A new generation of display interfaces is going to redefine AV and IT connections. Are you paying attention?
Do you own a tablet? A smartphone? Most of us have one if not both of these, and use them almost constantly. Both of these gadgets fall into the category of BYOD, a/k/a Bring Your Own Device. They can surf the web, take and show photos and videos, and make phone calls. They can also function as a GPS or a touchscreen control panel.
An increasing number of folks use them to process credit card transactions. We read daily newspapers and eBooks on them, and order goodies online. Sometimes we use them to “showroom,” going to a retail store to check out some new gizmo we want and then search for the best price online. And, of course, we stream TV shows and movies on them.
But there’s more to the story. Take another look at your BYOD: specifically, the power connectors. Sure, you can plug a transformer in and charge ‘em up. Or connect a micro USB cable to load files to and from your laptop or another computer. But did you ever try to connect them directly to a TV or a projector? Have you tried playing movies back through that same port?
You may not even be aware that your tablet or phone has a display connection. Well, surprise! You certainly do on your tablet, and if your smartphone was made in the past three to four years, you likely have a display connection on it, too.
“How is that possible?” you’re probably wondering. “That little power connector only has five pins on it. HDMI connectors have 19 pins! Even VGA connectors have 15 pins. That can’t possibly work!”
Wrong. As we will see shortly, five pins are plenty for making display and audio connections, along with hooking up power, USB and a bunch of other signals. You just hadn’t noticed. Read on, and learn all about a new crop of display connections that is changing the way we think about interfacing.
At their core, tablets and smartphones are simply computers with built-in displays. They run full-blown operating systems like Android and iOS. They can load and open files, such as documents, spreadsheets and even PowerPoint presentations. And, of course, they can take and display photos and videos.
Today’s “typical” tablet or smartphone also has lots of memory: usually 16 to 32 gigabits (Gb) for starters. That’s enough to store a few full HD movie files! And the motherboard for your tablet or phone also has a video graphics chip built into it, one that easily can drive an external monitor, television or projector. (Or matrix switcher, distribution amplifier or presentation switcher/scaler, for that matter.)
All you need is the correct connector to make the hookup. And there are a few variations to choose from, depending on who manufactured your BYOD and what OS it uses. The cables themselves are inexpensive and easily found online, and you can also locate adapters to full-sized versions of the same connections.
Not surprisingly; all of these connections are digital, and most of them are variations on the High Definition Multimedia Interface (HDMI). But there are some exceptions to the rule, especially if you use a laptop manufactured by Apple. Let’s look at the most popular flavors.
HDMI, which has become firmly entrenched in our industry, does, indeed, use a 19-pin connector (Type A). There’s also a “mini” version with the same number of pins (Type C), but the connector is much smaller. Did you know that an even tinier one (Type D, or Micro HDMI) exists, again with the same number of pins?
You’ll often find Mini HDMI connectors on digital cameras and compact camcorders. Yes, you can connect those to a display and sequence through all of your photos, and some models will let you show live video while recording it. That’s because your camera or camcorder also has a video graphics chip built in.
Micro HDMI is more commonly found on smartphones and, as of the date this was written, at least 20 models of smartphones offer this interface (most made by Motorola). Plug in a Micro HDMI/HDMI cable to your smartphone, attach it to a display and bingo: You’re watching video at 1920×1080 resolution, with a 60Hz refresh rate and 8-bit color rendering, just like a Blu-ray disc.
The 1080p/60 format is quite common on smartphones; if you plan to use them to play back video or even make a presentation (and why not?), you just need to make sure the display supports a 1080p/60 RGB signal. That shouldn’t be a problem, what with the proliferation of 1080p imaging devices available today.
Micro and Mini HDMI aren’t that exotic as interfaces. All they can transport is display and audio, just like a full-size HDMI connection, using three transition-minimized differential signaling (TMDS) channels. They support EDID and HDCP, just like their big brother. But there’s a variation on HDMI that is a bit more versatile.
Mobile High-definition Link (MHL) takes the basic HDMI interface to a new level. Instead of 19 pins, the MHL interface requires just five to make a connection. That’s the same number of pins found on a micro USB connection. In this case, video and audio (media layers) are riding along on top of the USB physical layer. So you not only get a display connection, you can also upload and download files, charge the device and provide phantom power to another connected BYOD (to the tune of 5 volts@500mA).
If you’re up on HDMI technology, you may be wondering how MHL can do with just five pins what it takes HDMI 19 pins to do. Simple: MHL uses only one differential pair of wires to transmit the TMDS signal. That means that MHL and HDMI connectors aren’t plug-and-play compatible: An MHL connection requires a different transmitter and receiver chipset at each end.
Sense The Difference
MHL connections can also sense the difference between a standard USB/power connection and an MHL hookup, and switch the operating mode of the port accordingly.
That’s how it can support so many different formats. The newest version of MHL, 3.0, was announced a year ago and, like HDMI 2.0, supports 4K (3840x2160p/60, 8-bit color). It also offers a high-speed data connection plus HID connections for mouse and keyboard. MHL can also provide up to 10 watts of charging power and can even drive multiple displays.
At the 2014 CES, Silicon Image demonstrated a “dumb” laptop computer (no keyboard or CPU, just display and input/output connections) that functioned only when a Sony Xperia smartphone was snapped into its cradle. The phone provided the CPU, control interface and video card. Another SI demo had an Xperia phone controlling a Samsung TV (both Sony and Samsung support MHL on their LCD TVs and phones), working as a remote control and also streaming content.
As of mid-June, there were several dozen MHL-compatible smartphones listed on the MHL LLC website, most of them branded by Samsung and Sony. There were also models from HTC, Huawei and LG. You’ll have to check specific models of televisions to see if they support the MHL connector, which has also been used to interface a Roku “stick.”
Amazing as the MHL interface sounds, it wasn’t the first miniature connector to support multiple media and physical layers. That honor goes to Mini DisplayPort, a shrunken-down version of the 21-pin connector we occasionally see on new computers and displays.
Mini DisplayPort is the default interfacing standard for Apple laptops (MacBooks). Unlike HDMI, DisplayPort is a 100% digital, packet-based connection that uses four separate lanes to move display and audio data. Each lane can support up to 5.4 gigabits per second (HDMI 1.4 is capped at 10.2Gb/s), and all four of the lanes in a version 1.2 connection can display a Quad HD signal (3840×2160 pixels) with a 60Hz refresh rate and 10-bit color.
Mini DP also has 21 pins and supports the full DisplayPort specification in every other way, including a data channel and even Ethernet connectivity. A new wrinkle for Mini DP appeared in 2010, when the Thunderbolt media layer was added. Thunderbolt can transport high-speed data, emulating a PCI Xpress bus and running at 20Gb/s, all while connected to a display.
Pretty cool, right? Intel has even offered demonstrations of a virtual Ethernet connection (peer-to-peer) using nothing but Thunderbolt links daisy-chained together. And a few companies have come out with Thunderbolt breakout boxes, extracting FireWire, two or more USB connections, Ethernet, Thunderbolt loop-through ports and analog audio jacks from a standard MacBook.
But that’s not all, as they say in TV commercials! At CES, the Video Electronics Standards Association (VESA) announced DockPort, a new media player that combines USB 3.0 with DisplayPort. Unlike MHL, DockPort and display/audio connections can be active at the same time, as can phantom power (3.5 volts@500mA). That means you could, in theory, build a switcher to handle video, audio, serial data and a data bus simultaneously! It’s all made possible by the digital packet format integral to DisplayPort.
Not all applications require the full bandwidth of the standard DisplayPort connection. So, VESA introduced a slimmed-down variation for smartphones and tablets, known as Mobility DisplayPort, or My DP for short. (This connection also goes by the name SlimPort, which we’ll use going forward.)
SlimPort connections use only one lane instead of four, but the latest iteration can still deliver video signals with resolutions up to 4096×2160 (UHD) and multi-channel Dolby or DTS audio. Like MHL, SlimPort rides as a media layer atop the micro USB connector ubiquitous to smartphones, tablets and even Chromebooks.
When a SlimPort connection is made, the BYOD reads EDID and begins sending video and audio to the connected display (which, of course, must have a compatible SlimPort input). The power function remains on all the time, so power can be sent to a tablet or phone (charging) or to a connected device (phantom power).
If SlimPort sounds like a variation on MHL, it is. The difference is that SlimPort is 100% digital, with packet transmissions, while MHL is still a TMDS system. To connect SlimPort to displays that aren’t already compatible, you can use inexpensive adapters that cross-convert to HDMI, DVI and even VGA. (Remember VGA?)
Apple’s smartphones and tablets stand apart from other BYODs in how they make external display connections. Unlike MacBooks, the iPhone and iPad do not have built-in video graphics drivers; their older 30-pin connectors, and the newer 16-pin Lightning jack, are strictly for power and serial data, just like a micro USB port.
When you want to connect your iPad or iPhone to an external display, you need to go through one of Apple’s AV adapters, which actually contain the video graphics driver. (That’s why they’re so expensive!) These adapters support full-size HDMI and VGA (again?), but there is no support for DisplayPort connections at present, which is ironic considering that Mini DisplayPort is Apple’s display interface choice on all other platforms except Apple TV (HDMI).
The Lightning connector is intriguing in that it is symmetrical. You can plug it in with the pins oriented either way, and that’s quite a departure from the polarized micro USB connector everyone else uses. Apple breakout cables separate the display and data/power interfaces, unlike MHL and SlimPort. That makes for a bulkier dongle hanging off the bottom of your tablet or phone.
Given the prevalence of HDMI-based connectors, there are plenty of adapter cables to convert to that format. Aside from Apple’s unique handshake, you will find adapter cables to convert full-sized DisplayPort and Mini DisplayPort to HDMI. There are also MHL to HDMI adapters along with SlimPort to HDMI cables.
So why don’t we see any adapter dongles that convert the other way? Because HDMI doesn’t support phantom power, essential to run the tiny conversion ICs present in signal format converters. As mentioned earlier, DisplayPort provides 3.5 volts@500mA to power external devices, more than enough to convert the DP packet format to HDMI’s TMDS structure. You can convert HDMI to DisplayPort, but it takes a much larger interfacing box to do the trick.
There are also umpteen million companies selling adapter plugs, such as HDMI “A” male to Micro HDMI female or the other way around. Converters that output a DVI signal can carry embedded audio, which you’ll need to extract with additional electronics. And converters that export to a VGA signal require a separate analog audio connection. (But why in the world are you still using VGA?)
By now, you’ve surely caught on to the significance of this new generation of interfaces. They’re small, but powerful. They can transport multiple signals in their physical layer, which results in fewer cables to do the job. And at least one format (Thunderbolt) can be daisy-chained among connected devices. Corning has been showing pre-made multimode optical fiber extensions that use Mini DisplayPort interfaces at either end for some time now.
As tablets, smartphones and “phablets” (large smartphones) gain in popularity, interfacing them into existing AV systems will become quite the challenge. Both MHL and SlimPort hold promise as dual-function systems (control and display/audio), and could replace dedicated touchscreen control panels entirely, using simple apps to operate AV equipment.
There’s also the wireless angle. Several platforms exist to transport wireless display connections, and the two most prominent are Amimon’s 5GHz Wireless High Definition Interface (WHDI) and Silicon Image’s 60GHz Wireless High Definition (WiHD) platform.
Both of these are 100% compatible with HDMI 1.4, which means, believe it or not, that they can stream 4K video@24Hz and 30Hz.
The marriage of wireless and BYODs seems logical, but there’s the issue with sending control signals over a wireless connection. At present, there aren’t any wireless DisplayPort products on the market, although there is a detailed wireless specification for this format. Given its packet architecture, a wireless DP interface would be the best choice for controlling an AV system from a BYOD (or a secondary WiFi channel could be used for that purpose).
Long-term, if we see a migration to packet-based display interfaces like DisplayPort, our industry will take a big step into what’s called “software-based switching,” just like how telecom and IT switches work. And that will enable compression and stream multiplexing, pushing bandwidth requirements even higher for future AV systems design.
Are you paying attention?
Contributing Editor Pete Putman, MS, is the president of ROAM Consulting LLC. He is a Senior Academy Instructor for InfoComm and was named their Educator of the Year for 2008. Pete is a member of SMPTE and SID, and holds CTS and ISF industry certifications.
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