TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

media aware
delivery unaware
Compression Layer
media unaware
delivery unaware
media aware
delivery aware
Sync Layer
Classification Layer
media unaware
delivery aware
Delivery Layer
Figure 4-1: Classification layer in the MPEG-4 architecture
The proposed MPEG-4 classification layer satisfies the following features:
• Object-Based Abstraction: Classification layer deals with MPEG-4 AVOs as a fundamental
calculation entity. This allows a flexible, extensible, scalable and simple manipulation of the
MPEG-4 scene.
• Flexibility: The flexibility of the proposed Classification layer is achieved by (1) allowing
different classification algorithms to be use (not only the one proposed in this section) (2)
enabling or disabling on the fly the classification process.
• Extensibility: The classification layer can be used to derive new elements for different
domains. As example, we mention the video surveillance system, which simply use a
classification to detect and track objects within the scene.
• Scalability: Classifying object into classes according to some criteria increases the scalability of
the system. The criteria can be specified in terms of visual features (e.g., size and color),
semantic relevance (e.g., relevance to user interest profile, background objects, foreground
objects), service quality (e.g., media features, bit rate, ratio loss), and/or temporal features. For
example, terminal with less capacity can choose to view only video sequence without logo
information, background or others banners.
• Simplicity: we specify an AVO classification based on media QoS. Additional objects and
features can be easily added in a modular and flexible way.
• Application Domain: The proposed classification layer is generic and supports a very broad
range of applications and media transport mechanism.
4.1.2 Audio Visual Object Classification Model
We suppose that we have a collection of MPEG-4 AVOs, which must be classified into
classes. The numbers of classes are well defined and each class has a well-known characteristics. A
class is viewed as a class of service of a network layer. It can be an IP Diffserv class (Best Effort,
EF or AFx class), an ATM class of service (ABR, VBR, UBR, etc.), or any others mechanisms that
deliver network QoS. Figure 4-2 shows a collection of MPEG-4 objects described by a collection of
object descriptors. These AVOs can be classified according to some attributes (features). The
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