VIDEOPengantar Multimedia

Definition: Video is an electronic medium for the recording,

copying, playback, broadcasting, and display of moving visual media.

Application : Entertainment: broadcast TV, VCR/DVD recordingInterpersonal: video telephony, video conferencingInteractive: windows

History: First developed for

CRT monitors1951 = first VTR =

$50,000, tape = $300.

1971 = Sony, VCR

Slim CRT

DigitalDVD – 1997, Blu-ray – 2006.Computers (tapeless production)Digital broadcastingDigital televisionDigital Film

Interlace – Progressive

Interlace (i)The interlace method was developed for TV broadcasting

because the allotted bandwidth for TV channels in the 1940s was not sufficient to transmit 60 full frames per second. It was decided that interlacing with 60 half frames was visually better than 30 non-interlaced full frames.

Progressive (p) Each refresh period updates all scan lines in

each frame in sequence.Interlaced signal in progressive monitor may

cause “flicker” if there is no de-interlace. Better image quality. De-interlace cannot produce as high quality of

progressive.

Aspect RatioDescribes the dimensions of video screens and

video picture elements. TV 4:3 (1.33:1), HDTV 16:9 (1.78:1)Uncommon H is taller than W, (3:4) (portrait

mode). Usually by physically rotating the display device 90 degrees from the normal position.

9:16 is technically possible but very rare.

Application : Entertainment: broadcast TV, VCR/DVD

recordingInterpersonal: video telephony, video

conferencingInteractive: windows

Digital Video Representation of moving visual images in the form of

encoded digital data. Digital video comprises a series of bitmap digital

images displayed in rapid succession at a constant rate (frame). Bitmap images = consist of pixels.

Pixels only have one property = color. Eg 640 x 480, 24bit color, 25 fps:

pixels per frame = 640 * 480 = 307,200 bits per frame = 307,200 * 24 = 7,372,800 = 7.37Mbits bit rate (BR) = 7.37 * 25 = 184.25Mbits/sec video size = 184Mbits/sec * 3600sec = 662,400Mbits =

82,800Mbytes = 82.8Gbytes

CODEC Compressor – Decompressor Convert uncompressed data (video) to

compressed format. Typically lossy – lower quality than the

original. Lossless = much bigger size. Eg : Audio CD – FLAC (500-600 : 400-500). The MSU Lossless Video Codec is a video

codec developed by the Graphics & Media Lab Video Group of Moscow State University. (Obsolete as of 23 Nov 2011).

Video Compression Basic – minimizing video redundancy in

video data. 2 most common compression:

Spatial (Intraframe / JPEG)Temporal (Interframe / MPEG, motion JPEG)

Spatial compression – only applies to individual frames (each bitmap).BMP – JPG (Chroma subsampling)Images are split into 8 x 8 pixels = macroblocks.

Higher compression – more artifacts. Images with solid color compressed more than complex

color. Temporal compression

More complex, images are grouped into P<redictive>, I<ntra coded>, and B<I predictive> frames.

Reduce redundancy (e.g.. Background image in video tutorial).

Break images into 8 x 8 px macroblock. Each macroblock contains info about changing color,

movement, rotation (called P frames). I frames are JPEG images (approx. 2x larger than P frames).

B frames are interpolation or prediction between P and I frame (contains approx. ¼ data than I frame).

One aspect of Video Compression (as in audio) is bitrate.

Lower bitrate = lower quality.

H.265/MPEG-H HEVCx265: A GPL-licensed implementation of the

H.265 video standard. Encoder only. H.264/MPEG-4 AVC

x264: A GPL-licensed implementation of the H.264 video standard. Encoder only.

MPEG-4 codec developed by Nero AG.QuickTime H.264

○ H.264 implementation released by Apple.DivX Pro H.264 decoder and encoder

Common Codec

Microsoft codecsWMV, including WMV 7, WMV 8, and WMV 9.MS MPEG-4v3: A proprietary and not MPEG-4 compliant

video codec by Microsoft. Released as a part of Windows Media Tools 4.

A hacked version of Microsoft's MPEG-4v3 codec became known as DivX

Google (On2) codecs[edit]VP6, VP6-E, VP6-S, VP7, VP8, VP9: Proprietary HDVC

developed by On2 Technologies Adobe Flash Player 8 up, Adobe Flash Lite, Java FX,

720p - 1080p. VP9 = 2160p. VP8 and VP9 = paidlibtheora: Theora video compression by the Xiph.org

Theora is targeted at competing with MPEG-4.

OthersSchrödinger and dirac-research from Dirac

compression developed by BBC ResearchDNxHD codec, developed by Avid Technology.

VC-3.Sorenson 3, popularly used by Apple's QuickTime,

has many similar features with H.264.Sorenson Spark, licensed to Macromedia for use

in Flash VideoRealVideo, RealNetworks. Popular a few years

ago (not now)Cinepak: early codec used by Apple's QuickTime.Indeo, an older compression initially developed by

Intel.

Most common format

AVI (Audio Video Interleave)Microsoft, November 1992 as part of Video for

Windows Technology. One of the oldest format.Simple, can be played : Windows, Mac, Linux, and

web browsers. Raw AVI (Large), Compressed AVI (uses CODEC –

M-JPEG / DIVX)

Flash (Flash Video Format)Adobe Flash software - Sorenson Spark or VP6

video compression formats. Adobe Flash Player, web browser plugins All browsers are compatible with the Flash Video

format.Smaller file size with high quality.Videos on the Web load quickly and won’t spend a

lot of time using up bandwidth. Some notable users of the Flash Video are

YouTube, Yahoo! Video, VEVO, Hulu and MySpace.

WMV (Windows Media Video)Microsoft, originally designed for web streaming

applications, as a competitor to Real Video. Smallest file size after compression but poor video

quality. Probably the only video file format that allows users

to upload and share their videos through the e-mail system.

Being a Microsoft software, the Windows Media Player is the main application that is used to play WMV files on all Microsoft’s Windows operating systems.

MOV (Apple QuickTime Movie)Apple, Inc. the most popular type of video sharing

and viewing format amongst Macintosh users, and is often used on the Web, and for saving movie and video files.

Newer version called QuickTime XMOV files = Apple QuickTime Player for Mac.Quick Time Player for Windows. Considered one of the best looking file formats,

MOV files are of high quality and are usually big in file size.

MP4 (Moving Pictures Expert Group 4)MP4 MPEG-4 Part 14, a standard developed by the

Motion Pictures Expert Group in 1998, who was responsible for setting industry standards regarding digital audio and video, and is commonly used for sharing video files on the Web.

the MPEG-4 uses separate compression for audio and video tracks○ video MPEG-4 or H.264 video encoding; ○ audio AAC compression.

MP4 – one of the best format, quality remains high even after compression.

MP4 is the most popular for online video sharing, as it compatible with both online and mobile browsers and also supported by the new HTML5.