[Xerte-dev] Video playback quality in html5 LOs.

[David Goodwin]

Hi,

We've been asked to improve the quality/behaviour of video playback 
within html5 LOs.


I assume :

We shouldn't think about including a flash fallback player (given 
they're using a html5 template).



Therefore :

We should make sure there's a webm and mp4 format video available for 
the video playback.

and

We should re-encode the mp4 video to h264 basic profile to ensure it 
plays on mobile devices.




Does the data.xml/preview.xml file have an XSD to validate against - and 
specify which attributes/tags are legal?


Possible solutions are :



1. We could embed additional stuff in the xml files -

<?xml version="1.0"?>
<learningObject language="en-GB" name="Learning Object Title" 
navigation="Linear" textSize="12" displayMode="default">
.....
   <textVideo linkID="PG1400145368211" name="video test" align="Left" 
url="path/to/file" tip="Enter a Tooltipx" reset="true"
url_webm="path/to/file.webm" url_ogg="path/to/ogg"

transcriptTabTxt="Transcript" transcriptTabTip="Transcript" 
transcriptTabWidth="90"><![CDATA[asdasdasd asdasd asda sdas vide ov ideo 
video]]></textVideo>

....

(note the url_webm, url_ogg attributes).


Cons - presumably would get lost on re-edit - we'd need to have a 
post-save filter in XOT to add it into the xml files all the time.


Cons - attributes may not be legal/allowable.

Pros - we could add those attributes in, only if the underlying file 
exists - i.e. it's been transcoded in the background.




2. We could alter the html5 playback JavaScript to cause it to check for 
the existence of whatever the textVideo url attribute is pointing to 
plus a set of extensions which would be used to indicate that the file 
has been transcoded.

e.g. <textVideo url="foo" ... />

JS would check for :

foo.webm
foo.mp4
foo.ogg

And if it finds any of them, it'll use them. (http head request - to 
check for existence).

Pros : no need to touch data.xml/preview.xml, url attribute always 
points to what the user uploaded.

Pros : a simple cron job (perhaps) could rummage through USER-FILES 
looking for video files which haven't been transcoded. If the cron job 
is never run then the original file will always be used, if the cron job 
has run then hopefully there are some better files to use.


Cons : "magical"



Any other ideas/thoughts?

I don't suppose it's really feasible to just tell the template author 
they should upload the correct encoding - when they're unlikely to be 
aware of the nuances of video encoding, or the tools available for it?



thanks,

David.

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