Blackmagic Forum

I'm unable to get 12.5.5 to play anything smoothly. CPU is AMD Phenom 6-core, 16GB RAM NVIDIA GeForce GTX 980. OS is Windows 10 Enterprise 64-bit (10.0, Build 14393). Main project drive (P:) is a 1TB 10K RPM Velociraptor and the cache file drive (Q:) is a 500GB Samsung EVO 850 SSD. Just went back through all the startup programs and services to disable the nonsense services the Anniversary Update applied. All other drivers are up-to-date. Audio playback is ASIO through a Focusrite Liquid Saffire 56 with latest drivers.

My main project has the footage as 1920x1080p 30FPS in DNxHD MOV files. Playback audio and video stutters, with the FPS indicator occasionally hitting 30FPS, but most frequently between 25 and 28. Confirmed timeline resolution and rate are set to 1920x1080x30fps. Image scaling is Optimized for Playback. Smart cache is enabled, as is Use Optimized Media if Available. No color correction yet applied. Screenshot attached shows typical performance during playback, with GPU at 20% and all six CPU cores around 58%.


Now here's the weird part... I tried using Media Management to create a copy of the main continuous shot transcoded into low bandwidth 720x480 DNxHR. I created a new project, imported that clip, creating a timeline and setting all the project settings to NTSC standard def. I get the same poor playback FPS. Memory usage is a few GB lower, disc transfers are down over a half, GPU usage drops to 8-10%, but the CPU stays in the 58% range. (see second screenshot)


I'm at a total loss and in a tight timeline. Out of desperation, I tried a trial of Premiere Pro CC, hating every minute of it. Resolve used to work on this machine last September. What am I missing?

I would try two things:

1. Create a RAM disk and read the video from this RAM disk to determine it is a file throughput issue.

2. Determine if it is the ASIO driver or settings. Temporarily set the audio hardware to something like Windows default and see if it makes a change. Also double the check your ASIO audio settings. Video usually works with 48kHz sampling rates.

By the way, 58% on the Phenom might already be full CPU utilization as the Phenom uses shared floating point cores.

Cary Knoop wrote:
By the way, 58% on the Phenom might already be full CPU utilization as the Phenom uses shared floating point cores.

Could this be the reason why an FX-8320 with 8 cores has roughly the same CPU utilization as an Athlon II X4 640 while simply playing a h264 file (tried out of curiosity), that 8 core AMD can't scale its cores much beyond 4 cores of an athlon ? Is this to say that an AMD FX is barely adequate for Resolve and not recommended?

We might be onto something regarding the audio. Even though the footage is all 48KHz, Resolve is playing it as 44.1Khz. If I switch the interface to 48K and restart Resolve, I get no audio and visually playback looks worse, so Resolve must be trying to resample the audio.

I confirmed that 48K audio is working on this machine because the surround mix, recorded separately at 48L in Cubase, is working fine.

I've been all through the obvious (to me) places in Resolve and cannot see how to change the audio sample rate of the timeline or how to otherwise get it to use the standard 48K rate.

In Preferences > Video I/O and GPU try to turn "Use System Audio Output" off, and sse if it gets better.

In this case you will have to monitor your audio through your BMD card (mine is an Intensity).

thanks. I hadn't tried that option. Actually "Use System Audio Output" was off. Tried turning it on and making sure the default sample rate in Windows Sound Card Settings was 48KHz. It actually played through the Focusrite (the only audio device on the machine) in 48K that time. But same stuttering results.

I then took a cellphone video of some settings pages as they are now, and an example of the playback problem I'm experiencing. Although FPS vacillates below (and above 30) in Resolve, the apparent visual FPS is more like 1 or 2 FPS --then the audio glitches to go with it. Here's what it looks like...



See any smoking guns?

PS. since recording this, I tried setting the scaling preferences to Optimize for Playback and also tried half and quarter resolution in the Playback Proxy Mode. No difference.

In Master Project Settings, Check, Hide UI overlays for optimized playback. Should do the trick...

Did you ever figure this out? I'm in a very similar position that you are?

I never completely resolved it--until my daughter's gaming computer died a week afterward. I handed down my studio workstation to her and moved my graphics cards into an AMD Ryzen 1700X system with 32GB RAM and a 1Tb M.2 SSD.