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HPA Roundtable Presentation
February 2, 2007
Laszlo Zoltan, VP Sales & Marketing
© 2007 Computer Modules, Inc.
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Understanding Transport Streams
A video stream created by an MPEG-2 encoder (compressor) that is specifically encoded to be transmitted by modern digital networks and has the following characteristics:
1) It is packetized to 188 byte frames (Historical)
2) It has some basic tables appended to it every 100 milliseconds that conform to: • PSI – MPEG standard tables• SI or PSIP – ATSC or DVB video standard – tables
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Understanding Transport Streams
1) Short and fixed size packets are amenable to error correction and switching
2) Packets have headers which identify packet types and route packets to proper place in a sequence
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Why Packetization
188 Bytes
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Typical PacketTypical Packet
4 Bytes 184 Payload (Video or Data)
But
MPEG Header (Not TS Header)
The Enabling Technologies for MPEG-2 Transport Streams
1) Video rate analog to digital converters (ADC’s), 10-25 Mhz sampling rate
2) Digital computers fast enough to compute discrete cosine transform (the core algorithm of MPEG compression)
3) Space based Satellites for Video Traffic that use MPEG-2
4) Cheap Memory ICs for frame memories to buffer video frames
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
A Little Background
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Simple A/D Converter
Frame Buffers
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Frame Buffers
FR 1 Memory
FR 2 Memory
FR 3 Memory
FR 4 Memory
FR 5 Memory
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
A Processor Examines the Redundancies in Each Sub
Frame (Block)
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Bit of History of MPEG Streams
JPEG • Created in 80’s• Intraframe• 25:1
MPEG-1 • Created in early 90’s• Intraframe for motion• 100:1
MPEG-2 • Intra + Interframe• Created in mid 90’s• 200:1
MPEG-4 • Advanced version of MPEG-2• 400:1
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Multiplexing and Table Structures
A collection of information inserted recurringly in a “table structure” in specific locations of an MPEG-2 transport stream to help “humans” and “IRD’s” understand what is being decoded.
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
PSI/SI/PSIP Tables
Decoder Oriented: – Encoder bit rate
– Time Info– Channel ID’s
Human Oriented:– Time Info– Channel ID’s– Cost of Content– Text Messages
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
TablesConsist of Two Types
PAT (PID 00 – Always)
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
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PSI (MPEG) Table Hierarchy
NIT PMT 1 PMT 2 PMT 3
PES PIDS PES PIDS PES PIDS
(#36,#37,#38)
(Assigned PID #23 by Human)
(Assigned PID #34 by Human)
(Assigned PID #45 by Human)
A Typical PAT forA Three Program Transport Stream
PID – 00 PATPID – 23 – Program Map Table for Program 1PID – 34 – Program Map Table for Program 2PID – 45 – Program Map Table for Program 3
But, the PMT for Program 2 at PID 34 would show the following PIDs:
36 – Video and PCR 37 – Audio 38 – Data
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
A Typical PAT forA Three Program Transport
Stream
PIDs can be found at three layers:
• PAT
• PMT
• PES
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Remember!
STT – System Time
RTT – Rating Region (Voluntary)
MGT – Master Guide Table (Memory allocation, etc.)
VCT – Virtual Channel Table (All channels or will be channels)
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
PSIP Basic Tables (U.S.)(Content Distribution)
PSIP
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
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PSIP/ATSC Table Hierarchy
STT RRT MGT VCT
EIT ETT
Base Tables
1) Each channel in VCT is further described in an EIT (Event Information Table) that is good for three hours
2) There must be four EITs in every stream
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Notes About VCT
Interesting Notes
1) Some PSIP info can and often is used in cable systems, but the VCT becomes CVCT with different channel properties
2) On cable systems, EIT and ETT are optional
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Interesting Notes
Important Note
The most important table for decoding is the
VCT
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Important Note
Several Ways Transport StreamsCan Be Carried
1) DVB-ASI – Asynchronous Serial
2) SMPTE 310M – Synchronous Serial
3) IP – Packets
4) FireWire® – Packets
5) USB-2
11409 West Bernardo Court San Diego, CA 92127
Tel: (858) 613-1818 Fax: (858) 613-1815
www.dveo.com
Several Ways Transport Streams
Can Be Carried