1.ABSTRACT :
Video streaming applications are commonly
used in both wired and wireless environment; however, wireless links are burden
by higher packet loss ratio and delay variation. In order to make video
transmission possible in wireless networks MPEG video coding is usually used to
reach the bandwidth constrains of the links. The video quality and compression
ratio depends on Group of Pictures (GOP) structure, but it also affects the
distortion sensitivity of the video stream due to packet losses. In this the correlation between GOP size, packet loss
ratio and video quality is investigated. By increasing the distance between the
reference frames the effectiveness of coding can be improved, but on the other
hand the effect of error propagation due to packet losses also increases. Our
aim was to find the optimal GOP structure to maximize the coding efficiency and
minimize the quality distortion due to error propagation. We have implemented a
simulation tool to make the analysis of differently structured video streams
transmitted over lossy channels.
2.EXISTING SYSTEM :
The
real–time applications usually encode audio/video in a format that handles loss
of packets, e.g. MPEG coding standard. MPEG uses intra–frame and inter–frame
compression with different types of frames (I, P and B frames). The repeated
pattern of I, P and B frames in an MPEG video stream is known as the Group of
Pictures (GOP). The choice of GOP structure affects static MPEG properties such
as frame size and file size. This structure also impacts the streaming MPEG in
terms of network bit-rate and video quality.
The
successful decoding ability of the compressed video stream with inter–frame
dependencies depends heavily on the receipt of reference frames (I and P
frames). While the loss of packets in a frame can degrade the video quality,
the more problematic situation is the propagation of errors to dependent
frames. By the increase of the packet loss rate, the quality of the decoded
frames becomes too poor for viewing. The GOP structure defines the frame type layout
of the video; therefore the error propagation extent depends heavily on this
structure. The error will propagate till the next reference frame.
MPEG–4 is an encoding and
compression system for digital multimedia content defined by the Motion
Pictures Expert Group (MPEG).Inter–frame video compression algorithms such as
MPEG–4 exploit temporal correlation between frames to achieve high levels of
compression by independently coding reference frames. In this coding standard
the majority of the frames are represented as the difference from each frame
and one or more reference frames. However, these algorithms suffer from the
well–known propagation of errors effect, because errors due to packet loss in a
reference frame propagate to all of the dependent difference frames. In
existing works the error propagation due to packet losses was analyzed in the
GOP pattern through a theoretical model for the error propagation phenomenon
generated by a frame loss in a distributed video coding framework. Using
rate–distortion functions, they analyzed the impact of a frame loss on the
average distortion of a group of pictures depending on the position of the lost
frame within the GOP.
3.
PROPOSED SYSTEM
We proposed the
distortion due to error propagation and the MPEG–4 coding efficiency together.
We have modeled the error propagation and derived the expected number of
infected frames due to the error spreading in the GOP. Besides analytical
assumptions, we have performed numerous measurements. Based on our results, we
proposed video coding guidelines for videos transmitted over lossy wireless
links. Our measurement results showed that the coding efficiency is more
beneficial then the distortion caused by error propagation and several GOP
structures under different transmission conditions, and the optimal GOP structure, which provide the
best video quality were analyzed. Our aim was to find the optimal distance
between the reference frame in order to maximize the coding efficiency and
minimize the quality distortion due to error propagation. To make these
analyzes, we have implemented a simulation tool. As the result of our
measurements, we were able to recommend the adequate GOP structure for the
given link loss conditions, in order to achieve the best received video
quality.
The
presented related works tried to found a general GOP structure for different
conditions. These solutions can be acceptable, if there is no information on
the link loss ratio and an overall optimum is needed. However, with the new
cross layer solutions the measured link characteristics can be handed over to
the video coding application
4.HARDWARE
REQUIREMENTS:
•
System :
Pentium IV 2.4 GHz.
•
Hard Disk :
40 GB.
•
Floppy Drive : 1.44 MB.
•
Monitor :
15 VGA Colour.
•
Mouse :
Logitech.
•
Ram :
256 MB.
5.Software Requirements:
•
Operating
System : - Windows XP Professional.
•
Front
End :
- Asp .Net 2.0.
•
Coding
Language : - Visual C# .Net.
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