Broadcast monitoring issues

Hi all,
I just installed fcpx 10.0.5 on a MacPro with a BM Decklink HD Extreme 3D, and there's a strong strobe effect on playback when selecting AV output.
I've read this thread : www.fcp.co/forum/4-final-cut-pro-x-fcpx/...mit=20&start=80#7190 where all seems to be fine for people who were having this kind of issues, but I can't manage to make it work smoothly.

Here are the specs :
Mac Pro 2X2,66 GHz Quad-Core Intel Xeon
Mac OS Lion 10.7.4
14Go 1066MHz DDR3
NVidia GeForce GT 512MB
BlackMagic Decklink HD Extreme 3D

Events and Projects are stored on a Sonnet Fusion R800 RAID
(Write: 409MB/S, Read: 365 MB/s)

I'm working with XDCAM EX HD420 1080p25, ingested in FCPX after installing Sony XDCAM plugin for FCPX.

Blacmagic output is set on 1080p25 in system settings, same settings in FCPX.

I tried to uninstall, reboot, then install Blackmagic Desktop Video 9.5.3, then 9.6 (and reboot).

On this MacPro were already installed Avid MC6 and FCS3.

I read that some people changed this NVidia graphic card for an ATI, but I won't be able to do this.

I tried with both settings "Best performances" or "high quality" in fcpx playback preferences, it's a little better with best performances selected. Most of people seem to get best results with High Quality.

Am I forgetting something ?
I'm trying to convince the producer to let me edit a feature documentary with FCPX, I hope there's a solution to this issue !
Thanks for your help.

My Decklink Card can't do 25p as its not a broadcast standard. Try 50i or 720p and see if things improve.

I tried 50i but it wasn't better. I'll try 720p tomorrow.
But I have to admit I don't understand this non-standard issue about 1080p25.
Avid plays it fine on the same station, I'll test if FCP7 can play it...

I wonder if the Avid is converting the video on the fly? 1080p is not a broadcast standard. It requires too much bandwidth. It may be different on your Decklink as I only have the Extreme and in the system prefs there is no option for 1080p.

Why no one broadcasts in 1080p

Indeed I've got 1080p25 output settings in system prefs.

I tried 720p50 and it can play smoothly but only in "best performances", not in "High Quality".

I've noticed something else : clips play better in a project than from the event.

OK I was focused on broadcast monitoring but there's also drop frames issues even when AV output is turned off.
Primary when playing clips from the event. When played from a project, that's better.
I've got no clue what to conclude about that.

I tested same medias on my 2011 iMac (without broadcast monitoring...)on a FW800 Raid0 2 disks drive, and it seems to play fine in High Quality, from event or from a project.

So I guess I have to deal with hardware issues ?
I read several posts abouth replacing Nvidia card with an ATI 5770, but again, I can't do that on this post-house MacPro.

Shall I give up the idea of editing with fcpx on this station ?