[mythtv-users] Mac OS X choppy playback at high display resolutions, such as 1080p

[Eric Robinson]

> What sort of display are you connected to?   This problem, as far as I
> can tell, only happens on very high resolution displays.   I have seen
> several reports of it with 1080p displays, and I see it on a 24" iMac
> with 1920x1200 display.
>
> On my Mini, which is connected to a 720p display, I never see this
> problem.  So, I just want to make sure we're seeing the same thing.

I have three brand new 2.0Ghz minis.  One of them is connected to a
brand new Sharp LC52D64U through HDMI at 1080p (1900x1080).  That is
the only monitor that appears to have the issue.  I haven't been able
to confirm 100% with the other minis running on 720p Vizio TVs but the
playback seems smooth enough when it's not waiting for buffering
(they're wirelessly connected via a weak 802.11a signal currently).

I played around with the Sniperpad version of the binary
MythFrontend.app.  There's a checkbox in there with the following
information:

MENU: Utilities/Setup -> Setup -> TV Settings -> Playback -> Mac OSX
Video Settings 1/2
ITEM: Use Vector-enhanced color space conversion
DESCRIPTION: If checked, YUV 4:2:0 will be converted to UYVY 4:2:2 in
an Altivec/MMX enabled routine.  If unchecked, Quicktime will handle
the conversion instead.

This smacks of the function you mentioned in your findings.  I
unchecked it and the hiccuping playback ceased entirely.  However,
there was a cost: all picture fidelity went out the tubes.  The screen
was greenish and had something like four side-by-side copies of the
video playing all scrunched up awkwardly.  The video I was testing, by
the way, was yesterday's HD Heroes.

The Mini's running on the 720p monitors occasionally get a good thirty
seconds without stuttery playback due to bandwidth issues.  At those
times there is none of the jerkiness evident in the video playing back
on the 1080p monitor.

Does that help?  What do you get when you play with that setting in
the Frontend?

- Eric