Introduction to Interactive Media

11: Video in Interactive Digital Media

Introduction to Interactive Media

A SHORT HISTORY OF VIDEO

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Moving Pictures

• Film and video are a series of rapidly displayed still pictures.– Each image captures an instance of motion.– Persistence of vision results in perception of flow

of motion.

• Analog film records images on transparent medium projected onto a screen (invented in the late 1800s)

• Analog video records images as continuously varying electrical voltages that produce images on a CRT or projection screen (invented in the 1950s)

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Analog Video Formats

• Analog video: initially intended exclusively for broadcast television – NTSC: television standard in U.S. (1952).

• Standards for:– Aspect ratio (4:3)– Resolution (525 lines/frame)– Scan rate (60 Hz = 60 times/sec)– Scanning method (interlacing)– Broadcast techniques.

• Replaced by new digital standard in 2009.

– PAL: standard in England and much of Europe.

– SECAM: standard in France and Russia.

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Digital to Analog to Digital Video captured in component color

Red, Green, Blue light signals combine to create color range.

RGB = Better color quality because more colors a can be created with this method.

Until 2009, video was broadcast for TV in composite color Combines two signals:

Luminance or amount of brightness in the image. Chrominance or color hue in the image.

Television and computer screens display video with component color.

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Analog to Digital Video

• Other issues with conversion.– Display Area

• TV does not display full image it receives.• Must be aware of Safe Action Area and Safe

Title Area

– Color gamut• NTSC has smaller range of colors (composite

color – luminance/chrominance).• Computer (component - RGB color) is richer.

– Computer colors that cannot be displayed on NTSC are "illegal colors."

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Digital Television

• DTV standard for U.S. (2009)– Video is created and delivered as digital.

• Result: higher screen resolutions, richer colors, better video.

• DTV features include:– New aspect ratio for television screen (16:9 -

closer to the aspect ratio of film).

• Implication…analog video is becoming a thing of the past.

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WHAT IS DIGITAL VIDEO?

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Digital Video• Digital video is comprised of a series of bitmap

digital images in rapid succession at a constant rate.

• Rate at which frames are displayed are frames per second (FPS)

• Frame size is number of pixels along width x number of pixels along height.

• Color of pixel is represented by a fixed number of bits. The more bits, the more subtle variation of colors can be reproduced.

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Digital Video Challenges• Large file sizes• Hardware performance• Distribution methods (bandwidth, file

standards)

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Digital video made possible…

• Compression algorithms

• Fast computer hardware

• DVD storage

• Increasing bandwidth.

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Digital Video Quality

• Three factors contribute to quality.– Screen resolution

• Number of horizontal and vertical pixels used to present the video image.

– Frame rate• Number of individual video frames displayed per second.

– Compression method• Algorithm used to compress and decompress the video.

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Screen Resolution

• Screen resolution impacts processing, storage, and transmission requirements.

• High quality digital video (DV) format is 720 X 480 (or 350,000 pixels at rates of 30fps).

– CD-Rom and Internet are too slow to deliver that much data.

– Display size is often reduced to reduce the number of pixels/second to output.

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Frame Rate

• Standard frame rate for NTSC video is 29.97 frames per second (fps).

• Reducing the frame rate reduces the data to be transferred.– Video on Internet is often delivered at 15fps.

• Cautions:– Lowering frame rate will slow delivery of individual

images and drop out frames of video.– Result could be "jerky" motion.

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Video Compression

• Some digital video file types can employ different compression algorithms.

• Three general strategies for compressing video:– Intra-frame: re-encodes within the frame.– Inter-frame: eliminates intervening frames saving only

changes between the frames.– Variable bit rate (VBR) encoding

• Best type of compression determined by video footage.

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OBTAINING DIGITAL VIDEO

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Making Digital from Analog

• Sampling from existing analog sources such as VCR or Laserdisc

– Requires digitizing boards on computers to sample the electrical currents produced by playing the analog source.

– Store the resulting voltage levels as digital values.

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Evolution of DV Cameras

• DV tape was standard throughout late 90s and early 00s– Video content transferred to computer via

frame capture via Firewire cable.

• Newer cameras are tapeless– Video footage stored as files on camera

hard drive.

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Shooting Original DV

• Shooting video shoot requires preparation.

• Consider:– intended use– list of shots– weather– lighting– personnel

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Shooting Basics

• Framing a Shot– Rule of thirds—widely

embraced guideline for framing a video shot.

• Line subject up on intersection of lines facing empty area in frame.

• Helps ensure adequate side and headroom.

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Shooting Basics

• Keep camera still! Always best to use a tripod.

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Telling the Story with Shots

•Close up shot (CU)•Medium shot (MS)•Wide shot (WS)•Establishing shot

•Cutaway•Point of view shot•Reverse angle shot•Over-the-shoulder shot

• Pans - moving camera side to side - sometimes used to give perspective to a scene.

• Zooms - zooming in on a details - sometimes used to communicate an important detail or convey an emotion.

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EDITING VIDEO

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Editing Film

• Physical process of splicing and taping film together.

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Editing Analog Video

• Video on tape copied onto other tape.

• Video media degraded during editing process.

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Editing Digital Video

• Editing software options:– Consumer packages. (iMovie, MovieMaker)– Prosumer applications. (Final Cut Pro, Adobe

Premiere, Avid)

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Video Editing Software

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Video Editing Operations

• Tasks of Video Editing include:– Capture video from external source.– Arrange separate video clips.– Split clips (dividing into multiple parts) and trim

clips (removing unwanted frames).– Add transitions (cuts, fades, dissolves and wipes)

and special effects.

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Digital Video Editing Pros

• Can work non-linearly

• Media does not degrade.Introduction to Interactive Media

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Rendering

• Process of applying the editing operations specified by the master video to produce a new, independent video file.– Can be processor intensive and time consuming

process.

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Rendering Decisions

• Output options are based on video's intended use. – Screen Resolutions

• DVDs = 720X480• CD media = 320X240• Web = 240X180

– Compression– Frame Rate

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VIDEO IN INTERACTIVE MEDIA

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Delivery Methods

• Streaming – Most often for live video, requires special

streaming server– Never stored on user’s machine

• Embedded video– Video is downloaded– Progressive download allows user to start

watching video while still downloading.

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Video on Web

• Video sharing sites such as YouTube and Vimeo allow for easy integration of video on web sites.

• Quicktime video format is sometimes used as well

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Flash Video Format

• Flash is an interactive authoring application

• Video is converted to FLV format and integrated into interactive experience.

• Entire application is exported as SWF video displayed inside.

• Allows for progressive download.

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HTML 5 and Video

• New standards for integrating video into HTML 5

• http://www.w3schools.com/html/html5_video.asp