I see several bugs against various linux distros about the video corruption problem that appeared on intel graphics when the 3.14 kernel arrived, but I don't see an upstream bug here, so I'm making this one. Details of the problem can be found in various other bug reports:
Only seems to affect "xv" video, gl rendering is OK (and a good work around), but xv seems to be the default for most players, so it gets noticed.
Please attach your Xorg.0.log.
And a screenshot or photograph.
Created attachment 99223 [details]
photo of corrupted mplayer window
If I take a screenshot, the image provided in the screenshot is not corrupt (which probably says something about where the problem is). This is a photo I took of the screen while playing the video for the Doctor Who episode "Blink" with mplayer using the -vo xv option.
Horizontal bands seem to be leftover from old frames trying to catch up. In fact, if I pause the video, in a few seconds they will manage to catch up and everything will look normal till I start playing again.
Created attachment 99224 [details]
There are other copies of the log and dmesg and wot-not in the bugzillas pointed at. Perhaps they have something in common.
You are all using hsw + uxa. UXA Xv uses textured video, which should mean that there is no discrepancy between the GetImage screenshot and the image.
Are you using any form of compositing?
Have you tried a more recent driver with the switch to SNA? (That at least would provide us with more diagnostics.)
I don't know what the ksnapshot tool uses to take a screenshot, but it definitely shows an image without the banding (using gimp for screenshot has the same results - no banding).
I'm running a plain fvwm session with no compositing or any kind of fancy eye candy.
I see the debian bug says that adding an xorg.conf.d file to force SNA did fix the problem. I haven't tried that yet.
Created attachment 99253 [details]
Xorg.0.log with SNA enabled
OK I created the file /etc/X11/xorg.conf.d/intel.conf with this content:
Identifier "Intel Graphics"
Option "AccelMethod" "sna"
Then I rebooted and I can indeed play video now with mplayer -vo xv without the banding effect. Attached is the new Xorg.0.log file from booting with intel.conf.