Re: [Cellar] AD Review: draft-ietf-cellar-ffv1

[Michael Niedermayer <[e-mail]>]

Hi

On Thu, Jan 09, 2020 at 11:02:31AM -0500, Dave Rice wrote:
> Hi Adam,
> Thanks for your review. I have addressed some of these in a pull request at https://github.com/FFmpeg/FFV1/pull/185 and left questions or nudges to other authors below.
> 
> > On Jan 2, 2020, at 6:26 PM, Adam Roach <[e-mail]> wrote:
[...]
> > ---------------------------------------------------------------------------
> > 
> > §2.2.2:
> > 
> > >  "a >> b" means arithmetic right shift of two's complement integer
> > >  representation of a by b binary digits.
> > 
> > This needs to indicate whether the resulting value is sign-extended
> > or zero-padded. We can't rely on C's definition here, as right
> > shifting a signed value is implementation-defined by the standard:
> > 
> >     The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an
> >     unsigned type or if E1 has a signed type and a nonnegative value, the
> >     value of the result is the integral part of the quotient of E1 / 2E2. If
> >     E1 has a signed type and a negative value, the resulting value is
> >     implementation-defined.
> > 
> > Because this introduces an ambiguity into the specification, it will need
> > to be corrected before entering IETF last call.
> 
> I’m uncertain, nudging the other authors.

The implementation definedness can be avoided by simply refering to an implementation
and not just "C90" or other. not sure "twos complement" is strictly enough but it
may be the cleanest way to specify it.


> 
> > ---------------------------------------------------------------------------
> > 
> > §2.2.5:
> > 
> > >  a~b,c.  the 'b,c'-th value of a sequence of a
> > 
> > Please explain this with more words. I can't figure out what it means.
> 
> Same. I’m uncertain, nudging the other authors.

maybe this notation can be avoidded and array indexes [] used, iam not sure
this would work better in all cases though

Thanks

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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