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The EPFL MOOC Factory
Patrick Jermann, Gwenaël Bocquet, Gilles Raimond and Pierre Dillenbourg
ing software heavily compresses the video stream from
the camera, which leads to substandard image quality.
Finally, we installed custom software packages for some
teachers that led to unstable recording performance (i.e.
dropped video frames).
To alleviate these limitations, we are currently designing
a multisource ingest solution that is based on the capture
of three parallel SDI video sources and a separation
of the production and recording units (see Figure 4). This
solution will produce an automatic synchronization of the
three sources and associated audio will save some time
during editing and will also result in a better video quality.
Technical details about specific hardware elements are
beyond the scope of this paper but are available upon request
at the CEDE.
Figure 4. Multisource studio design. Three sources are the FACE
camera, the TOP camera that captures the hand of the teacher
over the tablet and the video signal from the tablet. Production and
recording of the signal are assigned to two dedicated machines.
Reliability
Time in the studio is precious and the studio has to work at
all times. From June to December 2013, the EPFL studio
has been occupied for more than 230 recording sessions.
At the peak of production, three sessions were organized
every day, in the morning, in the afternoon and a late session
starting at 5pm. Luckily, we did not experience major
failures over the summer but it is definitely recommended
to purchase extra light bulbs, a backup computer and if
possible to have a spare camera.
It is most efficient to record the sources in the format
that will be used during editing. We are currently setting
up a fast networking (10 GbE) and storage infrastructure
(32 TB) that will allow several editors to share a common
disk space that can hold the large amounts of data. Our
largest MOOCs take up 3-4 TB of storage space during
editing. After production, we intend to store the rushes
and master files for archival on long-term storage systems
that require less speedy access. The students finally
download 2-3 GB video files from the web to follow a
MOOC.
Conclusion
Our first year of activity has helped us identify the main
requirements of our MOOC production facility. We are
currently consolidating these insights in setting up a production
management solution that corresponds to the
main stages of video production (record, edit, review, finalize,
upload), implementing a multisource video ingest
solution and centralizing the editing process around a
high capacity storage solution.
The standardization of the production process and the
professionalization of the hardware are necessary to produce
10 MOOCs per semester. However, no one rule will
fit all teachers, topics and purposes. Producing a MOOC
should remain an opportunity for teachers to rethink the
way they teach. We have found that adapting to the constraints
of the MOOC format helps teachers to redesign
their course. This is only the beginning of the story. The
biggest change for students following courses on campus
is about what will happen in classrooms as a complement
to the online MOOC offerings.
Links
Center for Digital Education, http://cede.epfl.ch, http://MOOCs.epfl.
ch
Media Template, https://documents.epfl.ch/groups/m/mo/MOOCs/
www/EPFL_MOOCs_Template_PDF.pdf
Invisible hand effect, http://www.youtube.com/watchv=agbe9B5l_VI
Deictic gestures, http://www.youtube.com/watchv=_8ev-qaA4TM
Efficiency
The size of media files produced during the recording is
very large (especially when recording to formats like Pro-
Res) and network transfer rates (100Mb or 1Gb Ethernet)
become a bottleneck. Video editors literally had to
run around with external hard drives to get the data out
of the recording station and take it to the editing stations.
The large size of media also makes it unpractical to encode
and decode video from and to a variety of formats.
Experience Track |233