[M4IF Technotes] H.26L video coding

[Rob Koenen]

Kris,
> The ARTS and ACE profiles you mention are already defined, 
> and it is unprecedented for profiles to change their tool set 
> after definition.  We have one small exception so far, in the 
> exclusion of the interlace tool in one of the profiles (FGS, 
> I think), at a level where the nominal vop rate is only 15 
> fps.  

This is not true. The tool set of FGS Profile was *NOT* changed after 
its definition. It was dfined this way right from the start. 
The exception here is that interlace is excluded at a lower level, 
while usually tools are not deteremined by levels but only by 
profiles - as you accurately write below.
> But this exception is very sensible and deliberately 
> made for complexity reasons because interlace in the the 
> source material is so easily avoidable at low frame rates.  
> Normally any new tools only become part of new profiles 
> rather than being added as new levels to existing profiles.  
> Otherwise confusion is created about the tool set associated 
> with a profile, and the definition of profile as "tool set" 
> is violated.
> 
> Regards,
> Kris

Rob