Well I got all excited because I thought I solved it... AMD Catalyst control center, which is the settings screen for my video card driver, had a bunch of video options enabled like denoise, deblock, etc... a half dozen filters or something. I tried disabling them and the video seemed to play smooth. I reopened it and it was right back to being jerky again. And the options are still disabled when I return to the settings.
So anyway, before that, I tried your suggestion but I must be doing something wrong. Here's what I did.
1. Downloaded LAV nightly build installer at
https://files.1f0.de/lavf/nightly/ , installed it, went to settings page for splitter / audio / video, changed no settings except to enable DXVA2 (native).
2. Went to media player classic HC, options, internal filters, unchecked everything in both columns.
3. Went to external filters, added LAV spitter, LAV audio, LAV video decoder (in that order) then chose "prefer" for the merit setting on each of these.
Apply, then OK, closed the program, reopened it, reopened one of the problem MKVs.... still stuttering.
I'm not sure if I can upload a sample for you, because I don't have tools to make a short clip and also I don't want any copyright issues.
Would the info on this screen hold any clues?
http://i.imgur.com/XhaF7in.jpg