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Introduction to Digital Video Technology Dr' Edward Chow

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Introduction to Digital Video Technology. Dr. Edward Chow. 2. Agenda. Applications ... St. Andrews. MCU. Motion JPEG. M JPEG. M JPEG. M JPEG. M JPEG. Cisco ... – PowerPoint PPT presentation

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Title: Introduction to Digital Video Technology Dr' Edward Chow


1
Introduction to Digital Video TechnologyDr.
Edward Chow
2
Agenda
  • Applications
  • Image Compression Technology
  • Basic Network Planning
  • Implementation Examples
  • Source CISCO, Microsoft, C-CUBE, WWW.mpeg.org

3
Video Applications
Distance Learning Video Conferencing Tele
Medicine Surveillance Broadcast TV
4
ConferencingRoom to Room
5
ConferencingDesktop
6
ConferencingMultipoint
7
BroadcastLive
8
BroadcastPre-Recorded
9
BroadcastVideo Distribution
10
Video on Demand
VideoServer
11
Video Application Matrix
Point-to- Multipoint
Point-to-Point
Unidirectional
  • Considerations
  • Video Quality
  • Bandwidth
  • Latency

Bidirectional
12
Agenda
  • Applications
  • Image Compression Technology
  • Basic Network Planning
  • Implementation Examples

13
Technology
Bandwidth
QoS
ATM
PAL
RSVP
Standards
MPEG-2
H.320
H.323
NTSC
Lossless
Motion JPEG
Lossy
T.120
Latency
H.261
Ethernet
Multicast
ISDN
14
Video Quality and Bandwidth
Narrowband ISDN
Broadband Ethernet, ATM
Business Quality
Video ConferenceQuality
VHS/BroadcastQuality
1M
128K
10M
Bits Per Second
15
Video Data Requirements
3 Colors x 30 Frames/second 27 MBps 221
Mbps
640
480
16
Video Compression Standards
Video Quality
Motion JPEG MPEG-2 MPEG-1 H.261/H.263 MPEG-4
Broadcast Broadcast/HDTV VCR/Business Video
Conf Video Phone
Refer Mercury Technologies for revised bandwidth
requirements
17
Video Compression Standards
CompressionRatio
Bandwidth (bits/sec)
Motion JPEG MPEG-2 MPEG-1 H.261/H.263 MPEG-4
10 26 M 3 16 M .5 4 M 128 K 1 M 4.8 K
64 K
727 1 30100 1 25100 1
24200 1 501000 1
Refer Mercury Technologies for revised bandwidth
requirements
18
Video Compression Basics
  • The basic compression scheme can be summarized as
    follows
  • 1. Divide the picture into 8x8 blocks
  • 2. Determine relevant picture information
  • 3. Discard redundant or insignificant information
  • 4. Encode relevant picture information with the
    least number of bits.
  • Common functions are
  • DCT
  • Zig-Zag Scanning
  • Quantization
  • Entropy Coding
  • Motion Estimation

19
Discrete Cosine Transform (DCT)
  • Two dimensional (2D) DCT maps a picture or a
    picture segment into its 2D frequency components.
  • For video compression applications, since the
    variations in the block tend to be low, the great
    majority of these transformations result in a
    more compact representation of the block.
  • The block energy is packed into the corresponding
    lower frequency bins.

20
Zig-Zag Scanning
  • Since the mapping is from lower to higher
    frequencies in the horizontal and vertical
    directions, zig-zag scanning of the resulting 2D
    frequency bins clusters packets of picture
    information from low to high frequencies into a
    1D stream of bins.

21
Quantization
  • Represent the frequency bins by converting
    amplitudes that fall in certain ranges to one in
    a set of quantization levels.
  • Frequency quantization has no "contour"
    distortion effect

22
Entropy Coding
  • Statistically encoding the most frequently
    occurring patterns with the least number of
    bits.
  • A two step process
  • Zero Run-Length Coding (RLC)
  • Representation of the quantized bins which
    utilizes a pair of numbers.The first number
    represents the number of consecutive zeros while
    the second number represents the value between
    zero-run lengths.
  • Huffman Coding
  • Assigns a variable length code to the RLC data.
    Huffman tables are computed based on statistical
    properties of the image.

23
Motion Estimation
  • Compression ratios for motion video sequences may
    be increased byencoding the arithmetic difference
    between two or more successive frames.
  • Motion estimation is the process by which
    elements in a picture are best correlated to
    elements in other pictures (ahead or behind) by
    the estimated amount of motion. The amount of
    motion is encapsulated in the motion vector.
  • Forward motion vectors refer to correlation with
    previous pictures.
  • Backward motion vectors refer to correlation with
    future pictures.
  • Motion estimation is an extremely computationally
    intensive operation difficult to implement in
    real-time.

24
JPEG Compression
  • Encoding
  • Decoding

25
Motion JPEG
Spatial Compression
26
Video Compression
Video Sequence
Group of Pictures


Picture
Block
Macroblock
Slice
8Pixels
8Pixels
27
H.261 Compression
  • H.261 Encoding
  • 8x8 block, 16x16 macroblock
  • motion vector is used as a displacement vector to
    fetch a macroblock from the preceding frame to be
    used as a prediction.

28
MPEG-1 Compression
  • Motion estimation is also allowed over a greater
    range (up to /- 1023). Result in significant
    higher quality.
  • Forward predicted frames (called P frames) allow
    macroblocks predicted from past P frames or I
    frames or macroblocks coded from scratch.
  • I frames and P frames are used as past and future
    frames for Bi-directional predicted frames
    (called B frames).

29
MPEG Simplified
Delta
Key
Delta
Temporal Compression
Delta
Key
Motion Picture Experts Group
30
MPEG Sequence
31
MPEG Sequence
I Frames
10
1
32
MPEG Sequence
P Frames
10
7
4
1
33
MPEG Sequence
B Frames
10
9
8
7
6
5
4
3
2
1
34
MPEG Sequence
10
9
8
7
6
5
4
3
2
1
Sequence 1 x x 4 2 3 7 5 6 10
8 9
25
35
Video Traffic Pattern
KeyFrame
KeyFrame
Delta Frames
36
Video Effect of Delay
KeyFrame
KeyFrame
Delta Frames
37
Video Playback Point
Typical Delivery
Playback Point
Transmission Time
Unless Its Too Late
Application Buffers Data to Ensure Consistency
Distribution of Deliveries in Time
38
Compression Latency
lt45ms 200ms to 400ms 200ms to 500ms 400ms to
850ms
Motion JPEG MPEG-2 I Frame MPEG-2 I, P
Frames MPEG-2 I, B, P Frames
  • Varies by vendor
  • Network delay not included
  • Low speed network can increase delay significantly

39
Video Quality and Compression Data Rates
D1
MPEG-2 (IBP)
MPEG-2 (I)
Broadcast
Laser Disk
Motion JPEG
MPEG-2 (IP)
VHS
2
4
6
8
10
12
20
30
Bit Rate (Mbps)
27
40
Another Look from Mpeg.org
41
Motion JPEG vs. MPEG-2 Video Codecs
30K
25K
20K
MPEG-2
15K
Motion JPEG
10K
encoder/decoder2 ATM OC-3
encoder/decoder2 ATM OC-3
5K
42
Video Conferencing Standards
H.320 Room Systems
ISDN
WAN
H.323 LAN Systems
IP
LAN
43
Video Conferencing Standards
H.261
Video
G.711 G.722 G.728
Audio
ISDN H.320
T.120
Data
H.263 H.261
Video
G.711 G.723 G.722 G.728
LAN H.323
Audio
T.120
Data
30
44
H.261/H.263 Compression
  • Video conferencing specific
  • Lower resolution picture
  • Bandwidth optimization
  • Similar to MPEG

45
Audio Compression Standards
CompressRatio
BandwidthRequirement
Source BW
Method
G.721 G.722 CELP MPEG
2 1 3.54.6 1 13 1 311 1
32 Kbps 4864 Kbps 16 Kbps 64256 Kbps
64 Kbps 224 Kbps 64 Kbps 706 Kbps
46
T.120 Data Conferencing
  • File transfer
  • Image transfer
  • Applications plug in

47
ISDN and LAN Conferencing Gateway
Switched ISDN
GW
H.320/H.323 Gateway
48
Multipoint Conferencing
Switched ISDN
GW
MCU
Multipoint Control Unit
49
Adding Conferencing over a WAN Data Network
Intranet Internet
Switched ISDN
Gatekeeper and Proxy
Gatekeeper and Proxy
GW
MCU
Multimedia Conference Manager
50
Agenda
  • Applications
  • Technology
  • Network Planning
  • Examples

51
Network Planning
  • IP or ATM
  • Quality of Service
  • Bandwidth
  • Delay and Jitter
  • Multicast

52
IP Frames or ATM Cells?
IP
ATM
Ethernet(s) FDDI ATM
Transport
ATM Only
RSVP IP Precedence
VBR, CBR
QoS
Assured thru Routers
Guaranteed by Switches
Bandwidth
53
Bandwidth
54
Bandwidth and Load
Video ConferencingMPEG-1/MPEG-2 Video on
Demand
128 Kbps 384 Kbps 1 Mbps 6 Mbps 128 Kbps 512
Kbps 1 Mbps
100 pps 100 pps 85 pps 500 pps 11 pps 44 pps 88
pps
55
Delay and Jitter
Id like to talk about your proposal
What??!! I cant understand you!
56
Multicast
IGMP
Video Server
IGMP
IGMP
IGMP
57
Multicast with Pruning
IGMP
Video Server
IGMP
IGMP
IGMP
58
Agenda
  • Applications
  • Technology
  • Network Planning
  • Examples

59
Jefferson County Public Schools
IP/TV
IP/TV
IP/TV
IP/TV
IP/TV
60
Broadcast VideoBT MediaNet
Content Servers
Web Control
Cisco 7513 Headend Router
Management
FDDI
Video Feed
Cisco 4700 Headend Router
Cisco LS1010 ATM Switch
PC-Based MPEG-1 Encoding
Ethernet
622 Mbps ATM
155 Mbps ATM
Client PCs with MPEG-1 Decoding
Cisco 4500 Client Routers
Ethernet
61
Virginia Community College System
LS1010
ATM WAN
Cisco 7000
LS1010
Cisco 4700
Cell Mux
Cell Mux
LS1010
VTel
VTel
Cisco 4700
OC3c
Cell Mux
DS3
VTel
DS1
62
Scottish Metropolitan Videoconferencing Network
St. Andrews
ATM Network
Aberdeen
Edinburgh
MCU
Glasgow
Motion JPEG
63
Cisco Multimedia Training Network
H323 Station
P/GK
Proxy Gatekeeper
MCU
San Jose
384K
256K
1536K
Proxy Gatekeeper
Proxy Gatekeeper
Proxy Gatekeeper
P/GK
P/GK
P/GK
H323 Station
H323 Station
H323 Station
Irving
Salt Lake City
Denver
52
64
Summary
  • Applications
  • Technology
  • Video and Audio Compression
  • Conferencing Standards
  • Network Planning
  • Example Networks
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