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I am using Mathematica 11.3 with Windows 10.

When calling Export to export a List of Images as a QuickTime movie, the memory used by Mathematica 11.3 increases but it is not released after the evaluation. The code below is a simple example:

$HistoryLength = 0;
frame = Rasterize[Plot[x, {x, 1, 2}], RasterSize -> 1000, ImageSize -> {960, 720}];
frame = Table[frame, {i, 100}];
Export["D:\\example.mov", frame, "FrameRate" -> 100];

After runing this Cell, open Task Manager to check how much memory Mathematica is using. On my PC, it shows that Mathematica is using 769.0MB memory. Then run the Cell below:

Export["D:\\example.mov", frame, "FrameRate" -> 100];
MemoryInUse[]/1024.^2

Now Task Manager shows that Mathematica is using 1055.4MB memory, while Mathematica 11.3 shows that the memory in use in MB is:

91.6286

If you run the second Cell for more several times, the number in Task Manager keeps increaing but the number in Mathematica does not change obviously.

Anyone knows why this happens? This problem is forcing me to restart the kernal everytime i export a lots of images as a QuickTime video.

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    $\begingroup$ Not very surprisingly, this seems to be OS-dependent. I cannot reproduce this with version 11.3 on macOS 10.13.6. Anyways, I think it is a good idea to send a bug report to Wolfram Support along with a link to your post. Although this won't help you immediately, this may lead the issue to be fixed in the upcoming release. $\endgroup$ – Henrik Schumacher Jan 11 at 9:57
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    $\begingroup$ @HenrikSchumacher Thanks for checking. I have sent a report to Wolfram Support. I think the version 11.3 has made some changes in Export, and the same code does not lead to this problem in version 10.4 on Windows 10.The size and quality are quite different between the ".mov" files produced by version 11.3 &10.4.1, and it seems that 11.3 makes improvement in codec or something but leaves some bugs for Windows 10. $\endgroup$ – Taiyang Zhang Jan 11 at 16:38

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