Poor video performance since last mesa update

[Kevin Oberman]

Since the last update to mesa on my Ivy Bridge system I have been getting
very poor video performance for high resolution video. I'm not seeing he
CPUs saturated, but the video is jerky... lots of dropped frames when
playing full-resolution 1080p from youtube as well as with mpv. xine is
worse with the image getting blocky and with serious color artifacts.

If I play the same video H.264 codec) but set the view at half resolution,
it plays correctly. It was fine until the update to 17.2.4.

FresBSD 11.1 with all ports up to date.
Here is what mediainfo says about the mp4:
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High at L4
Format settings                          : CABAC / 2 Ref Frames
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 2 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 4 min 41 s
Bit rate                                 : 7 302 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.141
Stream size                              : 245 MiB (95%)

Is this a known issue or should I open a bug report? I've seen no similar
reports.
--
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman at gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683