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Topic: Amarok+libmp4v2=ReplayGain killer (Read 4372 times) previous topic - next topic
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Amarok+libmp4v2=ReplayGain killer

Some time ago I compiled Amarok including full MPEG-4 audio read/write support using the libmp4v2-dev (faad2) package available on Rarewares. Yesterday I had added some extra "Composer" infos to a few Nero .m4a albums using this player, which turned out causing quite a mess today:

Firstly, during a Windows session, loading these files into Winamp revealed an empty "Composer" field, i.e. the one written by Amarok wasn't compatible to the iTunes style. Using Winamp I edited the field once again, fixing the little issue... or so I thought. I hadn't noticed a further, much more annoying problem.

Secondly, back in Linux, the ReplayGain script used by Amarok complained that no ReplayGain tags could be found inside the files, though they had been scanned by aacgain before. Checking them revealed that Amarok had actually written the metadata without paying any attention to custom tags, resulting in the ReplayGain values and undo informations being permanently lost. Only the tag types Amarok can handle itself were left.

Using Google I stumbled across this site: http://mail.kde.org/pipermail/amarok/2006-...ber/001280.html
Quote
libmp4v2 (mpeg4ip 1.3 is recommended, faad2 is less reliable)

Does anyone know whether mpeg4ip provides flawless tagging support for m4a/mp4? I've really had my share with faad2 for now, hence I wouldn't want to run into similar troubles once again.

Amarok+libmp4v2=ReplayGain killer

Reply #1 –
Quote from: Junon on
Some time ago I compiled Amarok including full MPEG-4 audio read/write support using the libmp4v2-dev (faad2) package available on Rarewares. Yesterday I had added some extra "Composer" infos to a few Nero .m4a albums using this player, which turned out causing quite a mess today:

Firstly, during a Windows session, loading these files into Winamp revealed an empty "Composer" field, i.e. the one written by Amarok wasn't compatible to the iTunes style. Using Winamp I edited the field once again, fixing the little issue... or so I thought. I hadn't noticed a further, much more annoying problem.

Secondly, back in Linux, the ReplayGain script used by Amarok complained that no ReplayGain tags could be found inside the files, though they had been scanned by aacgain before. Checking them revealed that Amarok had actually written the metadata without paying any attention to custom tags, resulting in the ReplayGain values and undo informations being permanently lost. Only the tag types Amarok can handle itself were left.

Using Google I stumbled across this site: http://mail.kde.org/pipermail/amarok/2006-...ber/001280.html
Quote
libmp4v2 (mpeg4ip 1.3 is recommended, faad2 is less reliable)

Does anyone know whether mpeg4ip provides flawless tagging support for m4a/mp4? I've really had my share with faad2 for now, hence I wouldn't want to run into similar troubles once again.


Junon

mpeg4ip 1.3 is quite old and has some very bad bugs regarding metadata.  I remember that metadata editing in 1.3 would corrupt files, and the suggested "workaround" was to read all fields, clear the metadata and re-write.  Of course, this mean any fields that the program doesn't understand aren't saved.  Winamp had similiar behaviour until MPEG4IP 1.4.

The current MPEG4IP/lib/mp4v2 CVS (soon to be released as 1.6) has many fixes and improvements in this area.

Amarok+libmp4v2=ReplayGain killer

Reply #2 –
Thanks for these helpful informations. I just linked to this site as a small reference, the package I actually downloaded is the 1.5.0.1 one available on Sourceforge. But I'll follow your suggestion and wait for the 1.6 release prior to evaluating mpeg4ip.

Amarok+libmp4v2=ReplayGain killer

Reply #3 –
There's a chance that amarok is still using the old metadata crash workaround even though the problem has been fixed

Amarok+libmp4v2=ReplayGain killer

Reply #4 –
Good point. It would certainly make sense to test Amarok's behaviour using some lousy copies of the MPEG-4 files instead of the "real" ones.
 

Amarok+libmp4v2=ReplayGain killer

Reply #5 –
Small update in this matter:

I just installed mpeg4ip 1.6.1 from debian-multimedia and compiled the new faad2 2.6 sources. Afterwards, compiling Amarok caused a little trouble this way, because the 1.4.7 stable release isn't compatible to libmp4v2 1.6. Hence, anyone attempting to compile the player with MP4 tagging support has to stick to the SVN for now, the issue has already been adressed there. But anyone who scans her/his collection with ReplayGain should only do this for better reading support (without this Amarok fails at reading certain custom genres), because the problem still is as benski described above: The latest SVN release keeps utilizing this fantastic workaround, which results in the loss of all tags the player doesn't understand.