| What do they do?
Various hardware and software components allow the import and export of sound and video signals. Older Macs, based on the 68000 series of processors, generally only support sound input and output, with video added in later AV models. Power Macs all have full support for sound, and many have some means of acquiring and delivering video. In all cases, input requires the conversion of analogue electrical signals into digital form, while output reverses the process, from digital to analogue, suitable for delivery to audio amplifier and video/TV systems. How do they work?
Conversion between analogue and digital forms requires special electronics, often now integrated on the motherboard. Older AV Macs had a dedicated processor, while Power Macs use the main processor. The volume of video data is very large, so compression is normally performed using a QuickTime encoding module (codec). QuickTime provides system level support for encoding and decoding digital video for display and editing. Audio alone can be stored uncompressed in raw AIFF format files. Audio is handled by the Sound Manager, with the Sound control panel (or Monitors and Sound) acting as master control. Most recent iMacs, G3 and G4 systems use the FireWire interface with digital video devices, but this will only move video in digital form. What can go wrong with them?
Getting the input signals right and matching the output to external hardware can be tricky, particularly if you’re trying to get your Mac’s video to ‘lock’ onto an external video system, such as a VCR or TV. Otherwise, most issues relate to software and performance limitations. How can I upgrade them?
Keeping up to date with QuickTime and Mac OS releases is most important because their system-level support is crucial. However, if you wish to go beyond the limits of your hardware, you’ll need a third-party sound or video card (PCI or NuBus, depending on your Mac model) or, for USB-equipped iMacs and others, USB adaptors. Further info
Apple’s QuickTime information is helpful and Web sites worth visiting include: DV and FireWire Central, maintained by Bertel Schmitt and Alexei Gerulaitis, offering news and info at www.dvcentral.org/; and the ShareWare Music Machine a massive collection of tools and info on audio and music at www.hitsquad.com/smm | |
