ASI-IP-GTW User's Manual
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:
oPacket format of 188 bytes
oPacket format of 204 bytes, including padding
oPacket 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.
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