Advanced Digital Signal Processing Techniques For Image Processing In Remote Sensing
3. Digital Signal Processing
Microprocessors were mainly used for number crunching in financial departments. Today they are used for many control and decision-making processes. In the future they well be enquired to process numbers while executing algorithms for processing signals of audio and video. To process audio and video signals in real time, special processor architectures are required with special features. Some o these special architectures are listed in the next chapter. Today, most computers are equipped with Video Signal Processors (VSP) and Audio Signal Processors (ASP) of processing video and audio efficiently.
It is important to understand how do digital signal processors differ from micro-processors? In the first place a signal processor has to be capable of performing very large number of operations per unit time. The exact number depends directly on the bandwidth of the signal to be processed. At present the most advanced signal process can handle signals with the bandwidth o f up to several tens of MHz. One of the most common digital operations is the multiplication of pairs of numbers. From two sequences and addition of the product operation of this type are found in algorithms for filtering, correlation, spectral analysis etc. to perform these operations at a reasonably high speed the arithmetic unit must include a multiplier/accumulator combination.
4. The Architecture of a Digital Signal Processor
The basic Von Neumann architecture of the Conventional architecture has many limitations in signal processing .New technologies such as real-time video processing in multimedia are demanding high processing power from the microprocessors. They need to have many processing elements. These multiple processing elements will enable parallel processing. Therefore average instructions/per second will operate increase. This is usually measured in MIPS (million instructions per second ) and MOPS (million operations per second)
One way to overcome executing time barrier is to execute more than one instruction at a time (per lock cycle). Super scalar microprocessor have more than one processing element to process the data. General architecture for high performance microprocessor for signal processing are having super scalar, super pipe lined architecture. To achieve parallel processing (intra-processor parallelism), number of processing elements within I a microprocessor should be increased. In conventional general purpose microprocessor only one arithmetic and logic unit an be found. However in the Pentium processor, there are two ALUSs, enabling the processor to carry out pipe line processing. That is, two ALUs could perform two operations during a single machine (clock) cycle. This is a anther feature that is found in special microprocessor architectures which can be used for digital processing in audio and video application.
5. Harvard & Country Architectures
In Harvard Architectures data and instructions (code) are stored in two separate memories. This will enable to fetch data and code simultaneously. There are two separate connection for data and control information. This will enable to fetch data code simultaneously.
In country architectures, many processing elements are available with wider data paths. Counties are the separate processing elements with certain memory. In general, digital signal processing
For images and audio, simple operations such as addition, subtraction & average (division by 2) to be performed repeatedly for a data steam. Therefore in country architectures each processing element will perform a specific task and to due to many processing element being present in the processor, it is possible to perform many operations per clock cycle or per second.
6. Conclusions
There will be many advanced processor architectures that are used in general purpose computer for image processing. Since such advanced architectures are used in general purpose processors they will be affordable for the general computer users. This will enable remote sensed data to be processed on general purpose computers.
