Obtaining video clips

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Berenice Washington
5 years ago
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1 Video Using video Carefully planned, well-executed video clips can make a dramatic difference in a multimedia project Use video only when all other methods (text, still images) are not enough; don t use it just because it s possible 1

2 Obtaining video clips Shoot your own clips Buy footage; this can be a nightmare since the licensing rights and permission may be difficult to obtain On some projects you have no choice but to pay the price for required footage Some technical details Light is converted into an electric signal by a sensor called a CCD Good cameras have 3 CCD s (RGB) Component video is split into two separate chroma channels and a brightness channel Composite video has all signals mixed together and carried on a single cable 2

3 Broadcast video standards NTSC: Used in USA, Japan and some other countries PAL: Europe, Australia, South Africa SECAM: France, Russia and few other countries HDTV: High Definition TV. 16:9 aspect ratio. Video compression Even a small 10-second clip of full-motion video requires transfer of an enormous amount of data in a very short amount of time One frame of 24-bits requires almost 1MB of computer data, 30 seconds will require a one gigabyte Full-size, full-motion video requires that the computer deliver data at about 30MB per second This technological bottleneck is overcome using digital video compression schemes or codecs (coders/decoders) 3

4 Video compression A codec is the algorithm used to compress a video for delivery and then decode it in real-time for fast playback All popular codecs employ lossy compression algorithms Popular codecs: MPEG, Divx, RealVideo, DVI/Indeo, Cinepak Typical filename extensions avi - Audio Video Interleave mp4 - MPEG-4 Part 14 or MP4 file format mkv & mka - Matroska Multimedia Container mpg & mpeg - Moving Picture Experts Group flv - Flash Video wmv, wma & asf - Advanced Systems Format mov - Apple Quicktime Movie rm - Real Media File 3gp - 3GPP Multimedia File vob + ifo - Video Object & DVD Information File Wikipedia: Comparison of Container Formats, on

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6 (Net videos, CD-ROM videos, oldish) (DVD, digital TV, HDTV) (multimedia, digi-tv, mobile) (Edition software) (Post production software) 6

7 Use of video in multimedia (good video is illustrative) (use static video, near shots) (less than 1 min clips) (video is confirming and creates mental images) (divide long video into clips with interactivity) Animation 7

8 Principles of animation Animation is possible because of a biological phenomenon known as persistence of vision and a psychological phenomenon called phi An object seen by the human eye remains chemically mapped on the eye s retina for a brief time after viewing Combined with the human mind s need to conceptually complete a perceived action, this makes it possible for a series of images to blend together into a visual illusion of movement Computer animation Computer animation programs typically use layers, keyframes and tweening techniques These methods are commonly used also with traditional animations that are done without computers You can usually set you own framerate, but the rate at which changes are computed and screens actully refreshed will depend on the power of your display platform and hardware The smaller the object, the faster it can move 8

9 Animation file formats Some file formats are designed specially for animations; they can be often ported among applications and platforms Popular animation formats: Director (.dir and.dcr), 3D Studio Max (.max), Windows Audio Video Interleave (.avi), Machintosh Quicktime (.mov), Motion Video (.mpg), Flash (.swf) Video vs. animation Video includes something that is real; an animation has no limits When to choose video, when animation? money issues time issues artistic issues 9

10 (Animation software), Blender. (Camtasia Studio, Captivate) 10

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