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Real time playback issue (2xQ4000+GT120+MacPro4,1)

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John PilgrimReal time playback issue (2xQ4000+GT120+MacPro4,1)
by on May 30, 2012 at 10:23:20 pm

Hi all,

I have a playback speed issue.

The only way I can get 24fps playback is to switch the video monitoring to 8-bit on the Config page.
(Thanks Rohit for brining this up over at

If I set the video monitoring to 10-bit, even with no grades, I never get realtime 24fps playback, usually around 19-23fps.

I'd really like to monitor at 10-bit.

What gives?
Is the GT120 not up to snuff?
Does the GT120 dislike being in x4 speed slot #4 rather than x16 speed slots #1 and #2?



All the details:

Much of my media is 1080P24 ProResHQ (≈200mbit/sec), XDCAM EX (35mbit/sec) or XDCAM HD (220mbit/sec)
During playback, my CPU stays around 80% idle.
My RAM remains 75% free (9.35GB free of 12GB).
My media drives clock in around 200-250MB/sec according to BMD Disk Speed Test.

Resolve 8.2 full version
Mac OS X 10.6.8
MacPro4,1 8-core 2.26GHz, 12GB RAM
Slot 1: Quadro 4000 Mac headless
Slot 2: Quadro 4000 Mac headless
Slot 3: Decklink Extreme 3D
Slot 4: GT120 for GUI
Internal 1TB Boot drive
Internal 2TB 2-drive RAID-0 (BMD Disk Speed Test says 212MB/s write and 205MB/s read)
Internal 120GB Corsair Vertex3 SSD (BMD Disk Speed Test says 204MB/s write and 265MB/s read)

Standard Candle 8.2 results using 10-bit monitoring:
V1 2 nodes : 23.0-24.0 fps (fluctuates)
V2 4 nodes : 22.5 fps
V3 6 nodes : 22.0-24.0 fps (fluctuates)
V4 12 nodes : 13.0 fps
V5 NR 4 : 24.0 fps
V6 NR 3 : 21.5 fps
V7 NR 2 : 11.0 fps
V8 NR 1 : 3.0 fps

Standard Candle 8.2 results using 8-bit monitoring:
V1 2 nodes : 24.0 fps
V2 4 nodes : 24.0 fps
V3 6 nodes : 23.0-24.0 fps (fluctuates)
V4 12 nodes : 13.0 fps
V5 NR 4 : 24.0 fps
V6 NR 3 : 21.5 fps
V7 NR 2 : 11.0 fps
V8 NR 1 : 3.0 fps

FWIW, if I replace the original with an upresed 1920x1080 10butUnc MOV of the same file, using 10-bit monitoring, I get:
V1 2 nodes : 19 fps
V2 4 nodes : 19 fps
V3 6 nodes : 18 fps
V4 12 nodes : 13 fps
V5 NR 4 : 21 fps
V6 NR 3 : 19 fps
V7 NR 2 : 11 fps
V8 NR 1 : 3 fps

(Sidenote: If I'd get a performance boost, I'd consider ditching the GT120 and one of the Quadro4000's and putting in a GTX580 and using the remaining Q4000 for GUI, but I don't think my power supply would like me. TDP would increase by another 50 watts.)

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