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Presentation on theme: "LECTURE 8: DIGITAL VIDEO TECHNOLOGY EVI INDRIASARI MANSOR Tel ext: 1741 1."— Presentation transcript:


2 Outline  Using video  How video works?  Broadcast video standards  Analog video  Digital video  Video recording and tape formats  Video editing technology  Optimizing video files for CD-ROM 2

3 Learning Outcomes  Summarize the implications of using digital video in multimedia  Illustrate video recording and its relation to multimedia production  Prepare digital video and images for conversion to television 3

4 Using video 4  Video is an excellent for delivering multimedia  Video places the highest performance demand on computer and its memory and storage  Digital video has replaced analog as the method of choice for making and delivering video for multimedia

5 Using video (cont) 5  Digital video device produces excellent finished products at a fraction of the cost of analog  Digital video eliminates the image-degrading analog-to- digital conversion  Many digital video sources exist, but getting the rights can be difficult, time-consuming, and expensive

6 How video works 6  Light reflected from an object through the camera’s lens is converted into electronic signal by charge-coupled device (CCD)  This electronic signal contains three channels of color information and synchronization pulses (sync)  Several video standards exist that deal with the amount of separation between the components of the signal

7 How video works (cont) 7

8 Broadcast video standards 8  National Television Standards Committee (NTSC): These standards define a method for encoding information into electronic signal that creates a television picture It has screen resolution of 525 horizontal scan lines and a scan rate of frames per second

9 Broadcast video standards (cont) 9  Phase Alternate Line (PAL) and Sequential Color and Memory (SECAM):  PAL has a screen resolution of 625 horizontal lines and a scan rate of 25 frames per second  SECAM has a screen resolution of 625 horizontal lines and is a 50 Hz system  SECAM differs from NTSC and PAL color systems in its basic technology and broadcast method

10 Your TV  Each frame is a single picture When played rapidly one after another, it gives the illusion of motion Everybody knows that, right?  Take NTSC as an example: The overall signal has 525 lines ( only 480 are actually visible, the extra 45 gives the TV time to reset the electronic beam to the top of the screen ) A single frame is ‘painted’ on the screen in an INTERLACED fashion (line-by-line) Firstly: Odd-numbered lines (i.e. 1,3,5, …, 479) – takes ~1/60 seconds Then: Even-numbered lines (i.e. 2,4,6, …, 480) – takes ~1/60 seconds You might notice after this seeing 480i (or 525i). This means 480- interlaced! [Later you’ll see 480p? Apa itu?]  BTW, all the above is called Standard Definition TV – Digital TV format which is 480i

11 Your TV... As it gets bigger   When screens get bigger, scan lines during interlacing become visible. This produces ‘jaggedies’… No body likes ‘jaggedies’… (19” vs 60” example)  Solution: PROGRESSIVE SCANNING!!! ALL the lines from are ‘painted’ on the screen at just one single pass!!! Feasible with today’s technology since coding and transfer speeds have dramatically improved This called for a new name… Henceforth – Enhanced Definition TV was born [more of a marketing gimmick though… but hey, who really cares?] 480p, 525p

12 EDTV’s advantage  Most TVs cannot handle 480p   And what if we’re still getting interlaced signals? Won’t a progressive scan system be a waste, then?  EDTV can take interlaced signals, and pass them through a DEINTERLACER/LINE-DOUBLER  1 st : All the odd and even numbered scan lines are combined. This also improves smoother (‘jaggedies’ are smoothed out)  525i is converted to 480p here BTW, all of this is also 1/60 second  2 nd : The next 1/60 is used to feed the frame a second time! Increases brightness and stability of the frame Eliminates or reduces jaggedies, giving a cleaner picture 12

13 HDTV (High Definition TV)  What HDTV does?  1. Increases number of scan lines  2. Widens aspect ration from 4:3 to 16:9 ( baru la mcm wayang sikit, ye dok? )  Well.. That’s basically it… Comes with the same variation 1080i – interlaced. However, since there are so many lines, the jaggedies aren’t that visible (illusion of better quality!) 1080p – progressive scanning… but, do you really need it? … You yourself will be the decider (bionic eyes vs. normal human eyes)  Marketing hype however, will tell you otherwise  Full HD – max resolution possible (1920X1080)  HD-ready – Meaning ure non-HD TV can be connected to an HD external box if you want to received HD signals  HD – Takes the full HD signal and resizes it down a bit 13

14 HDTV (High Definition TV)  Alternatively, the 720-lines progressive scan or 720p is also available  However, some interlacing artifacts might still be visible at 1080i  Therefore, video with rapid motion would not be suitable at 1080i, and would be nicer to 720p  For drama swasta (soap operas), 1080i would be nice

15 SDTV, EDTV and HDTV side-by-side

16 The different TV resolutions

17 Analog video 17  Video information that is stored using television video signals, film, videotape or other non-computer media  Each frame is represented by a fluctuating voltage signal known as an analogue wave form or composite video

18 Analog video (cont) 18  Composite analogue video has all the video components:  brightness, colour and synchronization  Then combined into one signal for delivery  Example : traditional television  Problems: colour blending, low clarity, high generation lost, difficult to edit

19 Analog video (cont) 19  Video color:  Television sets use composite input. Hence colors are less pure and less accurate than computers using RGB component  NTSC television uses a limited color palette and restricted luminance (brightness) levels and black levels.  Some colors generated by a computer that display fine on a RGB monitor may be illegal for display on a NTSC TV.  While producing a multimedia project, consider whether it will be played on a RGB monitor or a conventional television set.

20 Analog video (cont) 20  Interlacing effects:  In television, the electron beam makes two passes on the screen while drawing a single video frame  It first lays down all the odd-numbered lines, and then all the even-numbered lines, hence they are interlaced  While capturing images from a video signal, they can be filtered through a de-interlacing filter provided by image-editing applications

21 Analog video (cont) 21  Text and titles for television and taking care of analog tapes:  Titles for video productions can be created with an analog character generator.  Computers can create titles digitally using video and image-editing software.  New tapes should always be fast-forwarded to the end and then rewound, to ensure even tape tension.

22 Digital video 22  Video clip stored on any mass-storage device can be played back on a computer’s monitor without special hardware  Setting up a production environment for making digital video, requires some hardware specifications  Some specifications include computer with FireWire connection and cables, fast processor, plenty of RAM, fast and big hard disk

23 Digital video (cont) 23  Digital video architecture  Digital video architecture consists of a format for encoding and playing back video files by a computer  Architecture includes a player that can recognize and play files created for that format

24 Digital video (cont) 24  Digital video compression  Digital video compression schemes or codecs is the algorithm used to compress (code) a video for delivery  The codec then decodes the compressed video in real-time for fast playback  Streaming audio and video starts playback as soon as enough data has transferred to the user’s computer to sustain this playback

25 Digital video (cont) 25  Digital video compression (cont)  MPEG is a real-time video compression algorithm  MPEG-4 includes numerous multimedia capabilities and is a preferred standard  MPEG-7 (or Multimedia Content Description Interface) integrates information about motion video elements with their use [NOT A COMPRESSION STANDARD]

26 Digital video (cont) 26  Digital video compression (cont)  The video compression/decompression programs are used so that video can fit on a single CD and the speed of transferring video from a CD to the computer can be increased  Let us say that a sequence of 25fps video is about 25MB  CD-ROM transfer rate is calculated as follows: 1X= 150KB per second 10X=1.5 MB per second 100X= 15 MB per second  To overcome large video size, CODECS were developed

27 Digital video (cont) 27 Compresses when saved CODEC File format used such as: Avi, Mpeg, Mov Decompresses when needed for display  Digital video compression (cont)

28 Digital video (cont) 28  Digital video compression (cont)  Digital video compression schemes or codecs is the algorithm used to compress (code) a video for delivery  The codec then decodes the compressed video in real-time for fast playback  Streaming audio and video starts playback as soon as enough data has transferred to the user’s computer to sustain this playback FULL VIDEO Taken from the CD into memory buffer DISPLAY ON SCREEN MEMORY BUFFER

29 Digital video (cont) 29  Digital video compression (cont)  Two types of COMPRESSION: Lossless compression preserves the exact image throughout the compression and decompression process e.g.,: text images is to identify repeating words and assign them a code

30 Digital video (cont) 30  Digital video compression (cont)  Lossy compression Eliminates some of the data in the image and therefore provides greater compression ratios than lossless compression Applied to video because some drop in the quality is not noticeable in moving images

31 Digital video (cont) 31  Digital video compression (cont)  Two types of CODEC (lossy): Spatial compression Digital compression of video data that compresses the size of the video file by compressing the image data of each frame Compression is done by removing redundancy from data in the same frame

32 Digital video (cont) 32  Digital video compression (cont) Temporal compression Digital compression of video data that uses similarities of sequential frames over time to determine and store only the image data that differs from frame to frame Compression is done by removing similarity between successive video frames

33 Digital video (cont) 33  Digital video compression (cont)  Flavors of file formats brand to choose: Microsoft’s AVI format QuickTime MPEG Div-X Wmv (Windows Media Video)

34 Digital video (cont) 34  Digital video compression (cont)  Standards have been established for compression programs, including JPEG (Joint Photographic Experts Group) and MPEG (Motion Picture Experts Group)

35 Digital video (cont) 35  Digital video compression (cont)  JPEG (spatial) Often areas of an image (especially backgrounds) contain similar information JPEG compression identifies these area and stores them as blocks of pixels instead of pixel by pixel reducing the amount of information needed to store the image These program reduce the file size of graphic images by eliminating redundant information

36 Digital video (cont) 36

37 Digital video (cont) 37  Digital video compression (cont)  MPEG (temporal) The changes in the image from frame to frame Key frames are identified every few frames the changes that occur from key frame Provide greater compression ratios than JPEG Initially, it requires extra hardware for multimedia

38 Digital video (cont) 38  Digital video compression (cont)  MPEG (temporal) – (cont)  MPEG – real-time video compression algorithm  MPEG-4 includes numerous multimedia capabilities and is a preferred standard  MPEG-7 (or Multimedia Content Description Interface) integrates information about motion video elements with their use

39 MPEG compression  On how MPEG compression works, please view these videos    Skip the technical (maths) parts in the second video, instead focus on the concept of how things are done 39

40 Video recording and tape formats 40  File size and formats  There is an important consideration: File size in digitized video which included 1. Frame rate 2. Image size 3. Color depth

41 Video recording and tape formats (cont) 41  File size and formats (cont)  Frame Rate animation is an illusion caused by the rapid display of still images. television and movies play at 30 fps but acceptable playback can be achieved with 15 fps [Show VirtualDub Example]

42 Video recording and tape formats (cont) 42  File size and formats (cont)  Image Size A standard full screen resolution is 640x480 pixels but to safe storing space a video with 320x240 for a computer display is still acceptable New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080, p60,HDTV 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second

43 Digital video (cont) 43

44 Video recording and tape formats (cont) 44  File size and formats (cont)  Color Depth The quality of video is dependent on the color quality (related to the number of colors) for each bitmap in the frame sequence

45 Video recording and tape formats (cont) 45  File size and formats (cont)  The color depth below 256 colors is poorer-quality image  The frame rate to below 15 fps causes a noticeable and distracting jerkiness that unacceptable  Changing the image size and compressing the file therefore become primary ways of reducing file size 24 bit 8 bit (256 colors)16 bit

46 Video Compression Digitizing full-motion video in the computer requires transfer of ENORMOUS amounts of data in a short period of time  Consider this:  Frame rate = 25 fps (FR)  Color depth of each frame = 65,536 colors (thus a bit depth of 16-bits) (BD)  Frame size = 320 X 240 pixel dimension (D) FORMULA FOR VIDEO SIZE (per second) = FR X BD X D For this particular video… the UNCOMPRESSED video would be:  25 X 16 X (320 X 240)  30,720,000 bits / second  3.67 Mbytes / second This is just for 1-SECOND!!! And we’re not even talking about AUDIO yet  A 1-hour video would thus be  3.67 X 60 X 60 = 13,212 Mbytes Which is equals to = 12.9 Gigabytes … Now… try fitting that onto a CD 

47 Video Compression A simpler example with less big numbers Consider this:  Frame rate = 2 fps … meaning, in every second of the video, TWO pictures are being displayed continuously (FR)  Color depth of each frame = 4 colors (thus a bit depth of 2-bits) … meaning that each frame of the video has a maximum of 4 colors (BD)  Frame size = 320 X 240 pixel dimension … each frame’s size (D) FORMULA FOR VIDEO SIZE (per second) = FR X BD X D For this particular video… the UNCOMPRESSED video would be:  2 X 4 X (320 X 240)  614,400 bits / second  Mbytes / second  614,400 / 8 / 1024 / 1024 As you can see… this rate is very2 acceptable due to the small data rate BUT! Your video is going to be very2 UN-colorful :P If there exists such a word… Not to mention it being very2 flicker-y…

48 Video about compression 48 The basics of Video CompressionThe basics of Video Compression MPEG videoMPEG video Codecs and Containers (formats) – 1Codecs and Containers (formats) – 1 Codecs and Containers (formats) – 2Codecs and Containers (formats) – 2

49 Video editing technology 49  Linear  It plays end to end in one direction, usually pertains to videotape editing specifically the editing of linear tape segments into one final master tape

50 Video editing technology (cont) 50  Non-Linear  Refers to the editing of disk-based digital video.  The software provides an on screen map of what the final video sequences should look like incorporating the edits, splices, special effects, transitions and sound tracks.

51 Video editing technology (cont) 51  Special effects  Transitions Such as fading, wiping, splatters, scrolling, stipple and many more are available by simply dragging and dropping that transition between the two video clips

52 Video editing technology (cont) 52  Special effects (cont)  Superimposing The ability to superimpose one clip over another is a valuable technique The technique of green screening is identical except that the color green is used for the screen and later digitally removed The blue screen and green screen superimposing are just two of the superimposing technique available

53 Video editing technology 53 Superimposing

54 Video editing technology (cont) 54  Video digitizing  Digital video is often used to capture content from movies and television to be used in multimedia  A video source (video camera,VCR, TV or videodisc) is connected to a video capture card in a computer  As the video source is played, the analog signal is sent to the video card and converted into a digital file (including sound from the video)

55 Video editing technology (cont) 55 VCR Video Overlay Board / Video Capture Card PC  Video digitizing (cont)  mana-nak.html

56 Video editing technology (cont) 56  Video digitizing (cont) Analogue signal from VCR Converted to DIGITAL by VIDEO CAPTURE CARD The converted signal is entered inside a computer Signal is processed Video is edited using video editing software software

57 Video editing technology (cont) 57  Video editing software  Incorporating transitions such as dissolves, wipes and spin  Superimposing titles and animating them, such as fly- in logo  Applying special effects to various images, such as twisting, zooming, rotating and distorting  Synchronizing sound with the video  Apply filters that control color balance, brightness & contrast, blurring, distortions and morphing

58 Advantage of using video 58  Captures interest  Increase retention  Clarifies complex physical actions and relationships  Can incorporate other media

59 Disadvantage of using video 59  Is expensive to produce  Requires extensive memory and storage  Requires special equipment  Does not effectively illustrate abstract concepts and static situations

60 Shooting and editing video 60  Import video and sound at the highest resolution and with the least amount of compression possible  Resolution should be reduced and footage must be compressed later according to the requirements  A steady shooting platform should always be used

61 Shooting and editing video (cont) 61  Good and even lighting is extremely important  Blue screen in digital video editing applications is a popular technique for making multimedia  Wide panoramic shots and camera motion should be avoided when shooting for a small computer window on CD-ROM or the Web

62 Optimizing video files for CD-ROM  CD-ROMs provide an excellent distribution medium for computer-based video  When preparing video for CD-ROM distribution, interleave the audio track(s) with the video track  Key frames should be used every 10 to 15 frames and the size of the video window must be kept small  The Sorenson codec is optimized for CD-ROM playback 62

63 Summary  Digital video method is used for making and delivering video for multimedia  Compression techniques help to reduce the file sizes to more manageable levels  Two types of compression lossless and lossy  Standards for compression program are JPEG and MPEG 63


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