Transcript Interesting Collaboration Oriented Product by Small
Understanding Transport Streams
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
Why Packetization
1) 2) Short and fixed size packets are amenable to error correction and switching 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
Typical Packet
188 Bytes But 4 Bytes 184 Payload (Video or Data) MPEG Header (Not TS Header) 11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com
A Little Background
1) 2) 3) 4) The Enabling Technologies for MPEG-2 Transport Streams Video rate analog to digital converters (ADC’s), 10-25 Mhz sampling rate Digital computers fast enough to compute discrete cosine transform (the core algorithm of MPEG compression) Space based Satellites for Video Traffic that use MPEG-2 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
Simple A/D Converter
11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com
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 MPEG-1 MPEG-2 MPEG-4
• • •
Created in 80’s Intraframe 25:1
• • •
Created in early 90’s Intraframe for motion 100:1
• • •
Intra + Interframe Created in mid 90’s 200:1
• •
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
11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com
PSI/SI/PSIP Tables
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
Tables Consist of Two Types
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
PSI (MPEG) Table Hierarchy
PAT (PID 00 – Always) (Assigned (Assigned PID #23 by PID #34 NIT PMT 1 PMT 2 PMT 3 (Assigned PID #45 by Human) PES PIDS PES PIDS PES PIDS (#36,#37,#38) 11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com
A Typical PAT for A Three Program Transport Stream
PID – 00 PAT PID – 23 – Program Map Table for Program 1 PID – 34 – Program Map Table for Program 2 PID – 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
Remember!
• • •
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
PSIP Basic Tables (U.S.) (Content Distribution)
STT RTT MGT VCT – System Time – Rating Region (Voluntary) – Master Guide Table (Memory allocation, etc.) – 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/ATSC Table Hierarchy
PSIP STT RRT MGT VCT EIT ETT Base Tables 11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com
Notes About VCT
1) 2) Each channel in VCT is further described in an EIT (Event Information Table) that is good for three hours 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
1) 2) Some PSIP info can and often is used in cable systems, but the VCT becomes CVCT with different channel properties 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
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
Several Ways Transport Streams Can Be Carried
1) 2) 3) 4) 5) DVB-ASI – Asynchronous Serial SMPTE 310M – Synchronous Serial IP – Packets FireWire® – Packets USB-2 11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com
SMPTE 310M
– .8V P-P – Biphase Mark Encoded – 75 Ohm – Self Clocking 11409 West Bernardo Court San Diego, CA 92127 Tel: (858) 613-1818 Fax: (858) 613-1815 www.dveo.com