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Animation and Video on PCs

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Written, edited, compiled, and transformed to HTML by UDI Latarre © 1995-98

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This article covers the known (and common) methods and applications used for displaying video on a PC, as well as how and why compression methods are used for video (especially on networks).

Click on an application name to skip to the relevant subject:


Video for Windows

Video driver and utilities from Microsoft for Windows 3.1 and higher, including Windows 95.
It supports the AVI movie file format and three video compression methods: Microsoft Video 1, Microsoft RLE and Intel's Indeo.
The following utilities are included:
VidCap video capture
VidEdit video editor
BitEdit bitmap editor
PalEdit palette editor
WaveEdit sound editor
Media Player video playback
The quality of Video for Windows playback depends on PC performance. It is a tradeoff between resolution and frame speed. At 30 frames per second (fps), the eye perceives a totally smooth animated sequence At rates below 10 fps, the image is jerky.
Following is the typical playback frame rate based on CPU speed and the resolution of the video window.
CPU 160x120 320x240 640480
486/25 30 15 1
486/66 30 30 10
Pentium 30 30 20

AVI

(Audio Video Interleaved)
Windows multimedia video format from Microsoft.
It interleaves standard waveform audio and digital video frames (bitmaps) to provide reduced animation at 15 fps at 160x120x8 resolution. Audio is 11,025Hz, 8-bit samples.

MCI

(Media Control Interface)
High-level programming interface from IBM/Microsoft for controlling multimedia devices.
It includes text commands such as open, play and close for languages such as Visual Basic, as well as functions for languages such as C.

MPEG

An image-compression scheme for full motion video proposed by the Motion Picture Experts Group, an ISO-sanctioned group.
MPEG image scheme offers more compression than the JPEG scheme, which is largely for still images, because it takes advantage of the fact that full motion video is made up of many successive frames consisting of large areas that are not changed - like blue sky background. While JPEG, compresses each still frame in a video sequence as much as possible MPEG also performs "differencing," noting differences between consecutive frames. If two consecutive frames are identical, the second can be stored with the appropriate information.
MPEG condenses moving images about three times more tightly than JPEG.

QuickTime

Multimedia extensions to Macintosh's System 7 that add sound and video capabilities.
A QuickTime file can contain up to 32 tracks of audio video, MIDI or other time-based control information. Most major Macintosh DBMSs (database management systems) support QuickTime. Apple also provides a QuickTime for Windows version for Windows-based PCs.

RUNTIME

A runtime environment is the software that plays back multimedia materials.
The runtime material is created by the author. Examples of runtime applications are presentations are training, where the material cannot be edited but only viewed. The runtime software could be a slide show viewer, a software-only video playback application, or a hypermedia runtime document.


Video Compression Standards

(With relation to networks)
Uncompressed video would be totally unwieldy on today's LANs, not to mention on WANs.
An uncompressed stream of video for creating a full-screen (640-by-480 pixels), 30 frames per second (fps), 24-bit color picture requires about 208Mbps of bandwidth, and disk space to match. Compression can reduce the massive video stream to manageable proportions.
Video compression and decompression can take place in hardware or software. The content provider may perform the compression, or the user may do it. Decompression takes place at the workstation. Software, decompression usually limits playing rates to less than 15fps. But 20fps 25fps, or even 30fps speeds are not impossible with the right client hardware, such as a fast graphics card and video bus.
Hardware-based decompression supports rates of 30fps, but it requires a compression/decompression (codec) card from vendors such as Intel, RasterOps (Santa Clara, CA) or Sigma Designs (Fremont, CA). Codecs can cost as little as $400; however, prices of $800 and higher are more typical.
MPEG is the most popular type of hardware decompression. It's used for distributing non-editable full-motion video. The current version, MPEG-1, typically requires 1.2Mbps of transmission capacity, which translates to 9MB per minute of storage. However, higher-quality video can be attained with 2.4Mbps transmission and 18MB of storage.
Digital Video Interactive (DVI) is another compression standard that usually uses hardware-assisted decompression. Its data rates and storage requirements are similar to those of MPEG.
The Joint Photographic Experts Group compression standard, or JPEG, is for compression of still frames. M-JPEG (Motion JPEG) takes JPEG into the video realm. M-JPEG requires hardware decompression. It's used for distributing full motion video in an editable format. Because its storage and transmission requirements are more than twice those of MPEG, it's not popular for networked applications.
Audio-Video Interleaved (AVI) is not a compression type but a file format supported by Microsoft's Video for Windows. Indeo, Intel's compression standard, is the most popular type of compression for video files in AVI format. Indeo uses software decompression. It requires 1.2Mbps bandwidth and 9MB per minute of storage.
Cinepak is the standard compression type for QuickTime, a multimedia environment for Macintoshes. Cinepak's requirements are similar to Indeo under AVI.
Second, video information must be provided continuously and smoothly to multiple simultaneous users. In other LAN applications, discontinuities in data flow are less visible or annoying to users. Where popular hardware and software environments are not optimal for video, video server products modify or enhance the environment through either hardware or software.


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This manual was prepared and edited by Udi Latarre for PCS - Personal Computer Services.
Copyright © 1995-98 by PCS - Personal Computer Services. All rights reserved.

Use of this manual is free of charge with the following limitations:
This manual may NOT be changed, modified or excerpted except if expressly permitted in writing by UDI Latarre and/or PCS - Personal Computer Services.
This manual can be freely copied/distributed as long as this copyright notice is maintained within the document.


Any trademark mentioned in this document is the property of its respective owner.

DISCLAIMER:

This document has been prepared on a voluntary basis. It does not claim to be an official document, nor does it claim to reflect the views of any of the mentioned manufacturers. Every effort has been made to check the information provided, but no guarantee can or will be given as to its accuracy. I hope readers will find it useful and I shall appreciate it if readers will draw my attention to any errors.


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