I have a candle flame image with which I'm using an .mp4 for the candle flame video, and another b/w .mp4 for the alpha. It works usually (and always on our other computers), but every now and then one of the computers gives me a fail to load error, with the "missing codec" error as the reason. It's a Windows 10 machine, so, yes, the .mp4 codec is on there. Also, it works from time to time, on various projects, using the same video--but then it will just stop working, and all projects (which work fine on other computers) which use an .mp4 give that error. The last time this happened reinstalling iClone fixed it, but that didn't help this time.

How can I fix this? Using other codecs shouldn't be the solution, as (a) this works fine on our other computers, and sometimes on the problem child, and (b) that would involve relinking the files across many projects, to a much more memory-intensive format.

mp4 files seem to be problematic. For this reason I convert everything to wmv files and that seems to resolve any issues. As to why, I don't know.

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I've never had a problem with mp4.
Maybe there is a problem with the codec.
You can install the K-Lite Codec pack.
If it is installed, you can update to the latest version again.


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People have had mixed results with the K-Lite Codec pack and I wouldn't recommend it. If you decide to install at anyway, make sure to create a restore point first.

Anyway, it shouldn't really be necessary to install any codec pack for Windows 10.

What is worth looking into is what codec has been used to create the MP4s. For compatibility it is best to stay with H264. The newer H265 has advantages by may cause compatibility issues.

Also, a reason that one system may be have different than another is that some applications install their own versions of codecs and make a mess of things. I have had major problems with the DivX player, and the only remedy was to uninstall it.

Right now, I'm not using any codec pack, but in the past I have had success with those from https://shark007.net/index.html. 

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It would be silly to have to install anything to get an .mp4 (h264, at that) onto a Windows machine--especially when rendering out of AE. At any rate, rendering a .wmv seems to have done the trick as a stopgap. Thanks for your help!