Re: [AVT] new draft on MPEG-TS preamble acquisition

["Ali C. Begen (abegen)" <abegen at cisco.com>]

> > > > - First of all, is this an RTP payload format draft or not? The draft
> > > > seems
> > > > to be defining that, yet, title does not say so, and the draft does
> > > > not
> > > > have
> > > > the sections needed for defining a new payload format. See the
> > > > guidelines
> > > > document.
> > > > Frank=>This draft did not define a new payload format.
> > > > This is negotiatable if RFC4588 can't be used directly.
> > > > Some further  related response see below.
> > >
> > > You are carrying something in RTP, so one way or another, you are
> > > defining
> > > a
> > > new payload format. As I mentioned earlier, usage of 4588 does not seem
> > > to
> > > be correct here.
> > > Frank=>Good point. However, I  still believe it is make sense  to reuse
> > > 4588.
> > > draft-ietf-avt-rapid-acquisition-for-rtp uses 4588 for unicast RTP burst
> > > which are not RETRANSMISSION packets as to the RR.
> >
> > I believe you are confused here. Burst packets are "retransmission"
> > packets - totally in accordance with RFC 4588. They are retransmissions of
> > earlier RTP packets sent in the primary multicast stream. And the receiver
> > considers them as retransmission packets.
> > Frank=>They are not retransmission packets.
> > In rapid acquistion (e.g fast channel change),
> > these packets are never sent to the RR before.
> 
> From RR's viewpoint, this does not matter (whether the packets were sent but
> they were lost or they were never sent - receiver cannot know the
> difference). The important thing here, the burst packets are the exact
> replicas of the original RTP packets encapsulated in 4588 format. But, the
> way you describe sending the raw TS packets does modify the source packets,
> which means 4588 should not be used.Hi
> Frank=>Copies of the original RTP packets are  not retransmission packets.

Ret packet payload = OSN field + original packet payload.

That is what I meant by "4588 format." That is what RAMS does.

> I just want to say  that "rapid acquistion" document also stretches a little
> bit
> of  4588.
> Using raw TS packets or whole RTF packet is not the point of our debate.
> We prototyped both.  If you feel more comfortable with the latter, we can
> do some minor change with the document.

It is not a matter of being comfortable or not. 4588 can be used only if original packet payload is not modified (which is OK but pretty inefficient way of priming the decoders). 

Please show us how you select the TS packets and put them in RTP packets in your AVT presentation. That way, it will be easier to discuss.

-acbegen