Presentation is loading. Please wait.

Presentation is loading. Please wait.

7 Video.

Similar presentations


Presentation on theme: "7 Video."— Presentation transcript:

1 7 Video

2 Moving Pictures Vision is probably the most important among our senses
Persistence of vision allows images shown in rapid succession to produce the illusion of motion Motion obtained above about 15 to 20 images (or frames) per second At lower frame rates, individual frames are noticeable – “flickering” At higher frame rates, motion becomes smooth An image is worth a thousand words Each second of video has about 25 images Therefore, a second of video is worth about 25,000 words

3 Generate Moving Pictures
Video Use video camera to capture a sequence of frames Animation Generate each frame individually either by computer or by other means

4 Basics of Video Analog video is represented as a continuous (time varying) signal Digital video is represented as a sequence of digital images Digital video when duplicated will always retain the same original quality for an infinite amount of time Crisp, and the highest quality video Can be kept on DVD discs or CD-ROMs

5 Types of Color Video Signals
Component video Each component is sent as a separate video signal Three components: Y (luminance), U and V (color) Often use in production and post-production Best color reproduction Requires more bandwidth and good synchronization of the three components Composite video Combine three components into a signal Color component (U and V) is allocated half bandwidth as the luminance (Y) Some interference between the two signals is inevitable Often use in transmission

6 … Types of Color Video Signals
S-video (Separated video) Separates the luminance from the two color (total two signals) A compromise between component video and the composite video

7 Television Broadcast Standards
NTSC 1952 by National Television Standards Committee Used in: USA, Japan, Korea, and others 525 lines/frame (vertical resolution) Two passes to draw a single frame at a rate of 60Hz per second (interlacing) 30 frames/second Resolution approx. 640 x 480 (4:3 ratio) uses YIQ color model "Never The Same Color"

8 … Television Broadcast Standards
PAL Phase-Alternative Line system Western Europe except France 625 lines/frame Interlaced at 50Hz 25 frames/second uses YUV color model SECAM The Sequential Color and Memory system France and Eastern Europe 50Hz

9 … Television Broadcast Standards
HDTV High-Definition Television The Image of the new millennium screen picture quality similar to 35mm film, along with compact disc (CD) sound quality Some American television stations began transmitting digital HDTV in 1998 Format Wars (18 formats) active lines active aspect ratio frame rate horizontal pixels / progressive , 30 or 60 / interlaced / progressive , 30

10 … Television Broadcast Standards
Features Higher-resolution picture Wider picture Digital surround sound (Dolby Digital (AC-3) ) Additional data DTV stands for digital television All HDTV broadcasts in the United States would be digital

11 How Video Works When light reflected from an object passes through a video lens, that light is converted into a electronic signal by a special sensor called a charged-coupled device (CCD) The signal from the camera contains three channels of color (RGB) and synchronization pulses (sync) The video signal is recorded on magnetic tapes One or two channels of sound may also be recorded on the tape Video Cassette Recorder (VCR) Audio track Each strip represents information for one field of a frame Video track Control track

12 Video Color One luminance component Two chrominance components
Original TV was black and white Adding color had to be done in a compatible way NTSC: YIQ PAL: YUV In general: YUV and YCrCb used as terms

13 Recording Formats YUV: Luminance, Hue, Saturation 4:1:1 YUV format
R B G Luminance (Y) Hue (U) Saturation (V) 4:1:1 YUV format 7-bit Y + U & V data are averaged for 4 pixels S-VHS Video (s-video) video signal with enhanced quality used for recording Color and luminance information are kept on two separate tracks 4-pin DIN connectors Oriented toward consumer with gaining acceptance among lower-end broadcaster 1 Ground 2 Ground 3 Intensity (Luminance) 4 Color (Chrominance)

14 … Recording Formats Video recording format Component (YUV)
VHS: Japan Victor Company VHS-C: VHS-compact used in camcorders Component (YUV) Laying the signal on the tape in three channels Four channels of audio Sony Betacam SP Component Digital The signal is converted to digital information and stored as bytes Can make unlimited copies without loss of quality Digital Betacam High price tag

15 Video Hardware Resolution
The lens used and the number, size, and quality of the CCDs determine the resolution Resolution (in horizontal lines) Video Type Resolution 8 mm VHS S-VHS Hi Beta-SP 550 MII (Panasonic) 550 Broadcast-quality 1000 Hi-8 is the most widely accepted format used for industrial and corporate video communication

16 Digital Video A video sequence consists of a number of frames
Each frame is a single image produced by digitizing time-varying signal generated by video camera CCIR 601 is a standard established for digitizing NTSC and PAL signals specifies the image format, and coding for digital television signals It uses Y'CBCR color with 4:2:2 chrominance sub-sampling. The data rate is 166Mbits per sec

17 … Digital Video Think about the size of the uncompressed digital video
NTSC video format Bitmapped images for video frame 640  480 pixels with 24-bit color = 0.9 MB/frame 30 frames per second 900 kb/frame  30 frames/sec = 26 MB/sec 60 seconds per minute 26 MB/sec  60 secs/minute = 1,600 MB/minute Strains on current processing, storage and data transmission !

18 Create Digital Video Get analog/digital video signal from
video camera video tape recorder (VTR) broadcast signal Digitize analog video & compress it

19 Digitizing Analog Video
In computer Video capture card Convert analog to digital & compress Can also decompress & convert digital to analog Compress through Video capture card (hardware codec) Software (software codec)

20 Digitizing Analog Video
In camera Digitize and compress using circuitry inside camera Transfer digitized signal from camera to computer through IEEE 1394 interface (FireWire): 400 Mb/sec USB: 12Mb/sec(version 1.1) ~ 480 Mb/sec(version 2.0)

21 Digitize in Computer v.s. Camera
Digitize in camera Advantage Digital signals are resistant to corruption when transmitted down cables and stored on tape Disadvantage User has no control between picture quality and data rate (file size)

22 Digital Video Camera DV camcorders store up to 90 minutes of digital video on small DV cartridges VHS tape format Encoded digitally Digital8 camcorders store digital video on Hi-8 tapes and can also play Hi-8 and 8mm tapes Digital8 cameras are usually larger than DV cameras DVD Camcorder Video Resolution The vertical resolution of a digital video image is determined by the number of scan lines in the image The horizontal resolution is the rate at which the moving beam can turn on and off to paint "dots" of color on the screen

23 Better image quality than previous analog formats
DV S-VHS/Hi8 8mm/VHS Lines of Resolution 500 400 240 Color Signal Component S-Video Composite Signal-to-Noise 60 45-46 43-45

24 Video Tape Formats Tape Analogue Digital DV DV (MiniDV) DV CAM DVPRO
Recording Format  Analogue  Digital DV DV (MiniDV) DV CAM DVPRO 8MM Video 8 Hi 8  Digital 8 VHS S-VHS D9 MII D3 Beta Betamax Betacam SP Beta SX Digibeta 24 P Other U'matic C - format (open reel) D1

25 Videotape & Digital Recorders/Players

26 Digital Cameras

27 Video Capture Cards Pinnacle Systems Capture DV series TARGA series
ViewCast Osprey series Capture to disk to memory full-screen drop frames non-real-time step-frame

28 Film & Video Editing Traditional Timecode VHS SMPTE timecode
Hours, minutes, seconds, frames VHS Two copying operations is to produce serious loss of quality Constructed linearly

29 Video Production Pre-production Production involves shooting the scene
script writing storyboarding production schedule for shooting the scene Production involves shooting the scene Post Production editing the best scenes into the final video program rough cut final cut

30 Video Time Time base frame rate how time is divided in your project
time base of 30 means each second is divided into 30 units frame rate number of frames per second frame rate of 30 means the camera records the scene every 1/30th of a second there are 30 frames per second

31 Video Time Time code how the frames are counted
SMPTE time code (society of motion pictures and tv engineers) hh:mm:ss:frames 00:05:31: minutes, 31 seconds, 15 frames

32 Steps Import clips Editing Compositing Reverse shot Transitions
still image audio video (capture) Editing Compositing Reverse shot Conversation between two people Transitions Titles/motion Export

33 Digital Video Editing Analog editing systems
Avid video editing software Avid Xpress DV Adobe Premiere After Effects Microsoft Windows Movie Maker Pinnacle Systems ReelTime Digital video editing software conversion and compression capture editing transition effects composition audio editing motion path control text editing

34 … Digital Video Editing
Random access Non-destructive Premiere The standard mid-range video editing application Three main windows Project, timeline, monitor Timelines Have several video tracks Transitions Cuts and Transitions In a cut, two clips are butted In transitions, two clips overlap Image processing is required to construct transitional frames

35 Digital Video Post-production
Over- or under-exposed, out of focus, color cast, digital artifacts Provide image manipulation programs Adjust level, sharpen, blur The same correction may be needed for every frame, so the levels can be set for the first frame and the adjustment will be applied to as many frames as user specifies. If light fades during a sequence, it will necessary to increase the brightness gradually to compensate. Apply a suitable correction to each frame and allow their values at intermediate frames to be interpolated Varying parameter values over time

36 Keying Selecting transparent areas Blue screening Select explicitly
Chroma keying: any color Alpha channel Luma keying: a brightness threshold is used to determine which areas are transparent Select explicitly Create mask In film and video, mask is called matte Matte out: removing unwanted elements Split-screen effects Alpha channel created in other application

37 Track matte Chroma keying and luma keying
Color and brightness changes between frames Use a sequence of masks as matte Separate video track: track matte Track matte Painstaking by hand Generated from a single still image applying simple geometrical transformations over time to create a varying sequence of mattes

38 Adobe After Effects Apply a filter to a clip and vary it over time
A wide range of controls for the filter’s parameters Premiere: parameter values are interpolated linearly between key frames After effect: interpolation can use Bezier curves

39 Preparing Video for Multimedia Delivery
Frame size, frame rate, color depth, image quality People sit close to monitors, so a large picture is not necessary Higher frame rates are needed to eliminate flicker only if display is refreshed at the same rate. Computer monitors are refreshed at a much higher rate from VRAM. Limiting colors Not all codecs support

40 The Bits and Bytes of Digital Video
Data rates of digital video depends on Frame rate: Frames per second (TV/HDTV/DVD uses 24-30fps) Frame dimensions: The width and height of the image expressed in number of pixels TV: 640 x 480 pixels DVD: 720 x 576 pixels HDTV: 1,920 x 1,080 pixels Pixel depth: The number of bits per pixel TV/DVD: 16 bits HDTV: 24 bits

41 … The Bits and Bytes of Digital Video
If we have DVD quality video, the uncompressed data stream would be 720 x 576 pixels * 16 bits/pixel * 30 fps = 199 Mbits/second HDTV quality requires significantly more 1,920 x 1,080 pixels * 24 bits/pixel * 30 fps = 1,492 Mbits/second Either way, this is huge amount of data

42 Video Formats and Compression
7.2 Video Video Formats and Compression

43 Video Formats VCD (Video Compact Disc) DVD (Digital Video Disc)
A compact disc with full motion video on it Once converted to MPEG (Motion Picture Experts Group), it can be put onto a CD Has capability to hold MB of quality video (approximately 74 minutes) Can be played on most DVD players, Computers with a CD-ROM drive, Sony Playstations, Sega Dreamcasts, etc. DVD (Digital Video Disc) A digital video disc that can store up to 2 hours of high quality video 4.7 gigabytes of information Played on DVD players and computers with DVD-ROM

44 Video Formats Streaming video:
AVI MOV RM WMV MPEG Other popular multimedia formats (not pure video formats): Shockwave Flash

45 Video Throughput The filesize (download time) that a video requires is dependent on: Window size (e.g. 640x480) Frames per second (e.g. 30 fps) Compression rate Inversely impacts image quality Quality also depends on compression algorithm

46 Video Throughput If you thought we needed compression with audio…
At 24bbp, 640x480, 30fps (which would produce a fairly standard looking TV video) it would take about 100GB to store an hour of uncompressed video

47 Video Throughput Videos can be fully downloaded to your computer and then played On formats that support streaming you can start watching the video before it is done loading Or videos can be played off a “streaming server” and sent to your computer via a special protocol You don’t get a copy of the file on your system

48 Video Throughput Because the streaming method is quite popular on the internet, video throughput is also often stated in terms of the speed of your connection Your computer can received (and play) X bits per second of video information So the actual size of the video file is not as important as the bandwidth required to play the video MPEG2 videos require a connection that can handle 100Mbits/second in order to show the video in real-time (without large buffering pauses in the middle of the movie)

49 AVI Microsoft’s Audio Video Interleave
The “Interleave” in the name is associated with the fact that packets of Video / image data are interwoven with audio data One of the first video formats on the PC Released with Windows 3.1 (early 90s) Considered an “old” format Compression is poor (long download times) Image quality is poor Cannot be streamed Makes is a bad choice for the web

50 MOV QuickTime Movie Was one of the first multitrack formats
Developed by Apple Was one of the first multitrack formats Can have different sound tracks aimed at different languages and then only using one of them Also released in the early 90s Compression is average (average bandwidth needed) Image quality is good Can be streamed Also useful as an editing format -- not just for delivery

51 RM Real Media Constructed specifically for the purpose of streaming
Developed by Real Networks Constructed specifically for the purpose of streaming Compression is good (low bandwidth needed) Image quality is low Was designed for low bitrates so they decided to sacrifice image quality If using a higher bandwidth, one would probably want to use another format that has better image quality (like MOV)

52 WMV Windows Media Video Designed to compete directly with RM
Developed by Microsoft Designed to compete directly with RM Compression is excellent (very low bandwidth needed) Image quality is somewhat grainy in comparison to QuickTime But the bitrates are also much lower Supports Streaming

53 MPEG The MPEG compression algorithm is quite similar to JPEG
MPEGs support streaming

54 3 Ways to Attach to Web Pages
<A> tag Similar to a normal link, but the href is the video file Pops up an external player to play the video <EMBED> tag Embeds to player in the web page This has been the most popular of the embedding methods <OBJECT> tag Embeds the player in the web page This is the embedding standard of the W3C Note: All these methods require a video plug-in to be installed on the system

55 How do I embed video in a page?
<HTML> <HEAD> <TITLE>Embedded Windows Media Player 7 Control</TITLE> </HEAD> <BODY> <object id="MediaPlayer1" CLASSID="CLSID:22d6f312-b0f6-11d0-94ab-0080c74c7e95" type="application/x-oleobject" width="280" height="256"> <param name="fileName" value="a1.wmv"> <PARAM name="autoStart" value=“false"> <param name="showControls" value="true"> <param name="Volume" value="-450"> </OBJECT> </BODY> </HTML>

56 How do I embed video in a page?
<HTML> <HEAD> <TITLE>Embedded Windows Media Player 7 Control</TITLE> </HEAD> <BODY> <OBJECT ID="Player" width="320" height="240" CLASSID="CLSID:6BF52A52-394A-11d3-B153-00C04F79FAA6"> <PARAM name="autoStart" value="True"> <PARAM name="URL" value=" </OBJECT> </BODY> </HTML> WebServer/MyFile.wvx (Windows Media Metafile) : <ASX version = "3.0"> <Entry> <Ref href = "mms://WindowsMediaServer/MyFile.wmv" /> </Entry> </ASX>

57 How do I embed video in a page?
<object width="320" height="260" classid="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B" codebase=" > <param name="src" value="mymovie.mp2"> <param name="controller" value="true"> <param name="autoplay" value="true"> <!-- Backwards Compatibility --> <embed src="mymovie.mp2" width="320" height="260" autoplay="true" controller="true" pluginspage=" </embed> </object> <a href="mymovie.mp2">Can't see the video above? Click here to download our video file, then launch it from your desktop.</a>

58 Audio/Video Player Plug-Ins
There are 3 main players used today: Windows Media Player Microsoft Real Player Real Networks QuickTime Player Apple

59 Video Codecs Codec (compression/decompression) Software codecs
(encoding/decoding) Software codecs Hardware-assisted codecs Installable Compression Manager (ICM) Audio Compression Manager (ACM) Techniques interframe analysis Intraframe analysis discrete cosine transform (DCT) vector quantization (VQ) Code book lossy compression

60 Video Codecs Software-only codecs (all uses VQ)
Cinepak by Radius Indeo by Intel Video 1 by Microsoft key frames delta frames Codecs can either be symmetric or asymmetric Real time applications

61 MPEG ISO Motion Picture Experts Group
Goal: bit-rate reduction for storage and transmission Produces VCR-quality at full-motion (30 fps) rates Hardware-assisted codec Can achieve a compression ratio of up to 200:1 (discard 99.5% of the information) MPEG-1 The standard for storage and retrieval of moving pictures and audio on storage media (approved 1992) Can deliver 1.2 Mbps of video Full-motion, full screen, VHS quality from a variety of sources (352  240 pixels at 30 frames per second) application: VCD (video compact disk)

62 … MPEG MPEG-2 MPEG-3 MPEG-4 MPEG-7
The standard for digital television (approved 1994) 3 to 15 Mbps at 720  480 pixels Serves the requirements of the broadcast industry MPEG-1 is a subset of MPEG-2, any MPEG-2 decoder will be able to decode MPEG-1 video application: DVD, HDTV MPEG-3 Targets HDTV and was dropped because HDTV became part of the MPEG-2 standard MPEG-4 The standard targets low bit rate coding of audio-visual programs (approved 1999) 10 frames/sec using 64Kbps bandwidth application: Internet, cable TV, virtual studio, etc. MPEG-7 The standard for multimedia information search, filtering, management, and processing application: Internet, video search engine, digital library

63 … MPEG MPEG is the standard for decoders
The type and quality of encoders Encoders: service bureaus, real-time cards, software-only

64 How MPEG Works JPEG Joint Photographic Experts Group
Example 640 bit RGB image Separate matrices for Y, I, Q, value (NTSC) Square blocks of 44 are averaged for I and Q to reduce them to 320240 Step 1 (Block Preparation) 128 is subtracted from each element in the three matrices, 0 becomes in the middle of the range Each matrix is divided into 88 blocks ( = 7200 blocks) Step 2 (Discrete Cosine Transformation) DCT DCT to each block DCT coefficients, (0, 0) is the average value of the block Each pixels DCT is calculated from all other pixel values The top left pixel in a block is taken as the datum for the block DCT's to the right of the datum are increasingly higher horizontal spatial freqs DCT's below are higher vertical spatial frequencies The smaller the difference between one pixel and its adjacent pixels, the smaller its DCT value

65 … How MPEG Works Spatial redundancy: pixel coding using the DCT
Lossless

66 … How MPEG Works Step 3 (Quantization)
Less important coefficients are removed Divide each of the coefficients in the 88 matrix by a weight from a table Lossy transformation The higher the DCT frequency, the higher the Quant Matrix value its divided by. This makes many coefficients go to zero Step 4 (Differential Quantization) Reduce the (0, 0) value of each each block to the difference from the corresponding element in the previous block. Change slowly because they are the average of their blocks The (0, 0) value is called the DC component, other values are the AC components Step 5 (Run-length Encoding) Liberalize the 64 elements and apply run-length encoding to the list using zig-zag scanning pattern to group zeros together Step 6 (Statistical Output Encoding) Huffman encode 20:1 compression or better, symmetric algorithm

67 … How MPEG Works MPEG-1 Compression Video and audio compression
Spatial and temporal redundancies Compress each frame using JPEG Consecutive frames are often almost identical 2 – 3 sec per scene Four kinds of frames I (Intracoded) frames Self-contained JPEG-encoded still pictures Inserted once or twice per second P (Predictive) frames Code interframe differences Macroblocks (1616 in L) and (88 in C) Difference from a previous macroblock Encoded macroblocks in JPEG B (Bidirectional) frames Difference with last and next frame D (DC-coded) frames Block averages for fast forward

68 … How MPEG Works Inter-frame prediction & motion estimation

69 … How MPEG Works Putting it all together

70 7.3 Video Microsoft Solution

71 Create Movie File Record your movie using a DV
Use Video Editing Software to capture the movie from DV to computer (e.g. Movie Maker) Edit the movie. E.g. Transition effect, add audio, etc. Save the movie as WMV format

72 Publish your Movie Prepare WMV files and put them in a directory on the Server Using Windows Media Services to publish the WMV files

73 What Is Windows Media Technologies?
Stream multimedia content across the Internet and intranets

74 Windows Media Services
Consists of a set of services that stream audio, video, and other data files to clients. Windows Media Services supports two streaming protocols Hypertext Transfer Protocol (HTTP) Microsoft Media Server protocol (MMS) Can deliver the streams as either unicast or multicast transmissions

75 Windows Media Services

76 Windows Media Tools It builds or converts live media into Windows Media streams or .wmv/.asf files. Content tools include Windows Media Author and Windows Media Encoder

77 Windows Media Tools

78 Benefits Delivers highest quality audio and video across network
Windows Media Technologies offers integration with most Microsoft Products Windows Media Services is Free of Charge Windows Media Tool is Free of Charge Windows Media Player is Free of Charge Movie Maker is Free of Charge

79 7.4 Video Applications

80 Video Conferencing Desktop Video Conferencing (DTVC)
Communications Infrastructure LAN DSL Modems (POTS) International Telecommunication Union (ITU) H.320 ISDN standard H.261 is the video code Multipoint Control Units (MCU) Multiple conference participants H.323 LAN standard H.263 is the video code Interoperability

81 … Video Conferencing Products Applications Disadvantages Advantages
Computer with codec compliant or video capture card Miniature video camera Microphone Intel ProShare PictureTel Applications Medical systems Distance learning Banking Management Disadvantages Information overload Advantages Social effects

82 Video on Demand Video Servers
A normal movie occupies roughly 4 GB when compressed in MPEG-2 ATM Distribution Network Mbone (Multicast Backbone) Internet radio and TV No standards yet

83 Reading List Text Chapter 5
Check:


Download ppt "7 Video."

Similar presentations


Ads by Google