An operating system is defined as a computer software component that coordinates and manages the resources or activities of the computer. There are two types of operating systems; system and application system. They are used in handling hardware and matching them with different programs that run in the computer making the computer to function. A trusted operating system must be very flexible in terms of security, scalability and performance in order to manage a larger workload in a specified time frame (Abiodun, 2011). However, the operating system security is balanced with performance in order to avoid interferences that can easily arise when security is considered more than performance.
Multimedia applications often handle large amount of data and processors. Distributed multimedia applications and systems play a very vital role in current and future information society. The main concept is borrowed from real time applications where systems operate concurrently without considering a distance or geographical location of the serves or machines and databases (Amis, 2013). However, there are soft-real time and hard real time where response time, synchronization skew, delays jitter and performance differ. Multimedia operating systems include UNIX, Windows systems and Linux systems.
Most multimedia applications and systems are grouped as soft-real time since they require timely support where if the deadline is missed, it does not lead to catastrophic events even though the QoS (Quality of Service) degrades. The user may be annoyed yet no major challenges are reported. Best operating systems must support real-time aspect of Quality of Service using real-time scheduling through algorithms (Hecox, 2007). Considering the introduction of new file systems and resource ownership, performance is taken seriously.
In order to come up with scheduling algorithm, the rate monotonic and the earliest deadline are scheduled depending on the disk and the CPU time. This methodology is often based on periodic models that characterize tasks using start time (s), execution time (e) and period (p). In this method, the deadline is considered to be equal to period termination. For instance, when an 8 bit and 8KHZ PCM are encoded, sampling rate and size are generated through a 1 bit stream at a speed of 20ms that are gathered. Period (k) starts at s + (k-1) p, while the execution (e) that has to be ended at s + (k-1) p + d.
Video schemes such as H.263, H.261, MPEG and MJPEG are generated in form of a fixed period with inconstant execution time and frames. However, bottlenecks such as paging, disk input/output and copy operations have been tackled so that the stringent performance requirements are fulfilled. The figure 1.1 below shows how the periodic task can be scheduled.
Figure 1.1 Periodic task model
With virtual memory and processor are given an illusion that they are actually running alone on every computer connected (Deepankar et al., 2005). The physical memory and processor, input/output buses, instruction cashes and other physical resources. In case the processor makes the call, the system gives it a library routine that is used to execute instructions.
When multiple processors are executing instructions at the same time, virtual processors interface with each other in order to share physical resources of the computer such as the power source, CPU, control Unit, and arithmetic logic units and other input /output devices. From the methodology above, there is a great need for latency communication should be achieved through the operating systems used. Windows NT and UNIX operating system are not required for multimedia systems and applications. This is because all the resources being allocated rely on the general purpose algorithms to balance the response time and the throughput leading to fairness in distribution.
However, the algorithm is actually limited to the feedback from application processes on their tasks. Having several architectures, monolithic kernel and other hybrids are executed in the hardware with the help of instruction set. The user is limited by the access controls that have been assigned to him or her hence limited instruction set and low control over resources. Switching overhead between kernel mode and user depends on the operating system in order to address challenges such as costs and address space. Kernels can be improved using SUMO OS and by reducing the protection crossings. In this way, the threads are supported at user level and are actually scheduled at the programmer.
Scheduler activation is considered to be based on user interface or kernel level thread combined in terms of functionality of those specific threads from the kernel. With the development of multiprocessors, cluster computers provide scalable approach in separating virtual machines from physical processors hence reducing interface that is between them. Shared resources such as networks, routers, servers, disks, gateways, file systems and switches are scheduled in the process.
Multimedia systems and applications often impose certain requirements on the operating systems. Multimedia however, have been in a more productive use since the year 1993 to date. The interactive classroom system, video and audio systems with an electronic whiteboard show the transparencies on how the distributed system is mounted (Jennings et al., 2009). There are specific requirements that must be adhered to include low latency, QoS guarantees, high data throughput and high responsiveness. The system has to produce high quality data as per the negotiated QoS parameters such as delay jitters bounded delay, data movement and context switching overhead are among the major challenges.
High responsiveness and low latency implies that delay for audio streams should always be below 150ms that is also acceptable for all the applications. However, if there are no hardware cancellations, therefore the end-to-end delay is same or below 40ms. Synchronization of music and skew often range at an interval of +5ms (Honari, 2011). All the audio streams existing in the telephony requires an average of 16Kbit/s within the CD-quality typically at 1.4Mbit/s. on the other hand, video rate is averagely 64Kbit/s to2Mbit/s. All these requirements may vary from one end to another based on the operating system being used at that particular time. Computer system is known to have several resources that are needed to solve Memory problems, CPU issues, Input/output devices and bandwidth issues. The figure 2.0 below shows these resources and their relationships.
Figure 2.0 Operating system resources
The entire Operating system works concurrently with hardware resources in order to provide a more efficient and flexible user and system related services. It is important to note that computer system efficiently and fairly allocate resources without any conflict through the aid of operating systems (Hemmatfar et al., 2010). Allocation and scheduling of resources happens when they are multiplexed on the temporal domain with the main focus on the disk input/output and CPU resources. Admission controls are always administered to test whether the resources are sufficiently shared at the same time with the available components and programs.
If all the programs and the applications are run concurrently, the queuing system is used in executing the same events without lapsing on each other. First in first out (FIFO) is used as a mode of operation no matter the type of the operating system used for the computer system. There are some commands that are run automatically when the system is restarted or is on depending on the scheduled time by the operating system developers such as Microsoft. All the resources are accounted for and tracked down after being run so that the user is able to know what has been utilized (Pielke, 2013). The user can obtain his/her feedback through feedback control system or adaptation that is inbuilt on the user interface.
Threads and resources are related to each other through their operations that are considered to be mutually dependent on the lottery scheduling within the operating system. Operating systems such as Solaris and Windows NT perform time scheduling that is granted a priority in real-time. These are not adjusted to critical multimedia tasks but are liked to them because real time scheduling takes place for both (Valante et al., 2014). Windows system does not handle high priority multimedia tasks such as video chocking it hence leading to a weak QoS for such applications or programs.
Considering the methodologies and arguments made on the paper, it is true to note that several solutions have been provided to the challenges highlighted regarding the resource sharing, scheduling and allocation of tasks in the computer system. Measures such as Admission control, resource support, paradigm, adaptation support are supported by newer versions of the operating systems such as Windows 2000 to Windows 7 as per Appendix A below.. As newer versions of operating systems come up, more features are incorporated as well making work more easily than before.
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