Airtame wants to mirror (almost) any screen to any other screen

A Danish startup called Airtame is in the midst of crowdfunding a new streaming gadget that, in the company's words, lets users "show any content from any computer on any screen, wirelessly."

Enlarge / An image from Airtame's press kit, showing the dongle connecting via HDMI to a remote display (the USB connection is for power).

The product from the six-person Danish team takes the form of an HDMI dongle that plugs into any HDMI-capable display, and it's combined with an application that you install on your computer. The HDMI dongle makes itself available on your LAN via Wi-Fi, and the Airtame app automatically picks up the dongle and lets you either mirror or extend your computer's display onto the Airtame-attached screen. The fun isn't limited to HDMI-equipped displays, either—the app also lets users mirror or extend one computer's display and audio onto another's without requiring any hardware at all.
Additionally, the Airtame application can create a "public stream," where one computer's screen (and audio) can be viewed from multiple computers running the Airtame app. The public streaming works via multicast on a LAN, and it can also unicast to remote displays on different network segments—or, potentially, over the Internet.

Enlarge / Airtame does display mirroring or extending, or public streaming to multiple viewers.

The main differentiating factor between Airtame and other screen mirroring solutions already available is that it works with (and in between) Windows, OS X, and Linux. The application will be available on all three operating systems so any one can push content to the dongle; additionally, any computer with the Airtame app installed can send or receive from any other computer running it, regardless of host operating system. Atilla Sukosd, CTO of Airtame, explained to Ars that the protocol Airtame uses to accomplish this is more sophisticated than existing platform-agnostic remote-view products like VNC. Instead of sending sections or slices of framebuffer, Airtame transmits an h.264 video stream of the host system's screen. Unlike other streaming solutions like Miracast, though, Airtame eschews Wi-Fi Direct and instead sticks with standard Wi-Fi, allowing it to function as a standard network host—and do a few other tricks, as well.
The Airtame dongle itself is running a modified version of Raspbian, a customized Linux distro based on Debian. Airtame has its own set of packages containing its specific customizations, which will likely include their own modified Linux kernel by the time the device reaches shipping.

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Fighting network congestion

Sukosd also explained an interesting feature of the Airtame—the device will optionally be able to function as a NAT router to cut down on Wi-Fi congestion in crowded environments. The dongle will be equipped with a pair of Wi-Fi adapters; one adapter can be used to connect to the on-premises LAN, while the second can be used as an access point by those who want to use the Airtame (or who want to watch a public stream via the Airtame). Users who are connected to the Airtame will still be connected to the LAN through NAT via the Airtame's LAN-connected Wi-Fi adapter.
"We found that in schools or in corporate environments, where you have either a captive portal or... simply 500 people on the same access point, it was just really, really, really slow," elaborated Sukosd. "So the solution we came up with was the wireless cards, where you can control the traffic that flows through the device, and you can prioritize video and audio data over all the other data that people might send and receive."
The feature is an optional one, but in crowded environments, it should go a long way toward ensuring smoothness. Airtame's Unix underpinnings should also help to ensure that functions like DHCP address assignment and NAT'ing are done efficiently, using mature open source utilities like isc-dhcp-server and iptables.

The big "but"

There's one big problem, though: Airtame does all kinds of mirroring to and from the desktop, but it doesn't support mirroring from or to smartphones or tablets.
"We see huge demand for that—it has been one of the biggest demands from the campaign," said Airtame CEO Jonas Gyalokay. "But we are constrained by the manufacturers to actually allow the screencast of smart devices to our dongle."
"You need system permissions," elaborated Sukosd. "You can't do it from a normal app." Rather than deliver browser tab sharing like the Chromecast, the Airtame crew wants to be able to offer full screen sharing of a mobile device, and at least for now, this isn't possible. Sukosd went on to explain that this is because Airtame would need access to the device's framebuffer in order to compress and stream its contents, and that's not possible—at least, not without action on the user's part.
"Technically it's possible with jailbreaking or rooting, but obviously, we can't support that," he said.
Mirroring an Airtame-equipped PC onto an iOS or Android device would be possible through the use of an app, but at this stage in development Airtame is focusing purely on desktop and laptop screen sharing. There are no immediate plans for an iOS or Android app, though one is on the roadmap and ought to be forthcoming later in 2014.

The silver FOSS lining

The Airtame application and the HDMI dongle's firmware image will both be open sourced (likely under the GPL or a GPL-like license, though that hasn't yet been decided) as the product enters its beta test stage. Right now, that's slated to begin around late February or March of 2014. "We're actually going to open source both of them and the protocol specification," explained Sukosd.
"We will actually add a dual license on the software," Gyalokay continued. "For personal use, you can take the software and you can hack around on it and stuff, but if you want to use it in commercial ways you have to license the software from us."

The Airtame prototype hardware features a 1GHz ARM CPU and 512MB of RAM, though the final specifications are still evolving.

The open attitude is good news for some of the "missing" functionality—the lack of mobile screen sharing could easily be overcome by community developers adding it in, even if it requires a jailbroken or rooted device to work properly. None of the Airtame folks had any issue with that—they made it clear that while it wasn't functionality they would provide support for, it also wasn't anything they'd try to stop.
"We have a very open attitude to people playing around with our codebase," laughed Sukosd. "The way we see it, the more people play around with it, the better it is for us!"
Airtame's crowdfunding drive has 21 days to go at this point, and the team has already exceeded their $160,000 goal by more than $65,000. Currently, reserving a single Airtame stick will cost $89, and Gyalokay told Ars that they will attempt to keep the post-crowdfunding purchase price under $100. The current production schedule calls for the devices to ship in May or June of 2014.

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