TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

much attention for its inherent multi-resolution and progressive characteristics. Many works
[31][32][33][34] have explored this techniques for adaptive video coding. DCT-based coding also
proposes video scalability techniques in many codec such as scalability provided in MPEG-2 and
H.263+. In video scalability, the video is coded in multiple representations. The major applications
of scalability include internet video, wireless video, multi-quality video services, video database
browsing etc.
Although a simple solution to scalable video is the simulcast technique that is based on
transmission /storage of multiple independently coded reproductions of video. A more efficient
alternative is scalable video coding, in which the bandwidth allocated to a given reproduction of
video can be partially reutilized in coding of the next reproduction of video. Figure 3-9 depicts the
different kinds of video scalability.
Video Scalability
bitstream organization
basic scalability tools
Single layer
Multi-layer
Multiple description
Temporal Spatial SNR FGS Data Content
partitioning (Object)
Figure 3-9: Video scalability coding modes
Grouping scalability according to the organization of the bitstream leads to single layer
scalability, multi-layer scalability, and multiple description scalability. In the single layer scalability,
the data is coded in a single segmented stream. In this case, a simple truncation can be performed
to get lower quality layers. This leads to a fine granularity. In multi-layer scalability the data is coded
in a base layer (BL) stream and one or more enhancement layers (EL) streams. The base layer is a
separately decodable bitstream. The enhancement layers can be decoded in conjunction with the
base layer to increase perceived quality by increasing the picture rate, increasing the picture quality,
or increasing the picture size. A third type of scalability is multiple description scalability, in which
the data is coded in several (at least two) different streams. Multiple description coding provides
two important properties (1) each description can be independently decoded to give a usable
reproduction of the original signal, and (2) the multiple descriptions contain complementary
information so that the quality of the decoded signal improves with the number of descriptions that
are correctly received. Unfortunately this scalability type is in principle less efficient, because
dependencies between the streams cannot be exploited. A number of video coding algorithms have
recently been proposed and they offered much functionality among which error resilient [35], [36],
[37], [38], and [39].
Grouping scalability for video coding according to basic scalability tools lead to temporal
scalability, spatial scalability, SNR scalability, fine grain scalability and object scalability.
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