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Re: MPE Question
Siva Veerepalli wrote:
A couple of questions about MPE-FEC framing.
1. The interim IP datacast standard A079 (meant to
facilitate DVB-H trials) specifies that only one
datagram should be used per MPE section i.e., no
fragmentation of IP datagram over multiple MPE
sections. However, the DVB Databroadcast specification
allows fragmentation of the IP datagram over multiple
sections. Does anyone know what the usual practice is?
In order to reduce encapsulation overhead, section packing is used, i.e.
if the (remainder of an) IP packet does not fit exactly in a TS packet a
subsequent IP packet may start in that TS packet as well.
In order to reduce jitter and latency, section packing is not used.
You can find both on existing services.
Do the final DVB/IP datacast standards specify this
for DVB-H?
The difficulty with section peckaing on the transmit side is that the
encapsulator needs to wait for subsequent IP packets to fill an
partially filled TS packet and therefor has typically a time-out
associated to that waiting, ie before flushing the buffer and
transmitting the final TS packet.
2. The MPE section has optional stuffing bytes at the
end of the section. Are these used? If yes, for what?
Whenver an IP packets leaves "enough" space in the last TS packet
another IP packet could be inserted. If not wanted or needed, stuffing
takes care that the empty space is filled up with pattern 0xFF.
thanks,
Siva
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