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Audio/Video compression An introduction

Audio/Video compression An introduction. Alain Bouffioux December, 20, 2006. Agenda. Introduction - The evolution of Audio/Video consumer products and the role of compression techniques. Audio & Video compression principles Audio demonstration Video demonstration. Agenda.

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Audio/Video compression An introduction

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  1. Audio/Video compressionAn introduction Alain Bouffioux December, 20, 2006

  2. Agenda • Introduction - The evolution of Audio/Video consumer products and the role of compression techniques. • Audio & Video compression principles • Audio demonstration • Video demonstration AV Compression / Alain Bouffioux

  3. Agenda • Introduction - The evolution of Audio/Video consumer products and the role of compression techniques. • Audio & Video compression principles • Audio demonstration • Video demonstration AV Compression / Alain Bouffioux

  4. Number of transistors per square inch doubles every 18 months Moore’s law AV Compression / Alain Bouffioux

  5. Moore’s law today Cost of a transistor divided by one million in 30 years AV Compression / Alain Bouffioux

  6. Moore’s law today (2) Itanium 2 (2004, 592,000,000) • “Self-fulfulling prophecy” = roadmap for the semiconductor industry AV Compression / Alain Bouffioux

  7. Moore’s law today (3) • Roadmap for semiconductor industry= only certainty in the current undefined future • Progress in semiconductors = fuels the innovation = fuels the software revolution = fuels the wireless revolution (WLAN, WPAN, WBAN, …) • Examples: WBAN & sensors, RFID applications, camera to swallow, flexible display… • New products & related needs motivate semiconductor industry( Self-fulfilling prophecy) • Moore’s law will continue to apply: 10 years, 20 years ? • Economical limitation ? Investment (fixed) cost / globalisation • Power consumption (Moore’s low in reverse direction) • Architectural gap between IP-blocks & application (middleware still more complex…) AV Compression / Alain Bouffioux

  8. Computer Consumer CD DVD Receiver Digital TV or Residential gateway Communication The evolution of CE products (1) • Past: every CE product was analogue • ~1983: Music becomes digital (CD players) • Early 90ies: microprocessor enters CE devices(Early DVD players incorporated processing power equivalent to their comtemporary PC) • Late 90ies: Communication features incorporated within a CE devices. AV Compression / Alain Bouffioux

  9. The evolution of CE products (2) • The Residential Gateway (Set-Top-Box, ADSL modem?) as the link between the home and the world-wide information infrastructure. World-wide communication infrastructure Home Network RG AV Compression / Alain Bouffioux

  10. The evolution of CE products (3) • The Residential gateway (in home) as the gateway to various services. Local Server provides 2 kind of services: • BroadcastAnalogue & digital TV, NVOD, PPV • Point-to-point (Home to local server)Home shopping, VOD, e-mail, Web browsing, PC connection... About 1000 homes Local server Network Internet Local server AV Compression / Alain Bouffioux

  11. The evolution of CE products (4) • The Residential gateway as a key element of the home network To telephone Network Computer Residential Gateway To satellite Network Home Network Television To cable Network Disk Recorder DVD Jukebox AV Compression / Alain Bouffioux

  12. The evolution of CE products (5) • Everything will become digital: audio, telephone, video, photography, newspaper…The question is not if a selected product will really become digital; the question is when? • Consumer/Computer/Communication Convergence is progressive • New products combine all 3 domains(e.g. New GSM devices – Television on mobile) • Products always more and more complex • Products have always new features • Lifetime of products is always shorter AV Compression / Alain Bouffioux

  13. Factors enabling such evolution Compression is one among the various factors (all powered by semiconductor progresses) that enable multimedia technologies. AV Compression / Alain Bouffioux

  14. BUT !! • Convergence of technologies (consumer, communication, computer) All products combine all three technologies • BUT ! • Divergence of applications • Home consumer, Multimedia phone, Camera, PDA, Office computer, Automotive… • High number of potential productsTechnology push Market pull (user centric approach) AV Compression / Alain Bouffioux

  15. Agenda • Introduction - The evolution of Audio/Video consumer products and the role of compression techniques. • Audio & Video compression principles • Audio demonstration • Video demonstration AV Compression / Alain Bouffioux

  16. Compression in first A/V CE Products (1) • First Audio/Video products made compression without knowing it was compression.How ?By removal of irrelevancies (sampling rate, quantization) • Audio and Video characteristics AV Compression / Alain Bouffioux

  17. Compression in first A/V CE Products (2) • Audio productsFrom 2 to 7.1 channels are enough to provide the spatial resolution. • Video productsThree colours (RGB) are enough to provide the spectral resolution. AV Compression / Alain Bouffioux

  18. The need for more compression (1/5) • Audio: Compression needed in spectral domain • Bitrate of a stereo audio source (CD-DA encoding)Sampling frequency : 44.1 kHzStereo16-bit per sampleBitrate = 44100 * 2 * 16 = 1.41 Mbit/sec AV Compression / Alain Bouffioux

  19. The need for more compression (2/5) • Video: Compression needed in spatial domain • Bitrate of a video source (CCIR 601 - 50 Hz countries) 25 images per secondYUV coding (Y: luminance - U,V : Chrominance)Y: 8 bit per pixel - U,V: 1 pixel on 2 coded, 8 bit per pixelBitrate = (576*720)*25*16 = 166 Mbit/sec AV Compression / Alain Bouffioux

  20. The need for more compression (3/5) • Channels availables for AV transmission • Analog television channel (compatibility)Cable (bandwidth = 8 MHz) Satellite (Bandwidth = 30-40 MHz) Capacity around 40 Mbit/sec • Compact disc (CD)For 74 min. play time : 1.41 Mbit/sec AV Compression / Alain Bouffioux

  21. The need for more compression (4/5) • MPEG-1 target (Moving Picture Expert Group)(Video-CD : 74 min. constraints)But quality was judged too poor (about VHS quality) AV Compression / Alain Bouffioux

  22. The need for more compression (5/5) • MPEG-2 target • Program stream (DVD) • Transport stream (DVB) AV Compression / Alain Bouffioux

  23. Principles of compression (1/2) • Compression (or source coding) is achieved by suppressing information : • redundant information • irrelevant information • Suppression of redundant information  lossless compression example: PCM to DPCM,DCTThe original signal and the one obtained after encoding and decoding are identical AV Compression / Alain Bouffioux

  24. Principles of compression (2/2) • Suppression of irrelevant information  lossy compression Example: bandwidth limitation, masking in audio The original signal and the one obtained after encoding and decoding are different but are perceived as identical AV Compression / Alain Bouffioux

  25. Agenda • Introduction - The evolution of Audio/Video consumer products and the role of compression techniques. • Audio & Video compression principles • Audio demonstration • Video demonstration AV Compression / Alain Bouffioux

  26. Audio Demonstration From “Borderline” Madonna - Stereo - 16 bit/channel Compression used AAC Original 705 kbps Compression 128 kbps 64 kbps 32 kbps 16 kbps Decompression - AV Compression / Alain Bouffioux

  27. MOS scale (1/2) • Signal distortion is not a good measure of the performance of a lossy compression method an other method is necessary: MOS scale (Mean Opinion Score) • The five-grade CCIR impairment scale (Rec.562)1(Very annoying), 2(Annoying), 3(Slightly annoying), 4(Perceptible but not annoying), 5(Imperceptible) • Example:Double blind test AV Compression / Alain Bouffioux

  28. MOS scale (2/2) AV Compression / Alain Bouffioux

  29. Agenda • Introduction - The evolution of Audio/Video consumer products and the role of compression techniques. • Audio & Video compression principles • Audio demonstration • Video demonstration AV Compression / Alain Bouffioux

  30. Compression to VBR or to CBR • CBR (Constant Bit Rate) vs VBR (Variable Bit Rate) • Scene more complex Higher bit rate for same quality • CBR  variable quality (example : Video CD artefact) • Constant quality  VBR necessary (e.g.: DVD-Video) AV Compression / Alain Bouffioux

  31. Video demonstration • MPEG-1 Example Video CD standard(288*352)video – CBR 1.4 Mbps • MPEG-2 ExampleDVD standard(576*720)video – VBR ~3Mbps AV Compression / Alain Bouffioux

  32. The compression trade-off • Compression techniques are still making progress • Trade-off Complexity/Quality/Bit Rate • New technique may result in new trade-off Complexity Quality MPEG Layer 2 MPEG Layer 1 MPEG Layer 3 Other Technique Speech coding MPEG AAC Bitrate AV Compression / Alain Bouffioux

  33. AV Compression / Alain Bouffioux

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