[M4IF Technotes] H.26L video coding

[Kris Huber]

Hello Rob,
I didn't mean to imply that the tool set changed *after* FGS profile
definition.  By "exception" I meant exception only to the general rule that
if you know the name of the profile a decoder implementation conforms to,
then you know all of its tools.  As you well know, the special case for a
lower level of FGS profile was discussed during definition the FGS profile
at the Noordwijkerhout, NL meeting, which I was also fortunate enough to
attend.
Best regards,
Kris
-----Original Message-----
From: Rob Koenen [mailto:rkoenen   intertrust.com]
Sent: Tuesday, September 25, 2023 10:34 AM
To: 'Kris Huber'; 'Biswajit Biswas'
Cc: technotes   lists.m4if.org
Subject: RE: [M4IF Technotes] H.26L video coding
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