Bob Currier, Synthetic Aperture
You have to give Intel credit: they have proven themselves willing to continually reinvent their digital video technology to deliver the best product they can. Not content with the quality of the DVI technology they originally purchased from General Electric's Sarnoff Labs, Intel made major changes for the software-only codec market giving us Indeo 2 and Indeo 3. They've just released the latest incarnation, carrying the new name of Intel Video Interactive (IVI). This is not just a minor tweak of Indeo 3, but rather a completely new product with many new capabilities. As always, I was eager to give it a test and see how I would be able to use it in future products.
The IVI codec is an interframe codec, based on a hybrid wavelet compression method. Wavelet compression works by encoding the image into a number of frequency bands, each representing the image at a different level of sharpness. By representing the image based on frequency content, it is possible to select which portions of the data to save, yielding the desired compression. For example, by reducing the high frequency content--which makes up the fine detail of the image--considerable compression can be achieved without some of the characteristic blockiness of other codecs. IVI takes it a step further, however, and adds a layer of the more traditional transform compression to the mix, achieving even greater compression. Wavelet compression has often been touted for its ability to avoid blockiness, and it is interesting to see it gain mainstream status.
In addition to the normal function of a codec--compressing and decompressing video--Intel has added several other interesting features to IVI. One is the concept of scaling: using the codec to adapt playback to the processor power of the particular machine being used for playback. Another is transparency, whereby the IVI codec will take care of matting moving video onto a background; ideal for use in games and other interactive applications. IVI also allows video to be compressed with an embedded "password" which must be supplied by the player software for the video to be usable. This allows content providers to make use of a standard codec, but still have some control over how widely their videos can be used.
IVI lets you choose where to place key frames when compressing video. This allows for rapid access to selected points in the movie, such as in interactive and game applications, without giving up the benefits of interframe compression. And one of my favorite features of IVI is on-the-fly contrast, brightness, and saturation adjustment. No more compromising on video that is too dark on the PC, but too washed-out on the Mac!
IVI is currently available only for use with Video for Windows, limiting the platforms that I could test it on. Intel supplies both 16-bit (Windows 3.1) and 32-bit (Windows 95 and NT) versions of IVI. Intel promises a QuickTime version for both the Macintosh and Windows in the first quarter of 1996--a date they obviously missed--providing more options on where Indeo Interactive content can be delivered. But in the meantime, I did my testing on a 120 MHz Pentium with a fast video card, running Windows 95 and the 32-bit version of IVI, using Adobe Premiere to perform the compression. I viewed the result on both the Pentium system and on a 25 MHz 486 with a slow video card, running Windows 3.1 and 16-bit IVI.
The first thing I noticed is that IVI is quite slow at compressing video. Using the same source material and settings, compressing a short clip took 28 minutes to compress with IVI, compared to 9 minutes with Cinepak. The results from IVI were quite pleasing, however. The colors are true, the image sharp, and playback was smooth on the Pentium. There was no problem getting 320x240, 15 frame/second material to compress to 2x CD-ROM data rates.
When IVI is "pushed" to compress video into low data rates, the visible artifacts are quite different than what one sees with Cinepak. IVI appears to favor areas of high-frequency content, maintaining detail there while further reducing the data in low-frequency areas. By keeping the high-frequency detail, the image looks sharper than it really is. Careful examination shows loss of detail in the low-frequency areas, including some blockiness, but from a normal viewing distance the image looks very good. And the high-frequency detail is maintained without the frame-to-frame "sparkle" that is so common with Cinepak.
When one really pushes IVI hard--I asked it to compress a 240 x 180, 30 fps movie to an impossible 90 KBps data rate--it takes a different approach from other codecs: the compressor drops frames to maintain acceptable image quality at the requested data rate. Cinepak and other codecs merely continue to degrade the image to lower the data rate. With the particular clip I was working with, Cinepak yielded a full 30 fps movie, but with image quality that was totally unacceptable because it was so blocky. IVI, however, gave reasonable image quality, but only at 7 fps. I'm not sure if I like this method of doing things, as it takes some degree of control away from me--hey, I may like the blocky look--but I suppose it is a valid approach to the problem of unreasonably low data rates.
The picture changes, though, when you use IVI on older, slower systems. Copying the movies that played fine on the Pentium over to the 25 MHz 486 showed just how processor-hungry IVI is. Although the data rate was quite low on the movies--it varied from 90 KBps to 300 KBps--playback yielded a large number of dropped frames, often dropping from the movie's 15 fps to 2-3 fps. Since the movies were playing back from hard disk the only bottleneck is the processor speed. While Intel is very up-front in their literature about IVI needing a "Pentium class" processor, I was surprised what a large difference it made. Intel had a novel solution for this, however. Instead of simply dropping frames, if you specify "scalability" when you compress a movie IVI will dynamically alter the image quality of the playback, based on processor capability. This ensures smooth, albeit visually degraded playback.
Given that Intel is in the business of selling processors, it is not surprising that their software requires a lot of computing horsepower. Certainly no one at Intel is going to complain if IVI entices you to go out and upgrade to the latest Pentium-based system. However, given that multimedia and codecs are a highly competitive environment, Intel could hardly force anyone to use their solution. Instead, they have produced a worthy product with good image quality, a unique feature set, and cross-platform capability to make you want to add that computing power.
Intel Video Interactive is available without a licensing fee. You can download the software, both 16- and 32-bit versions, from the Intel Architecture Labs Forum on CompuServe (GO INTELA) or from Intel's Internet site http://www.intel.com.
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Bob Currier is President of Synthetic Aperture, a multimedia production company specializing in digital video and QuickTime VR. He also serves as Sysop of the Macintosh Multimedia Forum on CompuServe.
He can be reached at firstname.lastname@example.org. Be sure to visit the Synthetic Aperture web site at <http://www.synthetic-ap.com/> for more tutorial information, sample content, and information on new media services.
This article orignally appeared in a slightly different form in Computer Video Production magazine.
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