What is Miracast?

I’m sitting with a bunch of friends, at Greg’s house.  Greg being a friend.  One of the bunch of friends.  Who I’m sitting with.  You get the picture.  I mention a particularly hilarious YouTube clip.  You’ve probably seen it, it’s the one with the cat.  Oddly neither Greg, nor any of my other friends have seen it.  So, in an effort to educate them, I summon all twelve of us to crowd around my phone and begin to play it for them.

This is life 12% of the way through the twenty-first century.

But what if things were different.  What if, instead of playing the video on my phone, I could beam it to Greg’s TV?

That’s where Miracast comes in.  With Miracast I could do just that.  We could all watch YouTube cats to our hearts content from the comfort of our Lay-Z-Boys.

So, why isn’t it here yet?

Well, as I write this, Miracast is quite a new standard.  And in a standard’s early days it takes time for things to begin to work well together.  But let’s look at what Miracast actually does:

Firstly we have to find out about the TV.  And we don’t want to go through all the hassle of connecting to Greg’s home network.  So we use WiFi Direct (which I’ve explained elsewhere) to create a peer to peer connection.

Now, for Miracast both devices have to be WiFi Direct compatible and both devices have to support Miracast.  So it will be a time before Greg gets all the bits of kit necessary.  Nevertheless, several companies have certified Miracast TV adapters, so we might be able to start playing with this quite soon.

There have been previous attempts to create video streaming solutions:  Apple have their proprietary AirPlay – which does the job, but requires you to tie yourself both to an infrastructure network (though I’m hearing rumours that this is going to change soon – hopefully in a WiFi Direct compatible way) and to Apple proprietary devices (and I’m hearing this will change just after snowflakes decide to remove their travel advisory about visiting Hell).  Everyone else has been playing with DLNA – but the manufacturers of DLNA devices have failed to play nicely with one another, and DLNA relies on everyone being able to decode every format of video.

So what Miracast does is specify one video format (H264 – which is pretty widely used) and then provides HDCP DRM wrappers around it which are identical to those used by cabled interfaces.  Miracast essentially becomes a cable in the ether.

And this will solve all our AV problems, right?

Well, Miracast doesn’t support audio only (which is a bit of an oversight), but the WiFi alliace certification does at least mean there will be some interop testing going on.  The key thing to remember though is that Miracast is just a virtual wire – it doesn’t control who can access a particular device, or allow you to control anythign about the device other than what is shown on the screen.  In short, its a technology which could well be useful in home AV, but it isn’t the complete solution.

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