RE: Adding ULE into a network already using MPE...

["Allison, Art" <AAllison@nab.org>]

After all this is transport of ULE (which is in MPEG-2 Transport Packets)...so being MPEG-2 compliant would tend to extend the utility, and not being MPEG-2 would reduce the utility.  But whatever...

__________________
Art Allison
Director, Advanced Engineering
NAB Science & Technology
1771 N St NW, Washington DC 20036
202 429 5418 

--Original Message-----
From: owner-ipdvb@erg.abdn.ac.uk [mailto:owner-ipdvb@erg.abdn.ac.uk] 
Sent: Thursday, August 04, 2005 11:45 AM
To: ipdvb@erg.abdn.ac.uk
Subject: RE: Adding ULE into a network already using MPE...

Sure, you can decide to not use the mechanisms already existent in an MPEG Transport Stream (B, C), but in doing so you merely cause redesign or purchase of special-purpose "MPEG" processing devices.

Make it a Transport Stream.  This has very little real overhead, requiring only a PAT and PMT.  The PMT is very lightweight but yet can easily signal which elementary streams (er, "PIDs") are encoded with what protocols.

This has many advantages:  You don't need to reinvent anything (inband
signaling) -- merely an identifying descriptor; you don't have to require multiplexers and other non-IETF MPEG processing devices do anything special (that is to say, you don't require existing MPEG processing devices to also process nonstandard IETF things); IETF streams would coexist peacefully with non-IETF streams in a Transport Stream; it's very extensible to other encapsulation formats yet-to-be-defined.

Adam Goldberg
Director, Television Standards & Policy Development Sharp Laboratories of America
8605 Westwood Center Drive, Suite 206
Vienna, VA  22182
703-556-4406
703-556-4410 fax
571-276-0305 cell
 


> -----Original Message-----
> From: owner-ipdvb@erg.abdn.ac.uk [mailto:owner-ipdvb@erg.abdn.ac.uk] 
> On Behalf Of Gorry Fairhurst
> Sent: Thursday, August 04, 2005 3:56 AM
> To: ipdvb@erg.abdn.ac.uk
> Subject: Re: Adding ULE into a network already using MPE...
> 
> There ways to do this I can think of three, and I think John you are 
> asking about C?
> 
> 
> A) You could parse the SI/PSI signalling (if any) and extract the 
> information from there.
> 
> B) You could configure it (out of band) or using IP 
> configuration/resolution, etc.
> 
> C) I once worked through an "auto-detect mode", where you knew the PID 
> but didn't know the type of encapsulation.
> 
> ----
> 
> The basic rule is only one type of encapsulation is allowed for a 
> single PID. So how can you find out which is used?
> 
> I note there is a reasonably strong CRC there in the ULE framing, and 
> you can easily extract framing alignment to the TS from the PUSI 
> setting in the TS header:
> 
> (i) Supposing your receiver starts as unconfigured.
> 
> (ii) The receiver looks for a PUSI setting and extracts the PP value.
> 
> (iii) It then tries reassembly of the first section as a ULE packet. 
> If it succeeds with a valid CRC-32 and Length, it is probably safe to 
> assume this is ULE.
> 
> (iv) If the CRC fails, it tries a DSM-CC section reassembly (being 
> aware the integrity check is interpreted in more than one way in MPE). 
> The MPE start code is also another "hint" that this may not be ULE, 
> but this value
> *could*
> appear as the start of a ULE field - (Note one needs to be aware that 
> MPE and ATSC use different start values).
> 
> (v) You could (probably should!!!) verify the next few SNDUs to 
> increase your confidence, as in any alignment algorithm.  It would 
> also be wise to re-initialise the detection if you suffer an alignment 
> failure. This could be a result of a change of mutliplexing policy.
> 
> Note: This is orthogonal to the generation of SI/PSI tables used to 
> control the TS multiplexing layer itself. If you use a transport 
> stream multiplexor as a part of your L2 MPEG transmission network, 
> this may need the SI/PSI to allow the PID to reach the Receiver.
> 
> Thoughts?
> 
> Gorry
> 
> On 3/8/05 8:39 pm, "John Border" <border@hns.com> wrote:
> >
> >     I was thinking along those lines.  The sender associates the 
> > encapsulation method with a particular PID and "knows" (via AR) 
> > which PID to use to send to a particular receiver.  Receivers which 
> > only understand MPE only use MPE PIDs.  Receivers which understand 
> > ULE and MPE determine which method is being used by which PID is 
> > being received.  (I think the ULE capable receivers will still need 
> > to support MPE for multicast traffic that is shared with "older" 
> > terminals.)
> >
> >     I was wondering if there is a way for the receiver to look at 
> > the header and determine if it is ULE or MPE on the fly.  I haven't 
> > taken a close look at it yet.  But, I suspect that it is not 
> > reliably
possible...
> >
> > John
> >
> >
> > Marie-Jose Montpetit wrote:
> >
> >> I think this is one thing that could be solved by some of the 
> >> configuration work that was started where you could associate a PID 
> >> to an encapsulation. You may not want to ignore the new encapsulation.
> >>
> >> Marie-Jose
> >>
> >>
> >>
> >>> -------- Original Message --------
> >>> Subject: RE: Adding ULE into a network already using MPE...
> >>> From: "Allison, Art" <AAllison@nab.org>
> >>> Date: Wed, August 03, 2005 2:05 pm
> >>> To: <ipdvb@erg.abdn.ac.uk>
> >>>
> >>> Use of the MRD will enable a device on a MPEG-2 network that does 
> >>> not understand that MRD's signaling/meaning to ignore the new
> encapsulation.
> >>>
> >>>
> >>> Of course if the existing network just used private data with out 
> >>> signaling what it was, a problem may exist.
> >>> __________________
> >>> Art Allison
> >>> Director, Advanced Engineering
> >>> NAB Science & Technology
> >>> 1771 N St NW, Washington DC 20036
> >>> 202 429 5418
> >>> -----Original Message-----
> >>> From: owner-ipdvb@erg.abdn.ac.uk 
> >>> [mailto:owner-ipdvb@erg.abdn.ac.uk]
> >>> Sent: Wednesday, August 03, 2005 11:32 AM
> >>> To: ipdvb@erg.abdn.ac.uk
> >>> Subject: Adding ULE into a network already using MPE...
> >>>
> >>>
> >>>    Has anyone looked at the operational problems associated with
> adding
> >>> ULE use to a network which has some deployed terminals which only 
> >>> understand MPE?
> >>>
> >>>
> >>> John
> >>>
> >>>
> >>
> >>
> >>
> >
> >