RE: Question on Continuity Counter field

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

IMHO, if a MPEG-2 TS parser was presented with out of order packets identified by the same PID, a receiver failure is to be expected as the stream would be non-conformant. 

However, the continuity_counter can be the same in sequential packets (which are then required to be the same except for the PCR).  Also, this count may be discontinuous when that is indicated by the discontinuity_indicator.  So it is not always a monotonically incrementing field.  Given the rules for this 4-bit continuity_counter, it is not apparent that it is possible to use it to reorder packets at the MPEG-2 level.

Therefore, IMHO, any lower level communication protocol must not reorder MPEG-2 transport stream packets that are identified by the same PID. If it has a potential to do so, then either constraints or an explicit method for restoring the order must be defined. 

Art
::{)>
Art Allison
Director Advanced Engineering
NAB
1771 N St NW
Washington DC 20036
202 429 5418


-----Original Message-----
From: Tarif.Zein-Alabedeen@space.alcatel.fr
[mailto:Tarif.Zein-Alabedeen@space.alcatel.fr]
Sent: Friday, February 13, 2004 9:05 AM
To: ip-dvb@erg.abdn.ac.uk
Subject: Question on Continuity Counter field
Importance: Low




Hi,
I have a question about the continuity counter field in the TS packet header. May be someone in this group has the right answer : what heppens if an MPEG receiver receives an out of order TS packet? that is, for the same PID, the CC field value of a received packet not equal to CC field value of precedent TS packet + 1

Is there one standard behavior or is it implmenetation dependent? can CC check as the receiver be disabled?

(oups, this makes 3 questions already)

thank's and best regards


T. Zein
ALCATEL SPACE
DRT/RST