mp4tag: in place support

[ghost]

I have been using the TagEditor project:

tageditor -s cover= --max-padding 100000 -f ki.mp4

However I noticed that Bento4 does not work on files in place:

$ mp4tag --remove Cover ki.mp4
ERROR: output file name missing

Please add in place file support, thank you.

[barbibulle]

The reason why mp4tag always creates a new output file is because in most cases it isn't possible to edit MP4 metadata in place. There are a number of cases where that's simply not possible. For instance, for files where the moov atom is before the mdat media data (which should be most well behaved MP4 files), then in-place editing would only work if the metadata being changed is smaller than the original.
So rather than attempting an in-place change and failing in most cases, the choice was to just take the safe default which is to create a new file. It should be possible to enhance the mp4tag program and detect whether in-place editing could be done safely, but that has never been an issue so far and thus never been a high priority. And with most systems getting faster and faster storage (SSD mainly), that is likely to remain that way.
Do you see a very compelling reason to have in-place metadata editing?

[ghost]

@barbibulle the reason is pretty clear: large files. If you have a 1 GB MP4 file, TagEditor for example can simply edit the original file, given that enough space is available. With Bento4 that file has to be written again