Compression2011

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from production format to distribution format …

from production format to distribution format

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  • 1. compressionfrom production format to distribution format erik.luyten@dml.kuleuven.be
  • 2. Whats this ?René Margritte: La Trahison des Images (1928-29)
  • 3. Moving images !?
  • 4. Temporal resolution 2 images/second 5 images/second12,5 images/second 25 images/second
  • 5. A very small image
  • 6. Spatial resolution7 x 10 = 70 14 x 20 = 280 28 x 40 = 1120 56 x 80 = 4480 112 x 160 = 17920 224 x 320 = 71680 448 x 640 = 309120
  • 7. graylevel resolution1 bit/ 2 2 bit/ 4 3 bit/ 8 4 bit/ 165 bit/ 32 6 bit/ 64 7 bit/128 8 bit/256
  • 8. Creating colour: mixing lightRGB triangle Red channel Green channel Blue channel 3 x 8 bits 256 red steps 256 green steps 256 blue steps
  • 9. Color resolution24 bit color pallet 8 bit color pallet 8 bit optimized pallet 4 bit color pallet 4 bit color pallet244 KB file 28 KB file 28 KB file No “dithering” 16 KB file
  • 10. Video signal(uncompressed) 768 pixels Each pixel has 3 values: (3 bytes) 25 images/second • Red: 256 steps (1 byte) • Green: 256 steps (1 byte) • Blue: 256 steps (1 byte)Datarate for the RGB video signal:768(pix) x 576(lines) x 3(byte) x 25(images)=32 MByte/sec(256 Mbit/sec)
  • 11. Video signal (component) 720 pixels Each pixel has 3 values: (2 bytes) • Luminace(Y): 256 steps (1 byte) 25 images/second • Cr (R-Y): 128 steps (1/2 byte) • Cb (B-Y): 128 steps (1/2 byte)Datarate for the component video signal:720(pix) x 576(lines) x 2(byte) x 25(images)=20 MByte/sec(160Mbit/sec)
  • 12. Audio signal Sampling Rate: 44,1 kHz (CD) Bit Depth: 16 bit (65.536 steps) Stereo: x 2 16 bit x 2 x 44.100 = 1.411.200 bps 1,4 Mbit/secProduction systems normally use a sampling rate of48 kHz16 bit x 2 x 48.000 = 1.536.000 bps
  • 13. Video distribution ?  1 second video: 32 Mbyte (256 Mbit/sec)  1 minute video: 1,9 GByte  1 hour video: 111 GByte Disk Network floppy disk = 0,05 seconds  Ethernet 100 Mbit/sec (shared) LAN 1/2.5 CD-rom = 20 seconds  Ethernet 10 Mbit/sec (shared !) LAN 1/25 1 Gbyte hard disk = 32 seconds  ISDN lijn ( 2B + D) : 128Kbit/sec 1/2000 16 Gbyte array = 8 min 30 sec  Modem connection : 56 Kbit/sec 1/4600
  • 14. Compression techniquesLossless No information lossLossy (Important) information is lost (f.i. medical applications)Intraframe (spatial compression) Compression within a single frameInterframe (temporal compression) Compression between successive framesSymmetric Coding and decoding equally processor intensiveAsymmetric Coding is more processor intensive than decoding
  • 15. Lower datastream ?320x240, 25fps, 24 bit 160x120 pix43,2 Mbit/sec 10,4 Mbit/sec12,5fps 8 bit21,6 Mbit/sec 14,4 Mbit/sec
  • 16. Intraframe compression (in one frame) Run Length Encoding •without compression: one line of 100 (white) pixels 100 x 3 bytes = 300 bytes100 • RLE compressionpixels 100 identical white pixels in a row 2 bytes: total amount of pixels involved 3 bytes for the colour information 2 + 3 = 5 bytes of info for 100 pixels • Compression factor of 60:1 without information loss
  • 17. Other Intraframe techniquesDiscrete Cosine Transformation •JPEG, MPEG, DV,… •Type of Fourier Transformation •Blocks of 8 x 8 pixels and/or 16 x 16Wavelet Compression •MPEG-4 (still image), JPEG2000 •Improving image resolution as more data are receivedVector QuantizationFractal Compression
  • 18. Interframe compression Image 124 Image 125
  • 19. Interframe: MPEG (Moving Picture Expert Group)GOP Group Of Pictures I-pictures: (Intra pictures) reference image with complete information for one frame (scene changes, ...) P-pictures: (Predicted pictures) images are “predicted” using the information in earlier I or P pictures. B-pictures: (Bi-directional predicted) pictures are recomposed from information in earlier or later I or P pictures. B-pictures are never used as reference for other images.I B B P B B P B B P B B I Group Of Pictures (GOP)
  • 20. Movie FormatsFile Format: Specifies how data are arranged in a file (interleaving video and audio)Codec: Specifies how (image) data is compressedArchitecture: Synchronisation of different media components (video, audio, language tracks, text,…. tracks) Control for interactivity, alternate tracks,…
  • 21. Movie Architectures QuickTime AVI Windows Media Player Real Media Flash ? MPEG-4
  • 22. Media platform platform distribution cost alternates remarks RTSP alternates QTVR, text, midi, SMIL,.. Player = free production and Mac CD rom HTTP alternatesQuickTim Windows Download (HTTP) Pro = €30 distribution Mixed alternates e (Linux) Streaming (RTSP) Server= open Skip prot.,instant - H.264 srce on Player = free RTSP alternates Windows Streaming (RTSP) Superpass=$13/ (Surestream only distribution and Real Mac Download (HTTP) m techn.) mainly for streaming Linux Server=payable Dynamic Windows Streaming ( ) Player=free Production anddistributionWindows (Mac) Download (HTTP) RTSP alternates Server= Version 9 on windows Media Dynamic (Linux) CD rom Windows2003 platform Flash Windows CD rom(Spark, Player=free Mac Download (HTTP) Server=€4759 ? H.264 On2, Linux Streaming h264) Player=QT, Industrie standaard Streaming (RTSP) Windows Real,… Download (HTTP) scalable (in the from handheld to HDMPEG-4 Mac CD rom Server=open future) srce Linux DVD, GSM, …. H.264
  • 23. File Formats DV MPEG-1 MPEG-2 MPEG-4
  • 24. Codec’s Picture: • Cinepak • Indeo (Intel Indeo) • H.261, H.263, H.264 • Sorenson • M-JPEG • MPEG-1, MPEG-2, MPEG-4 • DV Sound: • IMA • Qualcomm PureVoice, Qdesign Music,… • MP3 • AAC (Advanced Audio Coding) • WMA, RealAudio
  • 25. MPEG-1, MPEG-2 MPEG-4 difference MPEG-4 vs MPEG-1/2 display and video scaling Decompression compression Composition subtitles Rendering display and transport andbackground scaling graphics MPEG-4 display Scaling, Rendering Decompression video Bitmap stream transport Composition Compression subtitles ASCI code transport display andbackground Bitmap image transport graphics Vector code transport
  • 26. Codec’s and bitrate Web ? Distribution codec’s Production codec’s 56 kbit 200 kbit 1 Mbit 9 Mbit 25 Mbit 256 Mbit uncompr. MPEG-1 MPEG-2 H-261 H-263 Sorenson DV profile 0 profile 1 MPEG-4 MPEG-4 H.264PIM, GSM, ... HD distribution Studio production
  • 27. Comparing codecsCinepack : 4,2 Mbit/sec H-263 : 2 Mbit/sec MPEG 1: 1,8 Mbit/secSorenson : 1,35 Mbit/sec MPEG-4 : 960 Kbit/sec H.264 : 502 Kbit/sec
  • 28. Video to Computer• Video recording • Interlaced, 25 frames - 50 fields per second • Restricted to 576 effective lines (PAL) and 3x4 picture aspect ratio.• Computer image • Non-interlaced, 60 to 80 frames per second • No restrictions on picture format and aspect ratio• De-interlacing of video material is desirable.
  • 29. De-interlacing Field 1313 Field 2 1314 2315 3623 311624 312625 313
  • 30. Delivery methods DVD, CD, USB stick,… Internet • Progressive download (HTTP, FTP)  “file transport” type (TCP protocol)  No data loss: resent lost packages  No real-time events  Complete file must be downloaded to allow random access.  No special server needed (normal web service over http) • Streaming media (RTP)  RTSP transport (UDP protocol)  Lost data (probably) will not be recovered  Real-time events possible  “Random access” possibility (only needed fragments will be downloaded)  Needs one or more(worldwide proxy delivery) streaming servers
  • 31. (Progressive) download Web server http:// http:// www.avnet.kuleuven.be/ www.avnet.kuleuven.be/ staalkaart/2004/video04.mov staalkaart/2004/video04.html<object classid="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B"codebase="http://www.apple.com/qtactivex/qtplugin.cab"width="320" height="195"><param name="loop" value="false"> File : video04.mov<param name="cache" value="true"><param name="src" value="video04.mov"> TCP/IP<param name="autoplay" value="true"><param name="controller" value="true"><embed width="320" height="195"pluginspage="http://www.apple.com/quicktime/download/"src="video04.mov" type="video/quicktime" controller="true"autoplay="true" cache="true" loop="false"></object>
  • 32. (video) podcasting Audio or audio/video distribution via internet Download file to client computer Mostly used for handheld devices Broadcast channel ---> Feeds Programs ---> Episodes
  • 33. Podcast delivery: URL link Web server AVNet•Request for web pqge•HTML with itpc link•Request XML data•XML file + startup iTunes•Request for episodes•HTTP downloadepisodes to iTunes Client computer
  • 34. RTSP streaming (or RTMP) Web server Streaming serverhttp:// Datastreamwww.avnet.kuleuven.be/ RTP over UDPVideotechniek/medatech.html <object classid="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B" width="384" height="304" codebase="http://www.apple.com/qtactivex/qtplugin.cab"> <param name="autoplay" value="true"> <param name="controller" value="true"> <param name="pluginspage" value="http://www.apple.com/quicktime/download/indext.html"> <param name="target" value="myself"> <param name="type" value="video/quicktime"> <param name="src" value="jaarverslag0304_384k.mov"> rtsp://escher.avnet.kuleuven.be/ <param name="HREF" value="rtsp://escher.avnet.kuleuven.be/mediatechnologie/mediatech_384k.mov"> <embed src="comtechn.mov" width="384" height="304" autoplay="true" mediatechnologie/mediatech_384k.mov controller="true" border="0" pluginspage="http://www.apple.com/quicktime/download/indext.html" target="myself" type="video/quicktime" href="rtsp://escher.avnet.kuleuven.be/mediatechnologie/mediatech_384k.mov"></embed> </object>
  • 35. Streaming - unicast
  • 36. Streaming - multicast
  • 37. HTTP streaming (iPhone, iPad,…) Ordinary webserver (Apache 2.2) • Apple HLS Segmented distribution of material. • Microsoft Smooth Streaming  Material is chopped in 10 sec files • Adobe Flash HTTP Dynamic  Index file with info on different segments Streaming  Distributed to client using http protocol VOD via h.264 compressed material Live streaming possible  Latency 20-30 sec  Stream segmenter #EXTM3U #EXT-X-MEDIA-SEQUENCE:0 #EXT-X-TARGETDURATION:10 #EXTINF:10, http://media.example.com/segment1.ts #EXTINF:10, http://media.example.com/segment2.ts #EXTINF:10, http://media.example.com/segment3.ts #EXT-X-ENDLIST