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• Data transmission rate 270 Mbps on 75Ω coax or fiber
• 8-bit data converted to 10-bit for transmission for “DC-balance”
EN 50083-9:2002 - 28 -
Annex B (normative)
Asynchronous Serial Interface (ASI)
This annex describes a system for a serial, encoded transmission of different data rates with a constant transmission rate, based on a layered structure of MPEG Transport Packets according to EN ISO/IEC 13818-1 as a top layer (Layer-2), and a pair of bottom layers (Layer- 1 and Layer-0) based upon the Fibre Channel (FC) described in the ISO/IEC 14165-111 „Information technology - Fibre Channel - Part 111: Physical and signalling interface (FC-PH)“. Layer-1 and Layer-0 are based upon a subset of Fibre Channel Levels FC-1 and FC-0 . Transport Streams from different sources may have different data rates. The use of a constant transmission rate permits a constant receiver clock. To restore the original clock rate, a PLL circuit can be used. Annex E gives some proposals for how such a circuit can be designed. The input of the required transmission facility accepts MPEG-2 bytes and the output delivers MPEG-2 bytes. While the Fibre-Channel (FC) supports single mode fibre, multi-mode fibre, coaxial cable and twisted pair media interfaces, this standard defines only two distinct forms of interfaces: coaxial cable and multi-mode fibre-optical cable using LED emitters. Instead of a transmission rate of 265,625 Mbit/s, as required in the ISO/IEC standard, in this document the transmission rate is 270,000 Mbit/s.
B.1 ASI transmission system overview Figures B.1 and B.2 represent the primary components of the ASI transmission method over copper coaxial cable and fibre-optic cable, respectively.
Figure B.1 - Coaxial cable-based asynchronous serial transmission link (ASI type)
Sync Byte (FC Comma)
Insertion
Sync Byte (FC Comma)
Deletion
Clock/Data Recovery &
Serial/ParallelConversion
Coupling/ Impedance Matching
8B/10B Decoding
Amplifier/ Buffer
Connector
Parallel/SerialConversion
Coupling/ Impedance Matching
8B/10B Coding
Amplifier/ Buffer
Connector
Coaxial Cable
Packet-Synchronous MPEG2 TS
Packet- Synchronous MPEG-2 TS
Layer-1 Layer-0Layer-2 • Don’t have to use all 270 Mbps
• “Comma” 10-bit symbol inserted when no data ready to transmit
• Ignored by receivers
• Allows any bit rate <270 Mbps
IP – Internet Protocol
• A protocol for packet network intercommunication
• IP version 4 (IPv4) is dominant protocol of the Internet
• IPv6 its successor is starting to be used
IHL = Internet Header Length
TOS = Type of Service (now Differentiated Services Code Point, DSCP, and Explicit Congestion Notification, ECN)
If IP packet too large to fit downnetwork pipe, it gets “fragmented”
SMPTE Standards UpdateSMPTE Professional Development Academy – Enabling Global Education
ST 2022-3 Variable Bit Rate TS over RTP
• Real-time piecewise constant variable bit rate (VBR)
• Piecewise constant VBR means rate only changes at PCR-labeled packets of the program
• A max of 1, 4, or 7 TS packets per RTP packet per session (Packet_per_Datagram_max)
• Mode 1 – RTP packets always have Packet_per_Datagram_max TS packets. RTP packet send rate varies for VBR. Also has maximum_latency and maximum_bitrate.
• Mode 2 – RTP packets sent at constant rate, # of TS packets per RTP packet varies for VBR
SMPTE Standards UpdateSMPTE Professional Development Academy – Enabling Global Education
ST 2022-3 FEC Rules for Mode 1• Only block-aligned FEC
• maximum_latency limits FEC matrix latency, partially filled packets moved to next FEC matrix
ST 2022-3 Mode 1 FEC Header
• Like 2022-1 FEC header except…
• N=1 indicating ST 2022-3 Mode 1 FEC
• Maximum_latency - 10-bit number defining the multiplier of 10 ms (up to 10.24 seconds)
• Maximum_bit_rate - 10-bit number, first seven bits mantissa value and last 3 bits exponent value defining the multiplier of 10 Kbps (up to 1,280 Gbps)
The E bit is the extension flag reserved to indicate any future extension to this specification. It shall
be set to 0.
Reserved (R) 1 bit: Shall be set to zero by the sender. Padding Recovery field (P) 1 bit:
The Padding Recovery field shall be computed via the XOR operation applied to the corresponding P values from the RTP headers of the Media Datagrams Associated with the FEC Datagram.
Extension Recovery field (X) 1 bit: The Extension Recovery field shall be computed via the XOR operation applied to the corresponding X values from the RTP headers of the Media Datagrams Associated with the FEC Datagram.
CSRC Count Recovery field (CC) 4 bits: The CSRC Count Recovery field shall be computed via the XOR operation applied to the corresponding CC values from the RTP headers of the Media Datagrams Associated with the FEC Datagram.
Marker Recovery field (M) 1 bit: The Marker Recovery field shall be computed via the XOR operation applied to the corresponding M values from the RTP headers of the Media Datagrams Associated with the FEC Datagram.
Payload Type Recovery field (PT Recovery) 7 bits: The Payload Type Recovery field shall be computed via the XOR operation applied to the corresponding PT values from the RTP headers of the Media Datagrams Associated with the FEC Datagram.
Sequence Number Base (SN Base) 2 octets: The Sequence Number Base field shall be set to the lowest sequence number, taking wrap around into account, of those Media Datagrams protected by FEC.
Time Stamp Recovery (TS) 4 octets: The Time Stamp Recovery field shall be computed via the XOR operation applied to the timestamps of the Media Datagrams Associated with this FEC Datagram. This allows the timestamps to be completely recovered.
Length Recovery (LR) 2 octets: This field is used to determine the length of any recovered datagrams. The Length Recovery field shall be computed via the XOR operation applied to the unsigned network-ordered 16-bit