AE video preview output lag when working with UHD footage

[christopherm88473166]

I'm running a top spec mac pro, AE 14.1.0.57, and my I/O is handled by an UltraStudio 4k by blackmagic.  My problem is that when I do a ram preview with UHD footage, playback in my computer composition monitor is real time, but my production monitor (fed by the ultraStudio 4k) runs about 1/2 speed. It has been this way for the last few versions of AE.  When working with HD footage, everything works fine. I should also mention, that all 4k footage I work with is either shot with a Panasonic GH4 (mp4 clips) or a Panasonic VeriCam LT (mxf clips).

I'm guessing Adobe with throw this issue at Blackmagic, but my hope is that someone else has experienced this and maybe has a work-a-round.

[christopherm88473166]

Ok, so I found a work-a-round.  If I make a pre-comp of what would be my UHD output comp, but then change it to a HD comp and resize the precomp to %50, I can view the ram preview of that in real time.  So I do some work in the UHD comp, then tab over to the HD comp (containing  a precomp of my UHD comp at %50) and ram preview that.  Simple and Annoying, the hallmarks of any true work-a-round.

[Rick Gerard · Accepted solution]

Try just setting the Comp resolution to Auto instead of full. I almost never have my comp resolution set to Full because 90% of my animation work is done with the full UI visible and my comp's are seldom at a Magnification factor of 100%. I only check a few hero frames at 100% with the Comp Panel maximized (~ key) to make sure that things are lined up properly, but all of my animation and my previews are done at Magnification factors of 50% or even 25% for 4K work.

[christopherm88473166]

Setting Comp resolution to Auto is not working. Setting Video Preview to Auto also produces the lag. Setting Video Preview to 1/4 produces the same lag.  Again, when I ram preview UHD, I see real time playback of cached frames on my computer monitor, but my production monitor lags.  It works fine in HD. 

[fitzfilmfx]

I'm getting the same thing. I noticed If I have the comp resolution set to 100% it plays back fine...but I don't have a 4k monitor so I can only see a small portion of what I'm working on when I do this.