Multimedia storage, according to Gemmell, Harrick, Vin Dilip, and Venkat (1994) is, a server that “provide access to multimedia objects including text, images, audio, and video” (p1). The design of each server is different. It depends on whether it is conventional or traditional type of multimedia server. For example, it depends on the real-time storage and retrieval and the large storage space and the data transfer rate required for each digital multimedia.The new design allows the server to store wide range of information such as books, periodicals, scientific data, and even video clips.
The services of the storage is for data retrieval where the clients or customers can retrieve or download the data via high-speed networks from the server site and download it later at their own convenience. Even in the process of downloading, the clients or customers can either downloads it at one event or by stop, pause, and resume alternatively. Then the data is stored for later viewing.The fundamental characteristics of the difference in the traditional text/numerical storage of digital audio and video are:
- Real time storage and retrieval, which is also referred as continuous media because it consists of a sequence of media quanta. This media conveys meaning only when the data is continuously presented such as video frames of audio samples. In addition, when the video frames, which also consist of several media components, can be temporary played back while at the same time, it can also be played continuously.
- Large data transfer rate and storage space requirement. When digital audio and video are played back, they required or consume a very high rate. Therefore, it requires multimedia service to provide strong, efficient mechanism for storing, retrieving, and manipulating the data so that they can be retrieved at high speed.
Traditionally, storage servers are designed to provide efficient access to numeric data and textual information. Later the multimedia enhances the storage server to include document with images. From images, it is enhanced to include variety of multimedia research that includes the “analog transmission and storage of audio and video” Gemmell, Harrick, Vin Dilip, Kandlur, Venkat (1994, 2).
As electronic devices are growing in importance and need, market interest in multimedia technology also increases in its importance and need especially in digital multimedia. The term such as “on-demand” digital video server attracts wide attention in the cities and urban areas.To manage a multimedia data, it requires an efficient media information to be stored on individual disks, large disk arrays, and other storage devices. The multimedia data structure is also required to be maintained so that it can facilitate any random access and to ensure efficient support and editing operations. Besides individual multimedia servers, with privatization, commercial multimedia servers are growing.
Digital video yields a sequence of continuously video frames or audio samples such as a stream. It conveys “meaning only when presented continuously in time” (ibid, 5) and the multimedia server will ensure that the playback and recording of each media stream continuous at a real-time rate. At the same time, the server retrieves the data from the disk at the same rate for example microphone or camera in order to prevent buffer overruns.
Similarly, during playback, the server transfers the data to the device output such as speaker or video display. Although the speed rate between input and output is different, the process of retrieving media information and the playback do proceed at real time process and this enables the user to record the information similarly.The server is required to keep enough data in client buffers at all times so that the playback process never becomes vacuum. However, this would require a buffering of the entire stream prior to initiating the playback (ibid).
Large buffer would give large latency of the playback. In other word, small buffer means small latency playback.Generally, data transfer rates of disks is approximately “3-4 MBytes/s, while that of an MPEG encoded video stream is 0.5 MBytes/s, and uncompressed CD-quality stereo audio is about 0. 2 MBytes/s), employing modest amount of buffering will enable conventional file and operating systems to support continuous storage and retrieval of isolated media streams” (ibid, 3).
In practice, a multimedia server processes requests from different clients at the same time. Multimedia server retrieve the data from the media stream disk and multicast it to the clients but are processed at different part even though at the same time.Sometimes, the data transferred are at higher speed than the required speed the clients are using and the amount of storage required for the data transferred.
According to Eng (2007) “a quick look at the new consumer electronics products being developed by companies quickly reveals a fast emerging trend: many devices are turning into smart, digital data devices.”Coughlin (2003), on the other hand, claims that “The increasing sophistication of mobile electronic devices and the size of rich media files is leading to ever greater demands on mobile data storage.
We will continue to see a variety of data storage products filling the needs of this industry. We are also likely to see a continuation of embedded and removable data storage solutions offering advantages.”Cellular telephone, for example, either can capture and send digital pictures or videos through the wireless telephone of the recipients or can transfer the digital picture or videos to the computer, which in turn, will send the picture electronically through the email to the intended recipient.“One of the most critical design factors affecting the performance of mobile devices is their data storage capability,” says Coughlin (2003.)
Mobile devices have many requirements. This may include the “control of power consumption to meet the needs of battery-powered devices; physical size to fit into small electronic devices and possible removability; resistance to severe environmental factors such as shock, vibration, and temperature; and, of course, growing data-storage capacity requirements to meet the needs of rich multimedia content.” Additionally, for the consumers, the price of the data storage is very important criteria in calculating the total cost of the product, which makes the price is highly sensitive to the demand.
On one hand the price of the electronic devices is highly sensitive to the demand, on the other hand, the size of the devices is shrinking. It is getting smaller and smaller to meet the need of the market that requires easy, simple mobility, but easy connectivity, greater access to corporate environment or easy communication, and easy access to other sources of information.Workers today are becoming more and more dependent on the electronic devices. They are requiring electronic devices that are easily mobile, or ones that they can carry from one place to another or anywhere they go with less weight restriction. Computers such as Notebooks or Laptop are getting smaller in size to ease their mobility while traveling.
Like being at the office, they can travel and conduct business at the same time.“Data storage plays a large role in creating this mobile electronic infrastructure,” says Coughlin. He adds, “The growth in mobile information traffic, combined with limited wireless data rates, often interrupted wireless service, and the large file sizes of MP3, MPEG-4, and other multimedia content, makes local data-storage cache an important factor in the delivery of high-quality multimedia experiences.”
In a non-volatile memory, the data of the devices are retained even after the power is turned off. Flash memory can be kept in the device or removed from the device. PCMCIA devices is one of the popular devices with the size of a nickel flash memory card and “is very popular in mobile devices” (Coughlin, 2003) because it is rugged and very small in size.
The device has 128 MB or less and can be used for many applications and with the increase growth in similar product, the market price of this devices seems to be affordable.Another popular device is a small optical device, which is also called the DataPlay WORM – meaning write once, read many times – has the size of 34mm diameter optical disk. This device can store a total of 500MB data. Because the size of the device is very small, the time required accessing the data or information from this device is much less, than the typical CD or DVD drives of a laptop or a desktop.
The price of this device is less than the price of a flash memory.Today, companies such as Hitachi Global Storage Technologies, which is a joint venture between Hitachi and IBM, is developing smaller version of multimedia digital storage devices or is called Microdrive hard disk drive. This miniature storage device, which comes in 27mm, says Eng, has the size of traditional hard drives such as the ones in any computer. However, “the Microdrive can store over four gigabytes of data on disks roughly the size of a U. S. quarters” (Eng).In addition, Toshiba also produces an 1.8-inch or 48mm embedded or removable hard-disk drives.
The cost of this device is lower than the price of MicroDrive per megabyte, but it can handle a large size of video files the size of an MP3 jukebox.Other common storage devices are magnetic disk, floppy disk, magnetic strip and other card-based data storage. For the camera or DVD, for example, most digital video cameras are still using tape whose size is quite small or a MiniDV tape cassette (2.6 x 1. 9 x 0.5 inches). Floppy disk can be very cheap or the cheapest. Although in some cases it can store a large amount of data, the access to this diskette is quite low.
Small hard-dick drives such as flash memory card can be stored separately but it requires electrical connection if we want to read them. The size of this storage device is very small. The disadvantages of these devices are that they require larger volume in the host drive to support them. However, these devices have greater advantages.
For example, when the media application is changed, the content distribution will adjust itself. Whether it has capacity or lower capacity and whether it is removable or non-removable, it requires lower capacity in its application, which is similar to the size of capacity required by a desktop or laptop computers that have hard-disk drives and CD/DVD or floppy drives.In addition to the above data storage devise, WiFi wireless network allows the transfer of data from the server to the clients at a rate of “11 million bits per second (Mbps) depending on the proximity of the wireless network member to the WiFi hub” (Coughlin, 2003).
It allows the clients in this network to share files except for an MPEG-4 video stream, the transmission rate is about 1. 45 million bytes per second (Mbps). This indicates that MPEG-4 stream files requires greater bandwidth than a single WiFi channel, says Coughlin.Generally, digital content or video content requires “large local memory cache for storage such as a small hard-disk drive, optical disk, or even a small magnetic tape” (Coughlin, 2003). Sometimes, as the amount of transmission or data transfer increased, larger local memory cache is need.
Any interruptions in the connectivity, it causes disruptions on live video stream. In order to increase or be able to use the computer that requires large memory cache, it requires a decrease in power usage.The following figure (Figure 2) shows a schematic of a portable wireless multimedia device with a small disk drive, whose content can be down loaded over the World Wide Web. The picture shows the different transfer data rates for two-hour movie.
Some storage devices are non-removable. They are “more compact and mechanically simpler device and better protection from the outside environment” (Couhglin, 2003). These non-removable storage devices part of manufacture settings and as standard mounting hardware capability installed in the computer. Some of them are small such as the size of small hard disk drives in of audio box or about 1.8-inch.
Drive, there is also an even smaller storage device called Cornice with a size of 1.5 GB. It is non-removable and installed in mobiled devices. In addition, other non-removable devices that require low capacities, there is also flash memory that is installed permanently in the hard drive. They can be found in the portable MP3 players, smart phone, and PDA. Unfortunately, non-removable storage or permanent storage always requires expansion.
- Coughlin, T. M. (2003, 5/23). Data Storage for Mobile Devices. Mobile Imperative, Volume 1. Coughlin Associates.
- Eng, P. (2007, Jan. 10). Massive Data Storage in Tiny Devices: Nanotechnology Will Cram More Data in Tiny Storage Devices.
- Kandlur, P.; Venkat, R. (November 14, 1994). Multimedia Storage Servers: A Tutorial and Survey. Retrieved December 17, 2007 fromhttp://www.cc.gatech.edu/classes/AY2001/cs6235_spring/papers/multimedia-tutorial.pdf.