
Thunderbolt 3.

Now, this article explains DisplayLink nicely, but what happens when I use the
Targus Dock with and without a Thunderbolt 3 cable? Does it bypass DisplayLink
and just go directly to the dual 4K monitors at 60hz? Or does it still fall
victim of CPU overhead due to processing DisplayLink?

~~~
bloopernova
I've wished for a universal thunderbolt/usb diagnostic widget or software for
just these sorts of issues.

I wonder how many problems like this could be solved if people just had a bit
more information about which ports supported which standards?

------
dlevine
Interesting! Was wondering about this recently when shopping for a USB-C hub,
and couldn't find many that supported 4K@60hz. Ended up getting one that does
30hz because my Display at home is only 1440p.

I have used Displaylink adapters before (have one floating around somewhere),
and was not super impressed (my machine was a bit flaky when using it),
although I did have 2 external displays going on my Macbook at one point (this
was before the days of multiple Displayports on Macbooks), which was kind of
fun.

~~~
greggman2
I went through 3 of them before finding one that worked (the first was buying
before I knew the issue existed. The second was being impatient). I'm using
this one on a Macbook Air. ([https://www.hypershop.com/products/hyperdrive-
duo-hub-for-us...](https://www.hypershop.com/products/hyperdrive-duo-hub-for-
usb-c-macbook-pro-13-and-15-2016-2017-2018)). I'd prefer one that used a
single USB-C connection (assuming that's possible) and that used a cable so it
was useful for more than just the couple of devices that have 2 USB-C ports
exactly that far apart but at the time, a year ago, that was one of the few
choices. The good thing is it does work and I have it on 4k@60hz

------
adeeds
I wish I had come across this article when I was looking for a dock for my MBP
(connected to a pair of 4k monitors). It was a pain to try and figure out if
I'd be able to get 60hz video from a particular docking station. I went with
the Caldigit one and luckily it worked. It's nice to learn _why_.

------
sgt
Although a hub is useful, it's worth dedicating one of your USB-C /
thunderbolt ports to running your external screen, especially if you can't
afford a good hub at the moment. I use a DP to USB-C cable on my MacBook Pro.

As the article points out, it's not worth bothering with HDMI as you'll easily
end up with 30Hz at 4k. 30Hz is absolutely unbearable, and I think most
developers buying a new screen now will invest in a good 4K monitor.

Note about my setup: I then run 3008x1692 (2560x1440 is also good) scaled
resolution on my 4K monitor as the full 3840x2160 resolution will make
everything extremely small. Everything is crisp and running at a beautiful
60Hz.

------
nrp
This issue was the genesis of the short-lived VirtualLink effort:
[https://en.wikipedia.org/wiki/VirtualLink](https://en.wikipedia.org/wiki/VirtualLink)

VR headsets wanted four lanes of DisplayPort, USB 3.1 for data, and power over
a single connector, and no existing standard supported that.

~~~
flafla2
> Unlike most alt-mode; this will also remap A7, A6, B6, B7 to carry USB 3.0
> signal, instead of the usual passive USB 2.0 signal. This means that one
> will not be able to extend the cable using a standard USB-C 3.0 cable, which
> has these pins mapped only for unshielded USB 2.0 signals. Also this will
> require the VirtualLink port to also detect the correct orientation of the
> USB-C plug to ensure that the USB 3.0 TX and RX lanes are correctly
> connected.

A fun/interesting hack! But breaking superposition is a huge dealbreaker.
Imagine seeing notices in software saying to flip your cable upside down...

~~~
whoopdedo
Why couldn't the connections be swappable electronically inside the connector?
The way that modern Ethernet ports adapt to the correct Rx/Tx without needing
a crossover cable.

------
SlowRobotAhead
Entertaining read. What a blunder the USB group has made with v3.x, it’ll all
work out and eventually be awesome when every port and every cable just works
and things charge fast but, almost every major feature of USB has had issues
going back to first release. More reviews and articles should have a liars
section.

------
chx
So many wrongs in this article.

> To keep a 60 Hz refresh rate, you need to step down to 2K or lower
> resolution.

Nope. 3440 x 1440 @ 60Hz is the highest res currently used which still fits
half the bandwidth of DP 1.2, see here:
[https://linustechtips.com/main/topic/729232-guide-to-
display...](https://linustechtips.com/main/topic/729232-guide-to-display-
cables-
adapters-v2/?section=calc&H=3440&V=1440&F=60&timing=cvtrb&calculations=show&formulas=show)

> They are very likely DisplayPort Alternate Mode designs using four lanes.

If a hub claims to support 4K @ 60Hz and USB 3.0 it doesn't necessarily mean
it supports both at the same time. It can be convenient to have a flexible hub
which, when connected to a monitor where two lanes are enough then USB 3.0 is
provided, if you go above then it slows down to USB 2.0. At least one of the
hubs linked from the article (very small with one power, one USB 3, one HDMI
and a non-captive cable) is such, this was confirmed by one of the sellers,
this device is available with many, many labels.

The article also omits that many, _many_ notebooks with a single Thunderbolt 3
port will _not_ support multiple 4K @ 60Hz because they put only four
DisplayPort lanes in there using a cheaper, lower power controller called the
Alpine Ridge LP. And yes, that pos is still in use despite I hoped Titan Ridge
will deprecate it. Dual port Thunderbolt controllers are all full bandwidth,
single can be half or full. Hard to tell without looking up the TB controller
used in the device on social media / stackexchange etc -- the manufacturers
are often quite tight lipped on the topic.

Another fun fact: while the Thunderbolt 3 bus is indeed 40gbps, that's only
filled out when video is used, the data speed is nerfed to 22gbps by all
existing controllers. Dell admits this in one article
[https://www.dell.com/support/article/us/en/19/sln307875/thun...](https://www.dell.com/support/article/us/en/19/sln307875/thunderbolt-3-usb-
c-maximum-data-transfer-rate-on-dell-systems?lang=en)

> Thunderbolt 3 may only reach a maximum data transfer rate of around 7 to
> 22Gbps even though it is advertised with 40Gbps

but this is so rare, every other article, even the one linked from this rare
gem of truth claims some baloney like "Systems with 4 lane design will support
up to 40gbps of data transfer over PCIe" which is obviously not true because
even without nerfing PCIe 3.0 x4 is 32gbps only but it _is_ nerfed. The
official TB3 brief also tells you this but a little overt because it is never
stated in the text but Figure 7 shows what's up in
[https://thunderbolttechnology.net/sites/default/files/Thunde...](https://thunderbolttechnology.net/sites/default/files/Thunderbolt3_TechBrief_FINAL.pdf)
And make no mistake, there are only PCIe and DisplayPort signals on the TB3
bus, there are no USB signals, the TB3 controller in the dock provides a USB
root hub. Someone should bring a class action lawsuit to Intel and practically
all laptop makers for false advertising in this... (Side note: USB 4 will be
different in the signals, if my understanding is correct then the Thunderbolt
3-like bus which is an optional mode for USB 4 will finally contain PCIe, DP
and USB signals.)

I have written similar explanations in the past for eg
[https://www.reddit.com/r/thinkpad/wiki/newdocks](https://www.reddit.com/r/thinkpad/wiki/newdocks)
[https://superuser.com/a/1200112/41259](https://superuser.com/a/1200112/41259)

------
asutekku
There's a lot of complaining from the engineering side regarding the USB-C but
for the customer it is godsend. Now instead of million little different ports,
they can use one which in well-engineered (emphasis here) products will cover
most of their use cases.

Yes, I know it is a pain to manufacture and design software for but the user
doesn't care about that. They care about convenience.

------
ChrisMarshallNY
I was reading the comments, and saw my exact issue with USB-C reflected there.

I use a Thunderbolt hub (TS3), and I drive a 5120 X 1440 Big Ol' Honker
display.

The display has a USBC port, but if I use it, the resolution drops.

I learned to unplug the USBC port, and just use the DisplayPort. If I do that,
the display works great. Full width at 60Hz.

It's not a gaming rig, so that's fine for me.

------
Derbasti
Let's talk power:

The USB-C PD charger of my Nintendo Switch does not charge my phone, but it
does charge my Surface. My phone's USB-C charger does charge the phone and
Surface, but not the Switch. My USB-C battery pack charges my phone, but is
charged by my Surface. Yeah, it just works.

How do, say, a battery pack and a Surface negotiate who is charging who over a
symmetric USB-C-to-C cable?

~~~
ben-schaaf
On the topic of power, I really don't understand how USB-C is supposed to
replace charging cables. USB-C is limited to 100W. That's enough for a switch,
phone or low power laptop, but if this[0] is anything to go by the 6 core
intel laptop CPUs already eats 80W of power. Add an extra 2 cores and you
might not even be able to sustain a CPU load without draining the battery. Not
to mention much higher power draw GPUs.

My real question here is what's the plan? Because it's not possible to push
200-300W down a USB-C cable.

[0] [https://www.techspot.com/review/1847-intel-
core-i7-9750h-vs-...](https://www.techspot.com/review/1847-intel-
core-i7-9750h-vs-8750h/)

~~~
MaddAgent
So you're thinking the new MacBook Pro 16 with an 8 Core CPU and a GPU using
the included 96Watt USB-C charger may drain the battery under full load?

~~~
rhinoceraptor
It will drain the battery at full load, the i9 is a 45 watt TDP and the RX
5500M is 85 watt TDP (plus display, ram, disk, etc).

However, there's no way the cooling on the laptop can support that much power
draw, so I'd expect it to throttle itself way before you'd drain the battery
while plugged in.

------
kkarakk
i used to think usb c was awesome and would lead to a 1 wire for everything
world.

Now i have 4 different kinds of usb c wire i need depending on usecase -

passive usb c for charging my headphones since they didn't implement a
resistor, active usb c for charging laptop,usb c for charging mobile(fast
charging),usb c for data transfer/thunderbolt/video display

what a disaster of a spec

~~~
ProZsolt
The spec isn't a disaster. Vendors implementing is. The main problem is that
OEMs don't give a sh*t about the spec and cutting corners whenever they can.

~~~
kkarakk
The spec should require clear labelling of SOME kind to differentiate between
the different types of wires. I feel like that's been a common issue with the
USB spec and one they refuse to address

------
Eric_WVGG
I saw this headline and was briefly excited for a moment that a USB-C hub
finally existed. That is, a device like an ethernet hub or a USB hub, that
would turn one port into several other ports of the same kind.

This is an article about USB-C port replicators. Four years into this and not
a real single USB-C hub exists. I’ve never seen such a botched rollout.

~~~
garmaine
USB-C hubs are not permitted by the spec.

~~~
unionpivo
I just bought new PC, I spend almost 300 EUR on Motherboard alone, just so I
had 2 USB-c (one back one front) and 2 nvme slots.

Does that mean I'll only ever be able to hook up 2 devices to my PC ? If
that's the case this sucks.

I just cheeked there seems to be lack of usbc pci cards, and the ones that
exist only have single ports :(

~~~
Eric_WVGG
Here's a 4-port card: [https://amzn.to/2WuAt4x](https://amzn.to/2WuAt4x)

------
pandada8
Dell's DA300 can do 4k 60Hz with DP1.4 though. And intel added dp1.4 support
starting with Ice Lake.

------
fulafel
re "Driver availability and compatibility for Mac/Linux is spotty to non-
existent":

Is it true that DisplayLink doesn't work well with Linux? Some years ago
people were saying that the usb-to-monitor dongles worked well. A casual web
search also gives this impression, with good support provided by the
DisplayLink company.

~~~
yaantc
You can make Display Link (DL) work with Linux, there are drivers from the
vendor and an adaptation script for Debian based distros [1] (and variants for
others IIRC). You may have to fiddle with the configuration to avoid issues
like minor display corruptions or cursor glitches. I made it work clean once,
but in the end I returned the dock. DL is to me a bad idea, except is some
specific cases.

The way DL works is that a driver on your PC creates a virtual frame per
screen, composed on your PC. Then this screen(s) content is compressed and
send to the dock DL chip using a proprietary driver. The chip on the dock
reconstructs full images and send that to locally attached screen(s) using
local HDMI or DisplayPort interfaces. Now yes, those local interface(s) may
run at 60 Hz and be 4k. But the bottleneck is not there, it is in the
compression and transmission over the USB link. In my experience, any use-
cases with large changing content (e.g.: full screen video) will give a bad
experience on a laptop (which is what I used, and is natural with a dock). The
compression will ramp up the CPU load on the laptop, the ventilator will get
noisy, and the display content was choppy too. It's definitely not the smooth
experience you expect from 60 Hz.

I guess DL can provide very good results with a laptop for use-cases with
mostly static content: reading documents, spreadsheets, word, etc. Just don't
expect to have a nice experience when most of the screen content changes
quickly.

So I returned my DL USB-C dock, bought a super cheap one as actually I only
have a 1440pt external screen for which any cheap dock will support true 60
Hz, and I have a nice experience. For 60 Hz with 4k it'll have to wait, and it
won't be with DL as far as I'm concerned.

[1] [https://github.com/AdnanHodzic/displaylink-
debian](https://github.com/AdnanHodzic/displaylink-debian)

~~~
whoopdedo
I was curious about that compression and found an analysis[1] of the DL
protocol. The first thing I saw was that it doesn't just render to a
framebuffer on the PC, it renders twice, once at 16bpp and another at 8bpp
(which it will combine to achieve 24bpp). The use of Huffman encoding seems
consistent with the state of compression in 2003 [2]. If doing it today you'd
probably go with x264 lossless but that would have been too slow 15 years ago.
In conclusion I'd guess the lag is caused by the split framebuffers. Or an
inefficient proprietary driver.

[1]
[https://pdfs.semanticscholar.org/a3ed/739f229315fe8673f227e7...](https://pdfs.semanticscholar.org/a3ed/739f229315fe8673f227e7b2d67a05ec8b6c.pdf)

[2]
[https://forum.doom9.org/showthread.php?t=165545](https://forum.doom9.org/showthread.php?t=165545)

------
wavesquid
The HP ZBook Dock with Thunderbolt 3 tends to be on ebay for around US$50 and
should do 4K 60Hz.

~~~
phire
Avoid that one. There is a reason why it's so cheap on ebay.

Sure, it's a Thunderbolt 3 dock, but the two displayport ports aren't using
thuderbolt 3. The are actually connected via USB displaylink.

~~~
_trampeltier
Uh, yes. Avoid that one. We have ZBooks and these Docks at work and we all
have all kind of troubles. But the funny thing is, we all have different
troubles. Mostly the keyboard or one or two monitors does not work ..

------
craftinator
I'm actually a bit confused by why it matters at this point. HDMI is
ubiquitous, can handle a high enough resolution/ rate that most human eyes
can't distinguish better, and is relatively cheap. It's an optimized, widely
available format, and does a great job. USB is a downgrade for this particular
task. Other than novelty, I don't see a reason to ever do this.

~~~
greggman2
What do you mean? Plenty of computers now ship with no other connectors than
USB-C. In other words HDMI is not ubiquitous

What I love about USB-C is I plug in a single cable to my laptop and I get
keyboard, mouse, wifi, and monitor (4k 60hz)

At work I have a USB-C hub for my one cable to my computer. The hub has
Displayport so I can use HDMI on a different device. At home my monitor does
USB-C natively so my keyboard and mouse are plugged into that.

~~~
Shorel
> Plenty of computers now ship with no other connectors than USB-C. In other
> words HDMI is not ubiquitous

Sadly. Mine has USB-C and HDMI. I don't think I will buy a device without HDMI
in the next 15 years.

