Re: [Cellar] AV1 mapping Matroska

Moritz Bunkus <moritz@bunkus.org> Wed, 27 June 2018 08:59 UTC

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From: Moritz Bunkus <moritz@bunkus.org>
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Date: Wed, 27 Jun 2018 10:58:52 +0200
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Subject: Re: [Cellar] AV1 mapping Matroska
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Hey,

I've only had time to skim over it. It's definitely understandable.

For me the most important thing is to have the mapping in Matroska and WebM
be identical. As the reference encoder already produces WebM files, I
highly suggest we communicate with their developers regarding the
mapping. I cannot find a document for AV1/WebM bindings at the moment,
though…

> I will dig deeper but we may have to tweak CodecDelay to make it signed.

You cannot change the type of an existing element. It would potentially
break the interpretation of existing files created with the old
semantics. Let's take the value 144, which as an unsigned EBML integer
would be stored as 0x81 0x90. If you read that back as a signed EBML
integer, you'd get the value -128.

Kind regards,
mosu