Page 96 - DCAP303_MULTIMEDIA_SYSTEMS

Multimedia Systems

notes 3. The size of the video window and the frame rate you specify dramatically affect performance.
In QuickTime, 20 frames per second played in a 160 × 120-pixel window is equivalent
to playing 10 frames per second in a 320 × 240 window. The more data that has to be
decompressed and transferred from the CD-ROM to the screen, the slower the playback.
4. Although interleaving CD-quality audio into your video production will theoretically yield
the highest-quality sound, the volume of data required may be too great to transfer from
the CD-ROM in real-time. Try a lower sampling rate and sample size to reduce the quantity
of audio data.
5. The software compression algorithm you specify will make a dramatic difference in
performance. The Sorenson algorithm or codec, available within both AVI and QuickTime,
is optimized for CD-ROM playback. But take care: it can take many hours of computation
to compress just a few minutes of digital video.
6. Defragment your files before burning the master.
7. If you are working with QuickTime, consider using a specialized application such as
Media Cleaner Pro to automatically optimize your digital video file for playback from
CD-ROM.

5.9 Digital Display standards

Digital display standards are often a combination of aspect ratio, display resolution, color depth,
and refresh rate.

5.9.1 Monochrome Display adapter (MDa)
Introduced in 1981, MDA was a pure text display showing 80 character lines with 25 vertical lines
on the screen. Typically, the display was green text on a black background. Individual characters
were 9 pixels wide by 14 pixels high (7 × 11 for the character, the rest for spacing). If you multiply
that out you get a resolution of 720 × 350 but since the individual pixels were not capable of being
addressed there were no graphics.

5.9.2 Hercules Graphics Card

Noting the 720 × 350 resolution of the MDA display, a company called Hercules Computer
Technology, in 1982, developed an MDA-compatible video card that could display MDA text as
well as graphics by having routines to individually address each pixel in the display. Because
the screen height had to be a multiple of four, the full resolution of the Hercules Graphics Card
was 720 × 348.
The Hercules card addressed two graphic pages, one at B0000h and the other at B8000h. When
the second page was disabled, there was no conflict with other adapters and the Hercules card
could run in a dual-monitor mode with CGA or other graphics cards on the same computer.
Hercules even made a CGA-compatible card called the Hercules Color Card and later the Hercules
Graphics Card Plus (June 1986) followed by the Hercules InColor Card (April 1987) which had
capabilities similar to EGA cards.
5.9.3 Colour Graphics adapter (CGa)
The CGA card came with 16 KB of video memory and supported several different modes:

1. Text mode which included 80 × 25 text (like the MDA system) in 16 colours. The resolution,
however was lower as each character was made up of 8 × 8 pixels instead of the MDA’s

90 LoveLy professionaL University