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

[Gorry Fairhurst <gorry@erg.abdn.ac.uk>]

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
>>>    
>>> 
>> 
>>  
>> 
> 
>