thumbnail_tile URI is different from DASH-IF guidelines

Created by: dimitry-unified-streaming

I noticed that the schemeIdUri used for thumbnail tiles in ThumbnailTracks.js is http://dashif.org/thumbnail_tile.

However, in the DASH-IF Interoperability Guidelines, in section 6.2.6. Tiles of thumbnail images, it suggests http://dashif.org/guidelines/thumbnail_tile instead, e.g. with an additional guidelines/ subdirectory.

Maybe this should be changed in dash.js, but since the first URI has been used for a while now, and has possibly been picked up by other players (which might have been derived from dash.js), it might not be worth it. In that case, somebody should flag this with dashif.org, so they can either update the guidelines, issue an erratum, or fix it in the next version of the guidelines.