[Matroska-devel] Several (minor) issues or underspecified areas in the MKV spec

Moritz Bunkus moritz at bunkus.org
Fri Nov 20 19:56:27 CET 2015


Hey,

> How should mandatory master elements be handled if they are not
> present in the bitstream?

The Matroska spec notes[1] deal with this explicitly. Quote:

"If the upper element is not present or assumed, then the element cannot
be assumed."

So…

> Consider, for example, the ContentEncoding element. It's mandatory,
> and its children have appropriate default values such that a
> ContentEncoding element of zero size is perfectly fine. Now, taking
> things a step further, could this ContentEncoding element be
> completely removed from the bitstream? Or is it required to be present
> in the bitstream?

If it is absent then all of its children must be assumed to be absent as
well. And that's how today's parsers work, too.

Therefore EBML should specify it the same way.

Kind regards,
mosu

[1]  http://www.matroska.org/technical/specs/notes.html
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