Operating system: Windows 10 64 bit
Graphics card: Nvidia GTX 1060 256 bit 6 GB
Broken: (example: 2.80, edbf15d3c044, master, 2018-11-28, as found on the splash screen)
Worked: (optional) Blender 2.79b
Short description of error
While you're camera tracking or matching your clip with your cg element you need a decent frame rate to work with to be able to get the best feedback from your footage however in Blender 2.80 (the final built) when you add a clip the fps is not going above 15 fps( or simply is not making up for it's fps limit which was 29.97 for me with a basic scene had no more than 1k polygons) for me and it's just becoming so much harder to match the cg element with the playing clip whose base fps is 29.97. I wanted to try this with the older 2.79 built and though it worked butter smooth I've noticed something: Blender 2.79 seems to be baking its animation keyframes to some kind of a cache. While the fps wasn't that great at the first place just like it was in Blender 2.80, after finishing playing the clip till the end, it kept playing it at it's maximum fps limit which was 29.97 and i was able to get a perfect feedback out of it. I think it's some kind of a bug in 2.80. I looked for the settings to see if there were any animation caching settings but i couldn't find such a thing. Hope it'll be fixed soon.
Exact steps for others to reproduce the error
Just add a clip to your camera and see the playback fps in 2.80.