Play local videos on Chromecast, native resolution, no transcoding/WebRTC
I discovered this little hack/Rube Goldberg machine that lets you play local videos with no compression/downsampling on your Chromecast.
I installed apache on my MacBook Air and pointed it to my media directory. I opened up the video in my local chrome instance through the apache server and not as a file, and used the IP of my local machine (http://10.0.1.6/Mad.Men.S06E11.HDTV.x264-2HD.mp4) to make sure the file/server worked and played. Then I dropped that url into this nifty thing with the HTML5 setting, and chose my device.
That's it. This works really well since my MacBook Air can't handle the WebRTC/transcoding well at all, and this is decoding the video right on the Chromecast at native resolution.
So that is a bit of a workaround, but it's easy to see how this process could get hacked together into a nice app on any platform. It would be a bit battery intensive, but serving it via http is probably no worse than DNLA.