5.1 Different Video Attributes Video Standards

5.1 Different Video AttributesVideo Standards

Different countries use different video standards for broadcasting

Video standard Full name CountriesPAL Phase Alternate

LineThe United Kingdom, most countries in Europe, Hong Kong, China, Singapore, Australia

The United States, Japan, Taiwan

France, Russia

NTSC National Television Standards Committee

SECAM Sequential ColourAnd Memory

TV display standards in different countries

5.1 Different Video AttributesFrames

Digitized video consists of a sequence of framesSlightly different frames are displayed successively at high speed → continuous motion

A video actually consists of individual frames

Frame 1 Frame 2 Frame 3 Frame 4 Frame 5 Frame 6 Frame 7 Frame 8

Frame 9 Frame 10 Frame 11 Frame 12 Frame 13 Frame 14 Frame 15 Frame 16

5.1 Different Video AttributesFrame Size

The width and height of individual framesLarger frame size → higher video quality →larger file size

Frame size Aspect ratio Application720 × 576 5 : 4 PAL DVD

PAL SVCD

PAL VCD

Web video

Web video or video mail

480 × 576 5 : 6

352 × 288 11 : 9

240 × 180 4 : 3

160 × 120 4 : 3

Common video frame sizes

5.1 Different Video AttributesColour Depth

Each video frame is composed of pixels arranged in a rectangular gridThe colour depth of each pixel specifies the number of bits used to store colour information Most video has 24-bit colour depth

5.1 Different Video AttributesFrame Rate

The number of video frames displayed on the screen in one secondMeasured in frames per second (fps)Higher frame rate (above 24 fps) →smoother motion

Frame rate (fps) Multimedia system30 NTSC TV

25 PAL TV

24 Movie films

15

12Computer video or animation

(such as Flash movies)

Some common video frame rates and corresponding multimedia systems

5.1 Different Video AttributesBit Rate

Determines the number of bits used to store one-second videoCan also be regarded as the number of bits passing through a particular point in a video streamMeasured in bits per second (bps)

The idea of video bit rate. The bit rate of video stream B is double of that of stream A.

5.1 Different Video AttributesBit Rate

Increasing bit rate → higher quality →larger file sizeChoice of bit rate depends on user’s network connection speed

Low bit rate causes substantial quality loss

Bit rate: 20 kbpsFile size: 56 KB

Bit rate: 50 kbpsFile size: 127 KB

Bit rate: 100 kbpsFile size: 274 KB

Bit rate: 450 kbpsFile size: 1,113 KB

increasing bit rate

increasing qualityIncreasing file size

5.1 Different Video AttributesVideo File Size (uncompressed)

Can be estimated by the formula,

Video file size

Frame size

Colourdepth

Frame rate Duration ×× ×=

Consider a ten-second DVD-quality video clip (without audio), the uncompressed file size is:(720 × 576) pixels/frame × 24 bits/pixel × 25 frames/second × 10 seconds= 2,488,320,000 bits= 311,040,000 bytes= 296.6 MB

5.1 Different Video AttributesCodec (Compressor and Decompressor)

The software used to compress and decompress video filesCompression reduces the storage space and the video access time

Original video

CompressedvideoCompression Decompression

Storage Decompressed video

(playback)This step requires the appropriate codec installed on user’s computer

5.1 Different Video AttributesCodec (Compressor and Decompressor)

Different codecs use different methods to compress videoMost codecs are lossyFinal file size governed by a quality factor or encoding bit rateSome common codecs

MPEG-1, MPEG-2, MPEG-4Windows Media VideoDivXRealVideoIntel Indeo®VideoCinepak Codec by Radius

5.1 Different Video AttributesCodec (Compressor and Decompressor)

Different codecs use different methods to compress videoMost codecs are lossyFinal file size governed by a quality factor or encoding bit rateSome common codecs

MPEG-1, MPEG-2, MPEG-4Windows Media VideoDivXRealVideoIntel Indeo®VideoCinepak Codec by Radius

5.2 Capture Digital VideoConcept

To capture digital video, it is necessary to have

A capturing device (a camcorder)A storage mediumVideo encoding hardware and software

Video encoding hardware and

software

Video capturing device

Storage medium

5.2 Capture Digital VideoExamples

Video capturing devicesDV camcorder (or Handycam)Digital cameraWebcam

Video encoding hardwareVideo capture cardAn external video capturing device

Video capturing and editing software is usually bundled with the hardware product

5.2 Capture Digital VideoExamples

A video capture card (top left) and an external video capturing device (bottom left) from Pinnacle. Moviestar, the video capturing and editing software, is bundled with the capturing hardware (right).

5.2 Capture Digital VideoExamples

A video capture card (top left) and an external video capturing device (bottom left) from Pinnacle. Moviestar, the video capturing and editing software, is bundled with the capturing hardware (right).

5.3 Common Video File FormatsAudio Video Interleave (AVI)

Native Windows video format developed by MicrosoftData storage

Video data and audio data are stored in an interleaved mannerImproves the synchronization of audio and video playing

The structure of an AVI file

5.3 Common Video File FormatsAudio Video Interleave (AVI)

Large file size in uncompressed formatSupports many codecs

The same 15-second AVI video in 3 formats

AVI (MPEG-4 codec)File size: 3.28 MB

AVI (Cinepak Codec by Radius)

File size: 13.1 MB

AVI (uncompressed)File size: 111 MB

5.3 Common Video File FormatsMotion Picture Experts Group (MPEG, MPG)

A lossy compression file formatPreserves video quality yet supports high compression ratioStores only changes between successive frames, not all the image information of every individual frame → high compression

Keyframe1

Predicted frame 1

Predicted frame 2

Predicted frame 3

Predicted frame 4

Predicted frame 5

Predicted frame 6

Keyframe2

Coding order

The idea of MPEG compression – key frames are standalone frames providing basic information for predicted frames (keyframe + changes between successive frames).

5.3 Common Video File FormatsMotion Picture Experts Group (MPEG, MPG)

A family of compression standards

Standard Maximum resolution

Encoding bit rate Application

1.5 Mbps Video CDs, interactive CD-ROMs and MPEG-1 Audio Layer-3 music

DVDs and digital TV broadcast

Video in digital camera mobile phone, iPodand QuickTime

Varying up to 4 Mbps

From 64 kbps up to 4 Mbps

MPEG-1 (1992)

352 × 288 (PAL)352 × 240 (NTSC)

MPEG-2 (1994)

720 × 576 (PAL)720 × 480 (NTSC)

MPEG-4 (1998) -

MPEG-4 can be as good as MPEG-2, but an MPEG-4 video is of a smaller file size and at a lower bit rate

5.3 Common Video File FormatsWindows Media Video (WMV, ASF)

A streaming compressed video format developed by MicrosoftCan be played by Windows Media PlayerCan be created with Windows Movie Maker

Windows Media Player Windows Movie Maker

Encode video to RealVideo format using RealProducer (left) and play the output file using RealPlayer (right).

5.3 Common Video File FormatsRealVideo (RV, RM)

A proprietary compressed streaming audio format developed by RealNetworksCan be played by RealPlayerRealProducer can encode video in other file formats as RealVideo format

QuickTime pro

5.3 Common Video File FormatsQuickTime (MOV)

A streaming compressed multimedia file format on Macintosh computersCan store text, still images and animationCan be played with QuickTime Player

QuickTime Player

5.3 Common Video File FormatsQuickTime (MOV)

A streaming compressed multimedia file format on Macintosh computersCan store text, still images and animationCan be played with QuickTime Player

QuickTime proQuickTime Player

5.4 Simple Video Editing Editing Movies

Common video editing skills include

Adding titles and

background music

Adding titles and

background music

Applying video filters

Applying video filters

between video

Applying transition

effects

clips

Applying transition

effects

clipsbetween video

Windows XPIntroductory video editing softwareFree and simple to use

5.4 Simple Video Editing Editing Movies

Other video editing software

Ulead MediaStudio Pro Adobe Premiere

Includes more complicated functionsMore suitable for advanced users

5.4 Simple Video Editing Editing Movies

Other video editing software

Ulead MediaStudio Pro Adobe Premiere

Includes more complicated functionsMore suitable for advanced users