# \[F\] Unknown MP4 atoms are deleted on save

**URL:** https://community.mp3tag.de/t/f-unknown-mp4-atoms-are-deleted-on-save/10637
**Category:** Fixed Bugs
**Tags:** bug-fixed
**Created:** [August 12, 2010, 1:34pm UTC](https://community.mp3tag.de/t/f-unknown-mp4-atoms-are-deleted-on-save/10637 "2010-08-12T13:34:07Z")
**Posts on this page:** 1
**Showing post:** 1

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### Author: ![edrikk](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/e/c37758/32.png) [@edrikk](https://community.mp3tag.de/u/edrikk)
#### Post date: [August 12, 2010, 1:34pm UTC](https://community.mp3tag.de/t/f-unknown-mp4-atoms-are-deleted-on-save/10637/1 "2010-08-12T13:34:07Z")

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Hi Florian,

I hope you enjoyed your vacation, and am sorry to be PMing you... But I'm facing somewhat of a big issue... ☹

It appears that the following Apple MP4 tags are not seen in MP3Tag (even in extended dialog), and if any changes are made to the MP4 file (even if just clicking "save"), the tags are destroyed! ☹ ☹ ☹

I have attached an MP4 sample that contains the tags.

rate --\>\> Rating between 0 and 100 as a text  
hdvd --\>\> HD Video 8-bit integer (boolean)  
cnID --\>\> iTunes Catalog ID, used for combing SD and HD encodes in iTunes 32-bit integer  
keyw --\>\> Keywords Used for Podcasts UTF-8 string

DLNA servers such as Twonky for example, use the "rate" atom to group content.

If you could PLEASE allow us to WRITE the above tags in mp3tag as well it would be great/a life saver... I have half of these files backed-up so I'm not completely up the creek, but I still do need to run the files through mp3tag to modify their value. ☹  
And this will allow me manually re-enter the lost ones...

Source of information behind the atoms:  
[code.google.com/p/mp4v2/wiki/iTunesMetadata](http://code.google.com/p/mp4v2/wiki/iTunesMetadata)

Does this problem exist with all tags that MP3Tag doesn't recognize? Would the standard tags found in the attached PDF (Apple's spec for tags) also be deleted?

You can find the entire spec here: [http://www.twonkyforum.com/download/file.php?id=554](http://www.twonkyforum.com/download/file.php?id=554)

Thanks for your help in this Florian... It's truly appreciated!

EDIT: This is using the latest 2.46a version.

[ED\_Attachment.zip](https://community.mp3tag.de/uploads/default/original/2X/3/38c29e47c4fcb2bb0e00be7f85d5030f0fa7a50b.zip) (43.8 KB)

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