Broadcasting, Archiving, and Reuse of Videoconferences Through Streaming
By combining video streaming and videoconferencing,
it becomes possible for any number of people to view a videoconference — either live or recorded for on-demand access at a later time. A streamed
can be viewed on desktop PCs using standard streaming media players, such
as Real, Windows Media or QuickTime.
Streaming can dramatically increase the utility
of a videoconference. For example:
- The audience you wish to include in a meeting,
conference, or class may be so large that it's not feasible to
include them all in an interactive multipoint videoconference, but it is
to have a number of the key individuals participate in videoconference.
- You may wish to save the proceedings of a meeting.
- You may wish to make the content of a videoconference-based
class available on-demand for student review.
- In fact, there may be times when you simply
want to record and stream an event, lecture or meeting — you
don't need to videoconference — but you do have a videoconferencing
appliance in the room and wouldn't it be nice if you could employ
that equipment for
A streaming participant cannot interact in a live
videoconference. Streaming is a one-way delivery of media. Various methods
can be employed to provide a streaming participant the means to indirectly
participate, including e-mail and chat rooms.
There are four methods to stream a videoconference:
- All-in-one box solutions.
These devices act as an H.323 device and a streaming server. In operation,
the H.323 face of the device is brought into a point-to-point or multipoint
videoconference. The device removes the H.26x/G.7xx video and audio from
the H.323 envelope and repackages the H.26x/G.7xx into the envelope of
a streaming format such as QuickTime, Real or Windows Media. The streaming
face of the device then sends the content via unicast or multicast to
any user with the proper popular streaming player installed on their
computer. Some devices can also record and store, providing on-demand
access to the content. Examples include:
STARBACK  TorrentCE
This is the easiest option for the end-user,
since all they have to do is to dial into the H.323 streaming server and "invite" them
to join their conference. This "special guest" will then automatically
take up the recording and the streaming at predefined addresses and locations.
First Virtual  Conference Server with Streaming Support
VCON  VCB 1000
These solutions can archive or record a videoconference
with administrative assistance. This means that the end users should inform
the administrator that they need these services, so that they are activated
for the particular session.
Virtual Rooms Videoconferencing Service (VRVS )
This is not really a product but rather a worldwide
service and is mentioned in the Popular Collaborative Technologies section
of this cookbook. Its techniques are based on the same principles as the
Starbak Torrent device, however the implementation is open and free.
- Combination videoconferencing terminal and
streaming encoder. In this approach, two standard devices — a
videoconferencing terminal and a live streaming encoder are interconnected
the analog A/V output of the videoconferencing terminal is fed
directly to the input of a live streaming encoder. The encoder
can be of the
standard Real, Windows Media or QuickTime variety, or can be of
a specialty type such as high-bandwidth MPEG-1 or MPEG-2. Unicast
network transmission can be employed. The stream is viewed using
a standard streaming player appropriate to the encoding choice.
can be recorded and stored on the streaming server for on-demand
can find more details on how to build a streaming encoder from
scratch in the following section titled "A simple streaming encoder".
- Videoconferencing terminals with built-in H.26x
multicast streaming capability. Some high-end videoconferencing
terminals, such as the Polycom FX and the Tandberg 880, have the ability
stream a videoconference that the unit is participating in. VCON
products as well offer a multicast conference mode, where the communication
is conducted through multicast channels, which can be viewed
by many more remote participants, if the moderator allows it. The Quicktime
Player is the most suited for multicast viewing as it has better
default support to connect to multicast sessions. RealNetworks player might
to be tweaked slightly to get it to work with multicast sessions,
although it sometimes works just fine.
- Application service providers (ASP).
Many videoconference bridging service providers provide a streaming option.
The technology that a particular ASP employs will be either of the solutions
#1 (all-in-one box) or #2 (combination
terminal and encoder) described
above. ASP solutions are not included in the following Comparison Guide
because the service characteristics will depend on the technology
employed. Investigate which technology an individual ASP utilizes and
evaluate according to the Comparison Guide.
There are some pros and cons with these methods:
- Video and audio quality
- Con: Solutions #1 (all-in-one box), and #3 (terminals with built-in)
repackage the H.26x/G.7xx compressed video and audio. Although H.26x
compressed video can be streamed, it's not optimized
for streaming. The video quality of H.26x is more susceptible
to degradation from network congestion and packet loss than the made-for-streaming
formats such as Real and Windows Media, in case that is a problem on your network.
. Also, the H.26x formats don't
provide dynamic bandwidth adjusting capabilities such as Real SureStream
and Windows Media Intelligent Streaming.
- Pro: Solution #2 (combination terminal and encoder) decodes the H.26x of the videoconference to baseband
video and audio, and re-encodes to a made-for-streaming format. Solution
#2 provides video of a more consistent quality and can take advantage
of advanced streaming features such as dynamic bandwidth.
- Con: Solution #3 (terminals with built-in) requires IP multicast network transmission. Multicast
is sparsely supported in the commercial Internet. Support in university
and commercial sector intranets is varied. Internet2 supports multicast. Terminals
with built-in are only feasible
if your audience is on multicast-enabled networks.
- Pro: Solutions #1 (all-in-one box) and #2 (combination terminal and encoder) support unicast and multicast network transports.
- Operation and Management
- Con: Solution #2 (combination terminal and encoder)
can be complex to manage if your institution doesn't already support
live media streaming and have people managing that
infrastructure. Videoconference scheduling systems don't support viewing
the pair of devices (videoconference terminal and encoder) as a single
logical entity, and none of the popular scheduling systems currently
control a Real, Windows or QuickTime encoder. Some scheduling system
vendors are considering support for this configuration.
- Pro: Solution #3 (terminals with built-in) and Solution #1 (all-in-one box)
are very easy to operate and manage.
- Con: Solution #3 (terminals with built-in) doesn't
have the ability to record a videoconference.
- Pro: Solution #1 (all-in-one box) has only a very small time delay between the
video conference and the streamed video, unlike all others. This makes it possible to have
quasi-real-time interaction with streamed video using feedback methods such as chat.
#2 combo terminal
Initial set up
Ongoing management and operation
Quality of video and audio during network congestion
fair to poor
fair to poor
Can record conference for on-demand viewing
Cost to support a
small number of concurrent conferences
Cost to support a
large number of concurrent conferences
What to have in mind
Streaming over the Internet creates an unavoidable
delay in the delivery of a videoconference. This is in contrast to the
near-real time delivery of streams between the participants of an H.323
conference. H.323 protocols are fine-tuned to allow the fastest possible
delivery. Streaming protocols on the other hand focus on ensuring reliable
delivery at the expense of speed. All nodes in a streaming process, from
the source encoder to the servers or content delivery network and up to
the player software in the client computer, store a few seconds of the
passing stream in their memory, to recover from possible temporary data
losses over the network. This process is called "buffering". It is
obvious that the delay in the delivery of a stream is the combined buffering
all the transmission stages. This can easily reach 1 minute during a transmission.
So it is important to have in mind that someone watching a conference through
streaming will be at least a few seconds behind. This is useful to know
when tuning your settings. If the viewer of a stream reports low audio
quality and you fix it at the source, there will be this delay until the
viewer hears the improved audio on his side. The exception to this is the all-in-one box,
such as from Starbak. In that case, the time delay is very small because no decoding to
analog and re-encoding back to digital is done.
Another issue, often overlooked is that videoconference
sessions often are accompanied by some form of data sharing like a Power
point presentation in the simplest scenario. Archiving a videoconference
by itself without the presentation might leave the viewer wondering what
the speakers are talking about during the session. One technique is to
send the Power Point as part of the original video, so it gets streamed and recorded
automatically. Another useful technique is to combine
a recorded video with slides and other media via multimedia authoring
tools such as SMIL (Synchronized Multimedia Integration Language), which
creates combined presentations that can be played in most Media Players
today. This would however require post-processing time spent to create
the combined presentation. SMIL is outside the scope of this manual, so
if you need further information you may find it at the relevant pages of
the World Wide Web Consortium .
A simple streaming encoder
"Need forges the arts" as the Ancient Greeks
used to say. If you need to record a videoconference with little time and
at your hands, or just want to try out how it can be done, here is a short
recipe to build your own streaming encoder, to be used in combination with
a videoconference system as in method #2 above.
- Get a computer with at least 1GHz CPU, 128MB of memory and
enough hard disk to accommodate your recordings. A rule of thumb for storage
space is: if you are recording at xKbps
streaming bandwidth, then you need x/2 Mbytes of storage per recording hour. As an example if you
are recording at 300Kbps then you would need 150 Mbytes per hour of recorded
- Install a capture card that can accept audio and video
signals as inputs. Some VGA cards already have this feature, although it
is best to use a specialized card such as the Viewcast Osprey 210,
which costs less than $200.
- Download and install encoder software for the media format
of your choice. Microsoft offers Windows Media Encoder and Real Networks
offers Helix Producer for free on their Web sites.
- Connect audio and video outputs from your videoconference
system (you may find them labeled as VCR outputs) to the inputs of the
- Start the videoconference and then start recording or streaming
from the software package you installed. Both of the above software packages
include wizards that step you through the configuration process. Helix
Producer in particular offers a command line interface that can be very
useful when you want to make a turnkey system. If you include the command
to start encoding in the startup sequence, then you just need to press
the Power On button and the computer will start streaming or recording
with your predefined settings.
- When you are finished, stop the encoder software.
The most common problem that arises when streaming
or recording a session with method #2, is the mixing of the two sound signals:
the local and the remote. Many videoconference systems offer a "mixing"
mode that combines both signals, but its quality is below par. It is safer
use a small recording mixer with the following setup:
the microphone to one of the mixer inputs. This is usually impossible to
do with the microphones that come with videoconference systems, so you will
need an external one.
the audio output of the videoconference system to another mixer input.
an output of the mixer that contains only the microphone signal into the
audio input of the videoconference system.
a mix of the two input signals into your encoder machine, and possibly to
the speaker system of the room.