My system information:

Operating System - Windows 10 (64 bit) CPU - i7-5930K @ 3.50GHz
RAM - 32GB DDR4 (4x8GB)
GPU - AMD R9 Fury X
Storage - PCI-e SSD OCZ Revodrive (500 MB/s writes, 900 MB/s reads)
Radeon Software Version - 16.9.1

Blender version - 2.78 (Date installed: 2016-09-26)
No add-ons or other things installed with it.

Things I've done to try and remedy this issue:

  • Increased Memory Cache Limit to 20GB under User Preferences > System > Sequencer/Clip Editor.
  • Changed Compute Device to my GPU, switched to Cycles Render engine, and setting Render > Device as GPU Compute.
  • Setting OpenSubdiv compute to GLSL Compute and Images Draw Method to GLSL.
  • Using the new DepsGraph by adding --enable-new-depsgraph to blender's launch shortcut.
  • Setting Threads under Render > Performance to 10.
  • Disabling OpenGL Preview under Scene Preview/Render.
  • Setting the preview properties Proxy Size to 25% and making the preview window smaller.
  • Setting Preview Samples under Render > Sampling > Samples to 1 (minimum).

All I'm trying to do is use Blender as a video editor. I'm not doing any 3D modeling or animation. Whenever I am previewing an effect, even if I let it cache fully, my FPS drops to 5 or less, and blender is almost unresponsive until the effect is no longer being previewed. CPU usage jumps to around 70-80%. It would only jump to around 20-30% at times before I started using the new DepsGraph.

At any other time, when just video and audio are being played (no effects, animations, or otherwise), I get a constant 30 FPS. Even if I run the preview at the scene's render resolution (so 1440p), and set Preview Samples to 0 (unlimited), I get 30 FPS.

The clips I'm handling are 2560x1440 resolution running at 30 FPS that were encoded to HEVC (x265) at a bit rate of 2500 Kb/s. The entire project is only 7 minutes and 13 seconds long (12990 frames). Even if I limit the playback segment using P, it still essentially locks up when previewing effects. The entire clip I'm editing is 228MB in size.

I'm using 3 effects. A crossfade transition, a wipe transition, and a speed control effect. All at different times, and any of them causes this behavior immediately once they start.

This may be entirely unrelated, but I'm unsure:

Before I switched to the new DepsGraph, if I set OpenGL Render Options > Anti-Aliasing on, all previews hit 14 FPS maximum. If I change said Anti-Aliasing's Samples to 5, 8, 11, or 16 (those are the options it gives), the average FPS does not change (it's around 13).

After switching to the new DepsGraph, this is no longer true. I get 30 FPS until I hit the Effects I mentioned above.

I've researched and tested things for a while from various forums, as well as reading questions asked on this stack exchange. I'm at a loss for why I'm experiencing these issues.

  • 1
    $\begingroup$ Is the User Prefs>System>Sound> audio output device set to SDL? This has slowed performance for me in the past. Also did you know that the VSE only uses 1 thread anyway. $\endgroup$
    – 3pointedit
    Commented Oct 19, 2016 at 13:08
  • $\begingroup$ @David♦ - I tried switching the sound output device to SDL, every time I've rendered or previewed, I've had the FPS and resolution match the source material being edited (1440p30), and I've adjusted the samples in the Scene properties but even setting it to 1 doesn't affect FPS. 2nd link is about final render while my issue is preview rendering. Neither proxy resolutions or OpenGL preview affects the slow down caused by effects and Isti115's related answer is about final rendering as well. Refresh Sequencer didn't work. The files don't appear to be corrupt upon viewing, and no fcurves, $\endgroup$ Commented Oct 20, 2016 at 5:07
  • $\begingroup$ Toggling OpenGL Preview doesn't prevent the slowdown from happening when an effect plays. @3pointedit - No, it was set to OpenAL. That was the default because I have never changed that. Yes, I saw that mentioned. That's regarding final render, not preview render. Preview render is multi-threaded according to a comment in one of David♦'s linked issues. My issue is the Preview Renderer's performance during effects. When I start Video Editing, I use a setup I built from the defaults. All I change is Compute Device, Cache memory, and Dimension/Render settings. $\endgroup$ Commented Oct 20, 2016 at 5:13
  • $\begingroup$ Progress was made. I loaded Factory Settings and loaded up two clips into VSE and had a wipe effect between the two. It worked fine. Using this idea, I decided to build up to where I am at with settings from Factory Settings using Refresh Sequencer and see what causes the issue. After going through this process, Blender begins to get unresponsive, not when settings are changed, but when there is a notable length of clips in the VSE. i.e. having the 1440p30 source in the VSE when it's 2.65GiB and around 9 minutes long, with effects, causes effects to not render and just freeze up. $\endgroup$ Commented Oct 20, 2016 at 5:57


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