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    • Digital Video Class Spring 2006 Internet2 Member Meeting Larry Amiot Northwestern University [email_address] And Dave Devereaux-Weber University of Wisconsin at Madison [email_address]
    • Agenda
      • Analog/Digital Video
      • Digital Video ABCs
      • Digital Video Applications
      • Break
      • Digital Academic Television Network
      • Program Guide
      • Question and Answer
      • Demonstrations
    • Video – Analog and Digital
      • Analog
      • Original broadcast television was black & white
      • 262 ½ odd and 262 ½ even lines (fields) are interlaced to conserve bandwidth
      • 60 fields per second
      • 15,750 lines per second
    • National Television System Committee (NTSC)
      • A committee appointed by the Federal Communications Commission
      • Set standards for US television
    • Composite Video
      • Video and synchronizing pulses on the same wire
      • 1 volt peak-to-peak
      • 100 IRE (Institute of Radio Engineers) units of video
      • 40 IRE units of sync
    • NTSC does Color
      • Backwards compatible with B&W
      • Color information added with a subcarrier
      • Saturation represented by subcarrier amplitude
      • Hue represented by subcarrier phase
    • RGB
      • 3 connections: red, green & blue
      • Full bandwidth, full resolution, full detail
    • Digital Video
      • Over the air in the US, the standards body for digital is the Advanced Television Systems Committee http://www.atsc.org/
      • One family of digital video encoders & decoders (codecs) is MPEG
      • Named from the Moving Pictures Experts Group
      • http://www.mpeg.org/
    • Digital Video
      • DVB is a standard for digital vide broadcasting
      • Originally European, now used around the world
      • http://www.dvb.org
    • Digital Video
      • DV
      • Standard used by Sony, Avid, Apple Microsoft, others
      • (Doesn’t use MPEG)
    • IP, Codecs & Business Model
      • Codecs include Intellectual Property (IP)
      • IP often protected by patents
      • Need to license patented IP
    • IP, Codecs & Business Model
      • Windows Media (Microsoft), user cost is free, subsidized by sale of Microsoft software
      • Quicktime (Apple Computer), user cost is free, subsidized by sale of Apple Computers
      • Real Media player is free, server is paid, no hardware or software to subsidize
    • IP, Codecs & Business Model
      • License for MPEG-2 Player is $2.50 each
      • MPEG-2 codec not included with Windows Media or Quicktime
      • MPEG-4 codec included in Windows Media & Quicktime
    • IP, Codecs & Business Model
      • VideoLAN http://videolan.org/ is free, open source
      • Has codecs with IP issues (MPEG-2)
      • Does not pay a license fee for IP
      • Use of VideoLAN may carry IP risk.
    • Digital Video ABCs
    • Understanding Digital Video Quality
      • Three important factors
        • Image resolution
        • Compression
        • Bit rate of the compressed video stream
    • Image Resolution
    • Image Resolution
      • What is a pixel?
        • Tiny square or rectangular, colored picture elements on a LCD, plasma, DLP, or projection LCD monitor
        • Tiny round, color phosphor dots on a CRT
        • A value (e.g. 8 bit or 24 bit) defining color and luminescence
    • Image Resolution
      • What is resolution?
        • The number of pixels on an image or on a frame of a video
        • The more pixels, the better the resolution
        • Usually expressed as the horizontal pixels times the vertical resolution
          • E.g. 720x480
    • Image Resolution
      • Interlaced Scan
        • Draw odd lines first, then the even lines
        • Full motion video requires frames every 1/60 of a second
        • The way NTSC does it
      • Progressive scan
        • Drawn top to bottom
        • Full motion video is 30 frames per second
    • Image Resolution
      • Standard Definition Television (SDTV)
        • A set of digital television standards with 480 lines of resolution
        • At least as good if not better than NTSC
        • A subset of the Digital TeleVision standards (DTV)
        • All SDTV formats are interlaced
    • Image Resolution
      • DTV standards
        • ATCS is the standard in North America
        • All use MPEG2 compression
        • 18 digital formats covering:
          • Standard definition
          • Enhanced definition
          • High definition
      • High Definition TV
      • 1. 1920 x 1080 16:9 24p Square
      • 2. 1920 x 1080 16:9 30p Square
      • 3. 1920 x 1080 16:9 30i* Square
      • 4. 1280 x 720 16:9 24p Square
      • 5. 1280 x 720 16:9 30p Square
      • 6. 1280 x 720 16:9 60p* Square
      • Enhanced Definition TV - 480p
      • 7. 704 x 480 16:9 24p Rectangle
      • 8. 704 x 480 16:9 30p Rectangle
      • 9. 704 x 480 16:9 60p* Rectangle
      • 10. 704 x 480 4:3 24p Rectangle
      • 11. 704 x 480 4:3 30p Rectangle
      • 12. 704 x 480 4:3 60p* Rectangle
      • 13. 640 x 480 4:3 24p Square
      • 14. 640 x 480 4:3 30p Square
      • 15. 640 x 480 4:3 60p Square
      • Standard Definition TV- 480i
      • 16. 704 x 480 16:9 30i Rectangle
      • 17. 704 x 480 4:3 30i*Rectangle
      • 18. 640 x 480 4:3 30i Square
      • * most popular formats
      DTV Formats
    • Image Resolution
      • CIF
        • A video format widely used in videoconferencing
        • Common Intermediate Format (CIF)
          • QCIF - Quarter CIF (resolution 176x144)
          • SQCIF - Sub quarter CIF (resolution 128x96)
          • CIF- Full CIF (resolution (352x288)
          • 4CIF - 4 x CIF (resolution 704x576)
          • 16CIF - 16 x CIF (resolution 1408x1152)
    • Compression
    • Compression
      • Spatial Redundancy
        • Takes advantage of identical picture elements within a video frame
      • Temporal Redundancy
        • Takes advantage of identical picture elements between frames
        • Takes advantage of the movement of identical picture elements between frames (motion vector)
      • Psychovisual Redundancy
        • Takes advantage of human eyes limited response to fine spatial detail
    • Compression
      • Lossless compression
        • You can take the compressed data and uncompress it to obtain an identical copy of the original uncompressed data
        • E.g. TIFF image
      • Lossy compression
        • You can not get the original data by uncompressing
        • Allows much greater compression than lossless compression
        • E.g. MPEG
    • JPEG Compression
      • A standard of the Joint Photographic Experts Group
      • A lossy compression technique
      • Handles still images
      • The degree of lossiness can be varied by adjusting compression parameters- trade quality for file size
      • You can also trade off decoding speed against image quality
    • JPEG Compression
      • A 24 bit per pixel color scheme as compared to GIF which is 8 bit
      • Can easily provide 20:1 compression of full-color data (about four times better than GIF but slower to decode)
      • Motion JPEG (M-JPEG) provides a video stream
        • but it is not a standard
        • Does not use inter frame compression
    • MPEG Compression
      • MPEG is recognized standard for motion picture compression
        • Uses many of the same techniques as JPEG, but adds inter-frame compression
        • Compresses by about a factor of 3 better than M-JPEG except at very low frame rates
        • Takes more computation than JPEG to compress
        • Difficult to edit on a frame by frame basis
    • Intra Frame Encoding- I Frames
      • Every frame is encoded separately
      • Easy to edit
      • Fast to decode
      • Lost frame produces small artifact
      I I I I I I I I
    • Inter Frame Encoding- I and P Frames
      • Forward predicted from the last I-frame or P-frame
      • Better compression
      • A little harder to decode
      • More difficult to edit
      • More artifacts if a frame is lost
      • Buffering of previous frame required
      • Frames sent in order
    • Inter Frame Encoding- I, P, and B Frames
      • B-frames are both, forward predicted and backward predicted from the last/next I-frame or P-frame
      • Best compression
      • Hardest to decode
      • Most difficult to edit
      • More artifacts with lost frames
      • More buffering required
      • Frames not sent in order
      Sent IPBBBPBBB
    • So what’s a GOP?
      • A set of frames, typically between 4 and 20, is called a Group Of Pictures
      • At most one frame in the GOP can contain a reference to a frame in another GOP
      • Some GOPs do not reference any other GOP
        • E.g. IBBPBBP
    • MPEG Compression
      • Three defined standards
        • MPEG1
        • MPEG2
        • MPEG4
    • MPEG1
      • Optimized to work at video resolutions of 352x240 pixels at 30 frames/sec and 1.5 Mbps
      • May go as high as 4095x4095 at 60 frames/sec
      • Progressive scan only
    • MPEG2
      • Target bit-rate was raised to between 4 and 9 Mbps
      • Commonly used at 720x480 resolution video at 30 frames/sec, at bit-rates up to 15 Mbps
      • Also used for HDTV resolution of 1920x1080 pixels at 30 frame/sec, at a bit-rate of up to 80 Mbps
      • Can do interlaced
    • MPEG4
      • Originally optimized for very low bit rate communication at rates less than 64 Kbps
      • Currently used in videoconferencing for HD at speeds up to 4 Mbps
    • Videoconferencing Video
    • H.323-based Videoconferencing
      • An International Telecommunications Union (ITU) umbrella standard for videoconferencing across IP networks
      • Includes protocols for:
        • Video (i.e. H.261, H.263, and H.264)
        • Audio (G711, G722, etc)
        • Control (H.245, etc)
    • H.261 Compression
      • Part of the H.323 videoconferencing set of standards
      • Originally for two way communication over ISDN lines- now over the Internet
      • Supports intra and inter frame compression
      • Resolutions supported
        • QCIF(144x176 pixels)
        • CIF(288x352)
    • H.263 Compression
      • Part of the H.323 videoconferencing set of standards
      • Based on H.261 but with enhancements to improve video quality
      • Resolutions supported
        • QCIF(144x176)
        • CIF(288x352)
        • SQCIF (128x96)
        • 4CIF (704x576)
        • 16CIF(1408x1152)
    • H.264 Compression
      • Part of the H.323 videoconferencing set of standards
      • H.264, MPEG4, & AVC (Advanced Video Coding) are related codecs for achieving very high compression
      • Adds B frames to compression
      • Ultra-efficient technology that gives you excellent results across a broad range of bandwidths, from 3G for mobile devices to iChat AV for video conferencing to HD for broadcast and DVD
      • Used in QuickTime 7
    • H.264 Compression
      • H.264 delivers the same quality as MPEG-2 at a third to half the data rate
      • H.264 Part 10 delivers up to four times the frame size of MPEG-4 Part 2 at the same data rate
      • Resolutions supported
        • SQCIF (128x96)
        • 720p HD (1280x720)
        • 1080 HD (1920x1088)
    • DV and MiniDV
      • A format developed by several manufacturers for recording on cassettes
      • 500 line horizontal resolution
      • Utilizes the IEEE 1394 digital interface (Firewire)
      • Bit rate of 25 Mbps
      • The sampled video is compressed using a Discrete Cosine Transform (DCT), the same sort of compression used in motion-JPEG
      • 5:1 intraframe compression only
    • Bit Rate of Stream
    • Bit Rate
      • The quality of the video is directly related to the bit rate of the stream
      • Low compression streams require more bandwidth
      • Many codecs dynamically adjust the quality (compression) according to the amount of bits that are produced
    • Bit Rate
      • Variable bit rate
        • Number of bits produced by the codec and sent varies according to the redundancy and motion being compressed at any moment
      • Fixed bit rate
        • Bits to be transferred are buffered
        • If the codec starts producing information faster than the buffering can handle, feedback to the codec reduces the quality (compression) and thus the number of bits produced
    • Bit Rate
      • The quantization (Q) level of an MPEG stream is a measure of the amount of data the encoder throws away to bring the bit rate down
      • Higher Q values mean the encoder threw away a lot of data, implying a low bit rate, but also low visual quality
      • A low Q level implies a high bit rate, and high visual fidelity
      • You can keep a constant bit rate by varying the Q level
      • Alternatively, you can keep a constant Q level and allow the bit rate to vary
    • Compression Trade Offs
      • High Compression
      • Less video quality
      • More buffering required
      • More latency
      • Less bandwidth required
      • More complex hardware
      • Less storage required
      • More susceptible to packet loss
      • More difficult to edit
      • Low Compression
      • Better video quality
      • Less buffering required
      • Less latency
      • More bandwidth required
      • Less complex hardware
      • More storage required
      • Less susceptible to packet loss
      • Less difficult to edit
    • High Definition Video
    • Broadcast High Definition TV
      • Breathtaking quality on home monitors
        • Plasma
        • LCD and projection LCD
        • Projection DLP
      • Several carrier types
        • Through the air
        • Cable
        • Satellite dish
      • More and more HD programming becoming available
      • Downside- watch too much television!
    • High Definition Video
      • Two High Definition Formats
        • 720p
          • 1280x720
          • Progressive scan
          • Equivalent to 9CIF
        • 1080i
          • 1920x1080
          • Interlaced scan
        • Both 16x9 aspect ration compared to 4x3 of SDTV
    • High Definition Video
      • Uncompressed 1080i HD
      • 1920x1080x24x30 ~ 1.5 Gbps
      • HDV
        • Defined by four companies, Canon Inc., Sharp Corporation, Sony Corporation, and Victor Company of Japan, Limited (JVC)
        • Idea is to store high-def MPEG-2 video on standard DV media (DV or Mini DV cassette tape), and stream it across standard FireWire / IEEE 1394 interfaces
    • High Definition Video
      • HDV
        • The format supports MPEG-2 compressed video at two 16:9 resolutions:
          • 720p (1280 x 720, progressive), at approximately 19 Mbps data rate
          • 1080i (1440 x 1080, interlaced), at approximately 25 Mbps data rate- assumes a pixel aspect ratio of 1.33
    • High Definition Videoconferencing
    • H.323-based Videoconferencing
      • Compression/decompression architectures
        • Initially blurred and murky H.261 codecs
        • Major use today is H.263
        • Beginning to see H.264 (MPEG4)
      • Bandwidth requirements have been low (typically 1 Mbps or less)
    • H.323-based Videoconferencing
      • Resolutions have been limited
        • Typically CIF (352x288)
        • Recent use of 4CIF ( 704x576 )- e.g. the Gigaconference requiring bandwidths of 1 to 4 Mbps
      • Aspect ratio of 4x3
      • Several audio algorithms, but typically low quality at 64 Kbps
    • High Definition H.323-based Videoconferencing
      • High definition videoconferencing is becoming available
      • H.323-based high definition video and audio provides the quality necessary for media rich collaboration
      • Being standards-based, it offers
        • User simplicity
        • Promise of interoperability with other non-high definition H.323 systems
    • LifeSize H.323-Based Room Unit
      • Produces 720p high definition video
      • Utilizing H.264 codec
      • 16x9 aspect ratio
      • 9CIF quality
      • 1 Mbps bandwidth (can go at 2 Mbps point to point)
    • LifeSize H.323-Based Room Unit
      • Built-in 4 port MCU
      • Good acoustical quality
        • omni-directional architecture
        • circular array of 16 microphones
        • 100 Hz up to 22 kHz bandwidth
      • High definition camera with 70 degree field of view
    • What Are The HD Driving Forces?
      • Do you need high definition resolution?
      • How important is audio quality?
      • Is aspect ratio important
      • Do you have sufficient bandwidth?
      • Do you need two way interaction (conferencing)?
      • Is H.323 interoperability important?
      • What can you afford?
    • Other High Quality Video Options
      • MPEG2
        • VBrick, StarValley, etc
        • High quality video in the 7 to 16 Mbps range
        • Used at Northwestern for remote venues
      • DVTS
        • Lot of work being done in the Big Video project
        • Transports digital video over IP at 30 Mbps
        • HDV over DVTS becoming available
    • Other High Quality Video Options
      • Access Grid high definition experiments
      • Microsoft ConferenceXP
        • MPEG4 compressed high definition
    • DV Guide
    • Demonstrations
    • Display VideoLAN Client MPEG2 stream VideoLAN MPEG2 Stream Speaker VideoLAN Client Capture Card Composite Video DVD Player
    • Display VideoLAN Client MPEG2 stream VideoLAN MPEG2 Stream Speaker VideoLAN Client DVD
    • DVD Player Display VideoLAN Client StarValley Encoder Composite Video/Audio 7 Mbps (max) MPEG2 stream StarValley MPEG2 Stream Speaker
    • DV Camera Display DVTS Client (decode) Firewire Stream 30 Mbps DVTS stream DVTS Stream Speaker DVTS Client (encode)
    • Camera Display DVTS Client (decode) Composite Video 30 Mbps DVTS stream DVTS Stream Speaker DVTS Client (encode) Firewire Canopus A/D
    • HDV Camera Display VideoLAN Client Firewire Audio/video MPEG2 stream VideoLAN MPEG2 Stream Speaker VideoLAN Client
    • URLs
      • DV Guide
      • http://db.arts.usf.edu/dvguide/default.asp
      • VideoLAN
      • http://www.videolan.org/
      • DVTS
      • http://www.sfc.wide.ad.jp/DVTS/