AVI files contains the FOURCC Four Character Codes codec ID for the video

Avi files contains the fourcc four character codes

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AVI files contains the FOURCC (Four Character Codes) codec ID for the video compressor in the video stream header.
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Multimedia System 030728.ppt 93 Compression Data Compression data is becoming an important subject as increasingly digital information is required to be stored and transmitted. Data Compression techniques exploit inherent redundancy and irrelevancy by transforming a data file into a smaller file from which the original image file can later be reconstructed, exactly or approximately. Some data compression algorithms can be classified as being either lossless or lossy. Video and sound images are normally compressed with a lossy compression whereas computer-type data has a lossless compression. Multimedia System 030728.ppt 94 Bandwidth Requirement E.g. bandwidth of a typical video file with 24bit true colour and a resolution of 320 (H) x240 (V) pixels Data per frame = 320 x 240 x 24 / 8 = 230kB For desirable motion, we need 15frame per second. Therefore uncompressed data per second = 230k x 15=3.45MB If the video programme is 60 minutes in length, a storage capacity for the video programme requires = 3.45M x 60 x 60 = 12.42GB If we send it over the network, the bandwidth requirement is = 3.45M x 8 = 27.6Mbps Multimedia System 030728.ppt 95 Lossless Compression and Lossy Compression There are two broad categories of data compression: Lossless Compression: Such as planar RGB, tiff and gzip Lossy Compression: Such as mp3, gif and jpeg Lossless An exact copy of the original data is obtain after decompression Lossy Original information content is lost Structure data can be compression to 40 – 60% of original size Any data can be compressed. Sometimes by 90% or more Multimedia System 030728.ppt 96 Lossless Compression Lossless compression – where the information, once uncompressed, will be identical to the original uncompressed data. This will obviously be the case with computer-type data, such as data files, computer programs. Any loss of data will cause the file to be corrupted. A lossless compression algorithm the aim is to reduce the amount of source information to be transmitted. When the compressed information is decompressed, there is no loss of information. Lossless compression is reversible.
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Multimedia System 030728.ppt 97 Lossless Compression Methods An example application of lossless compression is for the transfer over a network of a text file since, in such applications, it is normally imperative that no part of the source information is lost during either the compression or decompression operations. Lossless compression consists of those techniques guaranteed to generate an exact duplicate of the input data stream after a compress/expand cycle. The most popular lossless coding techniques are Entropy , Huffman Coding and Arithmetic Methods .
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