[Matroska-devel] Tagging MKV files

Dan Hinsley danhi at cox.net
Sat Sep 1 23:41:39 CEST 2012


It wasn't just the validator.  Before I move the SeekHead, the title shows
up from the tag in the file (I'm using the cover_art.mkv sample file).
After I move the SeekHead, it defaults back to the filename.  So it appears
that VLC doesn't process the second SeekHead.  mkvinfo -v does show the
added SeekHead.  

Now it appears that you can have multiple TAG elements for the same item,
and it uses the last one.  But I'm think I can only have one TAGS, since it
is pointed to by the Seek item.

I'd be glad to send you either the modified cover_art.mkv or hex dumps of
any part of it if that would help.

Thanks,

Dan

-----Original Message-----
From: matroska-devel-bounces at lists.matroska.org
[mailto:matroska-devel-bounces at lists.matroska.org] On Behalf Of Moritz
Bunkus
Sent: Saturday, September 01, 2012 1:37 PM
To: Discussion about the current and future development of Matroska
Subject: Re: [Matroska-devel] Tagging MKV files

Hey,

On Sat, Sep 1, 2012 at 10:25 PM, Dan Hinsley <danhi at cox.net> wrote:

> Now this file still plays, but when I run mkvalidator it tells me:

Completely ignore mkvalidator in this case. It is buggy, doesn't take
several situations into account that are perfectly valid (when you
look at the Matroska specs at
http://www.matroska.org/technical/specs/index.html then you'll see
that SeekHeads are marked as "multiple", meaning it's more than valid
to have more than one SeekHead inside a segment) etc etc. This
situation is one of those that it doesn't account for. The first
"warning" means that it doesn't parse the secondary seek head. All the
other warnings are subsequent faults, of course, because those
elements ARE referenced.

Also: those things are WARNINGS. I've long argued with Steve Lhomme,
author of mkvalidator, that even printing a warning for such issues is
often mistaken by users to mean that a file is not valid. That is NOT
the case! A warning issued by mkvalidator solely means that the file
is not 100% over-the-top optimized. E.g. for playback situations in
which no seeking is possible (in such cases the secondary seek head
would not be parsable by a player). However, guess how often such a
situation occurs nowadays... Again: ignore them.

An error issued by mkvalidator is another thing, but you've only shown
warnings.

> So it seems that having one SeekHead point to another isn't really valid?

It is perfectly valid.

> My overall ambition in this is to be able to tag an MKV file without
having
> to rewrite the entire file (not to mention recalculate every offset along
> the way).

That's what mkvpropedit does as well with all of its actions.

Kind regards,
mosu
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