[Matroska-devel] Hi, question about the MKV tags

Steve Lhomme slhomme at matroska.org
Sat Feb 12 10:22:22 CET 2011


On Thu, Feb 10, 2011 at 12:10 PM, Santiago Jimeno <sjimeno at ya.com> wrote:
>>> Yes, I will change the specs to make sure it's clear that padding
>>> after SeekHead is recommended (even for things that don't even exist
>>> yet in Matroska).
>>
>> OK, I will first update mkclean to leave more space (right now there's
>> only space for one element).
>
> Testing files I see there are two possibilities to put space:
> - After SeekHead (This is what mkvmerge does ), as Segment child
> - Inside SeekHead at the end
> How do you plan to put it?.

mkclean puts the Void inside the SeekHead element. In the end the
result is almost the same. The only difference is that then the
SeekHead already has the right amount of bytes in the header for its
total side. The downside is that adding new elements at the level 1
would mean editing the SeekHead header to grab some octets from it so
they can be used around it. So maybe I should put the Void outside of
SeekHead but make sure it has the right space to edit its "internal"
size.

> On the other hand, in the same test I have found that there is apps that
> invert the elements placement in SeekHead and Tags
> In Tags (TagString before TagName) and in Seek (SEEKPOSITION before SEEKID)
> Example of AVI-Mux GUI :
> http://samples.mplayerhq.hu/Matroska/Mushishi24-head.mkv
>
> I know there is not a fixed elements order, but is it of common sense to do
> this in these cases?.
> Should we give as valid this fact or to ignore Tags data?

This is the intention of Alexander Noe (author of AVI-Mux GUI) to put
elements in random position when possible. So that readers don't
assume fixed positions. This is to ensure better long term
compatibility.

-- 
Steve Lhomme
Matroska association Chairman



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