Multimedia Streaming and Proxy Caching
Abstract
The information technology revolution has led to the explosive growth of
the Internet. There is an increased demand for real-time applications like
audio/video streaming and videoconferencing. The increase in demand for
real-time applications, coupled with the convergence of digital multimedia
and the World Wide Web, has ultimately led to the growth of a new technology
called Internet Multimedia. Multimedia transmission over the Internet
takes the form of Streaming.
Multimedia objects are delay sensitive and have timing constraints. Multimedia
streaming is resource intensive and as demand for multimedia data
over the Internet increases, the network will not be able to handle the traffic,
leading to scalability and latency problems. An elegant way to tackle
these problems is through the use of proxy caches. Caching video objects
is difficult because video objects are typically large in size and cannot be
stored in totality at the proxy cache. Video streaming takes place with the
use of real-time protocols like RTSP and RTP and the proxy must be able to
interact with the main server and client/s using these protocols. This thesis
deals with the use of proxy servers that cache streaming video objects. We
emphasize the need for an RTSP enabled proxy server that can communicate
with a group of clients as well as with the main server using RTSP. The thesis
describes a streaming architecture for layered video objects using a proxy.
The thesis also uses the concept of layered caching, where the video is stored
in the form of layers at the cache to increase cache utilization. Quality of
the streams delivered from the cache is also an important aspect of proxy
caching. Our thesis also proposes to measure the quality of streams cached
at the proxy.
Our thesis presents a framework for video caching. A method for the
efficient use of reserved bandwidth is proposed. The bandwidth allocated
using RSVP is used to increase the quality of cached streams. Quality enhancement is achieved with the help of an RTSP enabled proxy that exists
between the main server and the client/s.
A new weight assignment policy based on the playout time of a video
object at the client is proposed. The popularity of the object is evaluated
using the average playout time at the client across all sessions and weight
is assigned based on the popularity of the object. Other weight assignment
schemes are based on frequency of access, recency of access and size of object
and are compared with the new scheme.
A new metric to measure the quality of the cached streams is proposed.
The quality metric proposes to use information about the number of layers
of each object present in the cache, the total number of layers of the object
as well as the relative perceptual significance of each layer, to measure the
quality of the object.
The thesis also brings out a comparative study of various replacement
policies. We study the performances of the existing replacement policies and
the proposed new replacement policy in video caching experiments.
The performance of fine-grained replacement technique for layered video
objects is evaluated. The performances of fine-grained replacement technique
and atomic replacement technique for layered video objects are compared.