- From: Philip Jägenstedt <philipj@opera.com>
- Date: Tue, 10 Jun 2008 18:31:05 +0200
Hi! http://www.w3.org/html/wg/html5/#pixelratio The pixelratio attribute allows the author to specify the pixel ratio of anamorphic media resources that do not self-describe their pixel ratio. [...] The default value, if the attribute is omitted or cannot be parsed, is 1.0. This seems more than strange. Should this be taken to mean that the pixelratio attribute is defaulted to 1.0 even for ?media resources that DO NOT self-describe their pixel ratio? To be clear what we are talking about, here are some example pixel ratios: PAL (720x576) 4:3 DVD ?has pixel ratio 16:15 (=1.067) ?PAL (720x576) anamorphic 16:9 DVD has pixel ratio 64:45 (=1.422) ?NTSC (720x480) 4:3 DVD ?has pixel ratio 40:45 (=0.889) NTSC (720x480) anamorphic 16:9 DVD has pixel ratio 32:27 (=1.185) To display such video correctly, the pixel aspect ratio must be correct. Since many formats can specify pixel ratio (including Ogg Theora) this is trivial to do automatically, but it would be a spec violation. In my opinion, it would make a lot more sense to let the pixel ratio default to the media resources self-described pixel ratio, and 1.0 only as the last resort. Suggested change to http://www.w3.org/html/wg/html5/#pixelratio : The default value, if the attribute is omitted or cannot be parsed, is ?the media resource's self-described pixel ratio, or 1.0 ?for ?media resources that do not self-describe their pixel ratio. Suggested changes to http://www.w3.org/html/wg/html5/#pick-a 5. If candidate is not null and it has a pixelratio attribute, then let the chosen resource's pixel ratio be result of applying the rules for parsing floating point number values to the value of that attribute, or 1.0 if those rules return an error. Otherwise, let the chosen resource's pixel ratio be the media resource's self-described pixel ratio, or 1.0 ?for ?media resources that do not self-describe their pixel ratio. Just to be clear, the intended priority is: 1. pixelratio attribute 2. self-described pixel ratio 3. 1.0 Perhaps these changes are too verbose, they could be made shorter if the meaning is still clear. Comments? It is also worth noting that when the pixel ratio is < 1.0 it will make more sense for the user agent to adjust the height than the width if no width/height attributes have been set. This could be pointed out in the rendering section eventually. -- Philip J?genstedt Opera Software
Received on Tuesday, 10 June 2008 09:31:05 UTC