Indeo® Video Interactive Overview
Application Interactivity | Improved Visual Quality | Improved Support For Software Developers
Video is an information-intensive medium. Files representing even short video clips require many megabytes of storage. Because it is seldom practical to store such large files, video is typically compressed after it is digitized. The technology that compresses the video must also decompress it as the video plays back.
Indeo® video allows software-only playback of high-quality video on desktop multimedia PCs. It is Intel's digital video capture, compression, and decompression codec. The word codec comes from compressor- decompressor. A codec is a software driver used to compress digital video data for storage, and decompress it for playback on a multimedia PC. A video clip compressed with Indeo video can play back on any system that supports Microsoft Video for Windows* or Apple QuickTime* for Windows or Macintosh*. For a computer to play files compressed with a given codec, that codec must be installed on the computer.
How to Get the Drivers
Our goal is to help developers create exciting multimedia PC software, of which video is an important part. Video on a PC can be far more exciting than a linear, passive television show, because video on PCs can branch and change interactively. Desktop PCs must have video playback capability for users to enjoy this feature. To this end, a software-only video solution such as Indeo video is clearly an advantage, as PC users do not need to buy or install special hardware to play the video.
These special features take video beyond simple VCR-like functionality, allowing a new class of interactive applications that showcase the performance of the Pentium processor and audiovisual software such as Microsoft's ActiveMovie*.
This document presents an overview of the features that are new with Indeo video interactive. A variety of other documents, exploring these features in depth or discussing other apsects of Indeo technology, are available.
The features of the Indeo video interactive codec can be grouped into three categories:
Each of these categories is important to software developers, and the codec offers features and performance in each category to enable developers to create a new generation of powerful, sophisticated, and exciting PC multimedia and games applications.
Indeo video interactive incorporates unique features that make it possible to include video in interactive multimedia applications and games, challenging the traditional notion of video as necessarily having a fixed size and rectangular shape.
The Indeo video interactive codec supports this type of transparency. During encoding, a compression application can send information to the codec describing a color or range of colors that represents a transparent background (such as the blue wall in the example above, or the blue background in Figure 1). Indeo video interactive then analyzes each frame, separates the background pixels from the foreground, and makes the background pixels transparent, encoding only the foreground objects as compressed video.
Figure 1. Foreground Object With Transparency
Indeo video interactive's transparency encoding is flexible, allowing for multiple foreground objects of arbitrary shape. Foreground objects can also move from frame to frame, allowing you to create what might be called video sprites.
During playback, foreground objects can be dynamically composited over different backgrounds, as shown in Figure 2. The meteorologist, for example, can appear over different weather maps; on PCs based on sufficiently powerful Pentium processors, a foreground object can even appear over another video stream, such as footage of the tornado being reported.
Figure 2. Foreground Object With Background
In such a case, much of the source image does not need to be displayed and one would rather not waste processor resource decoding it. Indeo video interactive provides this capability through a feature known as local decode. As illustrated in Figure 3, the playback application can tell Indeo video interactive to decode only a rectangular subregion, called the view rectangle, from the source video image. The minimum possible size of the local decode viewport is defined during compression, but the display size and location of the viewport can be changed dynamically during playback.
Figure 3. Local Decode Viewport
Real-time Video Effects
The new codec provides excellent image quality, rivaling even that of hardware-accelerated video technologies. Video files created for playback from double-spin CD-ROM drives can be encoded at 320 by 240 resolution at up to thirty frames per second with outstanding image detail and clarity.
New Hybrid Compression Algorithm
Enhanced Compression Technology
Indeo video interactive, however, also makes use of a more sophisticated interframe encoding technology called bidirectional prediction, in which the contents of some frames are predicted based on both previous and future frames. Because a frame can be encoded based on both past and future frames, it is sometimes necessary to first decode a future frame in order to decode and display the current frame while the video plays. Therefore the Indeo video interactive codec sometimes decodes frames in a different order from that in which they are actually displayed. These complex encoding and decoding techniques allow the codec to display dramatically improved visual quality, particularly in video sequences with fast movement or many rapid scene changes.
In addition to application interactivity and improved visual quality, several other significant new features have been included in Indeo video interactive that will be of great value to multimedia application developers.
Improved Palette Handling
Video Access Protection
Key Frame Flexibility
0 Only the first frame in the file is a key frame. No other key frames occur in the file.
1 Every frame in the file is a key frame.
2, 3, ... n Every nth frame in the file is a key. The value of n has no upper limit.
NOTE: Because Indeo video interactive can generate higher quality at lower data rates, the default key frame interval is now 15.
In addition to this flexibility in key frame intervals, Indeo video interactive also allows for aperiodic key frames. During editing, the encoding application can tell the Indeo video interactive codec to place a key frame at any location, allowing video producers to specify access points anywhere within a video sequence, or to better control video quality by placing key frames on scene change boundaries.
* Legal Stuff © 1997 Intel Corporation