Introduction
Video conferencing has been around for over 30 years, but catapulted into mass use in March 2020 as a rush for business continuity & keeping in touch with Friends & Family began.

The requirement for video has increased dramatically. Zoom & Teams have become to VC, what Hoover is to Vacuuming

Up until about 2015 enterprise companies may have had a team setting up calls for you, or an external bridging company who joined the call and asked if all sites could see and hear each other & screen share.
This usually involved a lot of incoherent hand waving and other visual communication methods with the “Hi, I can see you OK. Can you see me OK?”.



Thankfully now with Teams, Zoom, SimplyVideo, Cisco and other platforms at the forefront, the most you need to worry about is a colleague saying "You're muted"! (while pointing at their ear and/or signing it out) 😊



We are going to cover off Bandwidth & Resolution. - This is quite an in-depth subject

You will probably be using one of the following methods:-
A PC/Laptop based solution with Webcam and/or a million devices on USB dongles.
A UC bar such as the Poly X/Cisco room or traditional video conferencing Codec with an LFD (Screen) (or projector If you're old school).

If you have a dedicated meeting room, this should be implemented according to industry guidelines.

When it comes to video quality there are a couple of important things to consider:

Resolution and Frame rate

Bandwidth is the amount of capacity you have both inbound (download) and outbound (Upload), this can be measured on sites like speedtest.net Normally ISP’s give you the headline speed which is download only.

Most credible video platforms use advanced compression and codecs to minimise the required bandwidth for highspeed HD video. However, there are limits.
HD720 video calls usually use a 24-bit image colour depth that refreshes 30 times every second (30 frames per second or fps).

This requires about 664Mbps of video traffic in & out (1280 x 720 x 24 x 30). This will be compressed down to between 2Mbps and 4Mbps (plus overhead) when it is transmitted over the network.

The table below summarizes the bandwidth requirement against various video qualities.

Bandwidth table

Resolution - (number of pixels in the image)

The higher the resolution the better the image.

Usually on a video call, you want the image to be as sharp and vivid as possible. The more detail displayed requires more pixels. Depending on the number of people or subjects in the room, the requirements are calculated differently. Using CIF as an example.

A single person in a call

Single person

A full screen CIF image uses about 100,000 pixels. Usually with one person on the screen, this covers around 1/4 of the total image on screen. This gives 25,000 pixels.
For a CIF call you need at least 384Kbps of bandwidth.

A group in a Call

Multiple people

There are still about 100,000 pixels in total. The people are about 10% of the screen. This gives a total screen pixel requirement of approximately 1,000,000 pixels, so the call needs to be an HD720 call, to match an identical level to the single person. This equates to a bandwidth requirement of at least 1.1Mbps.

Frame Rate (how quickly the image refreshes).

A moving image is made up of still pictures hitting the screen to make a moving image, so in a case of 30 still pictures hitting the screen a second, this becomes 30fps and 60 a second is 60fps.

In most video calls, your computer will vary the frame rate dependent on how much movement is on screen. If you are using a video conferencing codec, the same will occur, but in addition, the codec will take into account intermediate bandwidth also.

As an example, an empty room will not require a higher frame rate, which will reduce the bandwidth, where as if people suddenly walk into the room and start throwing shapes, the frame rate will spike and stay high while activity is ongoing. This will result in a matching spike and sustained increase in bandwidth requirements.

Dual Video or presentation channel

When you press 'share screen' or the 'presentation' button, the system will open an additional video stream. This typically uses the H.239 data protocol (excluding MSTeams which uses different protocols). When you share a screen into a call, this becomes the main participant in single screen solution, such as webRTC, so the resolution of the participants is automatically scaled down.

Concurrent Video Calls

Most of us now use video in place of telephone, when calculating bandwidth, account not only for meeting rooms, but the amount of users that can be using their Laptop/Desktop at the same time, a good starting point is 25-40% of your total bandwidth.

QoS
Never forget QoS this is vitally important. We have a separate document for this, but 40% of your available bandwidth should be reserved and devices QoS marking appropriately. Video & SIP telephony is the most important traffic on your network.
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