Friday, October 26, 2012

Apple AirPlay & Intel WiDi: Reshaping Presentations & Networks

Remember when LCD projectors came out and replaced transparencies and overhead projectors?  Presentations were reshaped in awesome ways.  These days almost anyone can afford an projector for their computer.  And when designing conference rooms and classrooms, building them into the design is becoming more and more common.  Up until recently, computers had to have a VGA, HDMI, or other cable connecting the computer to the projector.  But with wireless technology progressing, there are many solutions now that are easily implemented to avoid having to run cable.  Apple AirPlay and Intel WiDi are two of these technologies, but each is not without it's pitfalls...

These two technologies are wonderful for giving presentations and displaying cables needed.  They will each mirror what is displayed the device to another display (TV, projector, monitor, etc).  However, they each do it differently, and each requires their own specific hardware.

Apple AirPlay, probably the most common of the two, was developed originally as AirTunes to stream audio.  It was later modified to include video and photos and renamed to AirPlay.  There are lots of 3rd part equipment manufacturers that make AirPlay receivers for audio only, but for the sake of this article we're only going to skip the "audio only" equipment and implementation.  Only Apple devices can stream audio and video using AirPlay, and only Apple TV can receive the audio and video stream.  Also, not all Apple devices can stream audio and video.  For mobile devices, currently iOS5 or newer is required, and you must be using an iPhone 4S or newer or an iPad 2 or newer.  For desktops/laptops, OSX Mountain Lion (10.8) or newer is required, and you must be using a Mac made mid-2011 or newer.

If you have a simple, flat network (no routers), then AirPlay "just works".  You connect an AppleTV (with your choice of display device) to your network (wired or wireless), connect your iOS or OS X device to the network, and you can use the AirPlay tools to mirror the screen.  The devices magically find each other, which makes the process "zero-config".  However, if your network is even slightly more complicated and has a router involved, this doesn't go that smoothly...

The "magic" I mentioned is actually called Bonjour, Apple implementation of Zeroconf.  All you need to know is that Bonjour uses a protocol called Multicast DNS (mDNS) to perform service advertising and discovery.  Bonjour is also how computers running iTunes find each other on a network.  The problem is that the mDNS traffic does not traverse most routers or firewalls without some work.  With modern wireless networks, this poses a big problem because most wireless controllers act as routers or firewalls between the wired networks and the wireless networks.  But fret not...there is a way this can all work...

The most popular way to make this work is with an open source project called Avahi.  Avahi is a program that runs on Linux & BSD systems that listens on multiple networks for mDNS traffic and acts as a cache & proxy to rebroadcast the queries and answers out to all the different networks.  So, if you setup a host running Avahi and give it a "foot" in each network (either directly with multiple Ethernet adapters or with one adapter and 802.1q VLAN trunking), it can "share" all the mDNS information between the multiple networks.  Avahi can do a lot, and can be challenging to setup if you want more then the basic functionality, but once it's going, it just works.  There are some gotchas with this approach if you use Apple laptops and they will be jumping between networks, but for the most part, it works well.

Switching gears, Intel WiDi is much simpler to setup and offers a few different choices of hardware.  For the receiving side, Belkin makes a device called ScreenCast, and NetGear has a device called Push2TV.  These are the most popular, but as WiDi becomes more popular, more receivers are coming out.  Some TVs are even starting to come with WiDi.  The only devices that currently support sending video to WiDi receivers are laptops with Intel processors and Intel video cards. currently lists 145 laptops that come with WiDi it's becoming fairly common.

WiDi works over a modified WiFi / 802.11 network card and a special network stack.  What this means is the laptop talks directly to the receiver, bypassing any LAN or WLAN you have.  The process to pair is fairly simple.  Every receiver is slightly different, but the process is essentially as simple as selecting the receiver you want to "broadcast" to from a list in the WiDi software, and then entering the code that appears on the TV/projector the receiver is connected to into the WiDi software.

One nice benefit of Intel WiDi over Apple AirPlay is that in addition to screen mirroring, Intel also has an option where you can have the WiDi display as a 2nd monitor.  This means that for presentations, you can have you notes up on your laptop display and the presentation itself up on the projector.  Also, WiDi doesn't use your network at all, so there are no requirements or compatibility problems with networks.  This also means that you can bring a projector and WiDi adapter with you anywhere, and you know it will work with your laptop anywhere you go.

So which is better?  That's for you to decide.  It depends on your use case, network, etc.  If you're a 100% Apple shop, then AirPlay is clearly the winner.  If you're mostly Windows, then WiDi will suit you better.  WiDi is simpler to setup on your network (since it's NOT on the network), but Apple TVs can do more.  It all depends on what you need to do.  What I can tell you is using an Ultrabook and WiDi to watch Hulu and other TV websites on a TV is VERY cool. :)



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