Network Technologies DVB-ASI to IP - Manual (Page 63)

ASI-IP-GTW User's Manual
Page 63
5 Equipment Description
5.1 Introduction
This chapter provides an overview of transmission of MPEG-2 data over
IP networks and a high-level functional description of the ASI-IP-GTW.
5.2 Functional Description
5.2.1 Introduction
The ASI-IP-GTW consists of a main module and 1 or 2 ASI boards each
handling up to 4 ASI ports. Optical Gigabit is provided as a hardware
option.
The ASI-IP-GTW can be configured by the operator to be IP transmitter
or an IP receiver. A SW option is also available to enable bi-directional
operation of the IP data interface. In the IP transmitter mode, the ASI-
IP-GTW encapsulates MEG-2 transport streams received on the ASI
ports into IP streams. These streams are sent on an Ethernet interface
onto the IP network.
In IP receive mode, the ASI-IP-GTW receives and de-capsulates up to 8
transport streams from the IP network and outputs the MPEG-2
transport streams on the DVB ASI ports.
In bi-directional mode, half the ports are used as ASI outputs, while the
other half operate as ASI inputs.
5.2.2 IP Transmit Mode
In the IP transmit mode, the MPEG-2 transport streams are sourced
from the ASI ports on the ASI boards.
The ASI-IP-GTW is able to handle source transport streams on ASI on
the following formats:
o
Packet format of 188 bytes
o
Packet format of 204 bytes, including padding
o
Packet format of 204 bytes, including RS bytes (no RS checking
performed)
The sourced transport stream is then processed by the Main board. The
ASI-IP-GTW will always send 188 bytes packets over the IP network.
The MPEG-2 transport stream packets are encapsulated as described
in section 5.3.1. The user configures the IP address of the Ethernet
data port. For each transport stream to be sent over the IP network, the
IP destination address and UDP port are configured. The ASI-IP-GTW
handles both unicast and multicast transmissions.
The IP packets from one ASI input port are then merged with the IP
packets from the other ASI inputs. The combined IP stream is then
passed onto the physical Ethernet connector.