Chapter6-151010022251-lva1-app6892.docx

CHAPTER 6 VIDEO 6.1 Video Concept • Video is an excellent tool for delivering multimedia. 1

• Video places the highest performance demand on computer and its memory and storage. • Digital video has replaced analog video as the method of choice for making and delivering video for multimedia.

6.1 Video Concept • Digital video device produces excellent finished products at a fraction of the cost of analog. 2

• Digital video eliminates the image-degrading analog-todigital conversion. • Many digital video sources exist, but getting the rights can be difficult, time-consuming, and expensive.

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6.2 Analogue Video • 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.

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6.2 Analogue Video • Composite analogue video has all the video components: – brightness, colour and synchronization

• Then combined into one signal for delivery • Example : traditional television signal

DIGITAL

ANALOGUE 5

6.3 Video Display 1. Progressive scan : • used in computer monitors and digital televisions. • displays all the horizontal lines of a picture at one time as a single frame. 2. Interlaced scan : • used in standard television formats • displays only half of the horizontal lines at a time (the first field, containing the odd-numbered lines, is 6

displayed, followed by the second field, containing the even-numbered lines)

6.4 Video Signal Broadcast

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NTSC • National Television Standards Committee – Standards for coding information into an electronic signal, to make a TV picture – US, Japan

• Amplitude modulation • Frame of video: 525 vertical scan lines • 30 frames per second • Two passes drawing (Interlacing) – Odd-numbered lines 8

– followed by even-numbered (60 Hz) – Helps prevent flicker

PAL, SECAM • PAL: Phase Alternate Line – Europe, Australia, South Africa – 625 scan lines – 25 frames per second – Odd/even line interlacing – Amplitude modulation

• SECAM: Sequential Color and Memory – France, Russia 9

– Also 625-line, 25 frames per sec, interlaced – Frequency modulation

HDTV • High Definition Television – Advanced Television Systems Committee (ATSC, www.atsc.org)

• Six video formats (resolution & frame rate combinations) – 16:9 aspect ratio (width:height ratio) – 1080 x 1920-pixels or 720 x 1280-pixels – 24, 30, 60 frames/sec 10

• MPEG-2 coding for video • Digital Audio Compression (AC-3) for audio

6.5 Digitizing Video • Digital video combines features of graphics and audio to create dynamic content for multimedia products. • Video is simply moving pictures. • Digitized video can be edited more easily. • Digitized video files can be extremely large.

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6.6 Digitizing Video • 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).

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VCR

Video Overlay Board /

PC

Video Capture Card

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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

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6.7 Digital Video • Digital video is the digitisation of analogue video signals into numerical format • It creates the illusion of full motion by displaying a rapid sequence of changing images on a display device. • Conversion from analogue to digital format requires the use on an ADC (Analogue to Digital Converter) • A Digital to Analogue Converter (DAC) can be used to output digital video on analogue equipment

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Digital Video • 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.

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6.8 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.

File Size and Formats 1. Frame Rate –

animation is an illusion caused by the rapid display of still images. 17

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television and movies play at 30 fps but acceptable playback can be achieved with 15 fps.

File Size and Formats 2. 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. 18

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New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, •

1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.

File Size and Formats 3. Color Depth 19

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The quality of video is dependent on the color quality (related to the number of colors) for each bitmap in the frame sequence.

File Size and Formats 3. Color Depth –

The color depth below 256 colors is poorer-quality image. 20

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The frame rate to below 15 fps causes a noticeable and distracting jerkiness that unacceptable.

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Changing the image size and compressing the file therefore become primary ways of reducing file size.

24 bit

16 bit

8 bit (256 colors)

Video Compression • Two types of COMPRESSION: – Lossless compression. 21

•

Preserves the exact image throughout the compression and decompression process.

• E.g: text images is to identify repeating words and assign them a code.

Video Compression – Lossy compression. • Eliminates some of the data in the image and therefore provides greater compression ratios than lossless compression.

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• Applied to video because some drop in the quality is not noticeable in moving images.

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File Formats Video File Formats • AVI Format (.avi) The AVI format, which stands for audio video interleave, was developed by Microsoft. The Some of the most common players that support the avi format are: •

Apple QuickTime Player (windows & Mac), Microsoft Windows Media Player (Windows & Mac), VideoLAN

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File Formats VLC media player (Windows & Mac) AND Nullsoft Winamp

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Quicktime Format (.mov) The QuickTime format was developed by Apple and is a very common one. It is often used on the internet, and for saving movie and video files.

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File Formats •

The format contains one or more tracks storing video, audio, text or effects. . It is compatible with both Mac and Windows platforms, and can be played on an Apple Quicktime player.

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MP4 Format (.mp4) This format is mostly used to store audio and visual streams online, most commonly those defined by MPEG. It Expands MPEG-1 to support video/audio "objects", 3D content, low bit rate encoding and support for Digital Rights Management.

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File Formats •

The MPEG-4 video format uses separate compression for audio and video tracks; video is compressed with MPEG-4 video encoding; audio is compressed using AAC compression, the same type of audio compression used in .AAC files.

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The mp4 can most commonly be played on the Apple QuickTime Player or other movie players. Devices that play p4 are also known as mp4 players.

STREAMING VIDEO 1.

Windows Media Video Format (.wmv)

2.

3GP File Extension (.3gp)

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File Formats 3.

Apple QuickTime Player

4.

RealNetworks RealPlayer

5.

VideoLAN VLC media player

6.

Advances Streaming Format (.asf)

7.

Real Media Format (.rm)

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Video Editing Terminology • 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.

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6.9 Video Editing Terminology • Linear VS 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

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edits, splices, special effects, transitions and sound tracks.

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.

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Special Effects • CHROMA KEY

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– 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.

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Special Effects

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Video Hardware and Software VCR

MULTIMEDIA PC

Video Overlay Board / Video Capture Card

Video digital Editing Software

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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.

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Obtaining Video Clips • Shoot a new footage • Pre existing video clips • Buying from others (licensing rights) 37

Shooting and Editing Video •

Equipment needed :

1) Good camera 2) Lighting equipment 3) Powerful PC :

Advantages of using Video • Captures interest 38

• Increase retention • Clarifies complex physical actions and relationships • Can incorporate other media

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6.10 Disadvantages of using Video • Is expensive to produce • Requires extensive memory and storage • Requires special equipment • Does not effectively illustrate abstract concepts and static situations

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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 41

•

2 types of compression lossless and lossy.

• Standards for compression program are JPEG and MPEG.

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