Video playback in Windows guest badly compromised, as seen in Chrome and Firefox (but not VLC Video player!)

[mik_]

Environment is:

Machine: Thinkpad Yoga laptop with I7-4600U processor and Intel HD Graphics 4400.

Host: Debian 8.0 AMD64 latest (XFCE4 window manager, though should have no effect)

Guest: Windows 8.1 64bit pro , with 2D and 3D acceleration enabled in VirtualBox.

VirtualBox: 5.0

Installed the "guest additions" in the guest.

Problem description:

(A)

Playing any YouTube video (e.g. ​https://www.youtube.com/watch?v=1Y0kX7dfGKU ), in any resolution (even 144px!),

• lags so bad that viewing is unbearable,

• very clear vertical sync problem (i.e. half new frame on upper part of screen, half old frame on lower part of screen), and

• the audio output is stuttering (indicating CPU overuse).

So it looks like video presentation is unaccelerated!

(B) Installing VLC player and making it use the "Direct2D video output" rendering backend, produces *excellent* video playback though!

If I only knew how to switch the web browsers into this video output mode!

(There is a slight vertical sync but that's fine.)

(B.2) In VLC, using the "DirectX" backend shows a black window though!

(B.3) In VLC, using the "Direct3D" or "OpenGL" backend crashes VLC though - it just exits and there's no crash report dialog box or alike!

(B.4) In VLC, using the "Windows GDI" backend produces the same video display experience as in (A), i.e. stuttering video and audio - this indicates that (A) is made completely without acceleration?

(B.5) In VLC, using the "OpenGL (experimental)" backend gives no output.

(C) The video in (A) was HTML5 video playback. Also trying Flash video playback on ​http://www.adobe.com/devnet/flash/articles/vidtemplate-engage-with-flash.html gives some kind of stuttering in the video and audio playback, while not nearly as bad as in (A), it's still very laggy.

[mik_]

VBox.log

[mik_]

Clarifications:

Chrome and Firefox give maybe 4fps. So this shows complete absence of hardware acceleration.

By some reason, while my Windows guest says it takes 0% CPU, doing "top" in the Linux host shows VirtualBox takes 20% CPU, perhaps that's the source of the problem that:

VideoLan has the vsync flickering problem, and once every couple of seconds there's a very very tiny video or audio stuttering problem, enough to be noticed though -

Playing the same video in Chrome in the host has none of these problems i.e. no vsync and the playback is perfectly smooth also in presence of the 20% CPU consumption.

The VBox guest has 2 VCPU:s and the CPU has 2 cores, so the 20% CPU consumption should be a no-problem.

Any thoughts or suggestions for how to track further would be much appreciated!