A bitnoise allocation algorithm is used to determine

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Unformatted text preview: a variety of packet formats (including long and variable-length packets of from 1 KB up to 64 KB) and provides error-correction capability that is suitable for transmission over cable and satellite links. MPEG-2 is backward compatible with MPEG-1. The primary enhancement is centered around the addition of interlaced video. Thus, there are two coding structures (field and frame) in MPEG-2. Other improvements include enhancements on coding efficiency. 3. MPEG-4. Recently, the focus of video coding has shifted to object-based coding at bit rates of 8 Kb/s or lower and 1 Mb/s or higher. Key aspects of this newly proposed MPEG-4 standard include independent coding of objects in a picture frame; the ability to interactively composite these objects into a scene at the display; the ability to combine graphics, animated objects, and natural objects in the scene; and the ability to transmit scenes in higher dimensionality formats (e.g., 3-D). Also inherent in the MPEG-4 standard is the concept of video scalability, both in the temporal and spatial domains, in order to effectively control the video bit rate at the transmitter, in the network, and at the receiver so as to match the available transmission and processing resources. MPEG-4 builds on and combines elements from three fields - digital television, interactive graphics, and the World Wide Web. It aims to provide a merging of the production, distribution, and display elements of these three fields. MPEG-4 is now in the application-identification stage. It currently targets applications with very low bit rates of 48 - 64 Kb/s, such as videophone over the PSTN and visual transmission over mobile facilities. MPEG Audio MPEG audio is a standard for compression and decompression of digital audio. It has been found that whenever a strong signal is present, the spectral neighborhood of weaker audio signals becomes imperceptible to human ears. Measurements of human hearing sensitivity have shown that the ear integrates audio signals that are very close in frequency and treats them as a group. Only when the signals are sufficiently different in frequency will the era perceive the loudness of each signal individually. The coding technique used in M...
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