Re: [Cellar] Matroska Elements to support frame side data

Luca Barbato <> Mon, 12 November 2018 17:21 UTC

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From: Luca Barbato <>
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Date: Mon, 12 Nov 2018 18:21:39 +0100
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Subject: Re: [Cellar] Matroska Elements to support frame side data
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On 05/11/2018 12:20, Jerome Martinez wrote:
> On 05/11/2018 10:29, Moritz Bunkus wrote:
>> Hey,
>>> In other thoughts on this suggestion, I think it could make it difficult
>>> to easily understand if a file has a particular type of side data. For
>>> instance if only a few Clusters somewhere in the Segment contain a
>>> certain type of side data, it would require parsing every Cluster to 
>>> know
>>> what types of side data are available. This uncertainly wouldn’t be the
>>> same issue if the side data was itself a Track.
>> It's not entirely necessary to use a full track for side data. We can 
>> simply
>> signal the presence of side data in the track headers and refer to it 
>> from
>> the side data in the block groups. This would also mean we only have to
>> store the string identifying the side data type once (in the track 
>> headers)
>> instead of in each block.
> It would permit more efficient storage, but IMO it should be optional 
> only, because if we do real time transcoding to MKV we don't have always 
> all sidecar info. I have in mind some A/V content with ancillary data 
> coming only after few minutes, without any change in A/V part.

This should warrant for a stand alone track maybe?