Wireless Screen Mirroring
Screen Mirroring, Sharing, or Casting?
What is wireless screen mirroring?
Wireless screen mirroring is a term that describes the act of reflecting, or mirroring, the contents of a device screen, onto another screen. Most commonly, the term refers to mirroring content from a laptop, tablet or smartphone, onto a larger display screen as may be found in a classroom, meeting room, or conference space.
As wireless presentation systems gain favor in education, business and government applications, so the terms wireless screen mirroring, wireless screen casting and wireless screen sharing get rolled into the conversation. But what do these terms mean? What’s the difference between mirroring, sharing and casting?
In this edition, we’ll cover wireless screen mirroring. The concept of screen mirroring was technically possible long ago, but it wasn’t until the Wi-Fi Alliance decided that the future of display connectivity was going to be wireless, and that Wi-Fi was going to become the medium for that connectivity, that the term took off. In an homage to the mirroring term, the Alliance named this new protocol Miracast. Get it? “Mira” as in mirror, and “Cast” just for good measure.
Wireless screen mirroring was supposed to have a huge impact on consumer technology, as users would now be able to queue up content on their phones and tablets, then Miracast-it to the big screen. The concept was enticing, exactly at the time that phones became smarter, Wi-Fi became faster, and content moved to a streaming model. This perfect storm of conditions was to push Miracast and wireless screen mirroring into the hands and homes of billions of users.
What happened is far from what was expected. It turns out that wireless screen mirroring turned into a novelty, a little-known feature that although supported by almost every smart-TV and Android device manufacturer, had a fatal flaw. What happened to be a flop in consumer electronics, turned out to be a boon in the professional AV industry.
It turns out that wireless screen mirroring is a bad idea for home use by consumers, but a great option for classrooms, meeting rooms, and many other “presentation” applications. In fact, wireless screen mirroring is the genus of wireless presentation systems and serves as the technical foundation by which most all current solutions have evolved.
The reason that wireless screen mirroring never took off in consumer applications is technical, but easy to understand. Wi-Fi (and Ethernet) is a networking standard that transmits “packets” of data from one device to another over a common medium, used by all of the devices connected to it. If a packet collision occurs, the receiver might not get that data, so the device sending the packets will re-transmit the lost packets to make up for the loss. If this re-transmission takes place in the background, you never even notice it. If it happens in real time, it’s a disaster.
That’s why content-delivery systems like Netflix, Chromecast, and others, have avoided wireless screen mirroring in favor of other streaming methods. In other words, when you use your phone to select a movie that is played back on a Chromecast device, you’re not screen mirroring, you’re screen casting. The movie isn’t streamed to your phone, and then mirrored to the Chromecast, it’s sent directly from Amazon’s server to the Chromecast over the Internet. This is an important point to keep in mind.
The viewer sees a small delay of maybe a second or two, then the movie begins to play, generally without interruption. Sometimes, the display will start out pixelated, then settle into full resolution. What’s happening behind the scenes is that the data that makes up that movie, is accumulating in a memory buffer on the Chromecast device, always ensuring that even if packets are dropped, there is time for retransmission before the user sees any disruption in the stream. The viewer has no idea this is taking place, because they can’t see the movie at it’s origin, only after it has been buffered.
That’s great for consumers who want to watch a movie streamed from the Internet, but it still leaves the professional user in limbo. Inside a classroom or an office, users want to mirror content from their local device to the big screen, and that mirroring needs to be in real time. In other words, what happens on the display screen has to mirror what’s happening on the user’s device, at exactly the same time. Imagine if you’re demonstrating a website on your laptop while you’re screen mirroring; if there is a delay between when you click on a link and when the audience sees it, there will be confusion. Therefore, in a wireless screen mirroring application, low latency (delay) is key.
Wireless screen mirroring devices are sometimes tested by prospective users by streaming a YouTube video from a smartphone or tablet. The result is seldom satisfactory, especially when compared to a consumer screen casting adapter. This is the classic “apples and oranges” scenario where two different products, with two different missions are compared. Wireless screen mirroring products are aimed at minimal-latency, or real time, screen mirroring applications. By consequence that means they will work best with content that requires less bandwidth than say, full-HD video. Consumer streaming devices are still viable choices if Internet video is your primary application.
Wireless screen mirroring has found its place in the professional AV industry, serving the needs of people who want to make presentations, without wires. It is also very much capable of streaming video, web pages, documents and pretty much anything else that’s on your device screen. But because wireless screen mirroring consists of a peer-to-peer connection, between the user’s device and the mirroring receiver, it is prioritizing low latency over buffering for more fluid, high-resolution motion video. And that’s precisely why Miracast never delivered the screen mirroring revolution that consumer electronics manufacturers were in search of.
The core functionality of today’s wireless screen mirroring systems is in fact the ability to share your device screen with a big screen in real time, without wires. Screen mirroring is the way we describe how this sharing takes place, but it doesn’t define the technology that’s used to do so. It might be Miracast, but it could just as easily be some other protocol, or proprietary method. Wireless screen mirroring is simply a great way to show your audience what’s on your screen, and do it quickly and easily.
There are many advantages that wireless screen mirroring systems offer when compared to a cabled screen connection. First, making connections to the screen is much faster, especially if several presenters need access. Time savings add up fast, as one might have a room-full of people waiting for the presentation to start. Second, and just as important, is that wireless screen mirroring systems are compatible with a much wider range of devices, including mobile devices. No more hunting for adapters, dongles, or the right cable.
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