Global Video Teleconferencing-- What is it?

The Abstract

Video teleconferencing is an Internet phone that allows people to communicate visually and orally. The development of video teleconferencing (VTC) technology took place in the United Kingdom and the United States. The basic equipment needed for users to participate in VTC is a camera, microphone, strong internet connection, a display (laptop, desktop monitor, television screen, etc.), speakers (built-in computer speakers, external speaker, or headphones), and a video conferencing software/program.

To stream a live video, it must be digitized and packetized using real-time data on a packet-switched network. The playback buffer then separates the arrival time from the playback time, by storing the data until they are played back. When a session begins to play, the receiver only begins to display the data when the threshold (time units) is met. In addition to this, a sequence number for each packet is required because the timestamp alone cannot inform the receiver if a packet is lost. The data is distributed using multicasting methods because conferencing requires two-way communication between receivers and senders. A translator then changes the format of a high-bandwidth video signal to a lower-quality narrow-bandwidth signal. In order to converge multiple streams of traffic, data from different sources are mixed. A mixer mathematically adds signals coming from different sources to create one single signal. Thus, source synchronization is available to several sources to receive the same audio and video to be received.

The Major Parts of Video Teleconferencing

Multicasting

Multicasting allows group communication by transmitting data that is addressed to a group of destination computers at the same time. Multicasting can be used for either one-to-many or many-to-many distribution. A server only needs to send each packet once for it to reach all of its recipients. This is useful for situations where a large number of receivers need to receive the same data. The replication and distribution of these packets are done by the network rather than the head end server, it scales well to extremely large numbers of receivers. This is a key component of video teleconferencing. 

Mixers

A mixer, or a frequency mixer, is an electronic device that is often used for changing the quality and the levels of audio and/or video signals. Mixers are nonlinear electrical circuits that create new frequencies from two signals applied to them. In its most common application, two signals are applied to a mixer, then it produces new signals at the sum and difference of the original frequencies. This plays an important role in video teleconferencing because a signal can be sent via bandwidths that are different frequencies.

User Needs

For a video conference to be held, a user must have certain hardware and software. First, a display is necessary to show the incoming video data. Speakers are needed to hear the audio captured from the other party’s microphone. Likewise, a camera and microphone are required to capture your video and audio data. Next, a strong internet connection is necessary so that data can be transmitted quickly enough to match real-time. Lastly, a video conferencing program is needed in order to carry out and host the call.

Sequence Numbers

In video conferencing, data is transmitted in real-time, so it is essential for the data to come in the proper sequence. This includes missing data or data that is out of order. To fix this, a sequence number is given to the bytes of data. The sequence number is the byte number of the first byte of data in the TCP packet sent (also called a TCP segment). The acknowledgment number is the sequence number of the next byte the receiver expects to receive. The receiver packing sequence number x acknowledges receipt of all data bytes less than byte number x. The sequence number is always valid. The acknowledgment number is only valid when the ACK flag is one. The only time the ACK flag is not set, that is, the only time there is not a valid acknowledgment number in the TCP header, is during the first packet of connection set-up.

Playback buffer

Arrival time is separated from the playback time by using a buffer to store the data until they are played back. The buffer is referred to as a playback buffer. When a session begins (the first bit of the first packet arrives), the receiver delays playing the data until a threshold is reached. In the previous example, the first bit of the first packet arrives at 00:00:01; the threshold is 7 s, and the playback time is 00:00:08. The threshold is measured in time units of data. The replay does not start until the time units of data are equal to the threshold value. Data are stored in the buffer at a possibly variable rate, but they are extracted and played back at a fixed rate. The amount of data in the buffer shrinks or expands, but as long as the delay is less than the time to playback the threshold amount of data, there is no jitter.

Translator

A translator is a computer that can change the format of a high-bandwidth video signal to a lower-quality narrow-bandwidth signal. For instance, this is needed for a source creating a high-quality video signal at 5 Mbps and sending it to a recipient having a bandwidth of fewer than 1 Mbps. To receive the signal, a translator is needed to decode the signal and encode it again at a lower quality that needs less bandwidth.

Video teleconferencing 

In its most basic definition, video teleconferencing is an audio and visual communication between remote users. Teleconferencing involves multicasting. The individuals attending a video teleconference all need to receive the same information at the same time. Temporary or permanent groups can be formed for this purpose. As stated earlier, multicasting can be used for either one-to-many or many-to-many distribution. A server only needs to send each packet once for it to reach all of its recipients. Thus, video teleconferencing is made possible by means of multicasting and other technological factors.

Example: Zoom

To set up a Zoom call with someone out of the country, there are a few steps that must be completed. First, an account has to be created with Zoom, and depending on the length of the call, a fee/subscription must be paid. Then a meeting ID has to be created by scheduling a time for the meeting to take place. Next, the meeting ID is shared with the specified parties for them to join. Each party needs to have the necessary hardware to join the call and successfully participate in it. The call is then held over the Internet local to each party (LAN).