9/22/2002
ASI Transport Streams
MPEG-2 Transport Streams
Features
ISO/IEC standard for compressing, processing, decompressing and representing digital video, audio, and combined video/audio Scalable:
applications can range from high-definition television (HDTV) to lower-resolution video on telecommunication networks
How MPEG Works
MPEG encodes and dramatically compresses video
Tailored to weaknesses of human eye
Uncompressed = 270 Mbps
MPEG Compressed = 6Mbps
How MPEG Works
Reduces colors / shades
If the eye wont see it, dont encode it
Reduces redundant information
If the background doesnt change, dont encode it Approximately 75% of compression comes from reducing redundant data describing motion!
MPEG is a Lossy Algorithm
Data is discarded You can never get the original (uncompressed) signal back after MPEG encoding
How MPEG Compression Works
Video encoded as a series of Frames
I-Frames, B-Frames, P-Frames
I-Frames
Complete picture, all information, inclusive
B-Frames & P-Frames
Much less information Send the changed information, NOT the complete picture
I-Frames
P-Frames and B-Frames
I-frames: contain full picture information P-frames: predicted from past I or P frames B-frames: use past and future I or P frames Transmit I frames every 12 frames or so
Options for Transporting Transport Streams
DVB-ASI
Asynchronous Serial Interface
DVB-SPI*
Synchronous Parallel Interface
DHEI*
Digital Headend Interface
*Proprietary or limited implementation
ASI Introduction
MPEG defined only the encoding & the transport stream
Transporting the transport stream was originally left to the manufacturers
DVB wrote transport spec DVB-ASI
DVB = Digital Video Broadcasting ASI = Asynchronous Serial Interface
DVB-ASI Physical Layer
Standard method for interconnecting systems from different vendors Simpler connection, a single coax cable versus complex multi-conductor wiring Compatibility with existing video cables
75 coax cable Standard BNC connectors
Compatibility with varying bit rate signals Unidirectional Supports SPTSs & MPTSs
DVB-ASI Speeds
270 Mbps line rate
Consistent with SDI clock
27 MBps data rate
Consistent with PCR clock standard
Compatible with varying bit rates
Automatically stuffs pipe with null packets Null packets act as heartbeat
An ASI Signal
270 Mbps ASI signal carrying a Multi-Program Transport Stream (MPTS) Prog 1 Prog 2 Prog 4
Note the different bit rates carried by the ASI stream
DVB-ASI Interface
Parameter Connection medium Connector type Cable length Bit rate on link Value Coaxial cable BNC 300 meters 270 M bit/s Comments 75-Ohm, low loss, double shielded 75-Ohm version Depending on cable type used 27 MHz byte clock multiplied by 10 Input octets sent as 10-bit link characters 8 user bits encoded as 10 line bits Nominal into 75-Ohm termination
Link character length 10 bit Byte rate on link Voltage levels 27 M bytes/s 800 mV p-p
Header and Payload
1 b 88 ytes Transport Packet H eader 4bytes A daptatio Field n Payload V ariable len gth V ariable length
T sport ran Packet Header 4b ytes
Payload 184bytes
T ransp ort Pack et Head er 4 by tes
A daptation Field
1 b 84 ytes
Payload subpackets of: Video Audio
Adaptation field contains data for: Management Control (PCR)
Transport Stream Payload
Variable-length field Can contain:
up to 184 bytes of packetized program content, and/or PSI (Program Specific Information) data describing the transport stream
May include adaptation field containing information to reconstruct the stream
MPEG Program Stream
Many types of packets, each with a Packet Identifier (PID)
MPEG PIDs Each packet has one. PAT Defines the stream (channel) of the following packets. Its PID is always PID-0 (PID zero). PMT Defines the packet types to follow. Video (B, P & I) Frames Audio Frame
ASI (Asynchronous Serial Interface )
Transport Signal
Compressed Video
SD, HD, Low Res
Audio
AES, AC-3,
Data
Interactive Program Unassociated
Who is using it?
Satellite Program Distribution DTH DNSG Telco Cable
Compression Systems
Data Decode Audio A/D Frame Sync AES SDI MPEG-2 Encoder ASI
Transport Converter
DS3
Multiple Signals
Video Program 1 Video Program 2 Video Program 3 ASI MPEG 2 MULTI Program Transport Stream 270 Mbps
MPEG Transport MUX
Video Spare
Transport MUX
Telco Links
ASI is interim link for MPEG video for
ATM DS3 QPSK/8PSK QAM Fiber
Telco Costs
Local Loop
270 Mb/s loop Usually full Wavelength
Long Haul
ASI Muxed OC-48 SONET ASI payload onto ATM, IP or DTM
Existing Video Links
Video Audio
Mild Compression
A/D Signal Impairment
D/A
Existing Video Links
Video Audio
Mild Compression
Decoder Signal Impairment
Encoder
MPEG Video Links (DVB-ASI)
Mild Compression
SDI Audio Data
SDI Audio Data
Signal Impairment
Why MPEG Video Links
DS-3 Circuits
Standard link Availability Two Video Ciricuits Cost
Where can I use it?
Broadcast Facility
Routers Fiber Optic links Servers Incoming/Outgoing
SDI
Video Signal Transport of Other Signal Elements
AES AC-3 Data
SDI
VANC H A N C
Active Video
Transport Signals
SDI
270 Mb/s EAV/SAV Nerzi Encoding Uncompressed Video SDTV AES, Linear Data (AC-3) Data
ASI
270 Mb/s Polarity sensitive Compressed Video SD, HD, Low Res AES, AC-3 Program associated and Unassociated Data
Traditional Cable Headend
NTSC to SDI With FS/NR Mux Audio A/D
De Mux
MPEG
Program Record
ASI Based Digital Cable
Capable of SD, HD,AC-3, AES, Interactive Existing 270 Mb/s Router Commercial Insertion
Program Record
Why Do Everything Twice?
We Mux audio, captioning, data, etc in SDI and take it apart so we can do it all over again for DVB-ASI?
Design system to minimize signaldamaging conversions If damaging conversions are unavoidable, postpone until all multi-generation work is completed
MPEG
Packet Packet Packet Packet
188 Bytes Header Payload
Program Association Table
Conditional Access Table
Program Map Table
Time Switched Transmit Diversity
Beyond MPEG Tables
DVB Compliance
DVB-S DVB-T DVB-C
ASTC
PSIP
Transport Converters
Fiber 8PSK ASI DS3 ATM QAM DS3 DS3 QPSK
Transport Content
HD MPEG ATSC ASI AES SD MPEG VBI DS3 DS3 DATA
Why MPEG Links
ASI
Compatibility for Local Loop Easily Transportable over Telco System
DTM SONET ATM IP
MPEG Applications
Broadcast to Home Network Backbone Event to Network STL Link
Live Sports Application
Four or more ISOs Muxed at Stadium delivered over ASI local loop to ASI server
All the ISOs are locked together in time Easy to log content for Asset Management Reduce cost of covering live event
Video Over DSL to the Home
ASI
Bandwidth Management ASI
ASI Mapped to IP or ATM ATM or IP
DSLAM
DSL
ASI Server
SD, HD MPEG Encoder AES, AC-3 Data Storage SAN/NAS Stored as Transport Stream
Server
Video Server
Stored as Program Stream MPEG Encoder Server Application MPEG Decoder
Storage
Video Server File Transfers
Stored as Program Stream MPEG Encoder Server Application Occasional Video ASI FTP OC-3 OC-12
Storage
File FTP with ASI Server
ASI Server
Media Essence ASI Link
ASI Server
Meta Data & Transfer Schedule LAN / WAN
Media Tariffs
OC-12 Cost DS-3 Video DS-3 OC-3
8Mb/s ASI
Bandwidth
Web Sites of Interest
SMPTE ATSC DVB ETSI CDTV www.smpte.org www.atsc.org www.dvb.org www.etsi.org www.cdtv.ca
9/22/2002
Thanks !
