Audio digitized at 22.05 kHz eats up storage at about 1.3 MB per minute.Storage is a major consideration. Data resources such as images, audio, and animation consume awe-inspiring amounts of disk space. As you set up a multimedia development system, ponder your data storage and transfer requirements. Once you start working on multimedia applications, you will quickly learn that the resources that make a title compelling also require a lot of storage.
Audio digitized at 22.05 kHz eats up storage at about 1.3 MB per minute.
Full screen, 256-color images can easily require 200-300K each.
Since you'll want to capture original data to preserve maximum fidelity, you will probably be storing 16-bit audio files at 22.05 or 44.1 kHz, and 24-bit images. You can convert to lower quality levels for delivery with your title, and avoid having to recapture the data when more powerful equipment appears in the future. Recognize, however, that higher quality data typically requires substantial storage.
When you set up your development system, you face many data storage options. There are conventional hard disks of various types and capacities; removable hard disks; tape drives; and optical media, including WORM (Write Once, Read Many) drives and erasable optical drives. Each type of storage device has advantages and disadvantages. Each can play specific role as storage media:
Working Media. Used during working hours to process data.
Archival Media. Used for the long-term storage of images, audio, etc., in the highest resolution possible (24-bit images, 44.1 kHz audio).
Backup Media. Used for day-to-day backup of data.
Your computer's hard disk is your active working storage area. It has to have enough capacity to hold your development software and current data resources. It also has to be fast enough for efficient use.
Two main factors determine the performance of a hard drive: average access time and transfer speed.
Average access time, measured in milliseconds (msec), is how long it takes the drive to find the data the computer has requested. A reasonable range for average access time is 10 to 28 msec, with larger hard disks usually being faster.
Transfer rate is the speed at which the drive can move data in and out of the computer. This is really a critical factor when dealing with large files, animation, or audio. Transfer rate is typically measured in bytes per second. A fast hard disk will transfer data at about 2 MB/sec; a slow hard disk can be as low as 40K per second.
Hard disks are available in sizes from 20 MB to 1.2 gigabyte. (One gigabyte (GB) equals one billion bytes.) You will probably want to consider 150 MB as a minimum size. Although the development process can be distributed among several computers, at least one station should have a hard disk able to hold the assembled application and any associated software.
The critical elements for archival media are storage space, long-term viability, and cost. Optical media, specifically WORM discs, are excellent choices for this purpose.
The basic distinction between types of optical drives is whether you can only read data from it (CD-ROM), write data one time and then read it as many times as you want (WORM), or write and read to it as you would to a hard disk (erasable or rewritable). Each format has strong points: CD-ROM is a great distribution medium, WORM is good for archiving data, and erasable optical (which is often also removable) is ideal in a development system and for transferring data between computers.
Erasable optical drives usually have a slower access time than magnetic drives; typically ranging from 35 to 180 msec. The transfer rate, however, is quite often comparable. Removable cartridges for erasable optical drives extend in size up to about 600 MB.
For daily backup you want a highly reusable media. One that offers adequate storage and retrieval capabilities, and also provides reasonable performance at low costs. Magnetic tape has long served this need.
There is probably more computer data stored on 9-track magnetic tape than on any other medium, and it has long been the standard medium for transferring information around the country—for example, to CD-ROM mastering plants. But it is certainly not a fast or convenient method of getting to your information. And 9-track tapes typically only hold between 30 MB to 80 MB of data.
New developments in magnetic tape technology, however, allow it to remain viable as a storage, transfer, or backup medium. New formats have come out that are smaller, faster, and store more data. One excellent format for digital back-up is (Digital Audio Tape). Various implementations of this format store from 1.2 to almost 3 GB of data and have an average access time of less than a minute, or sometimes a lot less. These drives aren't cheap, but the price is dropping.
DAT is also an ideal format for recording high-quality audio. With its high storage capacity and excellent fidelity, it can hold almost 4 hours of audio digitized at a 44.1 kHz sample rate with 16 bits per sample.
There are a variety of tape drives filling the gap between 9-track and DAT. These range in capacity from about 20 MB to 120 MB and are relatively cheap and slow.
Simply obtaining a single massive storage device isn't necessarily the right solution for you. In many cases, you'll want to have the files distributed throughout your site on different types of devices. The exact details of resource flow will have to be determined for each site.
For example, you might perform all image collection, registration, and editing functions on a local workgroup of personal computers. Other PC workgroups could be dedicated to audio enhancement and text preparation. The central fileserver would only come into use after the resources have been prepared for final incorporation into the application.
Connecting these different types of storage devices to the different computers used at your site can be a complicated process, as various hardware interfaces exist. A SCSI interface is probably the best interface choice for a variety of reasons.
SCSI (pronounced “scuzzy”) stands for Small Computer Systems Interface. The power of this interface lies in its versatility and expandability. A single SCSI interface card lets you attach up to seven devices to a computer—such as hard disks, tape drives, CD-ROM drives, and scanners. And it will typically move information between them at a higher rate than any other interface.
Note, however, that all SCSI interfaces aren't 100% compatible. If you decide to base your development system on a SCSI interface, make sure you purchase your equipment from a dealer who either knows the subject or is willing to let you experiment and take back what doesn't integrate properly.