# Personalization of Mobile Multimedia Broadcasting

Authors: Harald Kosch; László Böszörményi; Günther Hölbling; David Coquil; Jörg Heuer
Journal: International Journal of Digital Multimedia Broadcasting
 (2008)

---

## Body

## 1. Introduction

This special issue is devoted to a
well-focused  subject: personalization of mobile multimedia broadcasting. Nevertheless,
the topics of the papers published here demonstrate an amazing diversity. This
phenomenon suggests that our subject is both highly relevant and experiencing a
period of rapid change. Until recently broadcasting has been a
well-established, relatively stable technology. However, new usage scenarios, mobile
consumers together with mobile devices, and the desire for personalized content
are providing new challenges. We currently have many more questions than
answers.We are confronted with a range of subtly
different techniques, such as digital TV, IPTV, video-on-demand, Web-TV, live
casts, mobile TV, peer-to-peer TV, and video-portals, which use different
encoding/decoding standards, transmission protocols, streaming methods, quality-of-service
levels, and interactivity features. In addition, they often require different
bandwidth and different infrastructure.In view of this diversity, it is
sensible to take a fresh look at the basic concepts. The rest of this special
issue is dedicated to presenting a nice selection of timely, ongoing research. Therefore,
this editorial introduction starts (Sections2–4) with a
contextual overview authored by László Böszörményi. This overview concentrates
on “the past and the future of this
topic”—leaving the present, together with all of its
unsolved questions, to be the subject of the rest of the papers.An overview of the different
contributions in this special issue closes this editorial introduction in
Section5.At first glance, broadcasting and
personalization seem to contradict one another. The idea of broadcasting is to transmit
a message from an authority to everybody; the idea of personalization is to
exchange messages between individuals. Broadcasting offers a high degree of
sharing and a low level of privacy. Personalization, on the other hand, usually
offers the opposite: privacy increases, but sharing decreases. There are a
number of basic issues requiring very different, often contradictory treatment,
and strategies. May be the most important of these issues are (1) authenticity
and popularity, (2) personalization and privacy, (3) sharing, (4) interactivity,
and (5) rights management.


## 2. A View at the Past

### 2.1. A Bit of Ancient (Mainly European) History

The idea of broadcasting might have
its roots—as almost everything—in the attitude of the ancient Greeks,
interpreting the thunderbolt as an expression of the anger of Zeus. This
message wasauthentic—coming from the main god directly—and everybody
could perceive it—actually had
to perceive it. There was no way not to listen to Zeus’s “word” and thus,
it did not leave much room for privacy.
There was, however, room for many different
interpretations.Zeus used the air as a common,shared medium, making this kind of
communication very efficient and reliable. If Zeus repeatedly created thunder,
this only emphasized his anger. Thus he used a combination of acoustic and
visual signals, ensuring that it was impossible not to listen to the acoustic
expression of his anger, even with the eyes closed. The combination of these
two modalities still plays an important role today.The first sign ofpersonalization lies in the diversity of
Gods, thus allowing at least a choice among them. In the great war between
Greeks and Trojans, the Greeks, especially Odysseus, followed the goddess Pallas
Athena, whereas the Trojans were advised by Aphrodite. Communication channels were
shared, but with a limited radius.
Privacy was higher and realized though the relative freedom of selecting which god
to follow.In the ancient Jewish religion, God
speaks often personally and in secret to selected persons. He can be heard but
cannot be seen. He speaks a more sophisticated and understandable language than
that of thunderbolts. Eveninteraction is often possible. A choice among gods is, however, not allowed as it is a
monotheistic religion. Greek mythology also permitted some people to interact personally with gods.
Interestingly, in these cases the corresponding god took the figure of a human.
For example, Odysseus meets Pallas Athena in the form of a young swineherd and
his son Telemachus meets the same goddess in the shape of King Menelaus. Incidentally,
they both recognize the presence of Pallas Athena by the phenomenon that their
partner appeared in a supernatural beauty. This suggests that a personal
conversation with a god was seen as something beautiful, whereas an impersonal message, such as thunderbolt, was frightening. Regardless of this, the
message was still very authentic, although personal. Although sharing of communication channels disappeared
for the sake of interactivity, a
certain level of sharing was still available, as some gods, such as Pallas
Athena, had the admirable capability to appear at two different physical places
at the same time—we would say a kind of virtual replication.Greek gods were omnipresent, and
thereforemobility was not a problem.
Greek people were extremely mobile and could listen to their favorite god or goddess
everywhere as, unlike some later people, they did not need a special church for
this. Communication seemed to work without difficulties also among people. The Greeks
(consisting of many small groups of people) and the Trojans were at war, but
they never experienced difficulty in speaking with or understanding one another.
Unfortunately, we do not know in which language they communicated.


### 2.2. Some Medieval History

The second major step in the history
of broadcasting was presumably the invention of printing by Gutenberg in the
fifteenth century. Previously, visual material on paper (or clay, etc.) had to
be physically replicated and transported in order to be broadcasted. This was
extremely expensive. Copying a book manually could take a small group of monks a
year or more and bringing it to a different monastery often took several weeks.
The printed book and especially the invention of the newspaper was a revolution
in the technology of broadcasting. Compared to the ancient Greeks, we can
observe a number of changes. Authenticity starts to decline. Although it was
originally only the Holy Bible that was replicated, fairly soon a large number
of publishers with different levels of authenticity appeared on the scene. Authenticity
was step by step replaced bypopularity. A thunderbolt had to be
perceived regardless of whether people liked it or not. A book or a newspaper
must be bought; it must be liked or “popular.” Whether they are still “true”—authentic—is another question. This obviously led to a
certain degree of contradiction and competition. At the same time, the level of
personalization starts to grow. People have a rich selection of choices. They
also have the opportunity to become
publishers, a process that is definitely easier than it was for Greeks
to become a god (or at least a half-god). At the same time, the issue of right
management emerges: authors of books and newspapers want to have some control
over their publications. Previously they remained even anonymous—their only reward was in the eternity of god.
This changed radically in the new age.


### 2.3. Radio, TV,
Telephony

The next revolution in broadcasting was the appearance
of analogous radio at the beginning of the 20th century and that of
television somewhat later. These “classical” broadcast media resemble in many
senses the communication paradigm of the Greek gods. They transmit a central,authentic message, essentially and continuously; the only “escape”
for listeners is to
change the channel or to switch off the receiver. Beyond channel selection, no
interactivity is provided. Each channel has fixed bandwidth, a fragment of the
spectrum. This channel is shared by all listeners of the same channel,
making broadcasting highly efficient. The senders themselves share the “air” as
a common medium, but try to avoid any kind of further sharing. Even though they
often transmit more or less the “same” information, they try to do this in a
different form—as competition and profit are the basic
principles keeping them alive.The first steps in switching from analog
to digital technology tried to maintain the traditional view of authenticity,
based on a limited number of highly trustable senders. As for sharing, new
competitors have emerged, especially the Internet. Interestingly, for a while,
wireless broadcasting was considered “old-fashioned” technology, as the new
technology was wired. This situation has changed once again.A further, very important aspect was
the appearance of telephony roughly at the same time as analogous radio, the
most important technological step in the development of personal communication.
Railway, beginning with its modern form in the middle of the 19th century, can be regarded as similarly important; however, transportation is not
primarily devoted to communication. Telephony allows people to communicate with
each other synchronized in time while being released from the constraints of
space. Analog telephony relies on circuit switching, giving their customers the
illusion of havingprivate connections while at the same time intensively sharing the same cabling system. Privacy is principally provided, but at
that time everybody is aware of the fact that even private conversations may
have uninvited listeners, not even necessarily on purpose but rather due to
usual errors. Telephone conferences and broadcasting remain rather rare
applications. It is interesting to note that the Internet has been strongly
connected with “plain, old” telephony from the beginning through its use of the
telephone system as a transportation medium.Furthermore, extremely significant
step is the appearance of wireless technology both in computer networking and telephony.
The idea of “ubiquitous” computing emerged in the eighties, strongly related with
pervasiveness and mobility.This is—very roughly sketched—the situation in which ongoing research finds
itself. A large number of papers have been published in recent years,
addressing a lot of the issues of this big picture. Instead of trying to
reflect on this diversity, we ask the following
question: what is the future of combined broadcasting, personalization
and mobility?


## 2.1. A Bit of Ancient (Mainly European) History

The idea of broadcasting might have
its roots—as almost everything—in the attitude of the ancient Greeks,
interpreting the thunderbolt as an expression of the anger of Zeus. This
message wasauthentic—coming from the main god directly—and everybody
could perceive it—actually had
to perceive it. There was no way not to listen to Zeus’s “word” and thus,
it did not leave much room for privacy.
There was, however, room for many different
interpretations.Zeus used the air as a common,shared medium, making this kind of
communication very efficient and reliable. If Zeus repeatedly created thunder,
this only emphasized his anger. Thus he used a combination of acoustic and
visual signals, ensuring that it was impossible not to listen to the acoustic
expression of his anger, even with the eyes closed. The combination of these
two modalities still plays an important role today.The first sign ofpersonalization lies in the diversity of
Gods, thus allowing at least a choice among them. In the great war between
Greeks and Trojans, the Greeks, especially Odysseus, followed the goddess Pallas
Athena, whereas the Trojans were advised by Aphrodite. Communication channels were
shared, but with a limited radius.
Privacy was higher and realized though the relative freedom of selecting which god
to follow.In the ancient Jewish religion, God
speaks often personally and in secret to selected persons. He can be heard but
cannot be seen. He speaks a more sophisticated and understandable language than
that of thunderbolts. Eveninteraction is often possible. A choice among gods is, however, not allowed as it is a
monotheistic religion. Greek mythology also permitted some people to interact personally with gods.
Interestingly, in these cases the corresponding god took the figure of a human.
For example, Odysseus meets Pallas Athena in the form of a young swineherd and
his son Telemachus meets the same goddess in the shape of King Menelaus. Incidentally,
they both recognize the presence of Pallas Athena by the phenomenon that their
partner appeared in a supernatural beauty. This suggests that a personal
conversation with a god was seen as something beautiful, whereas an impersonal message, such as thunderbolt, was frightening. Regardless of this, the
message was still very authentic, although personal. Although sharing of communication channels disappeared
for the sake of interactivity, a
certain level of sharing was still available, as some gods, such as Pallas
Athena, had the admirable capability to appear at two different physical places
at the same time—we would say a kind of virtual replication.Greek gods were omnipresent, and
thereforemobility was not a problem.
Greek people were extremely mobile and could listen to their favorite god or goddess
everywhere as, unlike some later people, they did not need a special church for
this. Communication seemed to work without difficulties also among people. The Greeks
(consisting of many small groups of people) and the Trojans were at war, but
they never experienced difficulty in speaking with or understanding one another.
Unfortunately, we do not know in which language they communicated.


## 2.2. Some Medieval History

The second major step in the history
of broadcasting was presumably the invention of printing by Gutenberg in the
fifteenth century. Previously, visual material on paper (or clay, etc.) had to
be physically replicated and transported in order to be broadcasted. This was
extremely expensive. Copying a book manually could take a small group of monks a
year or more and bringing it to a different monastery often took several weeks.
The printed book and especially the invention of the newspaper was a revolution
in the technology of broadcasting. Compared to the ancient Greeks, we can
observe a number of changes. Authenticity starts to decline. Although it was
originally only the Holy Bible that was replicated, fairly soon a large number
of publishers with different levels of authenticity appeared on the scene. Authenticity
was step by step replaced bypopularity. A thunderbolt had to be
perceived regardless of whether people liked it or not. A book or a newspaper
must be bought; it must be liked or “popular.” Whether they are still “true”—authentic—is another question. This obviously led to a
certain degree of contradiction and competition. At the same time, the level of
personalization starts to grow. People have a rich selection of choices. They
also have the opportunity to become
publishers, a process that is definitely easier than it was for Greeks
to become a god (or at least a half-god). At the same time, the issue of right
management emerges: authors of books and newspapers want to have some control
over their publications. Previously they remained even anonymous—their only reward was in the eternity of god.
This changed radically in the new age.


## 2.3. Radio, TV,
Telephony

The next revolution in broadcasting was the appearance
of analogous radio at the beginning of the 20th century and that of
television somewhat later. These “classical” broadcast media resemble in many
senses the communication paradigm of the Greek gods. They transmit a central,authentic message, essentially and continuously; the only “escape”
for listeners is to
change the channel or to switch off the receiver. Beyond channel selection, no
interactivity is provided. Each channel has fixed bandwidth, a fragment of the
spectrum. This channel is shared by all listeners of the same channel,
making broadcasting highly efficient. The senders themselves share the “air” as
a common medium, but try to avoid any kind of further sharing. Even though they
often transmit more or less the “same” information, they try to do this in a
different form—as competition and profit are the basic
principles keeping them alive.The first steps in switching from analog
to digital technology tried to maintain the traditional view of authenticity,
based on a limited number of highly trustable senders. As for sharing, new
competitors have emerged, especially the Internet. Interestingly, for a while,
wireless broadcasting was considered “old-fashioned” technology, as the new
technology was wired. This situation has changed once again.A further, very important aspect was
the appearance of telephony roughly at the same time as analogous radio, the
most important technological step in the development of personal communication.
Railway, beginning with its modern form in the middle of the 19th century, can be regarded as similarly important; however, transportation is not
primarily devoted to communication. Telephony allows people to communicate with
each other synchronized in time while being released from the constraints of
space. Analog telephony relies on circuit switching, giving their customers the
illusion of havingprivate connections while at the same time intensively sharing the same cabling system. Privacy is principally provided, but at
that time everybody is aware of the fact that even private conversations may
have uninvited listeners, not even necessarily on purpose but rather due to
usual errors. Telephone conferences and broadcasting remain rather rare
applications. It is interesting to note that the Internet has been strongly
connected with “plain, old” telephony from the beginning through its use of the
telephone system as a transportation medium.Furthermore, extremely significant
step is the appearance of wireless technology both in computer networking and telephony.
The idea of “ubiquitous” computing emerged in the eighties, strongly related with
pervasiveness and mobility.This is—very roughly sketched—the situation in which ongoing research finds
itself. A large number of papers have been published in recent years,
addressing a lot of the issues of this big picture. Instead of trying to
reflect on this diversity, we ask the following
question: what is the future of combined broadcasting, personalization
and mobility?


## 3. An Attempted Glimpse into the Future: the “French-Revolution” of Broadcasting

We assume that in the future
virtually everybody may broadcast any kind of message at any time and can of
course also receive any such message at any time, at any place, equipped with
any kind of device. We could say that broadcasting will becomedemocratic. That shatters the
fundamentals of broadcasting, as broadcasting is—as we tried to show—basically undemocratic. Therefore, the
development of personalization, mobilization, and enhanced flexibility is not
just an option—but a necessity. In the near future, we can expect
radically new usage patterns to arise, characterized by the following main features.(1)
Digital multimedia will
be produced by many sources and injected into a fully distributed and
multimodal environment at many different locations.(2)
A huge “web” of
multimedia data will be produced and consumed with various aims and
requirements.(3)
Beside entertainment,
professional use of digital multimedia will grow considerably.(4)
Production and
consumption of multimedia data will be better integrated into the computing
environment than is the case today.
In such a world, production, search,
access, delivery, processing, and presentation of multimedia data must become
much more flexible; in many cases it must become “spontaneous.” While spontaneity
is the enrichment in everyday life, it is extremely hard to apply to
technology. Thus research will be confronted with new challenges. Let us
consider a few example scenarios of this new multimedia world.


### 3.1. Some Usage
Scenarios

#### 3.1.1. Live Event with
Professional and Amateur Producers and Consumers

A first example is a live event—such as the “Iron Man” competition, where a
few thousand athletes are competing in swimming, biking, and running on a large
but limited geographical area for several hours—followed by tens of thousands fans. A huge
number of still and moving pictures are created by a variety of sources,
including some professional camera teams, static surveillance cameras, and a
great number of private people equipped with very heterogeneous photographic
abilities. In addition, people with a wide range of interests would like to consume
these pictures. Many of the consumers are watching just for fun, some others in
order to track a certain participant and yet others, such as the event organizers,
are watching to obtain a global view of the whole competition. How can these
users find easily and exactly what they need, without being bothered by long
sequences that they are not interested in? How can they get the required
content without substantial delay and in exactly that quality they require
(neither better nor worse)? Currently, there is no system that is able to cope
with (or even approximately cope with) such a complex and spontaneous world.


#### 3.1.2. Public Motorway
Equipped with Sensors and Cameras

A company operating public motorways
equipped with thousands of sensors and hundreds of cameras actually produces
more broadcast material than a number of TV channels together. This material is
obviously not of a trivial or entertaining nature; nobody wishes to watch
traffic on motorways for days or even hours. What is needed, is a system which
automatically identifies interesting events and offers them to the users (typically
professional staff of the company, may be police and ambulance officers, or even
public users planning their routes) to observe and evaluate. In many cases, the
pictures of one single camera do not suffice, a group of cameras and related
sensors should be identified, delivering relevant data for a certain, important
event (traffic jams, accidents, etc.) or for enabling a global view on a major
section (e.g., traffic in a certain area is quiet, whereas hectic at another,
connected area). Current systems are still very far from providing such complex
services.


### 3.2.
Popularity Management, as a Compromise Between Sharing and Personalization

We have known for many years that popularity of videos
essentially follows the laws of Zipf and Pareto. This means—albeit overly simplified—that roughly 20% of all videos, stored
somewhere accessible over the Internet, will be downloaded or streamed more
than once. The remaining 80% will remain essentially unused. What remains
unreported is that the same laws hold for the scenes inside videos. That is, only
portions amounting to 20% of all downloaded videos will be watched. Putting
these two observations together, we come to the result that ca. 4% of all video
material is watched by a second person (beyond the author), the rest is just
there. However, in the resource management, this issue is hardly considered and
even if, then at most on the level of the popularity of entire videos, but
hardly on the level of individual scenes. Efforts are typically made to provide
good resource management for the entire 100%—although instead what we need is effective
management of the relevant 4%. Even if the resource management takes popularity
into consideration on the level of entire videos and even if techniques, such
as partial caching, do consider popularity on the level of scenes to a certain
extent, a huge potential for savings, up to two orders of magnitude, still
remains. The difficulty is of course obvious as follows: we usually do not know which 4% should
be supported. Therefore, we need a new model of video delivery. Instead of
viewing videos as sequential streams of data (resembling the video-tape
paradigm), they should rather be regarded as direct-access media.
Direct accessibility in several
dimensions include that users should get exactly (1)what they
need, (2) when they need, and (3) how (in what quality) they
need.This implies a transition to a flexible management in
heterogeneous environments. The above observation may open a new chapter in combiningsharing and personalization. Even though classical broadcasting
(sending the same content to everybody) cannot work in future, even “democratic”
systems can efficiently share resources by carefully tracking popularity. To
explore this, let us take a look on such a possible, future delivery system. We
make the following basic assumptions for a new model of video delivery.


#### 3.2.1. Nonlinear Video Delivery

We assume that videos are rarely
watched sequentially. In many usage scenarios, and especially professional
situations, people want to quickly find certain scenes and avoid watching long
sequences they are not interested in.


#### 3.2.2. Two-Phase Delivery

We distinguish between videooffering and video delivery. Offering should be fast, interactive and should
provide information about the videos available within a certain context. During
the offering stage, the underlying resource management system should be able to
make preparations for an efficient delivery. We could use a restaurant as a
metaphor. In a good restaurant, guests are served essentially in two main
phases. In the first—the offering phase, they receive the menu and
some appetizer very quickly. This enables them to make their favorite choices
comfortably and also leaves time for the kitchen to be prepared which represents the
second, the delivery phase—the main dish. In a video delivery system, the
whole issue is much more complicated. We might have many “cooks” (video
providers) and many guests and they may even change their roles (and places).
Offering and delivering are overlapped activities all the time. Offering is
push-based, that is, the service provider more or less “aggressively” announces
meta-information about the available content. This must be very fast, as
studies show that it is better to present to the clients something they did not
explicitly require than to present nothing (or a rotating “hourglass”). “Real”
content can be delivered pull-based (or in a hybrid way).


#### 3.2.3. Video Composition/Decomposition

Data should be decomposed into units
of “meaningful” size (how large meaningful is depends on the actual context)
and can be composed under quality-of-service (QoS) constraints into continuous
“movies.” For performance reasons, the decomposition may be performed in a lazy
way, in order to avoid decomposing data which is never used or is only used for
“traditional” streaming in its entiretyA traditional, long, continuous video
is defined as a “special case” as a sequential composition of data units, under
certain QoS constraints (e.g., 25 frame/sec, jitter <10 msec). The
interesting point is that we may compose any data units in any order under
arbitrary QoS constraints. The user becomes thus from a passive consumer to an active
“composer.” This does not mean that the interactive human user always has to
take the burden of the composition: predefined profiles of user-classes may
serve as composition patterns. What is essential is that the system basically
supports free and flexible composition. In real usage scenarios, full freedom
must of course be reasonably restricted.Decomposition and composition
obviously come at a price. Using them only to support traditional usage
patterns is hardly a good idea. However, if we assume that videos are rarely watched
sequentially from the beginning to the end, rather certain important or
“popular” parts are watched often, then we are confronted with new optimization
possibilities. Popular parts may be replicated much more intensively than
others. Moreover, the same data might be replicated in different qualities,
following different replication strategies. Optimal data management is a most
challenging research question.


### 3.3. Self-Organizing Delivery

The delivery system should strive for
self-organization. Each node of the delivery system (no matter whether a
server, a proxy, or a P2P client) can follow a simple, localgoal-function.
A goal is a state of affairs where an optimal utility value is reached and
stabilized over a certain period of time. For example, a proxy could have the
local goal of maximizing of its own throughput by building groups with other
proxies sharing the same kinds of video segments. Even data units might have
goals (e.g., to be replicated somewhere). The system has a required global
behavior, expressed as a global goal. In an ideal self-organizing system,
this global goal emerges as a result of the local behaviors. In practice, some
parts of the global behavior might be controlled in a non-self-organizing manner,
leading to a nonideally self-organizing system.


### 3.4. Trust Management as a Compromise
between Authenticity and Popularity

Who will broadcast in the future? The
answer is simple: virtually everybody. This leads immediately to the question
ofauthenticity. How will we be able to decide on the value of the
received information, if the sender is not necessarily trustable, may be not
even known? This dilemma is of course already very well known, as demonstrated,
for example, by discussions on the value of Wikipedia entries. This becomes more
difficult if the information changes rapidly, as is the case in live events. This
already occurs in some extreme cases, for example, in the case of natural
catastrophes, where pictures and reports of eye witnesses are of high value,
even though the technical or artistic quality is low. If pictures are taken at
such an event, then they usually reach a trusted broadcaster via more or less
“private” communication, who subsequently checks them as far as possible,
before publishing them.It would be, however, much better, if future
broadcasting systems would offer well-defined services (1) to submit input
messages “spontaneously,” (2) to check them for authenticity and to assign a
certain level of trust, and even (3) to offer a way of rewarding the providers
of such input. Authenticity or trust management must become an integral part of
future services.


### 3.5.
Metadata Management as a Compromise between Sending Everybody the Same Versus
Sending Everybody Something Else

What will be broadcasted in the future? Theanswer is once again simple: virtually everything. The content will be multimodal
including continuous data. Moreover, as the previous considerations show, it is
not enough to deliver pure data; we need additional information, generally
called metadata. Level of trust is—for this aspect—an example of metadata. Current scientific literature on multimedia
delivery concentrates almost exclusively on the delivery of “real data.” If metadata
is required, its availability is simply “assumed.” (A good example for this is
the MPEG-7 metadata standard, leaving the delivery of metadata simply out of
scope.) However, in dynamic scenarios, as described above, users have no chance
to get the data they need without sophisticated metadata management. Much more
than a simple electronic program guide (EPG) is needed. As long as one has
the choice between two public TV channels, the selection is relatively easy. If
a user has to choose among 200 channels, then the decision is harder. If a user
has to choose between thousands of sources, some of which cannot be properly
identified but useful, then a radically new technology is required. In Sections
3.2.2, we introduced the idea of
a two-phase delivery, consisting of an offering and a delivery phase. This is a
possible, partial solution for the general issue is that the metadata management must be an
integral part of any future broadcasting system.Also digital right
management (DRM) belongs to the same category. The MPEG-21 standard offers the
necessary tools for interoperable DRM. Why its acceptance is lagging behind the
expectations is one of the questions which are harder to answer. Nevertheless, in
the long term, we can assume with certainty that a business model will be
generally accepted that enables consumers to access digital content as freely
as possible and producers not to starve. There seems to be no alternative. Even
if everybody has the possibility of becoming a broadcaster, no one is likely to
agree with starvation.


## 3.1. Some Usage
Scenarios

### 3.1.1. Live Event with
Professional and Amateur Producers and Consumers

A first example is a live event—such as the “Iron Man” competition, where a
few thousand athletes are competing in swimming, biking, and running on a large
but limited geographical area for several hours—followed by tens of thousands fans. A huge
number of still and moving pictures are created by a variety of sources,
including some professional camera teams, static surveillance cameras, and a
great number of private people equipped with very heterogeneous photographic
abilities. In addition, people with a wide range of interests would like to consume
these pictures. Many of the consumers are watching just for fun, some others in
order to track a certain participant and yet others, such as the event organizers,
are watching to obtain a global view of the whole competition. How can these
users find easily and exactly what they need, without being bothered by long
sequences that they are not interested in? How can they get the required
content without substantial delay and in exactly that quality they require
(neither better nor worse)? Currently, there is no system that is able to cope
with (or even approximately cope with) such a complex and spontaneous world.


### 3.1.2. Public Motorway
Equipped with Sensors and Cameras

A company operating public motorways
equipped with thousands of sensors and hundreds of cameras actually produces
more broadcast material than a number of TV channels together. This material is
obviously not of a trivial or entertaining nature; nobody wishes to watch
traffic on motorways for days or even hours. What is needed, is a system which
automatically identifies interesting events and offers them to the users (typically
professional staff of the company, may be police and ambulance officers, or even
public users planning their routes) to observe and evaluate. In many cases, the
pictures of one single camera do not suffice, a group of cameras and related
sensors should be identified, delivering relevant data for a certain, important
event (traffic jams, accidents, etc.) or for enabling a global view on a major
section (e.g., traffic in a certain area is quiet, whereas hectic at another,
connected area). Current systems are still very far from providing such complex
services.


## 3.1.1. Live Event with
Professional and Amateur Producers and Consumers

A first example is a live event—such as the “Iron Man” competition, where a
few thousand athletes are competing in swimming, biking, and running on a large
but limited geographical area for several hours—followed by tens of thousands fans. A huge
number of still and moving pictures are created by a variety of sources,
including some professional camera teams, static surveillance cameras, and a
great number of private people equipped with very heterogeneous photographic
abilities. In addition, people with a wide range of interests would like to consume
these pictures. Many of the consumers are watching just for fun, some others in
order to track a certain participant and yet others, such as the event organizers,
are watching to obtain a global view of the whole competition. How can these
users find easily and exactly what they need, without being bothered by long
sequences that they are not interested in? How can they get the required
content without substantial delay and in exactly that quality they require
(neither better nor worse)? Currently, there is no system that is able to cope
with (or even approximately cope with) such a complex and spontaneous world.


## 3.1.2. Public Motorway
Equipped with Sensors and Cameras

A company operating public motorways
equipped with thousands of sensors and hundreds of cameras actually produces
more broadcast material than a number of TV channels together. This material is
obviously not of a trivial or entertaining nature; nobody wishes to watch
traffic on motorways for days or even hours. What is needed, is a system which
automatically identifies interesting events and offers them to the users (typically
professional staff of the company, may be police and ambulance officers, or even
public users planning their routes) to observe and evaluate. In many cases, the
pictures of one single camera do not suffice, a group of cameras and related
sensors should be identified, delivering relevant data for a certain, important
event (traffic jams, accidents, etc.) or for enabling a global view on a major
section (e.g., traffic in a certain area is quiet, whereas hectic at another,
connected area). Current systems are still very far from providing such complex
services.


## 3.2.
Popularity Management, as a Compromise Between Sharing and Personalization

We have known for many years that popularity of videos
essentially follows the laws of Zipf and Pareto. This means—albeit overly simplified—that roughly 20% of all videos, stored
somewhere accessible over the Internet, will be downloaded or streamed more
than once. The remaining 80% will remain essentially unused. What remains
unreported is that the same laws hold for the scenes inside videos. That is, only
portions amounting to 20% of all downloaded videos will be watched. Putting
these two observations together, we come to the result that ca. 4% of all video
material is watched by a second person (beyond the author), the rest is just
there. However, in the resource management, this issue is hardly considered and
even if, then at most on the level of the popularity of entire videos, but
hardly on the level of individual scenes. Efforts are typically made to provide
good resource management for the entire 100%—although instead what we need is effective
management of the relevant 4%. Even if the resource management takes popularity
into consideration on the level of entire videos and even if techniques, such
as partial caching, do consider popularity on the level of scenes to a certain
extent, a huge potential for savings, up to two orders of magnitude, still
remains. The difficulty is of course obvious as follows: we usually do not know which 4% should
be supported. Therefore, we need a new model of video delivery. Instead of
viewing videos as sequential streams of data (resembling the video-tape
paradigm), they should rather be regarded as direct-access media.
Direct accessibility in several
dimensions include that users should get exactly (1)what they
need, (2) when they need, and (3) how (in what quality) they
need.This implies a transition to a flexible management in
heterogeneous environments. The above observation may open a new chapter in combiningsharing and personalization. Even though classical broadcasting
(sending the same content to everybody) cannot work in future, even “democratic”
systems can efficiently share resources by carefully tracking popularity. To
explore this, let us take a look on such a possible, future delivery system. We
make the following basic assumptions for a new model of video delivery.


### 3.2.1. Nonlinear Video Delivery

We assume that videos are rarely
watched sequentially. In many usage scenarios, and especially professional
situations, people want to quickly find certain scenes and avoid watching long
sequences they are not interested in.


### 3.2.2. Two-Phase Delivery

We distinguish between videooffering and video delivery. Offering should be fast, interactive and should
provide information about the videos available within a certain context. During
the offering stage, the underlying resource management system should be able to
make preparations for an efficient delivery. We could use a restaurant as a
metaphor. In a good restaurant, guests are served essentially in two main
phases. In the first—the offering phase, they receive the menu and
some appetizer very quickly. This enables them to make their favorite choices
comfortably and also leaves time for the kitchen to be prepared which represents the
second, the delivery phase—the main dish. In a video delivery system, the
whole issue is much more complicated. We might have many “cooks” (video
providers) and many guests and they may even change their roles (and places).
Offering and delivering are overlapped activities all the time. Offering is
push-based, that is, the service provider more or less “aggressively” announces
meta-information about the available content. This must be very fast, as
studies show that it is better to present to the clients something they did not
explicitly require than to present nothing (or a rotating “hourglass”). “Real”
content can be delivered pull-based (or in a hybrid way).


### 3.2.3. Video Composition/Decomposition

Data should be decomposed into units
of “meaningful” size (how large meaningful is depends on the actual context)
and can be composed under quality-of-service (QoS) constraints into continuous
“movies.” For performance reasons, the decomposition may be performed in a lazy
way, in order to avoid decomposing data which is never used or is only used for
“traditional” streaming in its entiretyA traditional, long, continuous video
is defined as a “special case” as a sequential composition of data units, under
certain QoS constraints (e.g., 25 frame/sec, jitter <10 msec). The
interesting point is that we may compose any data units in any order under
arbitrary QoS constraints. The user becomes thus from a passive consumer to an active
“composer.” This does not mean that the interactive human user always has to
take the burden of the composition: predefined profiles of user-classes may
serve as composition patterns. What is essential is that the system basically
supports free and flexible composition. In real usage scenarios, full freedom
must of course be reasonably restricted.Decomposition and composition
obviously come at a price. Using them only to support traditional usage
patterns is hardly a good idea. However, if we assume that videos are rarely watched
sequentially from the beginning to the end, rather certain important or
“popular” parts are watched often, then we are confronted with new optimization
possibilities. Popular parts may be replicated much more intensively than
others. Moreover, the same data might be replicated in different qualities,
following different replication strategies. Optimal data management is a most
challenging research question.


## 3.2.1. Nonlinear Video Delivery

We assume that videos are rarely
watched sequentially. In many usage scenarios, and especially professional
situations, people want to quickly find certain scenes and avoid watching long
sequences they are not interested in.


## 3.2.2. Two-Phase Delivery

We distinguish between videooffering and video delivery. Offering should be fast, interactive and should
provide information about the videos available within a certain context. During
the offering stage, the underlying resource management system should be able to
make preparations for an efficient delivery. We could use a restaurant as a
metaphor. In a good restaurant, guests are served essentially in two main
phases. In the first—the offering phase, they receive the menu and
some appetizer very quickly. This enables them to make their favorite choices
comfortably and also leaves time for the kitchen to be prepared which represents the
second, the delivery phase—the main dish. In a video delivery system, the
whole issue is much more complicated. We might have many “cooks” (video
providers) and many guests and they may even change their roles (and places).
Offering and delivering are overlapped activities all the time. Offering is
push-based, that is, the service provider more or less “aggressively” announces
meta-information about the available content. This must be very fast, as
studies show that it is better to present to the clients something they did not
explicitly require than to present nothing (or a rotating “hourglass”). “Real”
content can be delivered pull-based (or in a hybrid way).


## 3.2.3. Video Composition/Decomposition

Data should be decomposed into units
of “meaningful” size (how large meaningful is depends on the actual context)
and can be composed under quality-of-service (QoS) constraints into continuous
“movies.” For performance reasons, the decomposition may be performed in a lazy
way, in order to avoid decomposing data which is never used or is only used for
“traditional” streaming in its entiretyA traditional, long, continuous video
is defined as a “special case” as a sequential composition of data units, under
certain QoS constraints (e.g., 25 frame/sec, jitter <10 msec). The
interesting point is that we may compose any data units in any order under
arbitrary QoS constraints. The user becomes thus from a passive consumer to an active
“composer.” This does not mean that the interactive human user always has to
take the burden of the composition: predefined profiles of user-classes may
serve as composition patterns. What is essential is that the system basically
supports free and flexible composition. In real usage scenarios, full freedom
must of course be reasonably restricted.Decomposition and composition
obviously come at a price. Using them only to support traditional usage
patterns is hardly a good idea. However, if we assume that videos are rarely watched
sequentially from the beginning to the end, rather certain important or
“popular” parts are watched often, then we are confronted with new optimization
possibilities. Popular parts may be replicated much more intensively than
others. Moreover, the same data might be replicated in different qualities,
following different replication strategies. Optimal data management is a most
challenging research question.


## 3.3. Self-Organizing Delivery

The delivery system should strive for
self-organization. Each node of the delivery system (no matter whether a
server, a proxy, or a P2P client) can follow a simple, localgoal-function.
A goal is a state of affairs where an optimal utility value is reached and
stabilized over a certain period of time. For example, a proxy could have the
local goal of maximizing of its own throughput by building groups with other
proxies sharing the same kinds of video segments. Even data units might have
goals (e.g., to be replicated somewhere). The system has a required global
behavior, expressed as a global goal. In an ideal self-organizing system,
this global goal emerges as a result of the local behaviors. In practice, some
parts of the global behavior might be controlled in a non-self-organizing manner,
leading to a nonideally self-organizing system.


## 3.4. Trust Management as a Compromise
between Authenticity and Popularity

Who will broadcast in the future? The
answer is simple: virtually everybody. This leads immediately to the question
ofauthenticity. How will we be able to decide on the value of the
received information, if the sender is not necessarily trustable, may be not
even known? This dilemma is of course already very well known, as demonstrated,
for example, by discussions on the value of Wikipedia entries. This becomes more
difficult if the information changes rapidly, as is the case in live events. This
already occurs in some extreme cases, for example, in the case of natural
catastrophes, where pictures and reports of eye witnesses are of high value,
even though the technical or artistic quality is low. If pictures are taken at
such an event, then they usually reach a trusted broadcaster via more or less
“private” communication, who subsequently checks them as far as possible,
before publishing them.It would be, however, much better, if future
broadcasting systems would offer well-defined services (1) to submit input
messages “spontaneously,” (2) to check them for authenticity and to assign a
certain level of trust, and even (3) to offer a way of rewarding the providers
of such input. Authenticity or trust management must become an integral part of
future services.


## 3.5.
Metadata Management as a Compromise between Sending Everybody the Same Versus
Sending Everybody Something Else

What will be broadcasted in the future? Theanswer is once again simple: virtually everything. The content will be multimodal
including continuous data. Moreover, as the previous considerations show, it is
not enough to deliver pure data; we need additional information, generally
called metadata. Level of trust is—for this aspect—an example of metadata. Current scientific literature on multimedia
delivery concentrates almost exclusively on the delivery of “real data.” If metadata
is required, its availability is simply “assumed.” (A good example for this is
the MPEG-7 metadata standard, leaving the delivery of metadata simply out of
scope.) However, in dynamic scenarios, as described above, users have no chance
to get the data they need without sophisticated metadata management. Much more
than a simple electronic program guide (EPG) is needed. As long as one has
the choice between two public TV channels, the selection is relatively easy. If
a user has to choose among 200 channels, then the decision is harder. If a user
has to choose between thousands of sources, some of which cannot be properly
identified but useful, then a radically new technology is required. In Sections
3.2.2, we introduced the idea of
a two-phase delivery, consisting of an offering and a delivery phase. This is a
possible, partial solution for the general issue is that the metadata management must be an
integral part of any future broadcasting system.Also digital right
management (DRM) belongs to the same category. The MPEG-21 standard offers the
necessary tools for interoperable DRM. Why its acceptance is lagging behind the
expectations is one of the questions which are harder to answer. Nevertheless, in
the long term, we can assume with certainty that a business model will be
generally accepted that enables consumers to access digital content as freely
as possible and producers not to starve. There seems to be no alternative. Even
if everybody has the possibility of becoming a broadcaster, no one is likely to
agree with starvation.


## 4. Conclusions

Broadcasting is indeed in the state
of a revolution. Our well-known and well-understood concepts have to be
revisited.(1) The idea of a kind of “divine”
authority and authenticity will be replaced by the “democratic” notion of
popularity, tightly coupled with integrated trust management.(2) The traditional view of personalization
based on the free selection between a small number of channels is definitely
outdated. The user must get what she needs, when she needs it and how (in which
quality) she needs it. Especially she shouldnot be presented with
content that she does not need. The traditional view of privacy, of being
encapsulated in a kind of sand-box, will also disappear in the future. Future
broadcast systems will need to be able to switch dynamically between private
and public data and contexts.(3) The sharing of resources based on
sending everybody the same content is outdated. This can be efficiently
replaced by a delivery model that shares information on thepopularity of data and that subsequently favors popular data. This promises a good
compromise between share-everything and share-nothing standpoints.(4) Interactivity will become a
central issue. Not only in the sense that consumers must receive very detailed
metadata, which serves as a basis for making qualified selections, but also in
the sense that everybody may change from being a consumer into a producer and vice
versa.(5) Rights management is probably not
a workable concept and should be replaced by business model. Valid business
models, enabling the highly flexible scenarios as described previously, without
hurting the interests and rights of either producers or consumers must emerge
soon.


## 5. Overview of the Contributions in this Special Issue

This
special issue presents a selection of state-of-the-art research works in the
domain of mobile multimedia broadcasting (MMB) with a focus on personalization.In the first paper “Acceptance threshold: a bidimensional
research method for user-oriented quality evaluation studies,” S.
Jumisko-Pyykkö et al. present a survey of state-of-the-art
methods of acceptation assessment based on subjective user feedback, and study
their validity in the context of mobile television. Personalized multimedia
applications need to make use of multimedia adaptation methods. Two papers of
the special issue present contributions in this domain.In the second paper “Adapting content delivery to limited
resources and inferred user interest,” C. Plesca et al. present
adaptation policies specifically designed for highly dynamic and partially or
fully observable contexts typical of mobile environments with an application to
film browsing service.In the third paper “Efficient execution of service composition
for content adaptation in pervasive computing,” Y. Fawaz
et al. propose a method for executing multimedia documents
adaptation plans based on composition of services.In
the fourth paper “Two-level automatic adaptation of a distributed user profile for
personalized news content delivery,” the authors present a
work that pertains to two major issues of the domain. The first one is the
implementation of personalization features in the specific concept of mobility.
The second one is the collecting and usage of user feedback in order to offer a
better personalized service, which in this case is implemented using machine
learning techniques. An important application domain for MMB services is the
home multimedia environment, in which Universal Plug and Play Audio Visual
(UPnP-AV) devices are often used.In the fifth paper “Context-aware UPnP-AV services for
adaptive home multimedia systems,” M. Papadogiorgaki1 et al. propose
an enhancement of UPnP-AV that enables the adaptation of multimedia content
based on contextual information. In order to offer optimal personalization
features to their users, new MMB applications need to go beyond traditional
adaptation methods based on parameters such as image size, color scale,
bitrates, and so forth. by implementing finer-grained adaptation features. Two examples
of such applications are presented in this issue.In the sixth paper “Region-based watermarking of biometric
images: case study in fingerprint images,” K. Zebbiche et al. propose
a personalization method of biometric images using region-based watermarking. In
the last paper “Extracting moods from songs and BBC programs based on emotional
context,” M. K. Petersen and A. Butkus  make an initial contribution toward
the goal of  emotion-based
personalization by showing how moods can automatically be extracted from songs.Harald KoschLászló BöszörményiGünther HölblingDavid CoquilJörg Heuer



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