Image Processing Reference
In-Depth Information
12
The MPEG-4 Part 2 Codec
12.1
MPEG-4
The evolution of the video-compression systems designed by MPEG continues with
MPEG-4. Some people assume that MPEG-4 is just another video codec, but it is much
more than that. It includes a lot of multimedia capabilities for delivering a variety of
audio-visual experiences as well as interactive support.
There are two video-coding standards included in MPEG-4 (part 2 and part 10). Up
to the end of 2003, when people referred to MPEG-4 video, they were generally talking
about MPEG-4 part 2, which describes the visual content.
Today it is too ambiguous just to say, “I am coding my video in MPEG-4.” You must
qualify that by specifying the following:
Which version (1, 2, 3, 4, or another version)
●
Which part (2 or 10)
●
What profile
●
What level
●
12.2
New Terminology Introduced
MPEG-4 video coding introduces some new terminologies based on the concept that every
item in the stream is an object. Table 12-1 summarizes some of these new terms.
These groupings support the management of the video in a much more structured
way than was possible previously. This allows arbitrarily shaped regions and alpha-chan-
nel coding to be managed very easily.
12.3
What of Wavelets?
Wavelet transforms are a new mathematical approach that is an alternative to using
the discrete cosine transform (DCT). They work somewhat differently. Some codec
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