[Matroska-devel] Periodic thumbnails for seeking

Joseph Ashwood ashwood at msn.com
Fri Apr 12 14:00:11 CEST 2013

From: Adam Hunt
Subject: [Matroska-devel] Periodic thumbnails for seeking

> Why not embed this data into the container instead?

I can think of probably a hundred nitpicky reasons not to use the feature, 
but have trouble coming up with a reason not to add the feature as an 
option. Of course I can also see this as a feature that few use.

> Could a feature like this be added to MKV

Actually technically not difficult. Its just a matter of adding a new stream 
type. Along with Video, Audio, Subtitles, it isn't technically difficult to 
add a Thumbs stream consisting of pairs of  <timecode, image data>.

The problem comes in the next step:

> then eventually added to various software that encodes/multiplexes
> and decodes/demultiplexes MKV files?

There in lies the problem. From a technical perspective adding such a 
feature sounds trivial. From a realistic perspective the muxer would have to 
be fed it as a separate stream that is somehow generated out of band. This 
would be a matter of defining yet another format. Alternately, the format 
could be fixed for Matroska and the muxer could process the video to extract 
thumbnails. Either process adds complexity to the tool chain, which is why 
the feature would likely remain largely unused.

I'm not against having the feature, and I'm still working on the things that 
some here know about where I could benefit from it.

However, if we were to use the addition of the feature as an exercise in 
being able to add arbitrary streams, I have some usecases that have been 
proposed to me where privately defined streams would be useful.

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