RE: How does MPE handle the last byte?

[<juha-pekka.luoma@nokia.com>]

Hi Gorry et al.,

Just a comment that including a pointer in a TS packet that did not contain at least the first byte of a new section would seem to be against the MPEG-2 spec. Quoting 2.4.4.1 of ISO 13818-1,

"When no section begins in a given Transport Stream packet, then the payload_unit_start_indicator shall be set to 0 and no pointer shall be sent in the payload of that packet."

Best regards,

Juha-Pekka Luoma
Nokia Research Center

-----Original Message-----
From: ext Dr G Fairhurst [mailto:gorry@erg.abdn.ac.uk]
Sent: 21 August, 2003 14:44
To: ip-dvb@erg.abdn.ac.uk
Subject: How does MPE handle the last byte?



Before we suggest a strategy for the new encapsulation formats, 
can someone tell me what happens in real implementations when MPE 
employs section packing (i.e. is allowed to start a new encapsulated
MPE packet following the rpeviosu in the same MPEG-2 TS Packet).

Problem case:

When TS Packet payload is nearly full... i.e. when
a SNDI (IP packet, etc) occupies all but the last byte of
the final MPEG-2 TS-Packet Payload, and there is another 
IP packet waiting to be sent.

What does the encapsulator do if this TS-Packet has no PUSI
set, since setting the PUSI flag implies that encapsulator
would also include a Payload start pointer in the first
position after the TS-Packet header. This pointer consumes
the last byte... leaving nothing for it to point at.

A picture:

+----------------------\\------------------+--+
|........................ \\ SNDU..........|XX|
+--------------------------\\--------------+--+

^
|
NO PUSI - and Hence no payload pointer here.


Gorry