m4a ratings and atoms questions, possible problem?

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MrSinatra
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m4a ratings and atoms questions, possible problem?

Post by MrSinatra » Sun Apr 20, 2014 7:34 pm

hi all,

my understanding is that MM will write ratings to a %rate% atom using a 0-100 scale and that this is the atom mp3tag, winamp, and twonky use.

is that correct so far? if it is there may be a fly in the ointment.

apparently win7 windows explorer (and one presumes WMP / later vers as well) will write ratings to an unknown atom of its own choosing! this atom can not be seen by mp3tag or winamp etc at least by default.

can anyone confirm all of this, and / or specify which atom windows explorer is writing to?

can MM read this atom? and if not, can it still write only to the %rate% atom but read both, preferring the %rate% atom if both are present?

thanks.

Lowlander
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Re: m4a ratings and atoms questions, possible problem?

Post by Lowlander » Sun Apr 20, 2014 8:28 pm

What MediaMonkey does: http://www.mediamonkey.com/wiki/index.p ... erties/4.0

Note that when needing to transfer Ratings between applications that can't read each others Ratings that you can create a Playlist per Rating and then import the Playlists and set the Ratings accordingly for the files on the Playlist.
Lowlander (MediaMonkey user since 2003)

MrSinatra
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Joined: Fri Dec 14, 2012 9:21 pm

Re: m4a ratings and atoms questions, possible problem?

Post by MrSinatra » Sun Apr 20, 2014 8:46 pm

Lowlander wrote:What MediaMonkey does: http://www.mediamonkey.com/wiki/index.p ... erties/4.0

Note that when needing to transfer Ratings between applications that can't read each others Ratings that you can create a Playlist per Rating and then import the Playlists and set the Ratings accordingly for the files on the Playlist.
thx for the link, but I think maybe I was unclear.

a user can rate m4a files with windows explorer (and presumably WMP as well). however, they don't use the %rate% atom. ergo, MM does not see those ratings at all.

so what I want to know, is what atom does windows use? and moreover, I am asking MM to support reading that atom if %rate% is not available.

Lowlander
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Re: m4a ratings and atoms questions, possible problem?

Post by Lowlander » Mon Apr 21, 2014 10:35 am

You should consult WMP documentation as to what it uses as rating tag. A quick online search only returns plugins to do the tagging (so maybe nothing is tagged to the files).
Lowlander (MediaMonkey user since 2003)

MrSinatra
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Re: m4a ratings and atoms questions, possible problem?

Post by MrSinatra » Mon Apr 21, 2014 3:24 pm

no, it def is tagged, b/c the rating follows the file from one computer to the next.

I think what may be happening is that win exp uses a custom atom and then sticks a WMA style tag in it as a data blob.

MiPi
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Re: m4a ratings and atoms questions, possible problem?

Post by MiPi » Tue Apr 22, 2014 3:01 am

WMP/Windows Explorer in Windows 7 uses undocumented "Xtra" atom for some MP4 metadata. MM4.1 currently does not support them. Tracked as: http://www.ventismedia.com/mantis/view.php?id=12017

MrSinatra
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Re: m4a ratings and atoms questions, possible problem?

Post by MrSinatra » Tue Apr 22, 2014 3:50 am

cool. how did you figure out the list of tags at the bug?

is the atom known as:

moov.udta.Xtra

?

is it a data blob inside that atom or how is it storing the info? as a WMA tag?

will you just read these values? or will MM edit them as well? I think MM should only write ratings to %rate% (and prefer it on read) and its questionable if it should even read windows leveling info imo.

note that stupid windows rating scale is 0-99 with only 99 being = to 5 stars.

MiPi
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Re: m4a ratings and atoms questions, possible problem?

Post by MiPi » Tue Apr 22, 2014 6:17 am

I've found it in some other forum and verified it manually (tagged m4a file in Win7 explorer and looked inside the file in hexa editor).
Yes, it is moov.udta.Xtra. The format inside this atom is nearly the same as in WMA/WMV tags, in fact, Xtra works here only as the envelope for some standard WMA tags.

I'm going to implement reading these tags and probably edit/preserve them in case they are already present (i.e. write both - standard and Xtra tag - to avoid the situation, that Win. explorer will show different values, as rating, from MM4). Standard M4A tags (as 'rate') have definitely higher priority, conversion from windows rating scale will be the same as we do for WMA/WMV.

MrSinatra
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Re: m4a ratings and atoms questions, possible problem?

Post by MrSinatra » Tue Apr 22, 2014 8:15 am

was the other forum winamps? I've been discussing this there too.

sounds like you got it figured out, but is the data in the atom always going to be in there the same way? like is it crude matching or predictable parsing irrespective of what fields are present?

MiPi
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Re: m4a ratings and atoms questions, possible problem?

Post by MiPi » Tue Apr 22, 2014 9:57 am

It was this post.

The moov.udta.Xtra atom playload seems to have quite clear structure - list of WM tags (defined by Microsoft in WM/ASF standard, each tag has its specific name and value of specific type). It cannot contain something different, it would be unparsable even for WMP, because i does not have any additional payload identification (only name of the atom).

MrSinatra
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Re: m4a ratings and atoms questions, possible problem?

Post by MrSinatra » Tue Dec 11, 2018 12:05 pm

Forgive me for reviving this old thread, but I seek clarification on MM's behavior / handling of m4a tags.

My impression is that if u read m4a's into MM it will read both normal atoms and the windows custom atom with the WM style tag / data blob. If both are present, it will prefer the normal atoms over the custom one.

So what I want to know is what happens if the normal atom has say only an artist value, and the rest of the values are in the custom atom? Does it merge them for display?

And then if so, when u save the tag, does it write this merging to both all previously blank normal atoms and all available WM fields in the custom atoms WM data blob?

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