The bandwidth used by CoreNexa will be adjusted for the best experience based on the user‘s network connection. 

1:1 video calling

Upstream and Downstream

• 500 kbps (up/down) for High-quality video (default resolution)
• 1.2 Mbps (up/down) for HD (720p) video
• 2.5 Mbps (up/down) for FullHD (1080p) video

Group meetings and webinars

Upstream

• Number of users x resolution bandwidth
• 500 kbps up for High-quality video (default resolution)
• 1.2 Mbps (up/down) for HD (720p) video
• 2.5 Mbps (up/down) for FullHD (1080p) video

Downstream

• This will depend on the number of attendees and the resolutions they are sending. There will be a maximum of 3.5 Mbps used no matter how many users are in a meeting. The last two talking users will get the bandwidth they are sending and the remainder of the bandwidth is divided up between the remainder of the users.

Bandwidth requirements by resolution

Video is the largest consumer of bandwidth in CoreNexa. There isn’t even a close second place, so we’ll focus on identifying how to calculate the bandwidth required for a meeting.

General calculations for the different available video modes:

CoreNexa Video Modes	Horizontal Resolution	Vertical Resolution	Color Bits (depth)	fps	Single Frame Size (bits)	Single Frame Size (Mbit)	Single Frame Size (MByte)	Approximate Bandwidth (Mbps)	Approximate Bandwidth (MBps)	w/CoreNexa Compression (est. Kbps)	(est Mbps)	(est MBps)
Low	172	96	32	30	528384	0.504	0.063	15.12	1.89	150	0.15	0.02
Standard	352	192	32	30	2162688	2.063	0.258	61.88	7.73	300	0.29	0.04
High (Default)	640	360	32	30	7372800	7.031	0.879	210.94	26.37	400	0.39	0.05
HD (720p)	1280	720	32	30	29491200	28.125	3.516	843.75	105.47	700	0.68	0.09
Full HD (1080p)	1920	1080	32	30	66355200	63.281	7.910	1898.44	237.30	2000	1.95	0.24

Notes:

Kbps = Kilo bits per second (1024 bits sent per second)

Mbps = Mega bits per second (1024 Kbps = 1048576 bits sent per second)

MBps = Mega Bytes per second (8 bits in a byte, divide Mbps/8 = 131072 Bytes sent per second)

Single Frame Size = Horizontal Resolution (pixels across) x Vertical Resolution (pixels down) x Color Bits (depth = bits per pixel)

Approximate Bandwidth = Estimated without transmission overhead

Inbound video from participants

This is the calculation of the remote user’s upstream bandwidth available to the Internet (which is almost always less than their downstream bandwidth). We recommend utilizing ‘High’ resolution mode (640×360) for most meeting participants and this is the default unless a user changes it. This is adequate and the best compromise vs. bandwidth use.

In the CoreNexa Desktop Client, users have control over their upstream bandwidth use. For each camera on the user’s computer are the following settings:

The frame rate will be automatically tuned based on the bandwidth allowed and the resolution set. The defaults are the settings seen above. But, if a user sets their resolution to HD or Full HD and does not adjust the upstream Bandwidth allowed, the Frame Rate will be adjusted to try to compensate.

Outbound video to each participant

The total video outbound to each participant is controlled by the RNode. The system has a maximum bandwidth setting so that even if there are 100 people in a meeting, the video streams for the current talker and previous talker will be optimized and all other videos will share the remaining bandwidth available for the meeting. 

This system setting is set to 3584 Kbps (3.5 Mbps).

Calculation examples

Assumptions are for one office with 10 users watching and sending video at ‘High’ resolution:

Upstream (to the Internet) = 10 users x 0.39 Mbps (from table above) = 3.9  Mbps

Downstream (from the Internet) = 10 users x 3.5 Mbps (max downstream per user) = 35 Mbps

What if all of the users set their cameras to Full HD:

Upstream (to the Internet) = 10 users x 1.95 Mbps (from table above) = 19.5  Mbps

Downstream (from the Internet) = 10 users x 3.5 Mbps (max downstream per user) = 35 Mbps

These are estimates and do not consider traffic transmission overhead.

Miscellaneous

For screen sharing only (no video thumbnail): 100 kbps

For audio VoIP: 60-80 kbps

For Phone: 60-100 kbps