Performance :: Video Has A Mild Stutter / Streaming And Some Local Files

I upgraded to Windows 10 in October 2015 (clean install on a new SSD) and until recently all video looked fine. But recently, sometime after the 10586 update, streaming video started stuttering. It's subtle, like random frames are missing, and audio is smooth, but the picture is annoying enough to be annoying.

In a short while I found that many local files on my hard drive were stuttering, too. I tried every trick I could find and even replaced my onboard graphics with a new nvidia graphics card with 2gb of its own RAM, but nothing worked. Over the weekend, I found that the problem seems to be isolated to streaming files and, for some reason, local MP4 files created at 720p/30fps. Some of these local files were recorded on this PC with PlayOn, which records from streams, so I thought it was still a streaming issue. But a couple of 720p/30fps files I recorded with a Diamond GC2000 also stutter, and so do streams I recorded a year ago with PlayOn, which used to play back properly.

Local files recorded on a standalone device at 1080p/30fps play well. So do files from that same device recorded at 720p/60fps. Local files play better with PotPlayer than with VLC or WMP...Streams stutter with IE11, Edge, and Chrome. Flash is up to date, as are all drivers and Windows updates. For local files, PotPlayer works better than VLC, MPC-HC, or WMP, but video is still not right, and individual players don't work with streams.

The internet connection is not a problem; download speeds are reliably above 200 Mbps, and the modem was replaced to ensure it's not the issue. Besides, my old BD player streams properly, and by today's standards it's a dinosaur.I'm running an Intel Core i5-3570K with 8gb RAM with Windows 10 Pro 64 on an SSD. Data files are on a high-speed spinning drive that I've set to not spin down, and I've set the PC to never sleep, hibernate, or turn off the monitor. I've even turned off the screen saver.