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

[Paul Kyzivat <[e-mail]>]

On 12/17/20 3:54 PM, Christer Holmberg wrote:
> Hi,
> 
>      >> Q2:
>      >>
>      >> In Section 3, you require a specific order of the m- lines in the SDP. I think SDP explicitly says that the order of m- lines is not relevant. Also, I know that parsers may change the orders of the m- lines.
>      >>
>      >> (I also think that any counting should start from 1, not 0)
>      >>
>      >> My suggestion would be to have an explicit "order" attribute instead.
>      >
>      > I think it would be acceptable to use the order of the tokens in the
>      > a:group line to define the ordering of the "layers". The "lowest" layer
>      > would then be the background on which the others are overlain. (Whether
>      > the lowest layer is the first or last in the list is TBD.)
> 
>      Why not use the content attribute, and use content:main for the background?

Since the draft supports multiple layers of superposition, I don't see 
why there is need to have a special way to identify the "background" 
layer. ISTM that the lowest layer is by definition the background.

>      That might also be useful for a peer that does not support this draft, but  does support the content attribute.

IIUC there isn't any *general" support for the Content attribute. Rather 
there must be support for each specific value. Since this would be a new 
Content value, there won't be any existing implementations that support it.

It would be nice to find a way so that peers that don't support this 
extention end up only rendering the base layer while ignoring the 
superposition layers. But I don't have any idea how to achieve that.

	Thanks,
	Paul