Comtech EF Data CMR-5970 Manual - Manual (Page 73)

Digicast Media Router S2 Receiver CMR-5970 (MR-S2) & CRM-5990 (MR-S2-ASI) Revision A
IP Routing Support MN/MRS2ASIDC.IOM
Note that the upper 5 bits of the multicast IP address are ignored in the MAC so that 32
Multicast group IP addresses map to a single MAC address. This implies further filtering
is required at the end device.
Figure B-1. Multicast Mapping (IP to MAC)
B.3 Section Packing
Section packing is a technique utilized to provide more optimal utilization of the
MPEG-2 transport stream (TS) packet structure. When section packing is not used, each
TS packet (containing the MPE section) can carry no more than a single section. This
often results in wasted payload capacity when the sections are less than 184 bytes.
The section packing feature
allows more than a single MPE
section to be carried by an
MPEG-2 TS packet, thereby
minimizing wasted payload
capacity.
In the case of a large MPE
section that spans multiple
MPEG-2 packets, the ending of
an MPE section may occur in the
middle of an MPEG-2 packet.
In this instance, with section
packing, a new MPE section
begins immediately after the first
MPE section has finished
without any ‘fill’ (wasted) bytes
having to be inserted before the
start of the next MPEG-2 packet.
Figure B-2. Section Packing
B–3