Re: [MMUSIC] New Version Notification for draft-abhishek-mmusic-superimposition-grouping-00.txt(Internet mail)

[Christer Holmberg <[e-mail]>]

Hi,

...

>>> *Rohit: The ordering mechanism will be needed. Suppose we have a 
>>> background X with transparency=100, and a superimposed media A with 
>>> transparency=50. A over X would mean that X would visible partially 
>>> through A, however X over A would mean that A wouldn't show through 
>>> X.*
>> 
>> If the ordering is needed, then you need to specify how it is 
>> determined. IMO it is permissible to use the order of values in the
>> a=group: line to specify this ordering. (RFC5888 doesn't ascribe any 
>> semantics to this ordering of values, but neither does it forbid 
>> assigning meaning for particular grouping semantics.) I am not certain 
>> if Christer agrees with me on this point. The alternative is to use a 
>> new attribute in the grouped media descriptions for this purpose.)
>
> Perhaps a clean way to do this would be to replace the "transparency" 
> attribute with one that specifies both the transparency and the order. E.g.,
>
>    a=superposition:transparency=80,layer=3

And let's make that the ABNF allows new values, to avoid some of the pain if additional value(s) would be needed at some point :)

Regards,

Christer