Thoughts on the Chromecast

I’d love to get a bunch of those, but not for the reasons most people would think.

I’ve been tinkering with digital signage (after a fashion) for a year now (it’s been my little side project at work, with great results at Codebits last year), and the Chromecast hardware seems perfect for the most common use case – i.e., playing videos on large screens.

We’ve been using Raspberry Pis for that (and rendering web-based status boards) at the office for a long while, but that has a number of issues:

  • They’re too unreliable by my standards (even with various degrees of paranoia coded into our custom client and swap disabled, I have to re-image corrupted SD cards every couple of weeks or so).
  • Even with the watchdog timer enabled and running the latest firmware, the things still crash and lock up mysteriously (often causing SD card corruption).
  • Without a decent browser rendering pipeline, it’s simply too slow for rendering many web pages (hence my having fiddled with streaming a live desktop to it and setting it up as a bare-metal RDP client).
  • The boards are still a tad too big to mount unobtrusively in some situations (and they have lots of bits sticking out).
  • We can’t stream our laptops to them trivially for quick presentations.

This last bit has been a particular niggle of mine, especially since pretty much every modern TV has some form of UPNP support that just sits there unused. A desktop PC can stream video to literally hundreds of clients depending on refresh rates and overall quality (streaming a full-screen browser is a no-brainer, and takes up very little bandwidth), and this is, after all, the XXIst century, so why haven’t we figured out a universal standard for doing presentations wirelessly yet?

So up to last week I’ve been looking for ways to implement something like AirPlay mirroring (which is a shady deal at best, but entirely feasible).

The trouble with most solutions so far is that you need some sort of client software, which is a major pain.

But the Chromecast’s browser integration should (mostly) fix that – albeit with another, equally proprietary and fiddly protocol, but a much more widely available client.

And in a world where 90% of most people’s work eventually gets rendered on a browser, putting a Chromecast dongle in every meeting room is a no-brainer (even if some form of adapter might be required).

I’ve been fiddling with a couple of Android HDMI dongles in an attempt to fix all of the above, but every single hardware and firmware combination I tried was too iffy to consider deploying, and thanks to high-pressure, throwaway hardware design cycles it’s pretty damn near impossible to find an ubiquitously available, cheap and minimally open platform. Ironic, I know.

But the Chromecast is almost perfect – even if Google, in their characteristic US-centric way, has yet to emit more than vague noises regarding selling it worldwide – by which I mean “including Portugal”, of course.

Looking at the publicly available source code, using the Chromecast for digital signage should be trivial – the thing uses SSDP for discovery, the basic protocol seems easy enough to implement/clone/spoof, and there’s even a barebones, Python-based emulator already – which, obviously, runs on a Raspberry Pi. Well, at least it’s already crashing on mine1.

The devil, of course, is in the details. There’s still a fair amount of work to be done (and likely a fair amount of network tweaking) to design a signage system that can manage a bunch of Chromecast dongles and still allow for ad-hoc presentation use, but I’m positive it can be done.

Obviously, I need to get my hands on one first – so if you’re sitting in one of these offices reading this and can help me with that, feel free to drop me a line. There seems to be a fair amount of legalese involved in developing for it, but I’m game, and have a couple more ideas for it besides this.

  1. Sorry, no nice code yet - I’m having some trouble extracting video info that can be passed on to omxplayer, but I’m sure there’s a thundering herd of geeks trying to do the exact same thing right now (or running to their keyboards as they read this), so fear not, turning your Raspberry Pi into something resembling a Chromecast will happen – to a degree, at least. ↩︎