NUI Galway – UL Alliance First Annual ENGINEERING AND - ARAN ...

Abstract
The delivery of multimedia over IP Networks has
seen exponential growth in recent years. IP Networks
provide a flexible delivery system to deliver all type of
information and media data to final users but were not
originally designed with such data in mind.
If IPTV private services providers want to compete
with free cost Internet they need to offer added value to
their product; synchronising multiple media streams
and displaying them to the user-end is one example.
Multimedia synchronisation over IP Networks acquires
particular relevance in sports events and is main focus
of our research.
1. Introduction
The delivery of multimedia service employs two
types of IP Network, public, free and non-managed on
one hand, i.e. public Internet, and private, admission
controlled and managed networks, such as those used
for IPTV, on the other.
One of the main uses of multimedia is the
transmission of sport events where time and timing is
crucial. The challenge we address in our research is to
synchronise logically and temporally related media
streams from different sources and delivered over IP
Network to display combined media. Examples include
a mosaic of multiple video streams, a video and radio
audio or a video visualised with a twitter account. [1]
2. Time/Timing
All humans follow a collection of established
parameters to be able to synchronise among themselves.
People don’t fully appreciate how their lives follow
universal time norms.
An important condition for synchronisation is each
element to synchronise shall have a clock. Two people
can never be synchronised if one of them does not have
a clock thus does not know the time.
Three parameters shall be considered in clocks, time
resolution, time frequency and timestamps.
First of all, time resolution, the smallest time unit
with which a clock is updated; humans typically use
seconds. Secondly time frequency, the rate of time
change, again seconds for human perception. Finally
timestamps is the set time humans establish to meet.
Multimedia systems follow the same structure. To
synchronise multiple multimedia all of them shall have
a clock and run at the same frequency and set up
timestamps to arrange to be synchronised at a precise
moment in time.
3. Multimedia Types
Multimedia Synchronisation
Lourdes Beloqui Yuste, Hugh Melvin
Discipline of Information Technology
College of Engineering & Informatics
lbeloqui@gmail.com, hugh.melvin@nuigalway.ie
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Figure 1: Synchronised Multimedia systems over IP Network
There are multiple type of multimedia each of them
with particular characteristics and a specific way of
convey time and timing, clock references and
timestamps. The most wide spread media types are
video, radio, and web-content.
3.1. Video
The two audio-visual standards used by professional
TV delivery systems are MPEG2 and MPEG4.
MPEG2-2 is actually widely employed whereas
MPEG4-2 use is expanding due to its great
improvement in data compression. MPEG2 and
MPEG4 use as a container MPEG2-1, Transport
Streams, which specifies who to packetise and deliver
video standards.
3.2. Audio
The standard commonly use for audio, internet
radio, is MPEG2-3 using as a container MP3 defined
within the same part.
Audio Advanced Codec (AAC) is defined in
MPEG2-7 and its container is MPEG4-14 MP4 file
format, it has not yet substituted the previous standard.
3.3. Web pages
Web pages include information about different
areas. Web pages such as Twitter include the idea to
follow whatever a person has to say.
8. References
[1] Beloqui Yuste, L., Melvin, H., “Enhanced IPTV Serviced
through Time Synchronisation” The 14 th IEEE International
Symposium on Consumer Electronics (ISCE2010) June 2010.