Video Conference Room: Creation Experience

    A classroom, it is also a hall for video conferences.
    A classroom, it is also a hall for video conferences.
    The class was created from scratch both from the point of view of construction (there were bare walls), and from the point of view of experience in implementing and using VKS (Skype and the like do not count), in 2007-2008.

    What I wanted to get

    • Classroom with approximately 30 computers.
    • Video conferencing room.
    It was originally planned that foreign teachers would give lectures to our students, and various seminars would be held.
    Based on this, the requirements were formulated for equipment, its configuration and location:
    • The audience is very elongated in length (12 meters), so the information should be displayed on several screens.
    • During the conference you need to be able to transfer the image from the computer.
    • The ability to film both the speaker and the participants in the class.
    • The ability to use modern codecs for video transmission, for a higher degree of compression and lower bitrate (at that time we had a narrow Internet access channel - 2Mbps to the entire university)
    There is no sense in describing the process of choosing hardware in detail - google, forums, manufacturers' websites, documentation for different hardware.
    The main thing is that we quickly decided that we would use a ready-made hardware solution, and not software on a regular computer. Further it will become clear what advantages we got from this. Foreign universities acted as a guideline when choosing equipment, in which such classes already existed and with which we planned to hold regular video conferences, lectures, and seminars.


    It’s not interesting to write about a network and a class: ordinary PCs, Ethernet network 100 Mbit; and video conferencing equipment will be considered in detail.
    The basis was chosen Polycom VSX 7000e in the variant VSX 7800e Presenter. Briefly, what can he (first of all, what interests us):
    • Support for many standards: SIP, H.323, H.239, H.264
    • Connect up to 2 controlled cameras
    • D-sub input for capturing video from a computer
    • Image output to 2 monitors (D-sub and S-video)
    • Video transmission up to 704x576
    • Data transfer (computer image) up to 1024x768
    • Simultaneous participation of up to 4 parties (multi-point video conferencing)

    This kit includes: Polycom VSX 7000e server, PowerCam managed camera, desktop microphone, remote control.

    Polycom VSX 7800e Presenter

    I’d like to say a few words about the camera separately: autofocus, can rotate (± 100 °), tilt (± 25 °) and has 10x optical zoom. Together with the ability to save the position of the camera, this allows you to very quickly (pressing 1 button on the remote control, camera rotation speed of 300 deg / s) transfer the view to the desired part of the audience. There is a more advanced version of this camera: it has a built-in microphone and can track the speaker itself.
    In addition, 2 plasma panels, a second PowerCam controlled camera, a projector, a radio microphone, 2 video dividers (d-sub), KVM for 2 ports, a sound amplifier and speakers mounted in a suspended ceiling, a 19-inch wall-mounted 9U cabinet, a UPS were purchased.

    All the equipment was installed in the closet, and the closet itself was "hidden" under the teacher's desk and locked. The UPS is rack-mountable at 1500VA, everything from the cabinet and the projector is powered by it.

    Cabinet Content

    Later, a second radio microphone (loop) and a mixer / preamplifier were added.
    Only a computer and a KVM switch are available to the teacher.

    Teacher's desk

    Connection diagram in the figure below.

    Wiring diagram

    This whole thing works in 2 modes:
    • Normal computer class:
      KVM switches to the mode when video and audio signals (via a divider) are sent from the computer to the teacher's monitor and projector.
    • Conducting video conferencing:
      Video from the computer goes to the server through the divider, and the output of the D-sub server to the teacher’s monitor and the projector through the KVM switch.

    How is a videoconference and how to manage it

    Prior to the conference, the main parameters can be configured through the on-screen menu using the supplied remote control (the receiver for the remote control is located not only in the server case - which is located in the cabinet, under the table, but also in cameras), or through the web interface from any computer .

    Remote control

    In general, the remote control is a very necessary thing, all control during video conferencing goes through it:
    • Make and answer a call
    • Control your cameras and, if the far side allows, control remote cameras (camera selection, pan, tilt, zoom - PTZ)
    • Sound control (on / off microphone, volume, ...)
    Before the conference, the main points where the cameras will look are set using the remote control (the camera position and focal length are set). During the conference, by pressing one button on the remote control, we switch between modes (like selecting a channel on a TV). It is very convenient to switch between pre-selected zones in the audience: for example, from a speaker to a person asking a question from the audience or from one speaker to another.
    Examples of transitions from general plans to large ones, and between different points for large plans.

    Side view of the camera. At first, the camera moves from one extreme point to another with a remote control: the speed is low, you can definitely visit; in the second half of the video, transitions between predefined positions.

    Video from a remote participant is displayed on the screen from the projector (either the screen is divided into several parts, according to the number of participants), and on the plasma screens (they are connected in parallel) - local video. If the conference is multipoint (that is, more than 2 participants), you can enable the mode when the video of that participant who is now "speaking loudly" will be automatically displayed on the whole screen.

    When the remote speaker includes data transfer (video from the computer) - it is displayed on the projector, and the image of the remote speaker moves to the plasma. Those. we simultaneously see the “presentant” from the computer and the speaker himself, and this does not badly enhance the “presence effect”.

    The microphone that comes with the kit is omnidirectional, but the audience is very elongated, so an additional radio microphone is also used. In general, according to the instructions, omnidirectional microphones can be cascaded, but we did not need this. In the case of a conference, when an interpreter is involved on our part, omnidirectional microphones are not needed at all - only the translator uses the microphone.

    To connect a computer (it is not necessary to use a teacher’s computer, sometimes you need to connect a speaker’s laptop), use this box:

    Image share II

    Ideal interface: it has only one button. We press it and the picture from the computer connected to it starts to be transmitted to the remote side; press again - the transmission stops.

    Video and sound quality

    As it was said at the very beginning, at the time of creation, we had a 2 Mbps Internet channel in the Internet. During working hours, the canal was almost always 100% full. Therefore, initially during conferences, calls at a speed of 256 or 384 kbit / s were used. Packet loss (loss is meant not only really packet loss, but also significant delay, i.e. when the data is no longer relevant) periodically there were more than 10%.
    With all this, we got a great sound (there was no noticeable loss of sound), and not a bad picture (7-10 frames / sec). With this bitrate, a 1-2 second pause was noticeable when the first frame from the computer appeared. At first, the frame appeared with very strong compression artifacts, and in 1-2 seconds it became completely clear. These figures are approximate, by eye, moreover, it strongly depends on the chosen priorities: the bitrate will be spent much more - on the speaker’s video or on the data from the computer.
    It is clear that when the packets disappear, the picture freezes, but in fact it was surprising that people of different professions had an attitude to this fading. IT people "painfully" reacted to fading, the attitude to these fading as in the joke is "not neatly, doctor." At the same time, ordinary users, even at 256 kbps, with packet loss and periodic fading of the picture, were delighted with video conferencing. Apparently the whole thing is in perception: the IT specialist first of all sees technique, equipment, technologies, protocols; and a simple user participates in a video conference and does not care how it is done. Although it may be that IT professionals are more difficult to surprise.

    Experience gained and conclusions

    Someone will say: they would put the software “XXX” or “YYY” and get the same thing, but for less money (or even free of charge). I do not agree with this. Typically, these people offer solutions such as Skype, SIP clients, but they forget about some very important things:
    • Cost of equipment with comparable characteristics. Isn't it necessary to buy cameras for software implementation? Necessary. But for some reason, people forget that controlled (PTZ) cameras cost money and not small. A monitor, projector, acoustics?
    • The complexity of software maintenance: you need to configure, somehow cross with additionally purchased hardware.
    • Difficulty of using the software: during the presentation, we get by with one remote control. What about software? Take out the keyboard and mouse? Connect the remote control (another piece of hardware that you need to connect, configure and cross with existing software)

    During the study of this subject area there was not found (maybe they were looking badly) not a single completely ready-made system based on software for an ordinary PC.
    In our case, we got a ready-made, finished system that needed to be configured at a minimum, and using this system is no more difficult than a TV or DVD player, i.e. it can be used by anyone who knows how to handle the remote control.

    The operating experience of this class proved once again what we did right when we decided to use a ready-made hardware solution. As a rule, problems on the “other side” arose in the case of using different software, rather than hardware solutions.
    In my opinion, the main difference between hardware and software solutions is their great thoughtfulness and completeness. Those. either we buy a ready-made solution and apply it at home, or we buy a bunch of cubes, and as in a children's designer we are trying to collect something. It is logical that for 1 on 1 conversations, sitting in front of a computer, a simple webcam with skype is enough, for larger projects this is not enough.

    If we draw an analogy with the servers, then the hardware solution is like a brand HP or IBM server in comparison with a self-assembled server. Both solutions have the right to exist, and both will work, but they are distinguished by reliability, well-thought-out use cases, ease of use. But it is precisely from pleasant trifles, or vice versa, inconveniences that the general impression of the product is formed.

    What now?

    If we were to assemble this class this year, we would most likely choose Polycom with its HDX series (this is a continuation of the VSX series, but with the ability to transmit video in HD quality), but not because of the fact that you want and need HD quality, but due to the fact that previous models are discontinued.
    Even after a few years, there is no need to change our VSX 7000e system to something from the HDX series, for two reasons:
    1. We need a much wider Internet channel, to a large extent this is a purely Russian problem, foreigners have fewer problems with this.
    2. And with whom to communicate in HD quality? This is not only our problem, it is a global problem, the era of HD video conferencing has not yet arrived, it is only approaching.

    About the participants

    The project was implemented by two programmers: Novikov Alexander (author of the article) and Gubaev Alexander (editing the article), under the leadership of Kurbanov Eldar Alikramovich.

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