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Topic: Vorbis comment padding issue (Read 6387 times) previous topic - next topic
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Vorbis comment padding issue

I'm using Traktor with vorbis ogg files. I've run into an issue where every so often, Traktor corrupts one of the files when it writes Tag information. I've managed to do this repeatedly with certain files,noting that they play OK, but on import into Traktor they are analysed and as soon as Traktor updates the tag info in the file, the file becomes unplayable.

To get around this, I could "fix" certain files by removing the cover image from the file, PRIOR to scanning in Traktor, and then using mp3tag to reinsert the cover image afterwards. This led me to believe that it was Traktor having issues writing tags that was the issue.  My solution wasn't perfect though as periodically, files still became corrupted occasionally.

Anyway - for various reasons I decided to start using flac files instead - (my collection is flac, I'd converted to ogg for use in Traktor) - all seemed fine, and no corruption (yet), but I suddenly noticed that ALL the cover images have been removed from my files!

I'm trying to recreate the problem, but not sure what caused it as I have processed the files with Traktor, mp3tag, and MusicBee, so any could be responsible, but I wondered if it had something to do with the way Vorbis comments are stored?

So questions:

1) Is there a size limit to the amount of info that can be stored in a flac file tag - once that limit is reached, the cover is removed to make way for more??
2) I've heard that you can rip tracks with extra padding in the comment area so that the entire file is not rewritten when a tag is added - can padding be added later be any utility?

Re: Vorbis comment padding issue

Reply #1
There is no (practical) limit in the specification, but that's not to say that a particular encoder can't have a problem tagging, or may even impose a limit of its own.

You seem to be mixing up questions about flac (raw or in ogg?) and vorbis.  The standard flac encoder allows padding blocks to be written and even adds one by default just in case.  Since the metadata is in a known position at the start of the file, padding allows tags to be extended or added without having to also rewrite the much larger audio data, up to the space available from the padding block.  Vorbis allows similar padding to be used, although not using explicit padding blocks; pages are simply written larger than would be necessary to contain their contents.

Re: Vorbis comment padding issue

Reply #2
Thanks for your reply.

My understanding is that both flac and ogg files use vorbis format tags which is why I mentioned my earlier problem with ogg files.

It looks like you're suggesting I simply reconvert the files telling the converter to insert more padding - I looked at the standard encoder and dbpoweramp, but I cant find any settings on padding.

Re: Vorbis comment padding issue

Reply #3
The tag names and contents in flac and vorbis are (largely) the same but the container formatting is very different.  Except that flac can be placed in an ogg container, that's very rare though and you should probably just forget I said it.

I have no idea if including more padding will help in your situation.  The tagger is clearly doing something undesirable that could possibly be considered a bug.  You can play with padding but a more reliable solution might be to try different software.  Even just as a test, it would show that you aren't doing something completely crazy and that it is just one program that is messing up.

Just for the record, I've tagged a lot of flac and vorbis files without seeing symptoms like you describe.  They aren't inherent to the tag format.

Re: Vorbis comment padding issue

Reply #4
Maybe one of your programs doesn't support proper METADATA_BLOCK_PICTURE tag and uses COVERART instead?