DPX Render Glitch = analysing every cut

Hi, I've been colour correcting a 2k scan of a 35mm film print in DPX 10 bit with Resolve 15 Beta (since v. 02) and have successfully done three of the five reels, rendering out to DPX.

In rendering the 4th reel there are several frames of glitches between every cut:

When rendering it reaches a cut and does maybe 2 or 4 frames of that next shot, then stops and goes back to the the previous shot, apparently randomly 2, 3 or 4 frames and recolours them with the setting for the next shot, obviously resulting in those frames being discoloured. This is exactly the behaviour I except when rendering with handles, only in this instance there are no handles set and because it is rendering individual frames these 'handles' are not hidden.

Also the timeline is set to 24fps but Resolve is rendering out at 15fps (which was the frame rate of the scan).

I tired rendering a piece of the previous reel which rendered successfully and it still renders as it should without going back and re-colouring the last frames incorrectly and yet the source material and timelines are identical.

I was using a combination of nodes to clean this film up including Automatic Dirt Removal, Noise Reduction and Grain in addition to the colour nodes. The initial render for the 20 minute reel was nearly 15 hours (yes I have a woefully inadequate graphics card but never had an issue before with much bigger and more complex files - I am a patient renderer). I simply cannot figure out what is causing it to analyse every cut like this. I have removed all the OpenFX filters and just left the colour on but the glitch persists.

I did have the Automatic Dirt Removal set to 2 or 4 frames and thought it might be that OpenFX filter causing the issue but this 'analysis' glitch even appears on this reel with no filters at all - obviously there is no colour shift because nothing is set but it still goes back and redoes the last few frames of every cut - something it hasn't done for the last three reels.

Any suggestions would be EXTREMELY appreciated, thank you.

Resolve 15.0.0B.065
Mac OS X 10.13.4 (17E202)
Mac Pro 2 x 3.33 GHz 6-Core Intel Xeon
32 GB 1333 MHz DDR3
ATI Radeon HD 5870 1024 MB
DeckLink HD Extreme 2

I was also getting these errors in Premiere Pro on importing the rendered DPX sequence - wonder if this is all related?

[Peter Chamberlain]

I dont know if its simply that the 1GB of GPU memory is not enough but DPX itself is the first format we ever did more than a decade ago so im not sure where the issue is there.

Can you try a test project/24fps timeline with he same source and no effects?

I dont know if its simply that the 1GB of GPU memory is not enough but DPX itself is the first format we ever did more than a decade ago so im not sure where the issue is there.

Can you try a test project/24fps timeline with he same source and no effects?

Thank you Peter. Yes I agree that it is most certainly my small GPU. By a process of elimination I can identify and isolate the 'bad' section and export it successfully. I have also created and tested multiple codecs and find the glitches move in time. The fact that I can re-export successfully proves it is not a software fault. I only posted out of being a responsible Beta Tester.

Initially I was rendering these reels to ProRes HQ but had so many of those 'electric ladyland' GPU glitches I switched to DPX and exported three 20 minute reels successfully, which proves how rock solid your DPX is. Must be close to frying my GPU though.

I have I think the same issue as do a lot of my peers in not wanting to spend $1500 on a new graphics card into what is rapidly becoming an obsolete machine which still works perfectly in every other application. Hence I was so excited about your eGPU and would buy one in an in instant if only you made one for USB3 and not thunderbolt - or is it possible to still connect that to a luddite Mac Pro? (me: secretly praying)

Thank you for all that you guys do!

Might be possible with an adapter but wouldn’t make sense. Even TB3 is just about enough for a single eGPU. USB-3 would be far too slow.

Might be possible with an adapter but wouldn’t make sense. Even TB3 is just about enough for a single eGPU. USB-3 would be far too slow.

As I thought. Thank you Uli.