TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

varying. If the sender transmits more than the available bandwidth, video packets may be lost in the
channel, especially in the bottleneck links. If the sender transmits lower than the available
bandwidth than the receiver playback a poor video quality. One of techniques to deal with
bandwidth variation is to use adaptive video streaming. The server estimates the available
bandwidth and then adapts it sending rate to much the available bandwidth. Specially, to deal with
the bandwidth it is necessary to choose the best codec that can produce video at certain rates and
when the channel conditions change it applies an adaptive behavior. Some of the video codec
designed for video streaming are presented in Section 3.2.1.1. On other hand, the techniques for
adaptive video streaming are presented in Section 3.2.1.
Packet looses is affected by the traffic pattern and its volume in the network. Packet loss
occurs in general in network routers. Before the packet will be routed, it must be buffered. If the
router buffers are full, all incoming packets will be automatically dropped because of the drop tail
policy used by best effort routers. Many techniques can be used to make TCP source reducing it
sending rate such as implementing RED queue management. This allows avoiding network
congestion and preventing the application entering congestion collapse in which the network link is
heavily used and little useful work is being done. Another type of packet loss is considered when
there is a bit-error in the received packet. Bit error is generally afflicted in wireless environment. To
combat the effect of losses, the video streaming system must be designed with error control in
mind. There are many techniques that can be used to deal with this problem and are presented in
Section 3.2.2.
The transfer delay is the time that the packet experiences from the time when leaving the
server until its reception by the client. This delay varies from one packet to another. It is affected by
the pattern and volume of traffic entering the network. The variation of this delay is called the jitter.
Jitter is a problem, because when a video packet arrives at the client too late it becomes unused. On
other hand, when a packet arrives too fast, it must be buffered and then could produce buffer
overflow. To compensate delay variation, the client includes a customized smoothing buffer also
called playout buffer. Section 3.2.3 addresses this problem.
3.2.1 Bandwidth Management
As seen before, transmitting packet video stream over the IP encounters three major
problems: bandwidth fluctuation, delay variation, and packet losses. It is desired to have techniques
to adapt coding video stream to channel condition, namely adaptive video streaming. Adaptive
video streaming aims to adapt the sending rate to the available data-rate in the network. It addresses
also the problem of heterogeneous receivers. Many techniques exist to implements adaptive video
streaming. In this subsection, we focus on existing techniques for adaptive video streaming.
3.2.1.1 Video Compression Standards
Audio video coding algorithms are greatly correlated to the growth of computation speed of
systems. The most important compression standard for streaming video are proposed by ITU
(International Telecommunication Union) and ISO (International Organization for
Standardization) standardization bodies such as H.261, H.263, MPEG-1, MPEG-2, MPEG-4 and
recently H.264. The majority of available video codec does not survive to streaming in IP
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