Desktop Video AGOCG Report
The new breed of AV Macintosh not only consolidates new features into a desktop computer but also provides new ways for the user to both work in the office and collaborate with other people, whether they are down the hall or across the country. Telephone services enable the Mac to call people, act as a speakerphone, send and receive faxes and operate as a modem to access on line services. Built in live video hardware lets the user record and play back video and, with the telephone services, handle videoconferencing over a network or an ISDN line. Sophisticated speech recognition technology allows the user to direct the Mac by voice command, while a text to speech engine enables documents to be read out loud with 16 bit CD quality stereo sound, freeing the users to do other tasks as they listen. They can also record QuickTime movies from a camcorder or other video source, or send the screen image to a video recorder or a TV set. These AV Macs treat live video as just another data type that is manipulated by the system and applications.
Apple firmly believes that for multimedia production, as a low cost platform for delivery of multimedia information, as a platform for telephony or video conferencing applications, or for applications requiring speech recognition or text to speech technology, these machines provide a price/performance trade-off that is unrivalled by any other product from any other PC vendor. At the time of writing it is hard to dispute this claim.
There are two new Macs in the vanguard of these developments: the high end Quadra 840AV, with a Quadra 800 hard drive and a 40MHz 68040 processor; and the low end Centris 660AV with a Centris 610 hard drive and a 25 MHz 68040 processor.
Several new hardware and system software components work together to give the AVs their capabilities. There is an analogue to digital (A/D) converter circuit which converts continuously varying signals, such as sound waves, into digital data which the computers can process, and a digital signal processor (DSP), a microprocessor designed to manipulate, convert and modify streams of digitised sounds and video signals. The DSP has the advantage over a traditional microprocessor in that it can do this in real time.
The new AVs can be connected directly to any TV set with a composite video or S-Video input. The Mac's video signal can then be routed to the television set. This means that a conventional television set can be used to show presentations using any of the multimedia authoring tools. This is advantageous, particularly since a 35 inch TV set is much cheaper than a 35 inch monitor. The AVs can also be attached to a video recorder and the Mac's microphone can be used to record a voice over, or mixed in with the QuickTime movie's sound track. Two people with AV Macs can use them as videotelephony machines.
The DSP chip doesn't play a direct role in the video input/output capabilities. These features are provided by a new subsystem located on the computer's logic board. However with appropriate CODEC, the DSP chip could handle video compression in order to reduce the storage requirements of QuickTime movies.
At the time of writing there is talk of Apple releasing the MacTV, which is essentially a Mac LC520 with a TV tuner. It is currently being made in a limited quantity and test marketed. As yet there is a scarcity of information on the product and hence no details can be included in this report. Also, the Power Macs have AV potential by the addition of a low cost board.
Graphics Multimedia Virtual Environments Visualisation Contents