Introduction to Interactive Media 11: Video in Interactive Digital Media

Introduction to Interactive Media A SHORT HISTORY OF VIDEO

Introduction to Interactive Media 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)

Introduction to Interactive Media 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 –PAL: standard in England and much of Europe. –SECAM: standard in France and Russia.

Introduction to Interactive Media 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.

Introduction to Interactive Media 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."

Introduction to Interactive Media 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.

Introduction to Interactive Media WHAT IS DIGITAL VIDEO?

Introduction to Interactive Media 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.

Introduction to Interactive Media Digital Video Challenges Large file sizes Hardware performance Distribution methods (bandwidth, file standards)

Introduction to Interactive Media Digital video made possible… Compression algorithms Fast computer hardware DVD storage Increasing bandwidth.

Introduction to Interactive Media 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.

Introduction to Interactive Media 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.

Introduction to Interactive Media Frame Rate Standard frame rate for NTSC video is 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.

Introduction to Interactive Media 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.

Introduction to Interactive Media OBTAINING DIGITAL VIDEO

Introduction to Interactive Media 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.

Introduction to Interactive Media 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.

Introduction to Interactive Media Shooting Original DV Shooting video shoot requires preparation. Consider: –intended use –list of shots –weather –lighting –personnel

Introduction to Interactive Media 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.

Introduction to Interactive Media Shooting Basics Keep camera still! Always best to use a tripod.

Introduction to Interactive Media 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.

Introduction to Interactive Media EDITING VIDEO

Introduction to Interactive Media Editing Film Physical process of splicing and taping film together.

Introduction to Interactive Media Editing Analog Video Video on tape copied onto other tape. Video media degraded during editing process.

Introduction to Interactive Media Editing Digital Video Editing software options: –Consumer packages. (iMovie, MovieMaker) –Prosumer applications. (Final Cut Pro, Adobe Premiere, Avid)

Introduction to Interactive Media Video Editing Software

Introduction to Interactive Media 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.

Introduction to Interactive Media Digital Video Editing Pros Can work non-linearly Media does not degrade. Introduction to Interactive Media

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.

Introduction to Interactive Media Rendering Decisions Output options are based on video's intended use. –Screen Resolutions DVDs = 720X480 CD media = 320X240 Web = 240X180 –Compression –Frame Rate

Introduction to Interactive Media VIDEO IN INTERACTIVE MEDIA

Introduction to Interactive Media 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.

Introduction to Interactive Media 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

Introduction to Interactive Media 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.

Introduction to Interactive Media HTML 5 and Video New standards for integrating video into HTML 5 ideo.asp