Apple's Little System Extension Takes a Big Step Forward
Jeffy Milstead and Andrew Gore
ALREADY THE LEADING FORMAT for development and delivery of multimedia applications to desktop computers -- Macs as well as Windows machines -- QuickTime is a key ingredient in Apple's recipe for success. The latest version, 2.5, boasts sophisticated new multimedia features yet retains the cut, copy, and paste simplicity that has distinguished Mac technology since day 1.
At its most basic level, QuickTime is a system extension for capturing, editing, and playing back video -- no expensive analog editing equipment is required. But in the
scheme of all things Apple, it's much more. QuickTime is an all-encompassing data architecture and universal file format for creating, storing, editing, and delivering media-rich content.
That's the small and large of it, but what exactly is in the QuickTime software? A major component is a set of codecs that ensure that any computer equipped with the QuickTime extension will be able to play a file encoded with one of QuickTime's built-in compressors. And QuickTime is extensible. With the addition of drop-in codecs, it can support new video-capture and -compression hardware as well as any new software compression schemes that come down the pike.
New components in 2.5 make QuickTime more talented and versatile. It is now truly multiplatform (see the "ActiveMovie" sidebar). Software-based MPEG decoding provides powerful video-playback capabilities, without requiring special hardware. QuickTime's musical capabilities have been beefed up, and QuickTime has made its debut on the Web (see the "QuickTime Plugged In" sidebar). Apple has also made QuickTime much more attractive to video pros.
MPEG for the Rest of Us
Even if you possess only a passing knowledge of QuickTime, you know it has everything to do with playing movies on your Mac. Most of the QuickTime movies on today's CD-ROMs are encoded with QuickTime's Cinepak, a video-compression algorithm that can deliver playback rates as high as 30 fps (frames per second). Frame-playback rates are a key factor influencing how smoothly a movie plays.
MPEG, QuickTime's newest built-in video-compression algorithm, delivers better image quality than Cinepak does. The quality is comparable to what you get with standard VHS tape. As an industrywide standard for motion-video compression, MPEG is the basis for the technology in such common household products as DirectTV, those minisatellite TV systems you find in the local consumer-electronics emporium.
To compress a movie, MPEG uses the keyframes at the start and end of a sequence -- where there is the least motion -- and discards the frames in between. When the sequence is played back, MPEG interpolates between the two keyframes, so the movie plays at the correct length.
In the past, playback of MPEG files, which are compute-intensive, usually required dedicated hardware, such as Apple's MPEG Media System for Performas. The beauty of having MPEG built into the QuickTime software is that no additional hardware is required. You do, however, need a PowerPC-based system to run the QuickTime MPEG extension. With MPEG integrated into QuickTime, you can cut and paste MPEG movies, just as you would any other data type.
Sound in Motion
Sound on the Mac has been inextricably linked to MIDI since the addition of a MIDI track to QuickTime 2.0, in June 1994. The good news was that MIDI's compactness enabled game developers to add impressive soundtracks to their products. But there were limitations: The MIDI track could play only through the QuickTime MIDI synthesizer, which was limited to the 43 built-in instruments and sounds licensed from MIDI-keyboard manufacturer Roland. Because Apple didn't publish the spec for its instrument format, many existing sound libraries available for other MIDI products couldn't be used with QuickTime.
But all that has changed with QuickTime 2.5. Apple's spec is now available, so developers can create MIDI voices by using additional third-party high-quality instrument and sound libraries. And QuickTime can play back MIDI files at 16-bit, 44-kHz stereo. Also worth noting is the new Settings control panel, which lets QuickTime connect its MIDI stream to external instruments, using either Apple's MIDI Manager, Opcode's Open Music System, or Mark of the Unicorn's FreeMIDI system.
These advances, combined with Apple's QuickTime plug-in for Netscape Navigator, allow sophisticated musical interludes to play in the background as graphics-intensive Web pages are loaded. Because MIDI files are tiny compared to their digital-audio counterparts, it takes only seconds for a Web page to deliver an entire Mozart concerto over even the slowest connection (for an example of background MIDI, check out the Mozart page at http://enuff.apple.com/users/chris2x/quicktimeplugin/movies/mozart.html).
The Third Dimension
MIDI is an important non-Apple technology that's gradually been integrated with QuickTime. But look for Apple to use QuickTime to bring its own technology into the mainstream. Case in point: QuickDraw 3D.
Apple's QuickDraw 3D rendering system provides real-time feedback for 3-D modeling and a comprehensive interchange file format for describing model geometry. It has support for dedicated rendering hardware that will reportedly be built into future Apple machines and, like QuickTime, is extensible. In essence, QuickDraw 3D aims to do for 3-D visualization what QuickTime has done for multimedia.
With QuickTime 2.5, you can import and paste QuickDraw 3D objects into QuickTime movies. Full integration means not only that QuickDraw 3D works transparently with existing QuickTime applications but also that 3-D objects placed into QuickTime movies retain all their characteristics: You can resize, edit, or rerender them without affecting other movie tracks.
QuickTime for Pros
In the past, professional video editors have turned to non-QuickTime-based high-end systems, because of QuickTime's limitations for serious video work. Version 2.5 has several features that will make it more attractive to pros. For starters, it offers a common file format for Motion JPEG (MJPEG), the preferred compression algorithm for professional video editing. Unlike MPEG, which works its compression magic by interpolating between keyframes, MJPEG retains information about each individual frame in a movie -- important to video pros.
Currently, there's a multitude of video-capture cards that allow professionals to digitize video from tape. All these high-end cards save digitized video in the MJPEG format, but unfortunately, each card uses a different flavor of MJPEG, so users can't exchange video among systems equipped with different cards.
To address this problem, QuickTime 2.5 includes two new codecs that recognize two common flavors of MJPEG. Out of the box, QuickTime 2.5 can open MJPEG files and convert them to one of the two common flavors, facilitating exchange among systems.
Professional video editors also need speed, and one of the best ways to get it is to divide compression tasks among multiple processors. With this in mind, Apple has added multiprocessing support to QuickTime 2.5. Cinepak compression is now more than twice as fast on a DayStar Genesis MP 600, which is equipped with four processors, as on an otherwise equivalent single-processor machine such as a Power Mac 9500/150.
Among the other professional-video enhancements is support for fields within QuickTime. In NTSC and PAL video, two interlaced fields comprise a single frame. Because QuickTime can now recognize and tag these fields, video-editing tools will be able to accurately convert movies captured from video at 30 fps to film at 24 fps.
Last, reliable synchronization of video and sound has been an issue with very long QuickTime movies used in video production. Version 2.5 aims to address this problem too, by including a new clock component that should make synchronization easy.
Additional Goodies
One of QuickTime 2.5's coolest new features is a Photoshop compression algorithm, which preserves the transfer modes in Photoshop alpha channels. Apple has also made working with QuickTime's text track easier in version 2.5. Using third-party tools such as MovieStar Maker, from Intelligence at Large, you can now modify such text attributes as typeface, color, fade-in/out, and scrolling.
Support for closed-captioned text has also been added. As the video signal from a TV broadcast is digitized, any closed-captioned text embedded in the signal can now be captured and stored in QuickTime's text track. This feature will initially be supported by Apple's TV-tuner card.
Multimedia Landmark
Although many Apple technologies have come and gone, QuickTime has been a solid, consistent performer that has dominated the multimedia landscape. And QuickTime just keeps getting better. Version 2.5 is more than just another milestone on the QuickTime highway -- it marks the beginning of a brave new open-platform world. If you don't believe it, look where the QuickTime team now resides in Apple's new org chart. With the most recent restructuring, Apple CEO Gil Amelio has placed QuickTime in the Alternative Platforms division -- where it truly belongs.
Jeffy Milstead is a senior project leader for MacUser Labs who specializes in video hardware and software. He's been waiting his entire life for the ability to play back ActiveMovie files on his Mac. Andrew Gore is the editor of MacUser.
FOR MORE INFORMATION or to download the latest version of QuickTime, go to Apple's QuickTime site at http://www.quicktim .apple.com/.
