Thumbnails in DASH

[maral]

Dear all,

I would like to notice the lack of an important functionality for ffmpeg DASH, which is adding tiled thumbnails to the current manifest.

Those can be generated attaching an adaptation set in the manifest according: DASH-IF IOP version 4.2, section 6.2.6 defines the notion of image-based tracks in DASH: ​https://dashif.org/docs/DASH-IF-IOP-v4.3.pdf.

So would it be possible to implement the option for dash to generate thumbnails at same time that DASH content is generated, and to attach them in the manifest? For dynamic and static manifests.

Tiled thumbnails can be generated with the following command:

ffmpeg -i INPUT -q:v 20 -vf "select=not(mod(n\,<<framerate>>)),scale=480:270,tile=<<tileduration>>x1" -vsync vfr output%d.jpg

An then an adaptation set could be added according to:

<AdaptationSet contentType="image" id="4" mimeType="image/jpeg">

<BaseURL><<httpURL>></BaseURL>
<SegmentTemplate duration="<<tileduration>>" media="output$Number$.jpg" startNumber="1" />
<Representation bandwidth="12895" height="270" id="thumbnails_256x144" width="43200">

<EssentialProperty schemeIdUri="​http://dashif.org/guidelines/thumbnail_tile" value="<<tileduration>>x1" />

</Representation>

</AdaptationSet>