How to optimize the system and the process to get a shorter render time?

Kirdnevs Posts: 1 Just Starting Out
edited March 2021 in HitFilm

I have recently been editing videos more regularly with Hitfilm. Previously my processor seemed to limit rendering, so I bought a better one. My current specs:

AMD Ryzen 9 3900X | 2x 8 GB 2133 MHz DDR4 | NVIDIA GTX 960 4GB | Samsung 970 Evo Plus | using HitFilm 16

The rendering is already much faster, but since the processor is only at about 30% load, there must be a way to speed up the rendering even more. But I can't estimate due to lack of experience what I can change next, or easiest (on my workflow or on the hardware) to get a shorter render time.

I mostly just render MP4 videos (MPEG-4; AVC; variable frame rate) cut together in the editor without adding any effects. (Maybe just a video or audio fade). There I am aware that this is not the most ideal either.

During rendering I get the following load:

CPU ~30%,

RAM: 11-14 GB of 15.9 GB,

GPU 25-45%; 25% in 3D, 40% in Video Decode, 3.7 GB of 4 GB dedicated VRAM

SSD: 1%

So do I need a graphics card with more VRAM? Does the RAM already limit with capacity and/or speed? Or are there other ways to optimize the process without buying new hardware?


  • Triem23
    Triem23 Posts: 20,292 Power User

    You're basically proceeding from false assumptions here.

    Hitfilm uses the CPU and GPU in SERIES, not PARALLEL.

    In short, the CPU in Hitfilm basically handles video decode (read from drive) and encode (write to drive), particle physics calculations (if applicable) and a few other things. While the CPU is doing it's thing, the GPU is INACTIVE.

    The GPU calculates all effects and renders all frames (and, in your case is doing frame decoding after the CPU reads from drive). While the GPU is doing this the CPU is INACTIVE.

    Which means, obviously, you'll never see your CPU and GPU both pegging at 90+%.

    While Hitfilm does multithread it's using a single CPU thread per video stream (so you won't see "blazing fast" with one video stream getting sloer and slower as you add more. You'll get a performance level with one stream that should remain constant as you add more streams.

    The numbers you're seeing are pretty typical for Hitfilm and indicate things are working about as well as possible. If, in Hitfilm you're seeing something like "90%" GPU it means you're REALLY pushing a lot of effects and Hitfilm's having to take time to think about things. If you're seeing a CPU load of 90% it means there's a serious bottleneck in your system.

    You've hit an "it is what is it" stage on this topic.

  • Kirdnevs
    Kirdnevs Posts: 1 Just Starting Out

    Thanks for the quick reply. I have read similar from you in other threads and was aware that there is no parallel processing. That all makes sense.

    I asked how I can reduce the render time. Your answer sounds to me like I already have the maximum rendering speed that Hitfilm has to offer. And there is no hardware that would help. But why did I have a load with my old CPU (Intel i5 6600K) that was close to 90% (I don't know the exact value).

    I also had the effect that I rendered a video two times in a row. Without much change to the video. However, the second render process took 60% longer. That's why I was thinking if this is something that has to do with the full VRAM. Because I had read something similar somewhere else.

  • Triem23
    Triem23 Posts: 20,292 Power User

    The forum is user based - including Mods/Ambassadors - so the info above is from a file of notes I keep when devs occasionally drop information. From this point, lots of guessing and speculation.

    The difference in CPU load could come down to the Ryzen just being a faster chip - also, recent Ryzens have overtaken Intel performance, especially on things like video decoding.

    It's possible Hitfilm has some memory leakage, which could account for longer renders of the same video. However I've been generating test renders today of the same project and am NOT experiencing significant changes in render times. Looking at my Export Queue the four renders all were within 5 seconds of each other (from a 20 minute render). That said, my current machine is running an Nvidia 2060. My prior machine was an Nvidia 980m, and that one DID have some memory issues in older versions of Hitfilm that had been report to Support. It's possible it's something about the 9xx generation, but, I repeat, here I'm guessing and speculating.

    Now that I'm not multitasking (browsing forums while waiting for renders) I can say there are a few things to maximize throughput in Hitfilm, but mostly depend on how a project is set up. For example, Composite Shots are procedural media, and an embedded Comp takes more processing time. Pre-renders of embedded Comps improve render time - sometimes significantly. I'm remembering a project where I left my Comps procedural and had something like a 12 hour render time. I pre-rendered the Comps (which took 4 hours) and that took the final render down to 2 hours... Which cut total render time in half. Waiting for Pre-renders can FEEL like a waste of time, but it makes a difference.

    If you have layers that fade in and out, trim any transparent bits. Hitfilm's still processing the "invisible layer." This also applies to Grade Layers. If there's a Grade Layer over an entire (let's say 30 second) Comp, but it's got effects that fade in for only a couple of seconds, trim away the bits where the effect is off. Again, that keeps Hitfilm from taking time to calculate an "invisible layer." Again, taking the time to clean up timelines feels tedious and wasted, but it cuts down on renders.

    Getting familiar with Task Manager helps. If I'm working in Hitfilm and I know I don't need to go online I can turn off my computer's WIFI which ALSO means I can turn off my firewall and virus scan. This frees more resources for Hitfilm. Killing ANY process I know I won't need (print spoolers, pen input if I'm not using a tablet, font management when not using that software, etc) helps.

    Within Hitfilm itself there's not much else to tweak.

    Of course newer/better/faster hardware always helps - an Nvidia 2060 benches about 160% faster than the 960 - but that costs money.

  • Kirdnevs
    Kirdnevs Posts: 1 Just Starting Out

    Thanks for the info and the good advice.

    Then I will probably try a little bit myself soon and see how changes affect the rendering time.