I'm using Mathematica 12.1 on windows 10 (Microsoft Windows [Version 10.0.16299.1686])

When going to the Help file about VideoPlay I tried the standard example and it crashes the Kernel.

For me it's easy to simulate I just use:

stream = VideoStream["ExampleData/Caminandes.mp4"]

The errors I get:

enter image description here

enter image description here

When using another piece of code:

stream = VideoStream["ExampleData/bullfinch.mkv"]
      "Seconds"], (stream["Position"] = #) &], {0, 
     QuantityMagnitude[stream["Duration"], "Seconds"]}],
    Dynamic[If[stream["Status"] === "Playing", "Pause", "Play"]],
    If[stream["Status"] === "Playing", VideoPause[stream], 
   }, Alignment -> Center]

I can scroll through the frames but pressing Play will result in the same errors. Using 1 or 2 monitors doesn't make a difference.

Any thoughts?

  • $\begingroup$ Same on macOS. I reported it an hour ago. $\endgroup$
    – Szabolcs
    Commented Mar 19, 2020 at 10:05
  • 1
    $\begingroup$ Same on Windows, filed a report 2 hours ago. $\endgroup$ Commented Mar 19, 2020 at 10:13
  • $\begingroup$ Should I file a report also? $\endgroup$
    – Lou
    Commented Mar 19, 2020 at 10:17
  • 2
    $\begingroup$ This bug is being fixed via paclet update. $\endgroup$
    – ilian
    Commented Mar 19, 2020 at 13:48
  • 2
    $\begingroup$ Many components are in paclet form, but the kernel, FE, runtime library and some other libraries cannot currently be updated in this way. I think that would be a desirable feature. $\endgroup$
    – ilian
    Commented Mar 19, 2020 at 18:09

1 Answer 1


This bug has been fixed by a paclet update.

This would be applied automatically whenever the functionality is used in a new kernel (as long as the paclet manager has updated its local site index, which typically happens once per session).

To force an immediate installation, evaluate

PacletSiteUpdate /@ PacletSites[];


which should result in FFmpegTools version 1.0.1 being installed.

  • $\begingroup$ Is version 12.1 available across all product lines including WolframOne / WolframDesktop not just Mathematica? $\endgroup$
    – user13892
    Commented Mar 19, 2020 at 19:39
  • $\begingroup$ The 12.1 versions of these should be available soon, they are currently in the QA pipeline for final release $\endgroup$
    – ilian
    Commented Mar 19, 2020 at 19:43

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