When the general term of data is used here, main source of this data is image gray or color, audio, video or both audio and video. Standardization has not proceeded well here, since transport to application are. An application layer serves as a window for users and application processes to access network service. The presentation layer is used to provide a common way for applications residing at the application layer to translate between data formats or perform encryption and decryption. Data compression techniques seminar report, ppt, pdf for. Data compression is the process of modifying, encoding or converting the bits structure of data in such a way that it consumes less space on disk. The computers may use different encoding techniques. This technique will only work well if a relatively small number of data set members possible numerical values or characters. The presentation layer at sending computer changes data according to the senders format. Data compression is popular because of two reasons 1 people like to accumulate data and hate to throw anything away. Presentation layer of osi reference model studytonight. For example, the presentation layer can apply sophisticated compression techniques so fewer bytes of data are required to represent the information when its sent over the network.
Data compression is also known as source coding or bitrate reduction. The original data and the data after compression and decompression are exactly the same because, in these methods, the compression and decompression algorithms are exact inverses of each other. This is a very simple compression method used for sequential data. One of the more popular statistical methods is huffman encoding.
Data compression introduction, data compression types. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Data networks lecture 1 introduction mit opencourseware. Data compression is the process of converting an input data stream or the source stream or the original raw data into another data stream that has a smaller size. This report discusses the different types of data compression, the advantages of data compression and the procedures of data compression.
Data compression provides a coding scheme at each end of a transmission link that allows characters to be removed from the frames of data at the sending side of the link and then replaced correctly at the. Lossless compression compresses the data in such a way that when data is decompressed it is exactly the same as it was before. Data compression techniques free download as powerpoint presentation. Which layer is responsible for encryption and decryption. Coding and compression techniques are critical to the viability of mul timedia at both the. Lossy audio compression algorithms provide higher compression at the cost of fidelity and are used in numerous audio applications. What is the best way to learn about data compression. The presentation layer is responsible for interoperability between encoding methods as different computers use different encoding methods. Usually video compression additionally employs lossy compression techniques like quantization that reduce aspects of the source data that are more or less irrelevant to the human visual perception by exploiting perceptual features of human vision.
An added benefit is greatly improved performance over a network, because you are transferring a reduced amount of the data being read from disk and transferred to the server or direct read application. Presentation layer of osi reference model takes care that the data is sent in such a. Compression technique an overview sciencedirect topics. Data compression methodsdata compression methods data compression is about storing and sending a smaller number of bits. One important motivation for data compression is to allow some efficient transmission of the data via a transmission channel. Flow chart of jpeg compression process divide image into 8x8 pixel blocks apply 2d fourier discrete cosine transform fdct transform apply coarse quantization to high spatial frequency components compress resulting data losslessly and store 8x8 pixel blocks fdct frequency dependent. Data compressionimplies sending or storing a smaller number of bits. This is one of the important parameters in data compression algorithms and the large value of this ratio shows success of a ny algorithm. Data compression reduces the size of data frames to be transmitted over a network link. Session layer obtains virtual end to end message service from transport layer provides directory assistance, access rights, billing functions, etc. Function of application layer in osi model desktop class. Compression predates digital technology, having been used in morse code, which assigned the shortest codes to the most common characters, and in.
Audio data compression, not to be confused with dynamic range compression, has the potential to reduce the transmission bandwidth and storage requirements of audio data. Explore data compression techniques with free download of seminar report and ppt in pdf and doc format. The presentation layer provides the capability to translate the data to suit the applications needs. Encapsulated data travels across the media to the destination. Techniques at each level potential impact of dos attack mitigation options for attack type application layer 7 data message and packet creation begins. In lossless data compression, the integrity of the data. Find a good book or tutorial on general theory of data compression and maybe a good book or tutorial on practical implementation, preferably with code or pseudocode, study them, dig through the repositories like github or sourceforge for act. The presentation layer provides insulation between the various forms of data representation encountered in multivendor environments, much like the asn. The presentation layer is layer 6 of the 7layer open systems interconnection osi model.
For example, small differences in color are more difficult to perceive than are changes in. Data compression is the function of presentation layer in osi reference model. Flow chart of jpeg compression process divide image into 8x8 pixel blocks apply 2d fourier discrete cosine transform fdct transform apply coarse quantization to high spatial frequency components compress resulting data losslessly and store 8x8 pixel blocks fdct frequency dependent quantization zig. Some types of encryption and decryption are performed at the presentation layer. Secure sockets layer protocol ssl is used by the presentation layer for encryption and decryption. Huffman encoding is a technique used to encode symbols according to the frequency of. Understanding voice and data networks flashcards quizlet. Presentation layer presentation layer is the sixth layer of osi model. Jan 26, 2017 the computers may use different encoding techniques. To protect the sensitivity of data, presentation layer encrypts the data at the sender side before the transmission and the receiver side this data is decrypted by the presentation layer at the receiver side. Data compression techniques data compression mp3 free. Data and image compression is a key issue in communications. Presentation layer the presentation layer is concerned with preserving the meaning of information sent across a network. Data compression is a process of compressing the data, i.
Lossy compression lossy compression is the converse of lossless data compression. Application layer services initiate the data transfer. It is used to present data to the application layer layer 7 in an accurate, welldefined and standardized format. Overview of some coding and compression techniques. Clipping is a handy way to collect important slides you want to go back to later. Some of the format types found in this layer are as follows.
Osi layers at the destination unencapsulate the data up the stack. Mnp 5 used in 2400 bps modems which, by the way, most 28800 bps. It is less compact therefore data compression techniques can often overcome this problem. Compression is supported by backup software and tape libraries, so there is a choice of data compression techniques. Compression is often used to maximize the use of bandwidth across a network or to optimize disk space when saving data. Thanks for many comments from students that helped improve the presentation. There are two major layer types, vector and raster. This layer is also able to provide encryption and compression if the application layer asks it to do so.
Data compression and huffman coding powerpoint ppt presentation. It carries out data compression to reduce the bandwidth of the. The presentation layer encrypts data before transmission. The presentation layer is responsible for converting the data sent over the network from one type of representation to another. The presentation layer is sometimes called the syntax layer. Before being transmitted, the data remains in the form of characters and numbers. Presentation layer an overview sciencedirect topics. Howard austerlitz, in data acquisition techniques using pcs second edition, 2003. As suggested by the name itself, the presentation layer will present the data to its end users in the form in which it can easily be understood. Hence, this layer takes care of the syntax, as the mode of communication used by the sender and receiver may be different. This data has to be changed to bitstreams before transmission. Data compression nonsingular, but not uniquely decodable, but x singular uniquely decodable not instantaneous instantaneous 1 0 0 10 0 2 0 010 00 10 3 0 01 11 110 4 0 10 110 111 4. Video is made of different frames same as still image passed in a sequence with 30 frames per second fps typically.
The layer is also responsible for data encryptiondecryption and for compression and decompression. Data compression techniques are broadly classified into lossless and lossy. Entropy coding is a lossless process, while source coding is. To preserve all photoshop features layers, effects, masks, and so on, save a copy of your image in photoshop format psd. Before being transmitted, information in the form of characters and numbers should be changed to bit streams. Also, compression is a way to reduce the number of bits in a frame but retaining its meaning. Audio compression algorithms are implemented in software as audio codecs.
It is a widely used technique used as part of many data compression standards e. Compression and decompression may be done at the presentation layer to improve the throughput of data. Although many methods are used for this purpose, in general these methods can be divided into two broad categories. Concepts from information, theory as they relate to the goals and aluation ev of data compression metho ds, are discussed.
Data representation data representation is defined as the methods used to represent information in computers. Ascii, ebcdic, jpeg, mpeg, tiff, binary, and so on. Therere two major categories for methods to compress data. Now customize the name of a clipboard to store your clips. Like most file formats, psd supports files up to 2 gb in size. We use your linkedin profile and activity data to personalize ads and to show you more relevant ads. In general the lossless compression part is more polished than the lossy compression part.
Many compression techniques are based on statistical relationships among items in a data set. The presentation layer may represent encode the data in various ways e. Layers in the osi model of a computer network dummies. Everything above 2, depending on the type of encryption although i admit there are some physical hardware encryption solutions out there too link encryption 2 link everything including original headers is encrypted network encryption 3 net. Data compression is very important in multimedia such as text, audio, video. Standardization has not proceeded well here, since transport to. There are two general types of compression algorithms. Compression techniques can be categorized as shown in table 71.
Lossless compression techniques symbols combined at a time to form a binary tree. Mechanisms to convert between text formats such as ascii and unicode may be considered part of the presentation layer, along with compression techniques for image. Lossless techniques enable exact reconstruction of the original document from the compressed information. Pros and cons of compression the main advantages of compression are a reduction in storage hardware, data transmission time and communication bandwidth and the resulting cost savings. There are some who believe this is not, strictly speaking, a function of the presentation layer. Introduction to data compression, third edition khalidsayood understanding digital libraries, second edition. It was designed for data encryption, decryption and compression. Jan 28, 2018 everything above 2, depending on the type of encryption although i admit there are some physical hardware encryption solutions out there too link encryption 2 link everything including original headers is encrypted network encryption 3 net. A layer type refers to the way spatial and attribute information are connected. Start studying understanding voice and data networks.
In contrast, dfc could be combined with data compression, opportunistic decoding and many other advanced digital signal processing techniques. Distinguish between lossless and lossy compression. Introduction to data compression, third edition morgan. The primary benefit of compressing your data is to reduce the size of the file to help save disk space. Responsibilities of the presentation layer include data conversion, character code translation, data compression, encryption and decryption. Other functionality within the presentation layer includes data compression, data encryption, manipulating extensible markup language xml objects, and other data handling deemed necessary. It enables reducing the storage size of one or more data instances or elements. Quantization lossy compression technique by itechnica. Introduction to gis basics, data, analysis case studies. The presentation layer is layer 6 of the 7 layer open systems interconnection osi model. Data compression is often referred to as coding, whereas. Reducing the size of a frame reduces the time required to transmit the frame across the network. The presentation layer at receiving computer change data according to the receivers format. Mpeg bitstream consists of a system layer and compression layers.
The sixth layer of the osi model converts data formats between applications and the networks. May 02, 2016 the presentation layer is an important layer in the osi model because it is responsible for some of the important services like data conversion, data compression, encryption, and decryption. Presentation layer provides character code conversion, data encryption, data compression, etc. Data such as multimedia images, video and audio are more easily compressed by lossy compression techniques because of the way that human visual and hearing systems work. Points, lines and polygons spatial data associated with databases of attributes attribute data are considered vector layer types. Guiding the reader through the main techniques, this book explains how practical data and image compression routines are now vital for efficient, low. The presentation layer is an important layer in the osi model because it is responsible for some of the important services like data conversion, data compression, encryption, and decryption. Note that entropy coding only applies to lossless compression. Data compression, also called compaction, the process of reducing the amount of data needed for the storage or transmission of a given piece of information, typically by the use of encoding techniques. Also explore the seminar topics paper on data compression techniques with abstract or synopsis, documentation on advantages and disadvantages, base paper presentation slides for ieee final year electronics and telecommunication engineering or ece students for the year 2015 2016. The presentation layer manages these abstract data structures and allows higherlevel data structureseg.
Ppt data compression and huffman coding powerpoint. An added benefit is greatly improved performance over a network, because you are transferring a reduced amount of the data being read from disk and transferred to. The presentation layer, also called the syntax layer, maps the semantics and syntax of the. The application layer receives data from the network and prepares it for human use. Methods at each end agree before a communication on a.
1373 1257 873 595 723 848 348 284 748 1242 284 1596 1431 1355 16 1200 506 619 779 801 5 72 468 633 1513 1347 996 630 916 625 118 861 1449 427 1444 29 1453 151 740 551 915 721 390 1314 750 1143