[mythtv-users] OSX: Quartz-blit has problems with 720p, OpenGL does not

TJ Harris tjharris at weaselworkz.com
Sun May 16 21:19:52 UTC 2010

I recently upgraded by backend to 0.23-fixes, and decided to give my
Mac frontend another try (I switched to an Atom / Ion / VDPAU Linux
frontend a while back because of Mac playback problems).   Most
stations worked great for me, but I had the same problems I had
experienced earlier on my Fox / 720p station.  The video looks jumpy,
and debug output shows a never ending stream of NVP messages like:

NVP(1): Video is 3.15771 frames behind audio (too slow), dropping
frame to catch up.

After experimenting with the settings some more, I found that OpenGL
playback seems to work fine for me and I don't get any NVP error
messages.   Of course, this comes at a price.  With Quartz, CPU usage
is ~ 50%.  With OpenGL, CPU is ~70% for 720p and 97-105% for 1080i.

Is this consistent with what other Mac OS X users are seeing?

My system:
Mac Mini (NVidia GPU)
 Mac OS X 10.6.2
 4GB RAM (256MB Video RAM)
 Mythfrontend 0.23-fixes, r24651
720p DLP Projector display (Mini DisplayPort to HDMI output)

Setting 1 (Bad): Renderer: Quartz-blit, OSD: softblend
   Extra Audio Buffering: ON = Good;  OFF = unwatchable

Setting 2 (Good): Renderer: OpenGL, OSD: OpenGL2
   Extra Audio Buffering: Doesn't effect playback

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