What are the common format for video files?What are the common format for video files?

What are the difference between VCD and DVD?What are the difference between VCD and DVD?

How can we produce video files to fit our needs?How can we produce video files to fit our needs?

Activity --- Video Editing

5.1 Different Video Attributes Video Standards

Different countries use different video standards for broadcasting

Video standard

Full name Countries

PAL Phase Alternate Line

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

NTSC National Television Standards Committee

The United States, Japan, Taiwan

SECAM Sequential Colour And Memory

France, Russia

TV display standards in different countries

5.1 Different Video Attributes Frames

Digitized video consists of a sequence of frames

Slightly 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 Attributes Frame Size

The width and height of individual frames

Larger frame size → higher video quality → larger file size

Aspect ratio the ratio of the video width to its height What are the common aspect ratio used?

4:3 16:9

5.1 Different Video Attributes

Frame size Aspect ratio Application

720 × 576 5 : 4 PAL DVD

480 × 576 5 : 6 PAL SVCD

352 × 288 11 : 9 PAL VCD

240 × 180 4 : 3 Web video

160 × 120 4 : 3Web video or

video mail

What are the frame size of TVs?

Traditional TV: 500 x 375

LCD/Plasma TV (32”): 1366 x 768

HD TV: 1920 x 1080(i./p)

5.1 Different Video Attributes Colour Depth

Each video frame is composed of pixels arranged in a rectangular grid

The 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 Attributes Frame Rate

The number of video frames displayed on the screen in one second

Measured in frames per second (fps) Higher frame rate (above 24 fps) → smoother motion

Frame rate (fps) Multimedia system

30 NTSC TV

25 PAL TV

24 Movie films

15 Computer video or animation (such as Flash

movies)12

5.1 Different Video Attributes

Effect of frame rate

5.1 Different Video Attributes Bit Rate (Encoding bit rate)

Determines the number of bits used to store one-second video

Can also be regarded as the number of bits passing through a particular point in a video stream

Measured 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 Attributes Bit Rate (encoding bit rate)

Increasing bit rate → higher quality → larger file size Choice 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 kbps

File size: 274 KB

Bit rate: 450 kbps

File size: 1,113 KB

increasing bit rate

increasing qualityIncreasing file size

The following videos have different bit rate, can you see the different?

80 kbps 700 kbps

5.1 Different Video Attributes

5.1 Different Video Attributes Video File Size (uncompressed)

Can be estimated by the formula,

Video file size

Frame size

Colour depth

Frame rate

Duration ×× ×=

Consider a ten-second DVD frame size 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 Attributes Codec (Compressor and Decompressor)

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

Original video

Compressed videoCompression Decompressio

n

Storage Decompressed video

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

5.1 Different Video Attributes Codec (Compressor and Decompresso

r) Most codecs are lossy Final file size governed by a quality factor a

nd encoding bit rate Some common codecs

MPEG-1, MPEG-2, MPEG-4Windows Media VideoDivXRealVideo Intel Indeo®Video Cinepak Codec by Radius

5.3 Common Video File Formats

Audio Video Interleave (AVI) Native Windows video format

developed by Microsoft Data storage

Video data and audio data are stored in an interleaved manner

Improves the synchronization of audio and video playing

The structure of an AVI file

5.3 Common Video File Formats

Audio Video Interleave (AVI) Large file size in uncompressed format Supports 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 Formats Motion Picture Experts Group

(MPEG, MPG) A lossy compression file format Preserves video quality yet supports high

compression ratio Stores only changes between successive

frames, not all the image information of every individual frame → high compression

1 2

5.3 Common Video File Formats

Motion Picture Experts Group (MPEG, MPG) A family of compression standards

Standard

Maximum resolution

Encoding bit rate

Application

MPEG-1 (1992)

352 × 288 (PAL)

352 × 240 (NTSC)

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

MPEG-2 (1994)

720 × 576 (PAL)

720 × 480 (NTSC)

Varying up to 4 Mbps

DVDs and digital TV broadcast

MPEG-4 (1998) -

From 64 kbps up to 4 Mbps

Video in digital camera mobile phone, iPod and QuickTime

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 Formats Windows Media Video (WMV, ASF)

A streaming compressed video format developed by Microsoft

Can be played by Windows Media Player Can be created with Windows Movie Maker

Windows Media Player Windows Movie Maker

5.3 Common Video File Formats

RealVideo (RV, RM) A proprietary compressed streaming audio

format developed by RealNetworks Can be played by RealPlayer RealProducer can encode video in other fil

e formats with various bit rate. Example 1 Example 2

RealVideo support video streaming a user does not have to wait to download

the whole video file before watching it

Without streaming With streaming

5.3 Common Video File Formats

5.3 Common Video File Formats

QuickTime (MOV) A streaming compressed multimedia file

format on Macintosh computers Can store text, still images and animation Can be played with QuickTime Player

QuickTime proQuickTime Player

QuickTime VR support virtual reality (VR) for

mat can display 360º panoramas

of scenic

Example 1

Example 2

Example 3

QuickTime VR

5.3 Common Video File Formats

5.2 Capture Digital Video Concept

To capture digital video, it is necessary to haveA 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 Video Examples

Video capturing devicesDV camcorder (or Handycam)Digital cameraWebcam

Video encoding hardwareVideo capture cardAn external video capturing device

DVD-recorder IEEE 1394 (firewire/i-link) Video capturing and editing software is us

ually bundled with the hardware product

5.2 Capture Digital Video Examples

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).

5.4 Simple Video Editing

Common video editing techniquestrimming (cutting) video clipsadding titlesadding filtersadding transitionsimporting still imagesadding background music

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