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Sam McKenzie
Participant
September 28, 2026
Open for Voting

RAM Preview not working/extremely slow. Seems to target MXF files (MP2V) but have experienced it with other codecs too.

I’m using an M1 Macbook Pro and have updated to After Effects 26.5.0

Whenever I bring in an MXF file it either won’t play, or takes a few minutes to generate a few seconds of a preview. I’ve experienced this across the three Macs we use at my work. We’ve reverted to 2025 where the issue isn’t happening.

We use a daily ‘master project’ that we duplicate every morning and use for that days work (for work on a daily tv show). If I create a brand new blank project and import an MXF it’ll play it fine, but as soon as I import the original project, it slows again. If I save the project in 26 as a 25 project and open it in 25 there are no issues.

    8 replies

    defaulti1o0r0fybisq
    Inspiring
    September 30, 2026

    I am having a simlar issue and possibility related to ProRes 4444 at camera resolution (large). Only turning off Disk Cache works to kick Ram Preview back in gear.

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    Warren Heaton
    Community Expert
    Warren HeatonCommunity Expert
    Community Expert
    September 29, 2026

    This sounds like the kind of thing that a third-party plugin that’s compatible with Ae 25.x but not Ae 26.x could cause.

    I’d try running Ae 26.x in Safe Mode to see if that allows for MXF files to cache as expected.  If the issue goes away in Safe Mode, take a close look at which third-party plugins are installed.  If the issue persists in Safe Mode, get a clip to ​@Nishu Kushwaha see of he can reproduce the issue and if needed have the Ae team can take a closer look at it.


     

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    Nishu Kushwaha
    Community Manager
    Nishu KushwahaCommunity Manager
    Community Manager
    September 29, 2026

    Thanks for reaching out and sorry to hear about the issue. A few things that would help narrow it down:

    1. What are your system specs on the machine you're testing on?

    2. What are the specs of the affected media (codec, resolution, frame rate)?

    3. If it only happens when working from your master template, I'd recommend recreating the template from scratch in the latest version and testing again. Sometimes project-level state carries over corrupted references.

    If you can, feel free to share the media and project file with me for testing (via DM if you'd prefer not to share publicly).


    Thanks,
    Nishu

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    Sam McKenzieAuthor
    Participant
    September 30, 2026

    Operating System: macOS 26.3 on Apple Silicon (M1 MacBook Pro, 64GB unified memory)

    Steps to Reproduce:

    1. Import MXF footage encoded as XDCAM HD (FourCC xdv3 1080i50, 35Mbps, Long-GOP MPEG-2)
    2. Place clip on the timeline in a new or existing composition
    3. Press spacebar to begin RAM Preview / standard playback

    Result:

    • Initial playback takes 1–2 minutes to begin
    • Once playback starts, it only sustains for 5–10 seconds before stalling/stopping again
    • This cycle repeats through the timeline, making the footage effectively unworkable for review or editing
    • Behavior is specific to MXF/XDCAM long-GOP footage — not observed with other codecs on the same system

    Regression Note: This did not occur in After Effects 2025 with the same footage, project, and hardware. The issue appears specific to the 2026 (26.x) release line.

    Troubleshooting already attempted:

    • Updated to latest 26.5 point release
    • Purged all memory/disk cache (Edit > Purge > All Memory & Disk Cache)
    • Cleaned Media Cache database (Preferences > Media & Disk Cache > Clean Database & Cache)
    • Switched Disk Cache from Compressed to Uncompressed
    • Tested in Safe Mode / fresh project with a single MXF clip and no other plugins
    • Confirmed issue reproduces on more than one machine/project

    I’ll DM you a project and media to see so you can see. Thanks.

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    Nishu Kushwaha
    Community Manager
    Nishu KushwahaCommunity Manager
    Community Manager
    October 6, 2026

    Thanks for sharing the file and sorry for the delay, Sam.

    I am able to replicate the preview issue on my end. However, it works fine if I import the media into a new project. Do you mind testing again on a new project? Let me reach out to the product team and get their input. I'll update asap.

    Thanks again for your patience.


    Best,
    Nishu

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    Community Expert
    RobShultzCommunity Expert
    Community Expert
    September 28, 2026

    Have you tried doing a: Edit/Purge/All Memory and Disk Cache?

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    Sam McKenzieAuthor
    Participant
    September 28, 2026

    Actually further testing shows that opening a blank project in 2026 doesn’t fix the issue fully - I get around 10 seconds of preview before it freezes and slows.

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