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Uncompressed video files are enormous. MPEG, pronounced /EM-peg/, is an acronym for the Moving Pictures Experts Group, which was created in 1988 with the goal of created a standard for transfer of video and audio. MPEG is most often used to refer to a group of ISO/ITU standards that are used for compressing digital video and audio data, such as music, video, and movies. ISO/ITU refers to two groups: the International Standards Organization and the International Telecommunications Union; the reference to both of them means that the standard was co-developed. Currently in use are MPEG-1 for video CDs, MPEG-2 for DVDs and digital TV, MPEG-4 for audio and visual data, MPEG-7 for meta-data, and MPEG-21 for digital rights infrastructure.
MPEG-1, along with MPEG-2, forms the MPEG video standard. MPEG-1 was the first, with the standard being finalized as of 1991. Though it was first optimized for smaller resolutions and frame rates—352x240 pixels at 30 frames/sec (fps) or 352x288 pixels at 25 fps—it is capable of resolutions up to 4095x4095 at 60 frames/sec. The optimal transfer rate is 1.5 Mb/sec, but can be higher if necessary.
The two smaller resolutions that MPEG-1 was optimized for are the NTSC and the PAL/SECAM standard respectively. NTSC stands for the National Television System Committee is the body that created the broadcast standard for television in the most of the Americas and parts of Asia. PAL and SECAM are two other television standards. PAL stands for Phase Alternating Line and is a television standard originally developed in Germany and used internationally. SECAM stands for Sequential Couleur Avec Memoire and is a television standard developed in France and used internationally. High Definition (HD) television has superseded all three.
MPEG video, in both MPEG-1 and MPEG-2, is composed of layers of data. The order is: the video sequence layer followed by the group of pictures, then the picture layer, and finally, the slice layer. MPEG-1 and MPEG-2 uses a compression algorithm to selectively encode a “minimum set” of information from the original, removing some of the built in redundancy. This is called a “lossy” coding technique because when the data is decoded, it is not identical to the original: some date has been “lost.” The alternative is a “lossless” technique in which the decoded data is identical to the original.
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