Subject: [Cellar] Unknown Size Element

From: Steve Lhomme <[email-masked]>
Date: Tue, 1 Nov 2016 09:29:43 +0100

So far the Unknown Size element didn't require its parent to have an
unknown size.

I propose that all parents of such an element must also have an
unknown size. If it's known later it's better to update the children
elements that have their boundaries known too. That's also a way to
restrict unknown size usage to case where we can't do without.

https://github.com/Matroska-Org/ebml-specification/pull/125

-- 
Steve Lhomme
Matroska association Chairman

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From: Michael Bradshaw <[email-masked]>
Date: Tue, 1 Nov 2016 05:37:17 -0700

I'm in favor of this change. Note that even with this wording change, it's
still permitted to create a parent element with a known size and the child
element with an unknown size within a particular file. I think prohibiting
that too would be nice. It would have simplified the WebM parser I wrote.

On Tuesday, November 1, 2016, Steve Lhomme <[email-masked]> wrote:

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From: Steve Lhomme <[email-masked]>
Date: Sun, 6 Nov 2016 10:17:34 +0100

> that too would be nice. It would have simplified the WebM parser I wrote.

How is that possible ? If the Element has an unknown size, its parent
must have an unknown size as well, its parent's parent too and so on.

This is a MUST requirement so it should not be allowed to do
otherwise. I wonder if files exist in the wild where this requirement
is not met. The only possible way I can think of is if a live stream
that was recorded and then the Segment size was updated at the end. I
doubt that ever existed. If one wants to do that they will now have to
edit each Cluster size as well.

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