MA5400 IP Video Gateway. Introduction. Summary of Features

Transcription

1 MA5400 IP Video Gateway Introduction The MA5400 IP Video Gateway bridges the gap between the MPEG-2 and IP domains providing an innovative solution to the need to transport real-time broadcast quality video over IP networks. The units design provides encapsulation or de-encapsulation and streaming of up to 8 individual DVB-ASI MPEG-2 Transport Streams. A single MA5400 can operate as either a transmitter or receiver, and can be switched dynamically from the units web interface providing flexible distribution architecture. With the use of IP networks for transmission of broadcast quiality content in real-time protection is required against packet loss, the MA5400 supports the Pro-MPEG CoP r3 FEC standard to provide for reliable transmission over the IP network. When operating in transmit mode each MPEG-2 TS presented on the individual ASI ports is encapsulated as an IP Real-Time-Protocol (RTP) stream. The multiple RTP streams are combined onto a single electrical or optical Gigabit Ethernet interface for transmission over an IP network, After transmission accross the network, an MA5400 in recieve mode de-encapsulates the RTP streams from a single or combination of sources presenting back the original DVB-ASI MPEG-2 transport streams on the ASI ports for connection to downstream equipment. Each of the ASI ports can encapsulate either a Single Program Transport Stream (SPTS) or Multi Program Transport Stream (MPTS) carrying a combination of Standard Definition (SD) or High Definition (HD) video streams. The MA5400 is agnostic to the compression technology used allowing either MPEG-2 or MPEG- 4 AVC encoding. The MA5400 provides leading edge technology, including Pro-MPEG CoP r3 Forward Error Correction and q VLAN tagging per a ASI port basis allowing each transmission to be tailored to specific requirments. Summary of Features Transport of MPEG-2 TS over IP network 100/1000 Electrical Ethernet Connection Optical Interface (SFP socket) Up to 8 DVB ASI ports per a unit User configurable as transmitter or reciever Carriage of MPTS or SPTS per an ASI port Pro-MPEG CoP Rev3 Forward Error Correction 802.1Q VLAN Tagging Type of Service (TOS) setting per ASI port User-friendly configuration and control WEB based control (IE, Mozila, Firefox) Redundancy management by ncompass Control IP flow statistics via SNMP for monitoring MA5400 IP Video Gatway page 1

2 The MA5400 IP Video Gateway consists of a main board which provides a 10/100 control and 10/100/1000 BaseT data electrical ethernet interfaces and a combined RS232/Alarm relay 9 port. In addition to the main board a single ASI card provides 4 ASI ports, leaving space for fitting of upto two option cards, one ASI option card providing 4 additional ASI ports and one Optical SFP card providng optical network connectivity all within a single half width 1RU unit. The MA5400 is a half width 1RU high unit and comes in two mounting configurations. The MA5400/SOLOBAS is a single unit with a full width front panel and the MA5400/ DUOBAS which is two units mounted side-by-side with a single 1RU front pannel. A MA5400/SOLOBAS can not be upgraded in the field to an MA5400/DUOBAS and vice versa. The MA5400/SOLOBAS provides upto 8 ASI ports while the MA5400/BASDUO provides 16 ASI ports and allows a transmit and recieve configuration within 1RU of rack space. The MA5400/BASDUO requires two power connections as each half width unit requires has it s own power supply. All input and output connectors are presented on the rear panel of the MA5400 and the unit has no front panel keypad or display. Management and control is provided by means of a easy to use web interface allowing control directly from any standard web browser. In addition the unit can be configured through ncompass control providing redundancy management. The MA5400 is a uni-directional unit providing either transmit or recieve functionality. The mode of opertaion is user configurable through the web interface between transmit or recieve mode. When operating in transmit mode the ASI ports are input ports and the data port is an output (transmit) port onto the network and when in recive mode the ASI ports are output ports and the data interface is an input (recieve) port. The polarisation of the ASI ports and the Ethernet Data port is dependent on the mode of operation. The MA5400 has a single Ethernet 100/1000 BaseT electrical data port for high-speed transmission or reception of broadcast quality video streams. The data port can either be set to auto-sensing or to a specific speed to minimise router synchronisation. In addition to the Date port, a 10/100 BaseT electrical control port is provided giving a separate port for out of band control. The Data port can be used for in-band controll, meaning only a single connection is required per a unit on the network. A separate 9-pin connector is also provided for a single alarm relay and as a engineering interface. This MA5400 Rear Panel port can be used to set the IP address of the control and data port. If an optical connection to the network is required then an SPF option card can be fitted providing an Optical Data port. The MA5400 has a single power supply capable of auto sensing between 110V or 240V AC and if required, can be supplied with a 48Vdc power supply. Hardware and Software Options The MA5400 is highly configurable to suite the exact needs of the broadcaster and contains both hardware and software options. These options are described in the following section. 4 additional ASI ports (MA5400/HWO/4ASI) As a factory option, the unit can be fitted with an additional ASI module, providing 4 additional ASI ports, giving a total of 8 ASI ports. SFP Module (MA5400/HWO/GIGE/OPT) As a factory option, the MA5400 can be equipped with an SFP connector for connection to optical networks. The SFP module itself is not provided. Functional Description The MA5400 IP Video Gateway consists of a main module and 1 or 2 ASI boards each with 4 ASI ports capable of operating in IP transmit or IP receiver mode. If two ASI modules are fitted then both must operate in the same mode. In transmitter mode, the MA5400 encapsulates each MPEG-2 transport stream received on each ASI port into IP Real-Time-Protocol RTP streams. All the IP streams are streamed on the Data Ethernet interface onto the IP network. In receive mode, the MA5400 can receives up to 8 RTP IP stream from one or more sources, de-encapsulate the MPEG-2 packets and stream a maximum of 8 simultanoues MPEG-2 transport streams, one per ASI port. Transmit Mode In transmit mode, the MPEG-2 transport streams for encapsulation are presented to ASI ports. The MA5400 can accept the following MPEG-2 transport stream ASI formats: Packet format of 188 bytes Packet format of 204 bytes, including padding Packet format of 204 bytes, including RS bytes (no RS checking performed) For efficient transmission over the IP network the MA5400 will only encapsulate the 188 bytes packet the additional 16 bytes will be removed. For transmission MA5400 IP Video Gateway page 2

3 IP Transmit WEB Page IP Recieve WEB Page over the network each transport stream is assigned a seperate destination IP address and port number. The IP address can either be a unicast address or a multicast address. The IP streams associated with each ASI port are streamed over a single electrical or optical connection onto the transmission network. Receive Mode In receive mode, the MA5400 receives IP packet streams from the data Ethernet interface. If the transmission is unicast the MA5400 will check for a matching UDP port, if a matching port is found then the IP stream will be de-encapsulated and streamed on that ASI port. For a multicast transmission the recieve MA5400 must be configured to join the multicast address. A multicast address can be defined per an ASI port, on defining a multicast address an IGMP join message is sent over the data interface requesting a join, on joining the multicast the recieved IP packets are de-encapsulated and streamed out on the associated ASI port. When reception is disabled, the MA5400 will send an IGMP leave message to the network. For each ASI port the reassembled MPEG-2 transport stream packets are held in a buffer to allow removal/ reduction of network introduced jitter and support adaptive rate recovery. The buffer is assigned per an ASI port and is configurable from 500Kbytes up to 8Mbytes. After clock recovery, the MPEG-2 transport stream is stream out on the ASI port as 188 byte packet. Management The MA5400 IP Video Gateway provides two options for control, either through a dedicated management port or by in-band control on the data port. Both ports give access to the same control and management information. The dedicated management port has its own IP address allowing increased network security by separation of control and video traffic. Both interfaces provide the following features: WEB interface for remote control SNMP for alarm and status monitoring Protocol Mapping for Video over IP The core function of the MA5400 is the IP encapsulation and de-encapsulate of MPEG-2 transport stream packets and the streaming of these packets over an IP network. An IPv4 packet allows for a payload of 1500 bytes and given that MPEG-2 packets are 188 bytes long, up to 7 transport stream (TS) packets can be encapsulated into a single IP packet. Packing the maximum of 7 TS packets per an IP packet gives optimum packing efficiency at the cost of lossing 7 TS packets per a lost IP packet. Packing only one MPEG-2 TS packet into one IP packet minimises MPEG-2 packet loss on IP packet loss, but at a cost of increased transmission overheads, which in turn place greater demand on the transmision network. The MA5400 supports both Multi-Program Transport Streams (MPTS) and Single-Program Transport Streams (SPTS). The unit will encapsulate and de-capsulate complete transport streams without changing the streams. This means that no insertion or removal of NULL packets are performed and the PCR is sent transparently through the unit. The MA5400 does not care about the video format inside, so MPEG-2, MPEG-4 and even uncompressed SDI (MA5410) packets can be encapsulated and transmitted over an IP network. RTP and UDP LAYER Video and audio can be carried over an IP network using two different types of protocols. The User Datagram MA5400 IP Video Gateway page 3

4 Joining and leaving multicast addresses IP Packet Payload Protocol (UDP) is intended for data traffic only but many devices uses this layer for carrying video. In general the use of UDP for video, is mainly used for transmission over short distances where a high quality of service can be guaranteed. The UDP layer provides no protection for the carriage of video over an IP network. The UDP layer will not support any Forward Error Correction (FEC) schemes. The Real-Time-Protocol RTP runs on top of the UDP layer and is used for carrying livereal-time video and audio traffic. The RTP protocol carries packet sequence and time-stamping information. The MA5400 uses the sequence information to determine whether the packets are arriving in order and it uses the timestamping information to determine the jitter. The Pro- MPEG CoP r3 FEC specification uses an extention of the RTP protocol for the transmission of FEC packets alongside the MPEG-2 TS stream encapsulated in RTP. The use of RTP will in give a slightly higher over-head than UDP due to the additional information carried in the header. The MA5400 IP Video Gateway supports the Internet Group Management Protocol (IGMP) for joining and leaving multicast groups. To minimise the bandwidth usage in a network it is essential that routers have a list of devices requesting a multicast stream in order to avoid broadcasting unnecessarily traffic. IGMP is used to establish and break down memberships to particular multicast groups on the network. The mechanisms of the protocol allow a host to inform its router that it wants to receive a specific multicast group. The IGMP protocol is defined in two versions also referred to as IGMP v2 and v3. IGMPv2 allows multicast routers to send out a group-specific query and determine whether there are any remaining hosts interested in receiving the traffic. IGMPv3 supports a more active approach where the source signals when it is joining or leaving the multicast group allowing a more dynamic bandwidth allocation. VLAN Tagging VLAN Tagging is an open standard that has been introduced to increase the security and prevent unauthorised access across Layer II virtual local area networks (VLAN). Tagbased VLAN (IEEE 802.1Q standard) uses an extra ID in the IP header to identify the VLAN membership of an IP frame. This tag is used for VLAN managenent and possible Quality of Service QoS priority identification. The VLAN Tag associates a frame with a specific VLAN and provides the information that switches need to process the frame across the network. The MA5400 IP Video Gateway supports VLAN Tagging on a MPEG-2 TS IP stream and has a separate menu for giving each associated MPEG-2 IP stream the required ID and priority when operating both in Tx and Rx mode. With the inclusion of VLAN Tagging in the MA5400 removes the need to perform VLAN Tagging in a Layer III router before connection to the core network. Type of Service/DiffServ Internet Protocol Stack Type of Service (ToS) refers to the capability of a network to provide better service to selected network traffic over IP-routed networks that may be used to transport multiple types of traffic. Due to the nature of video it will typically require a high level of quality to provide an uninterrupted video stream. Type of Service is also referred to as Differentiated Services or Diffserv. Diffserv takes the IP ToS field, renames it the DS byte, and uses it to carry information about IP packet service requirements. The primary goal of QoS is to provide priority including dedicated bandwidth, controlled jitter and latency within the network for the life of the transmission. The following mechanism has been defined MA5400 IP Video Gateway page 4

5 and supported by the MA5400 for prioritising of video traffic: Delay low or normal delay Throughout high or normal throughput Reliability high or normal reliability Cost low or normal cost The MA5400 supports the insertion of ToS bits in the header of each IP header through a value between 0 and 255 on the control interface. A higher ToS value will typically give a higher priority. Receiver Buffer Setting The MA5400 has a configurable recieve input buffer per multicast stream. The input buffer provides the ability to buffer MPEG-2 TS packets allowing packet re-ordering, reduction of network introdiced jitter and adaptive rate recovery. Each buffer enables a maximum of 8 Mbytes buffer size per input stream and a control loop will adjust the buffer to typically operate half full. The size of the buffer will have a direct relation to the delay of the presentation of the MPEG-2 TS stream on the ASI ports. Maximum buffer size will give the best protection against jitter but also give the longest delay. Forward Error Correction Pro MPEG FEC is an open standard designed for correcting common problems seen when transmitting live video over an IP network. These problems include excessive jitter, packet dropping and packet re-ordering. Pro MPEG FEC will give increased robustness of transmission and extend network reach on high loss links. This scheme is highly configurable to give the best compromise between bandwidth overhead, latency and robustness. A matrix is used to calculate the FEC packets where the size of the matrix is defined by Columns (L) and Rows (D). Media packets are placed in this matrix prior to transmission where the FEC data is calculated. Media and FEC packets are transmitted on separate streams. Column FEC stream are offset from media stream by 2-port numbers higher whilst row FEC stream is offset by 4. This means that non-enabled FEC receivers ignore the FEC streams and are able to receive the stream. One of the benefits with PRO MPEG FEC is that it is independent of video compression standard (MPEG-2, MPEG-4). Pro-MPEG FEC Transmission Model MA5400 IP Video Gateway page 5