Bandwidth & resolution explained
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, and Zoom becoming 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, Pexip, Gmeet, Cisco and other platforms at the forefront, the most you need to worry about is a colleague saying "Your 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 are 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:
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.
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
A full screen CIF image uses about 100,000 pixels. Usually with one person on the screen, this covers about a quarter 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
There are still about 100,000 pixels in total. The people are about 10% of the screen. This gives a total screen pixel requirement approximately 1,000,000 so the call needs to be HD720 call to match an identical level to the single person. This equates to a bandwidth requirement of at least 1.1Mbps.
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 depending on how much movement there is on the screen, If you are using a or video conferencing codec the same will occur, but in addition the codec will take into account intermediate bandwidth also:-
As 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 & stay high while activity is ongoing. This will result in a matching spike & sustained increase in bandwidth requirements
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 solutions, such as webRTC, so the resolution of the participants is automatically scaled down.
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.
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.
The requirement for video has increased dramatically, and Zoom becoming 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, Pexip, Gmeet, Cisco and other platforms at the forefront, the most you need to worry about is a colleague saying "Your 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 are 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:
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.
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
A full screen CIF image uses about 100,000 pixels. Usually with one person on the screen, this covers about a quarter 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
There are still about 100,000 pixels in total. The people are about 10% of the screen. This gives a total screen pixel requirement approximately 1,000,000 so the call needs to be HD720 call to match an identical level to the single person. This equates to a bandwidth requirement of at least 1.1Mbps.
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 depending on how much movement there is on the screen, If you are using a or video conferencing codec the same will occur, but in addition the codec will take into account intermediate bandwidth also:-
As 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 & stay high while activity is ongoing. This will result in a matching spike & sustained increase in bandwidth requirements
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 solutions, such as webRTC, so the resolution of the participants is automatically scaled down.
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.
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.
Updated on: 07/12/2022
Thank you!