Digital Signal Processing Reference
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Figure 7.1.
The Role of Content-Based Analysis in Universal Multimedia Access: If
the encoder has access to representations of MPEG-4 sequences and knowledge of
the viewer's bandwidth and hardware resources, the encoder may wish to limit the
bitrates of some objects to maximize the presentation of content.
dia Access (UMA) [Mohan et al., 1998]. UMA is a part of the MPEG-7
standard that describes presentation hardware available at the viewer's
end. In the spirit of MPEG-7, the syntax of UMA frames the roles of fu-
ture technologies without choosing a particular implementation. UMA
within the MPEG-7 syntax provides the means for the transcoder to
understand the viewing resources. Given the receiver's video resources
and hardware, we can recode the video stream for optimal viewing w.r.t.
its content.
Given a limited resource of bandwidth or display hardware, we lever-
age the MPEG-4 or MPEG-7 knowledge of the video content to optimize
the viewer's content (see Figure 7.1). This process of transliterating the
compressed bitstream is called
transcoding.
Unlike rate control which is
content-independent, transcoders recode the video to fit a given band-
width with minimal loss of content. For instance, given a video phone
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