MediaTrackConstraint structure (Re: Revised getUserMedia editor's draft available)

On 06/09/2012 03:05 AM, SUN Yang wrote:
> Hi Dan and all
>
> My question is : using MediaTrackConstrainst instead of option is for 
> what purpose?
> To my opinion, it seems make the constraint complex and more difficult 
> for understanding compared with previous edition.
>
> What's more,
> why
>
> dictionaryMediaTrackConstraints  {
>      dictionary MediaTrackConstraintSet?  mandatory  <http://dev.w3.org/2011/webrtc/editor/getusermedia.html#widl-MediaTrackConstraints-mandatory>;
>      sequence<MediaTrackConstraint>?      optional  <http://dev.w3.org/2011/webrtc/editor/getusermedia.html#widl-MediaTrackConstraints-optional>;
> };
> in MediaTrackConstraints object, the 2 parameters have different type, 
> can you telll me the real difference for these 2 parameters?I can not 
> get the meaning from the existing text?
>
This is a Media Capture TF item at the moment....

The algorithm requires that optional constraints be a sequence, so that 
the most important constraints come first.

There's no such requirement for mandatory constraints.