Transcript MPEG Standards - Florida International University SCIS

MPEG-2 Standard
By
Rigoberto Fernandez
MPEG Standards
• MPEG (Moving Pictures Experts Group) is a
group of people that meet under ISO
(International Standards Organization) to
generate standards for digital video and audio
compression. In particular, they define a
compressed bit stream, which implicitly
defines a decompressor.
The following MPEG standards exist:
• MPEG-1, a standard for storage and retrieval
of moving pictures and audio on storage
media.
• MPEG-2, a standard for digital television.
• MPEG-4, a standard for multimedia
applications.
• MPEG-7, a content representation standard
for information searches.
MPEG-2 Video Compression
The MPEG-2 video compression
algorithm achieves very high rates of
compression by exploiting the redundancy
in video information. MPEG-2 removes
both the temporal redundancy and spatial
redundancy, which are present in motion
video.
• Temporal
redundancy
arises
when
successive frames of video display images of
the same scene. It is common for the content
of the scene to remain fixed or to change only
slightly between successive frames.
• Spatial redundancy occurs because parts of
the picture (called pels) are often replicated
(with minor changes) within a single frame of
video.
Video Stream Data Hierarchy
Video Sequence
Picture Types
• The MPEG standard specifically defines three
types of frames. The picture type defines
which prediction modes may be used to code
each block. These three type of pictures are
defined as follows:
• Intra Pictures (I-Frames)
• Predicted Pictures (P-Frames)
• Bidirectional Predicted Pictures (B- Frames)
Frames
Profile and Levels
A profile is a subset of algorithmic tools and a
level identifies a set of constraints on
parameter values (such as picture size or bit
rate).
The profiles and levels defined to date fit
together such that a higher profile or level is
superset of a lower one. A decoder, which
supports a particular profile and level is only
required to support the corresponding subset
of algorithmic tools and set of parameter
constraints.
Interlaced Video and Picture
Structures
An interlaced video sequence uses one of
two picture structures: frame structure and
field structure.The interlaced video sequence
can switch between frame structures and field
structures on picture-by-pictures basics. On
the other hand, each picture in a progressive
video sequence is a frame picture.
MPEG-2 Advance Audio Coding
• It provides a low bitrate coding for
multichannel audio.
• In general there are five full bandwidth
channels.
• AAC basically makes use of the signal
masking properties of the human ear in order
to reduce the amount of data
Differences between MPEG-2 AAC
and its predecessor ISO/MPEG
Audio Layer-3
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Filter bank
Temporal Noise Shaping TNS
Bit-stream format
Prediction
Quantization
MPEG-2 standard features
• Video compression which is backwards
compatible with MPEG-1
• Full-screen interlaced and/or progressive video
• Enhanced audio coding
• Transport multiplexing
• Other services