[HELP] DaVinci Resolve render getting gradually slower as render progresses

[SirAhmix]

Been using DaVinci Resolve for a while now and I've never had any issues with the rendering of a finished video. That is, until I upgraded my entire computer recently. At the bottom of the post, you'll find hardware specs for both my old and my new computer. When I first started using Resolve on my new computer, I had no issues whatsoever. In fact, it was (rather predictably) better in every way; scrubbing was smoother, playback was smoother, rendering was faster, etc. Then, literally out of nowhere, my renders got painfully slow. I hadn't changed anything at all in the settings and in fact I use the same project for all my videos since all I do is replace the audio track and export. What's especially weird is the render starts out at upwards of 180 fps and gradually slows down to about 4 fps towards the end of the render. I hadn't updated Windows, Resolve, drivers, BIOS, or anything else. Since then, I've updated literally everything in hopes of fixing the issue to no avail.

 

For reference, I'm rendering a video with a static image, a static title, and a single audio track. I have 5 second fade in and out transitions at the beginning and end of the image and the title. I'm rendering at 1080p/24fps @ 2000 Kb/s using the H.264 encoder and the QuickTime format (.MOV). I'm also writing the final file to my mechanical hard drive that has a max sustained write speed of 250 MB/s (not hitting anywhere close to that).

 

Any and all help would be very much appreciated!

 

Old Computer:

CPU: i5-4690k @ 4.0GHz

GPU: MSI GTX 1070 Gaming X 8G

RAM: 16GB DDR3 @ 1600MHz

SSD: 250GB Samsung 850 Evo

HDD: 4x 1TB WD Blue

 

New Computer:

CPU: AMD Ryzen 9 3900X 3.8 GHz 12-Core Processor  (Purchased For $499.99) 
CPU Cooler: Corsair H100i PRO 75 CFM Liquid CPU Cooler  (Purchased For $124.99) 
Motherboard: Asus ROG Crosshair VIII Hero (WI-FI) ATX AM4 Motherboard  (Purchased For $379.99) 
Memory: Corsair Dominator Platinum RGB 32 GB (4 x 8 GB) DDR4-3200 Memory  (Purchased For $249.99) 
Storage: Samsung 970 Evo Plus 1 TB M.2-2280 NVME Solid State Drive  (Purchased For $229.99) 
Storage: Seagate IronWolf Pro 8 TB 3.5" 7200RPM Internal Hard Drive  (Purchased For $256.99) 
Video Card: MSI GeForce GTX 1070 8 GB Video Card  (Purchased For $446.98) 
Case: Phanteks Eclipse P400 ATX Mid Tower Case  (Purchased For $48.98) 
Power Supply: SeaSonic FOCUS Plus Gold 850 W 80+ Gold Certified Fully Modular ATX Power Supply  (Purchased For $138.03) 
Monitor: Asus VG245H 24.0" 1920x1080 75 Hz Monitor  (Purchased For $189.99) 
Monitor: Asus VG245H 24.0" 1920x1080 75 Hz Monitor  (Purchased For $189.99) 
Total: $2755.91
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-10-26 09:53 EDT-0400

[Bananasplit_00]

have you checked your temps for CPU and VRM?

[SirAhmix]

2 minutes ago, Bananasplit_00 said:

have you checked your temps for CPU and VRM?

I'm in the middle of a render now and my CPU is bouncing between 51°C and 56°C and, assuming I'm reading the right values, my VRMs are between 22°C and 38°C.

[Sauron]

43 minutes ago, SirAhmix said:

I'm also writing the final file to my mechanical hard drive that has a max sustained write speed of 250 MB/s (not hitting anywhere close to that).

Try writing to your ssd, see if the problem goes away. The top speed of your hdd is only reachable while its cache is available, once that runs out and you start writing directly to the discs it's perfectly possible for it to slow down to a crawl.

[SirAhmix]

1 hour ago, Sauron said:

Try writing to your ssd, see if the problem goes away. The top speed of your hdd is only reachable while its cache is available, once that runs out and you start writing directly to the discs it's perfectly possible for it to slow down to a crawl.

Just tried that and now I'm even more confused. To start, it started out at a slower max framerate (about 100) but is continuing to decrease at the same rate as it was when writing to the HDD. That said, it looks like it might be rendering a bit faster so I'll edit this comment when it finishes with the final render time.

 

EDIT: The render to the SSD took the same exact amount of time as the HDD...

 

EDIT2: I also tested with multiple codecs one of which was the DNxHD codec producing a 12.2 GB file for a 10 minute clip of my hour long video. It decreased in fps at the same exact rate as the regular H.264 export that took 46 minutes to export an entire hour long video at a 1 GB file size. With that in mind, I don't believe that the HDD cache is to blame here.

[SirAhmix]

Just ran another render whilst monitoring temps and utilization and all the temps are in check but I did notice something interesting.

 

My GPU utilization is getting lower and lower perfectly coinciding with the lowering of fps during the render (see below). The temps are no where even remotely close to thermal throttling (43°C peak) so that can't be it. I'm lost here. I've never seen something like this before.

 

EDIT: Also, my CPU is maintaining peak boost speeds at anywhere from 4212 MHz to 4266 MHz during the enter render and the temps aren't exceeding 60°C at an absolute max.

 

EDIT2: Even more lost now... The video that I've been talking about this entire time just rendered in half the time of my previous renders... My previous runs were about 46 minutes each whereas this one finished in 20 minutes. I have changed nothing at all between runs, not even rebooting my computer.

 

 

Edited October 26, 2019 by SirAhmix
More info added

[One21Productions]

I created an account just to comment on this post (I know im late). I have been experiencing the same issues and tried a few different things (driver updates, resolve updates, switching the GPU processing to cuda, etc). For me it was something silly, I noticed that the drive I was writing to (my desktop NVME) was at 100% utilization. I tried it on a few other drives (mechanical, SSD & NVME) and I was able to export at a constant speed without it tapering off to 5-7 fps.  Hopefully you figured it out by now, but that was my problem.

 

I guess my old system didnt do that because the drives could read/write faster than it could output and the new system is bottlenecked by the drive.

 

Old system

i7 8700k (OC 5GHZ)

GTX 1070 Ti

 

New System

Ryzen 9 3950x

RTX 2080 Ti

 

Same drives & ram in both systems

[TobyMcQuack]

I stumbled upon this post with a very similar problem and wanted to share just in case someone else finds this in the need to get their video out. I was doing a cut for a choir and apparently Resolve didn't like some of the clips they turned in. The render started great at ~40fps, but at the 16 sec mark it crawled to a stop at 0fps, infinitely counting up the remaining time. I've left my pc to render, but even after hours it was stuck at 11%. Same issue no matter what output file or codec I used.

 

Now what helped me finish the job is more a workaround than a solution but it helped getting it done. I cleared the render cache, set all optimized media to high quality, generated new optimized media with the new settings and, in the deliver tab in "advanced options", set "use optimized media" for the render. Completed in about 10 minutes without any problems.

 

Since then I've tried various settings, disabled each clip in the timeline individually, tried to get it working "the proper way", but there's some files Resolve just doesn't like to work with. I've seen many similar threads about the problem with no definite answer, so I just wanted to share what helped me get a render out in time. Hopefully it'll help someone someday.