Some years ago I wrote about my findings about the PRIV frame written from Native Instrument Traktor.
PRIV frame content is not displayed up to Mp3tag v3.28c for *.mp3 files.
Traktor 4 writes data in a PRIV frame (after all the ID3 fields) that looks like this:
Some content entered in Traktor 4 input fields are written into the expected ID3 tags for a mp3 track like this:
In the tested Traktor Pro 4 v4.1.1.23 there are at least 7 fields that are not written as ID3 tags into the mp3 track (yellow highlighted in the above screenshot):
a) Comment 2
b) Mix
c) Play Count
d) Imported
e) Autogain
f) Key Text
g) Cat. No.
The mentioned online tool is still able to decode the PRIV frame from v4.1.1.23 like this:
In the PRIV frame you find the above
a) as COM2
b) as TMIX
c) not sure, maybe BPMQ or CUEP?
d) as IPTD
e) not sure, maybe PCDB and/or PKDB?
f) as TKEY
g) as CTLG
Some remarks to the used tag like names:
a) COM2 is not a valid ID3 tag
b) TMIX is not a valid ID3 tag
c) Neither BPMQ nor CUEP are valid ID3 tags
d) IPTD is not a valid ID3 tag
e) Neither PCDB nor PKDB are valid ID3 tags
f) TKEY is a valid ID3 tag and contains the value for INITIALKEY.
Mp3tag reads 12d correclty in above example song.
It remains unclear why Native Instruments write "Key Text" in the same TKEY name but in the PRIV frame.
g) CTLG is not a valid ID3 tag
There is a CATALOGNUMBER (TXXX:CATALOGNUMBER) that could be used for that content.
For the cover art I could not find a way that the cover will be embedded in the mp3 track.
Traktor let you import a cover art picture and show it in a very small table view:
Such a cover picture seems not to be saved back into the track.
(I do not rule out that this could be a limitation of the used demo version.)
If you try to import a mp3 track into Traktor with prefilled ID3 tags, most of them will be imported.
But please carefully check special tags like BPM or INITIALKEY.
In my tests Traktor silently changed the content in the mp3 track for this fields and wrote its Traktor values back in the track.
These are the fields and content BEFORE I dropped it into Traktor:
These are the values - silently changed from Traktor after the import:
Have special look at BPM and INITIALKEY.
If you don't want Traktor to change the BPM and INITIALKEY content silently, you have to manually deselect them in the import window “Analyze”:
I hope that this information can help users of Mp3tag and Traktor to see the current compatibility and limitations.
Small addition:
In *.flac files the equivalent of the ID3-PRIV content is written as TRAKTOR4 field. This field can be read from Mp3tag.
Due to its binary content, however, it is almost impossible to change specific values and save them back as valid changes.