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BTC305 7 Compression Testing Presentation
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BTC305 7 Compression Testing Presentation

BTC305 7 Compression Testing Presentation

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BTC305 7 Compression Testing Presentation BTC305 7 Compression Testing Presentation Presentation Transcript

  • BTC305: Media Compression Compression System Testing 26 October 2009
  • Compression System Testing  First, why & how do we measure non- compressed video & audio systems? Work in pairs to write a list of 10 measurements that we carry out on non-compressed video Also write a list of 6 measurements that we carry out on non-compressed audio 2
  • Compression System Testing  There are two ways in which we can categorise measurements of picture and sound quality: Subjective & Objective What do each of these terms mean? Now against each of your measurements write down whether it is subjective or objective? 3
  • Compression System Testing  So, what is the basis on which our subjective and objective system is based? What are the assumptions about objective testing? What is ITU-R BT.500-7?  So, how should we measure the quality of systems that use data compression? 4
  • Compression System Testing  This is not very straightforward  We can look at pictures once they have been encoded and decoded  What will this tell us about the system?  What doesn’t this tell us about the system? 5
  • Compression System Testing  Two main approaches to compression testing have evolved: PQA & TSA Working in pairs, find out what PQA means in the context of compression system testing. Write a definition of PQA Now find out what TSA means in the same context. Write a definition of TSA 6
  • Compression System Testing  What is the fundamental premise of PQA?  In order to understand TSA, we need to find out what a Transport Stream actually is, so we will now investigate the MPG Systems Layer 7
  • MPEG-2 Systems Layer Video Video PS Data Storage Data Coder Applications Audio Audio Service Data Coder Multiplexer Cable RF Service Data TS Channel Cable Data Coder Adaptation Channel Terrestrial RF Transport Other Channel UHF Multiplexer Services Adaptation Channel PSI Service Satellite RF Information Channel Satellite Adaptation Channel 8
  • MPEG-2 Systems Layer 9
  • MPEG-2 Systems Layer Packetised Header Data Header Elementary Stream Synchronous Payload Payload Payload Payload Transport Multiplex 188 Bytes Alignment Header Adaptation Field 4 Bytes 184 Bytes Sync Adaptation Byte TEI PUSI TP PID TSC AFC CC Field Payload Data (47H) (Optional) 8 1 1 1 13 2 2 4 Adaptation Elementary Random Field Discontinuity Access Stream 5 Optional Stuffing Length Indicator Priority Flags Fields Bytes Indicator (7 bits) Indicator Transport Adaptation Splicing PCR OPCR Point Private Field Flag Flag Data Extension Flag Flag Flag 10
  • MPEG-2 Systems Layer  MPEG-2 PSI (Programme Specific Information)  PAT (Programme Allocation Table)  PMT (Programme Map Table)  NIT (Network Information Table)  CAT (Conditional Access Table)  DVB SI (System Information)  BAT (Bouquet Association Table  RST (Running Status Table)  SDT (Service Description Table)  EIT (Event Information Table)  TDT (Time & Date Table)  TOT (Time Offset Table)  SIT (Selection Information Table)  DIT (Discontinuity Information Table)  Stuffing Table 11
  • MPEG-2 Systems Layer MPEG Transport Stream Block Vid PMT PMT PMT Vid Vid Vid Snd Snd Snd Snd Snd Vid Text Text Vid PAT Content 5 1 2 3 1 2 3 1 2 3 4 1 3 1 2 1 PID 1025 0000 0801 0802 0803 1021 1022 1023 1131 1132 1133 1134 1131 1023 0931 0932 1021 PAT PID Prog A 0801 PMT PID 0801 Prog B 0802 Element PID Prog C 0803 Video 1021 etc. Audio (Eng) 1131 Audio (Fr) 1132 Teletext 0931 etc. PMT PID 0802 Element PID Video 1022 Audio (Eng) 1133 Audio (Fr) 1134 Teletext 0931 etc. PMT PID 0803 Element PID Video 1023 Audio (Fr) 1134 Teletext (Fr) 0932 Relationship Between PAT, PMTs & PIDs etc. 12
  • MPEG-2 Systems Layer Transmission System IRD V V A Demux A Mux Scrambler Mod Demod Descrambler Demux ECMs D D EMMs SI/ CAT PSI µprocessor Main IRD EMM ECM Processor Generator Generator CA Modem Module Smart Card Subscriber Studio Management Playout System System DVB CA System 13
  • MPEG-2 Systems Layer Normal Multiplex Statistical Multiplex Fixed Channel Capacity Constant Bit-Rate data Variable Bit-Rate data on each service allows on each service allows 5 services in multiplex. 6 services in multiplex. Statistical Multiplexing 14
  • MPEG-2 Systems Layer MPEG-2 Interleave Process 15
  • Transport Stream Analysis  TSA can be implemented in hardware or software  Working in pairs, find out who are the major companies selling TSA hardware or software  A free TSA called TSReader Lite for the Windows operating system is available from: www.tsreader.com/tsreader/index.html 16
  • Transport Stream Analysis - Tektronix www.broadcastpapers.com/sigdis/TektronixMPEGGuide%20-%20mpeg13.htm 17
  • Transport Stream Analysis - Tektronix www.broadcastpapers.com/sigdis/TektronixMPEGGuide%20-%20mpeg13.htm 18