Fast-pskip No-fast-pskip
Burn SSIM 0.816305 0.809181

rate 603.07 605.67
FiM intro SSIM 0.970886 0.970532

rate 622.86 625.07
Rush hour SSIM 0.897251 0.901464

rate 599.98 601.09
Students SSIM 0.986635 0.986645

rate 599.26 599.33

Burn SSIM 0.722376 0.712578

rate 294.58 298.1
FiM Intro SSIM 0.937741 0.934879

rate 320.88 324.85
Rush hour SSIM 0.854779 0.858797

rate 305.84 308.25
Students SSIM 0.979623 0.979623

rate 300.39 300.58

Four test videos were used: Three from the test-video library, and the opening title of Friendship is Magic as an animation comparison. Each of these was encoded four times: Once at 'standard' x264 defaults, one at the same with the addition of no-fast-pskip, once at 'extreme' settings as might be used when trying to encode for very low bitrates and once at the same settings with the addition of no-fast-pskip. Overall, sixteen encodes were performed: Four videos, each under four x264 settings. All encodes were performed under Scientific Linux using mencoder SVN-r34833-snapshot-4.4.5 and x264 core 122.

All but one of the videos both an increase in bitrate and a lowering of SSIM when no-fast-pskip was added. The only video in which SSIM increased with the addition of no-fast-pskip was the Rush Hour video, when the slight increase can be dismissed as a consequence of the increased bitrate. After these tests, I conclude that no-fast-pskip is of little practical use.