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Flexible and automated production of full-fledged electronic lectures [Elektronische Ressource] / Peter Ziewer

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Fakultat fur Informatikder Technischen Universitat Munc henFlexible and Automated Production ofFull-Fledged Electronic LecturesPeter ZiewerInstitut fur InformatikLehrstuhl IIFlexible and Automated Production ofFull-Fledged Electronic LecturesPeter ZiewerVollst andiger Abdruck der von der Fakult at fur Informatik der TechnischenUniversit at Munc hen zur Erlangung des akademischen Grades einesDoktors der Naturwissenschaften (Dr. rer. nat.)genehmigten Dissertation.Vorsitzender: Univ.-Prof. Dr. Arndt BodePrufer der Dissertation:1. Dr. Helmut Seidl2. Univ.-Prof. Dr. Johann SchlichterDie Dissertation wurde am 30. November 2006 bei der Technischen Universit atMunc hen eingereicht und durch die Fakult at fur Informatik am 24. Mai 2007angenommen.AbstractThis thesis describes the automated production of multimedia-based learning mate-rials. Recording of real live lectures enables a lightweight and cost-e e ctive way ofcreating electronic lectures. The exible screen grabbing technology can capture vir-tually any material presented during a lecture and furthermore can be integratedseamlessly into an existing teaching environment in a transparent manner, so thatthe teacher is not aware of the recording process.Throughout this thesis the design and development of a exible and easy-to-use lec-turing environment on the basis of Virtual Network Computing (VNC) is explained.

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Published 01 January 2007
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Fakultat fur Informatik
der Technischen Universitat Munc hen
Flexible and Automated Production of
Full-Fledged Electronic Lectures
Peter ZiewerInstitut fur Informatik
Lehrstuhl II
Flexible and Automated Production of
Full-Fledged Electronic Lectures
Peter Ziewer
Vollst andiger Abdruck der von der Fakult at fur Informatik der Technischen
Universit at Munc hen zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.
Vorsitzender: Univ.-Prof. Dr. Arndt Bode
Prufer der Dissertation:
1. Dr. Helmut Seidl
2. Univ.-Prof. Dr. Johann Schlichter
Die Dissertation wurde am 30. November 2006 bei der Technischen Universit at
Munc hen eingereicht und durch die Fakult at fur Informatik am 24. Mai 2007
angenommen.Abstract
This thesis describes the automated production of multimedia-based learning mate-
rials. Recording of real live lectures enables a lightweight and cost-e e ctive way of
creating electronic lectures. The exible screen grabbing technology can capture vir-
tually any material presented during a lecture and furthermore can be integrated
seamlessly into an existing teaching environment in a transparent manner, so that
the teacher is not aware of the recording process.
Throughout this thesis the design and development of a exible and easy-to-use lec-
turing environment on the basis of Virtual Network Computing (VNC) is explained.
The VNC infrastructure and protocol is adapted to build up an environment that of-
fers scalable transmission of live lectures and is capable of supplying a large number
of distance students in parallel. Furthermore, the suggested system provides com-
fortable lecture recording in order to produce electronic lectures for asynchronous
replay at any time later. These electronic lectures preserve the verbal narration of
the teacher and any material or applications presented during a lecture including
additional annotations (e.g. adding freehand drawings by use of an electronic pen).
Unlike other pixel-based recording environments, the suggested system o ers slide-
based navigation and full text search. This is achieved by automated post-processing
which generates appropriate indexing structures and search bases by analyzing the
recorded lectures. Several analysing concepts are introduced and compared by eval-
uating recorded lectures of di eren t presentation styles.
Furthermore, an implementation of the suggested concepts and ideas { the TeleTeach-
ingTool { is presented and usage scenarios are given in order to approve the usability
and the advantage of the system.Acknowledgment
I would like to thank
Thomas Perst and Pete Bankhead
for their patient e orts in proofreading and
their helpful suggestions and comments.Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Presentation Recording and Transmission . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Electronic Lectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 Terms and De nitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 Usage Scenarios and Bene ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.3 From Traditional to Digital Lectures . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Symbolic Representation vs Screen Recording . . . . . . . . . . . . . . . . . . . . 16
2.3 Lightweight Production and Transparent Recording . . . . . . . . . . . . . . . 23
2.4 Criteria and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.1 Criteria Catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3 VNC: Virtual Network Computing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.1 The VNC Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2 Remote Framebu er Protocol (RFB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.2.1 Common VNC work o w. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.2.2 RFB Message Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2.3 Pixel Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.4 Encoding Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.5 Hextile Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48XIV Contents
3.2.6 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.3 Distance Learning based upon VNC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.3.1 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4 Scalable VNC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.1 Limiting Individual Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.1.1 Reducing Pixel Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.1.2 Encoding Agreement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.1.3 Combining Framebu er Update Requests . . . . . . . . . . . . . . . . . . 60
4.2 One-To-Many Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.2.1 Routing Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.2.2 Communication Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2.3 Size Limitations and Message Dependencies. . . . . . . . . . . . . . . . 64
4.2.4 Splitting Framebu er Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.2.5 Splitting Hextile Encoded Rectangles . . . . . . . . . . . . . . . . . . . . . 67
4.2.6 Parsing and Bu ering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4.2.7 Format of Datagram Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.2.8 Unreliable Transmission: Packet Loss . . . . . . . . . . . . . . . . . . . . . 71
4.2.9 T Out of order Delivery . . . . . . . . . . . . . 73
4.2.10 Additional Unicast Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.2.11 Client Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.2.12 Framebu er Initialization and Late Join . . . . . . . . . . . . . . . . . . . 76
4.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5 VNC Session Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.1 File Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.1.1 Delta Pixel Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.1.2 Recording Distinct Rectangles . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.1.3 Event Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86