- From: Martin J. Dürst <duerst@it.aoyama.ac.jp>
- Date: Wed, 01 Jul 2009 18:18:34 +0900
- To: Yves Lafon <ylafon@w3.org>
- CC: www-tag@w3.org, public-media-fragment@w3.org
Just some random comments: - Whether transcoding is needed or not will depend on whether the server has prestored a certain piece of the big picture or not. Looks like it's purely server-internal. - Content-Range seems to be hard-coded to "bytes", no other unit is usable. (see RFC 2616, 14.16). - For a jpeg image, because of the lossiness of the coding and the numeric inaccuracy of the transforms used, it may not be possible to reconstruct the bit-by-bit exact equivalent image from covering parts. Regards, Martin. On 2009/06/30 23:26, Yves Lafon wrote: > All, > The Media Fragment WG is working on... defining how to identify and > server media fragments, the primary use case is of course video, but it > is not limited to it [1]. There is a aso a clear relation to the TAG WD > "Usage Patterns For Client-Side URI parameters" [2], as hash parameters > are used to generate range requests to send back to the clients only the > desired sub-part of the resource representation. > > There are different axis defined, the most obvious and easy to handle is > the time axis for video and audio, as in most cases the sub-part > extraction can be done in the compressed domain. > > The geometrical axis (like asking for a clipped version of a picture or > a video) is the origin of this email, as the WG did not reach a > conclusion on "Is it legal to do transcoding when serving a fragment". > > ie: the World Map is defined by http://www.example.com/earthmap.jpg and > is a 10000x10000 picture. > Small country M is defined by the following URI: > http://www.example.com/earthmap.jpg#xywh=pixel:5160,5120,32,24 > > Suppose that we have a way to construct a ranged request out of that, > serving only that 32x34 jpg file requires transcoding, while being > served as a partial response. > > Input needed :) > Thanks, > > [1] http://www.w3.org/TR/2009/WD-media-frags-reqs-20090430/ > [2] http://www.w3.org/TR/2009/WD-hash-in-uri-20090415/ > -- #-# Martin J. Dürst, Professor, Aoyama Gakuin University #-# http://www.sw.it.aoyama.ac.jp mailto:duerst@it.aoyama.ac.jp
Received on Wednesday, 1 July 2009 09:19:46 UTC