Re: draft-ietf-avt-rtp-vorbis confusion

De:     Luca Barbato <lu_zero@xxxxxxxxxx>

> the Identification and the Setup MUST be
> packed as they are, while the comment
> header MAY be replaced with a dummy
> one.

Yeah - but what is a "dummy" comment header? This is not defined in the I-D nor 
the Vorbis spec.

And how does this translate into the "number of headers" field, that comes at 
the beginning of the packed configuration packet? This does not seem to be 
specified anywhere. Add to that, that the xiph-rtp Vorbis example code does not 
sout of date, recipe for IOP failure.

(...)
> > A possibly more serious problem
> > concerns the 2-bytes length which is
> > prepended to "packets". The text
> > seems to imply that, in the case of a
> > fragmented packet, the field is found
> > once at the beginning of the first
> > fragment, and encodes the whole
> > (defragmented) packet length.

> Could you point me/us the exact line?

The first sections imply that each Vorbis packet is prepended with a 2 byte 
length. That would "intuitively" mean that the 2-byte length is part of the 
fragmented data (like the UDP length of a fragmented IPv4 packet).

You however indicate that EACH fragment contains a length field at its 
beginning. This is consistent with the fragmentation examples, but 
counter-intuitive and contradicts my understanding of the previous sections. In 
practice, both approaches work BUT the document ought to state how this works a 
LOT more explicitly. It cannot rely on schematics only.

-- 
Rémi Denis-Courmont
VideoLAN/VLC core developper

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