19Pinnacle Systems TARGA 3000
9. Why is the hard drive so important?
There are a number of hardware considerations that can influence your video
recording ability. Some involve the speed at which you can capture video frames
while others affect image quality.
The primary criteria for evaluating digital components of your system is their ability
to keep pace with the stream of data, both video and audio. TARGA 3000 has a
NTSC full frame resolution at 720 x 480 pixels, for a total of 307,200 pixels. At 30
frames per second, that’s 9,216,000 pixels per second. At 32 bits per pixel, that’s
about 36 to 37 MB per second (PAL is about 42 megabytes per second ).
Furthermore, adding sound can increase the data rate by up to 192K per second
(stereo at 48 kHz, 16-bit resolution).
Compression and resolution reduction can bring the data rate within range, but for
best quality videos, you’ll want to work as high in the range as possible. Use a CPU
and disk drive capable of high data rates. They are essential to keeping pace with a
steady stream of video data. (Consider a parallel disk array for fast-access mass
storage.)
In addition, it is imperative that you optimize and defragment your disk before video
recording. This will create contiguous blocks of disk space that can be accessed
more quickly. Disk fragmentation slows disk access, which can affect recording
and playback. And as the disk nears capacity, this problem increases. Use a disk
with a large amount of free space and use a disk utility program to defragment your
hard disk.
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