Is it possible to write XMP Metadata to an MP4 video file in place?

[Sean]

I am working with .mp4 files, mostly h.264.  As I work with and mark important sections in Premiere Pro, Premiere is adding markers to the original source .mp4 files via XMP metadata.  My task is to grab the markers added by Premiere, and write those back to a different copy of the same MP4 files on a different hard drive.

So, here's what I've come up with so far. 

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exiftool -api largefilesupport=1 -XMP -b source.mp4 will, in fact show my markers, and doing the same for target.mp4 will show that the target file doesn't have the markers yet.  I can then do:

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exiftool -overwrite_original -api largefilesupport=1 -tagsFromFile source.mp4 -xmp:all target.mp4
which will successfully output target.mp4 with the needed markers.  However, the issue is that the above command completely rebuilds the target file.  It creates a target.mp4_exiftool_tmp, and has to build the entire 6GB file.  While this works, it takes about the same time as just copying the file from one hard drive to another, which defeats the purpose.  My intention and hope was that exiftool could simply add the required markers, without having to make a new file.  Using -overwrite_original and -overwrite_original_in_place seemed to have no effect.  Perhaps I'm not being specific enough with -xmp:all?  Or maybe this is just a limitation of how exiftool works?  Any help appreciated.  Thanks!

[StarGeek]

This is FAQ #31, Why does ExifTool rewrite the entire file when I am only changing one small thing?

Short answer, no, exiftool never writes in place.

[Sean]

Apologies for inadvertently asking an FAQ, but I appreciate the clarification, thank you!