Compared to how HTML5 youtube player, VLC, or even Windows Media Player play
audio, video and subtitles at varying playback speeds (or even some higher end (S-)VHS players),
how do BDP3000 series (and the 5-9k series) play video/audio/subtitles at the different search speeds ?

Any difference whether playing from a blu-ray, or an MKV file from a USB HDD ?
Any better/worse if the MKV has a lower bitrate and/or no b-frames and low
keyframe interval ?

Mostly interested in the 2x speed I suppose, since you probably can't even freely choose
playback speeds between 1-4x at 0.1x steps.

At higher speeds, I'd be pleasently surprised if it showed anything other than an I-frame
every few seconds.