MPEG-1

MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to about 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively) without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting (DAB) practical. Today, MPEG-1 has become the most widely compatible lossy audio/video format in the world, and is used in a large number of products and technologies. Perhaps the best-known part of the MPEG-1 standard is the first version of the MP3 audio format it introduced. The MPEG-1 standard is published as ISO/IEC 11172, titled Information technology—Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s. The standard consists of the following five Parts: Systems (storage and synchronization of video, audio, and other data together) Video (compressed video content) Audio (compressed audio content) Conformance testing (testing the correctness of implementations of the standard) Reference software (example software showing how to encode and decode according to the standard) The predecessor of MPEG-1 for video coding was the H.261 standard produced by the CCITT (now known as the ITU-T). The basic architecture established in H.261 was the motion-compensated DCT hybrid video coding structure. It uses macroblocks of size 16×16 with block-based motion estimation in the encoder and motion compensation using encoder-selected motion vectors in the decoder, with residual difference coding using a discrete cosine transform (DCT) of size 8×8, scalar quantization, and variable-length codes (like Huffman codes) for entropy coding. H.261 was the first practical video coding standard, and all of its described design elements were also used in MPEG-1. Modeled on the successful collaborative approach and the compression technologies developed by the Joint Photographic Experts Group and CCITT's Experts Group on Telephony (creators of the JPEG image compression standard and the H.