[Matroska-devel] File with no SeekHead

Steve Lhomme slhomme at matroska.org
Sat Sep 15 11:57:54 CEST 2012


I don't understand the confusion in the spec (luckily). It says this
for SeekPosition:
"The position of the element in the segment in octets (0 = first level
1 element)."

That's an offset relative to the beginning of the data of the Segment.

On Sat, Sep 15, 2012 at 9:04 AM, Moritz Bunkus <moritz at bunkus.org> wrote:
> Hey,
>
> On Sat, Sep 15, 2012 at 1:19 AM, Dan Hinsley <danhi at cox.net> wrote:
>
>> So you're saying a SeekHead is required before the Clusters,
>> so I can count on that and reject a file that doesn't have one as invalid?
>
> No. A SeekHead is required in order to find stuff located after the
> first cluster. If all level 1 elements (tags, attachments etc.) are
> located before the first cluster then you don't need a SeekHead, and
> none is required. This can be the case e.g. for streaming. Such files
> are completely OK and you cannot rely on a SeekHead being present.
>
>> That still doesn't answer the question as to what the Seek Position should
>> be relative to.  The spec says the first Level 1 element,
>
> No, they don't really say that, though I have to admit that they're a
> bit vague and imprecise. The start of the data part of the segment is
> what is correct and what that part means.
>
> "The reference is the beginning of the first Segment element." <--
> This is the important sentence. The second sentence mentioning that
> level 1 element is an example meant to further clarify it, and you're
> right that those two don't HAVE to mean the very same position. I'll
> update that page to make it clearer.
>
> Kind regards,
> mosu
> _______________________________________________
> Matroska-devel mailing list
> Matroska-devel at lists.matroska.org
> http://lists.matroska.org/cgi-bin/mailman/listinfo/matroska-devel
> Read Matroska-Devel on GMane: http://dir.gmane.org/gmane.comp.multimedia.matroska.devel



-- 
Steve Lhomme
Matroska association Chairman


More information about the Matroska-devel mailing list