User:Vitrinekast/Checking out the media fragments URI

From XPUB & Lens-Based wiki

Example of a media fragment URI URL: http://www.example.org/video.ogv?t=60,100#t=20

Text below is from the Media Fragments URI 1.0 (basic)

The names and values can be arbitrary Unicode strings, encoded in UTF-8 and percent-encoded as per RFC 3986. Here are some examples of URIs with name-value pairs in the fragment component, to demonstrate the general structure: 

* http://www.example.com/example.ogv#t=10,20
* http://www.example.com/example.ogv#track=audio&t=10,20
* http://www.example.com/example.ogv#id=Cap%C3%ADtulo%202

Media fragment URI can be used on video, images, and audio(?) → altough mentioned in the spec as video only(?) but what is a video anyway...

Used on image

Following URL should show a cropped image, but it does not appear to work onchrome. 

http://placekitten.com/500#xywh=percent:5,25,50,50

https://caniuse.com mentions that all browsers that have implemented something of this spec, have actually only implemented support for the #t=n,n control for selecting a range of video, and possibly track=(name) & id=(name).

Used in Audio!

I've uploaded some files to chopchop to test with

The following URL should only play the video from 00:01 to 00:02! 

https://hub.xpub.nl/chopchop/~vitrinekast/videos/small.ogv#t=1,2

And... For mp3 it seems to work as wel!! 

https://hub.xpub.nl/chopchop/~vitrinekast/videos/small.mp3#t=1,2


However, it does seem to fully load the file, when inspecting the request, which does not save any data being downloaded. However 2: when throttling the request to slow3g, only 277 bytes are being downloaded according to the network tab. Something to investigate further.

  • Check with charles to see if the amount of bytes are actually correct, as a reduced amount of bytes downloaded could be a positive result of using this to interact with an archive
  • However, in terms of radio, m3u8 files are already broadcasted in "blobs" → so maybe this is more relevant to look into


Further checking and reading the spec

A glossary from the spec

Media fragments support addressing the media along two dimensions (in the basic version):

temporal This dimension denotes a specific time range in the original media, such as "starting at second 10, continuing until second 20";

spatial this dimension denotes a specific range of pixels in the original media, such as "a rectangle with size (100,100) with its top-left at coordinate (10,10)";

Media fragments support also addressing the media along two additional dimensions (in the advanced version defined in [Media Fragments 1.0 URI (advanced)](https://www.w3.org/TR/media-frags/#mf-advanced)):

track this dimension denotes one or more tracks in the original media, such as "the english audio and the video track";

id this dimension denotes a named temporal fragment within the original media, such as "chapter 2", and can be seen as a convenient way of specifying a temporal fragment.

  • Spatial Dimension does not seem to work in chrome → clipping the video frame
  • I'm not entirely sure yet what id/track should do, and also how to set this metadata, if it is even metadata?


next steps

  • Furher understand the Media fragment URI and what the current state of the spec is
  • Read about [OggKate - XiphWiki](https://wiki.xiph.org/OggKate) an open source codec which could be used for Karaoke, but essentially allows for attaching time based metadata (see example below)
 event {
   00:18:30,000 --> 00:22:50,000
   meta "GEO_LOCATION" = "35.42; 139.42"
   meta "DATE" = "2011-08-12"
 }
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