Predicting export times

Batvink Posts: 75 Just Starting Out*

Is there any guidance on what affects the time to export a project?

I have 2 projects, one is 29 minutes long and the other is 16 seconds. But they both take the same time to export, around 30 minutes.

For the longer 30 minute one, most of the composites have been pre-rendered, and then the full production is exported from a final composite at 1080p 30fps.

The 16 second project is also pre-rendered and exported with the same settings. The composites are the same resolution and the frame rates are the same.


  • Triem23
    Triem23 Posts: 20,294 Power User

    Too many variables. A CPU, GPU, RAM speed and Storage (HDD vs SSD and bus type, not to mention speed of drive) are all variables.

    Other software running in background (virus scanners, screen calibration, etc) is a variable. Even installing an "unrelated" program affects things. Having any Adobe software means the Adobe Update Manager is now always running. An MMO mouse uses more resources than a simple two button and wheel mouse as the system constantly checks to see if additional mouse buttons are pressed - yes that's a super minor variable but everything adds up.

    Footage itself is a variable as a Handbrake transcoded file will differ from any source footage.

    Effects and layers used are variables (for example, Levels and Curves do basically the same thing, but, before Hitfilm 16 Levels was a LOT slower (reading back the histogram), but has been sped up in 16. Using A>B colors slows down a glow while Neon Glow is generally slower than a regular glow. Here alone we have hundreds of variables.

    A Pre-render is USUALLY faster than leaving a Comp procedural... Up to a point, but pre-renders are large files and streaming several at once will cause a drive bottleneck. Uncompressed 1920x1080 30fps video is about 1.4 gigabits/second. Pre-renders are about 2:1 compression ratio, or 700 megabits/second. A slow (200 megabyte/second, or 1600 megabit/second) drive will bottleneck on the third concurrent prerender. My SSDs are about 580 megabytes/4680 megabits per second) that means my drive bottlenecks at concurrent pre-render 9. Any Hard drive will bottleneck at prerender 2. For 4k/30 fps a hard drive bottlenecks on any prerender. An enterprise SSD transferring 3500 megabytes/28000 megabits per second pretty much will never bottleneck.

    Number of drives is a variable. Reading and writing to the same drive can bottleneck since the computer keeps skipping around to access things. Writing to a different drive speeds things up.

    Bit depth is a variable - 16 or 32 bit is slower than 8-bit.

    MSAA is a variable - 8x, 16x, 32x is slower than 4x.

    Motion Blur is a variable - especially if changing number of samples.

    For 3D models map sizes is a variable. While editing/animating I'll turn map sizes down to 256 for speed, but back up to 4096 for render. Reflection map and shadow map sizes affect render times more than texture map size.

    Lights are variables. Shadow casting and falloff slow lights down.

    It might be possible for you to start making predictions for YOUR computer, but that would involve detailed testing while isolating variables.

  • Batvink
    Batvink Posts: 75 Just Starting Out*

    Thanks for the detailed rundown :)

    I'm a developer by trade so I appreciate many of the items here, although there are more I hadn't considered.

    In my scenario I am literally exporting a single pre-rendered composition to the same file format on the same SSD drive, from the same SSD drive. I would expect differences across sessions, but I am consistently getting around a 120x speed difference on a similar process.

    I'll keep scratching my head and hopefully uncover the culprit.