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 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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This document was uploaded on 04/07/2014.
- Spring '14