We actually use TagLib for all of our metadata processing needs -- we
didn't roll metadata writing ourselves or anything like that.
On Sat, Mar 31, 2012 at 10:18 PM, Scott <nappingcrac...@gmail.com> wrote:
> This sounds a bit like NIH (not invented here) syndrome.
>
> I suggest using id3lib to do the actual file manipulation and simply
> hook Mixxx's front end into that API. This would work for at least ID3v1
> and ID3v2 tags.
>
> id3lib http://id3lib.sourceforge.net/ has been around for a while and is
> used by many tagger / player programs. EasyTAG uses it, and I've used
> that program without problems for years on tens of thousands of files at
> a time.
>
> This would leave the quality control to a group focused specifically on
> manipulating audio file tags and metadata.
>
> -Scott
>
> On Sat, 2012-03-31 at 22:40 +0100, Adam Davison wrote:
> > Hi,
> >
> > I think Albert's general point was more that if you have any memory
> > corruption anywhere in Mixxx, then the results of our write to the
> > file are undefined. Even if we fix this specific memory corruption bug
> > then we have no way to guarantee there aren't more lurking. In fact I
> > could probably guarantee you that there are memory corruption bugs
> > lurking in code the size of Mixxx + all the libraries living in our
> > process space.
> >
> > One safe way to do it perhaps would be to have a very small helper
> > program which handled the writing in a different process.
> >
> > Adam
> >
> > On 31 March 2012 18:54, Ilkka Tuohela <ilkka.tuoh...@gmail.com> wrote:
> > >
> > > Maybe I'm asking the obvious, but why wouldn't following process work
> just fine:
> > >
> > > - Store new tags to database fields
> > > - Make a copy of the file on disk to temporary file, original being
> still mmaped or not doesn't matter
> > > - Write tag changes to the temporary file
> > > - If writing temporary file was successful (disk space was enough
> etc), unlink old file and rename new file to original name
> > > - If writing temporary file was not successful, remove temporary file
> and report error, maybe revert database fields?
> > >
> > > At least on unix-like systems, the mmap will hold a reference pointing
> to the original deleted file, and the changes to tags can't affect it,
> preventing corruption. This will use extra bytes from disk for all
> rewritten files (mmaped bytes + new file with new tags) as long as the mmap
> FD is open, but since we don't hold hundreds of files open in player, the
> extra disk space used should not be an issue and is released anyway on fs
> level when the FD is closed by mixxx (song has been played).
> > >
> > > Additionally, if we wish to show the updated tags in decks, I think
> the tags should be and are based on database entries not file tags and
> should reflect the current info correctly (as long as there is a slot to
> update the details in player on the fly).
> > >
> > > I have no idea if this works similarly on windows filesystems though,
> but I think so.
> > >
> > > *hile*
> > >
> > > On 31 Mar 2012, at 18:13, Owen Williams wrote:
> > >
> > >> I did develop an initial crappy workaround that prevents many of the
> > >> memory-corruption situations. Basically, if Mixxx can know for sure
> > >> that the music file is not open, it's safe to update the metadata.
> The
> > >> trick is figuring out if in fact that file is open or not.
> > >>
> > >> I don't believe there's any risk in corrupting the file on disk. The
> > >> corruption I experienced was only in terms of playback -- still a big
> > >> problem because it would cause static during sets.
> > >>
> > >> Mixxx is a nice interface for tag editing, though, so it might be
> worth
> > >> pushing up the importance of that bug.
> > >>
> > >> (one solution might be queuing the metadata update in the file reader
> > >> object itself, and then writing the data in the destructor. Is it
> safe
> > >> to assume only one file object per file, though?)
> > >>
> > >> Owen
> > >>
> > >>
> > >> On Sat, 2012-03-31 at 10:38 -0400, Albert Santoni wrote:
> > >>> Hi Keith,
> > >>>
> > >>> I'm sorry you had a crappy experience with this - Our intention was
> to
> > >>> reduce the risk of data loss.... which is the opposite of what
> > >>> happened to you.
> > >>>
> > >>> Mixxx did not write write metadata to any music files until 1.9
> > >>> because we were concerned that we didn't have the quality control in
> > >>> place to ensure we would never ship a library-destroying bug. Just
> > >>> imagine if we had a bug that caused your MP3s to get corrupted...
> > >>>
> > >>> And it turns out this fear wasn't totally unfounded. After 1.9
> > >>> shipped, Owen tracked down a subtle memory corruption bug related to
> > >>> Mixxx writing to MP3s, and although there were no reports of corrupt
> > >>> files, file writing and memory corruption are not a great
> combination.
> > >>> (You might be able to make an argument that Mixxx is more susceptible
> > >>> to heap corruption programming errors which may not affect the actual
> > >>> file writing itself if it's done on the stack. I'm sure the
> > >>> TrackInfoObjects are kept on the heap though, so maybe worst case you
> > >>> could just end up with corrupt metadata. But never say never...)
> > >>>
> > >>> As Daniel pointed, it was due to bug #728197 that we disabled
> metadata
> > >>> writing for Mixxx 1.10.0 and made a quick 1.9.2 release.
> > >>>
> > >>> If you have any suggestions on how we can communicate that metadata
> > >>> isn't written or want to work on #728197, you know how to get in
> > >>> touch... :)
> > >>>
> > >>> Thanks,
> > >>> Albert
> > >>>
> > >>>
> > >>> On Sat, Mar 31, 2012 at 4:32 AM, keithsalisb...@gmail.com
> > >>> <keithsalisb...@gmail.com> wrote:
> > >>>> Sorry guys, normally I wouldn't say this, but something happened
> today
> > >>>> which I really don't understand why this choice has been made, maybe
> > >>>> someone can explain.
> > >>>>
> > >>>> So in the last week or so, I've spent many hours tweaking the
> metadata
> > >>>> in my dj library, sorting out track titles, artists, labels, keys,
> > >>>> bpms all sorts of goodness which makes a record box more than just a
> > >>>> bunch of files.
> > >>>>
> > >>>> It was my assumption all this goodness was being baked into the
> files.
> > >>>>
> > >>>> Yesterday as part of building a new version I moved my .mixxx
> config,
> > >>>> and associated database etc out the way to create a new one.
> > >>>>
> > >>>> And here it is, to my surprise and quite honestly my shock, my files
> > >>>> we ALL back to their tatty messed up disorganised state - ALL my
> time
> > >>>> and effort had been reverted.
> > >>>>
> > >>>> Now you'll notice I was smart enough to backup my data before
> creating
> > >>>> a new database, so I've not really lost anything, however I AM upset
> > >>>> that this happened. I would expect more from Mixxx. I actually
> trusted
> > >>>> Mixxx more than Rhythmbox or those other media browsers to do the
> > >>>> right thing by my files.
> > >>>>
> > >>>> So what's the deal here - I can understand a concern allowing users
> to
> > >>>> edit their files - sure - but there should be a config/preferences
> to
> > >>>> allow me to choose. And more over, I should be made aware that all
> > >>>> this goodness is not really in my files. Somehow.
> > >>>>
> > >>>> My point is, I'm a power user, but I'm sure many users out there
> have
> > >>>> edited their files believing they're updating the files, and only
> when
> > >>>> they change computers, or rebuild their computer or whatever, that
> > >>>> they find out all that data is lost.
> > >>>>
> > >>>> Thoughts?
> > >>>>
> > >>>> Keith
> > >>>>
> > >>>>
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> > >>>> http://mixxx.org
> > >>>>
> > >>>>
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> > >>>> Mixxx-devel@lists.sourceforge.net
> > >>>> https://lists.sourceforge.net/lists/listinfo/mixxx-devel
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >>
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> > >
> > >
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