- From: Victor Carbune <victor.carbune@gmail.com>
- Date: Fri, 2 Mar 2012 17:46:28 +0200
- To: public-texttracks@w3.org
- Cc: Glenn Maynard <glenn@zewt.org>
Hello, On Fri, Mar 2, 2012 at 5:35 PM, Glenn Maynard <glenn@zewt.org> wrote: > If you try to represent an instantaneous metadata event with eg. "00:0.050 > --> 00:0.051", the metadata cue (and more importantly, its enter and > cuechange events) may never be fired, since the current playback position > may never lie within the cue. Worse, that particular cue would probably > work reliably for a 25 FPS video (a frame begins at 50ms), but break if the > video track is replaced with a 30 FPS one (a frame begins at 33ms). That > means changing the framerate of a video could affect scripts. > > It would be ideal if cues were always entered and exited, even if the > current playback position skips over the metadata's time range. (During > normal playback, that is, not if the user seeked past it, or if the UA had > to discard cues for performance reasons.) This situation is currently specified in the spec through the concept of "missed cues", so enter & exit events are dispatched as soon as such a cue is detected through normal playback (even if the playback position never lied within the exact range of the cue). This is mentioned in section 4.8.10.8 Playing the media resource [1]: specifically in the rules starting with "When the current playback position of a media element changes (e.g. due to playback or seeking) [...]": [1] http://dev.w3.org/html5/spec/video.html#playing-the-media-resource Regards, Victor
Received on Friday, 2 March 2012 15:47:24 UTC