[Matroska-devel] Tagging MKV files

Liisachan seelie at faireal.net
Sun Sep 2 07:27:05 CEST 2012


 > Now it appears that you can have multiple TAG elements for the same item,
 > and it uses the last one.

This part sounds like a more general limitation of VLC, and of Mediainfo.
For example, it seems normal that the first (e.g. Video) track has an 
ENCODER tag (e.g. x264 rev...), and the second (e.g. Audio) track has 
its own ENCODER tag (e.g. oggenc ver...).  That is, one <Tag> and 
another <Tag> with a different <Targets> may contain a <SimpleTag> with 
the same <TagName>.  When that happens, VLC and Mediainfo only show 
information from one of such tags (probably the one parsed last).
I'm not sure if this limitation has anything to do with what you're 
trying to do, though.

Liisachan



On 2012-09-01 21:41, Dan Hinsley wrote:
> 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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